SECTION 5

MILK PRODUCTION and QUALITY

240 Section 5 | Chapter 48 CHAPTER 48 ANATOMY AND PHYSIOLOGY OF LACTATION

“Remember a cow is a mother and her calf is a baby”

Introduction Seen from the back, the udder is divided into a right and left half by the udder or intermammary Very early in the development of the dairy groove. From a side view, the fore and rear industry in Britain, the way to treat cows for quarters are more smoothly joined together milking was described as follows: not having such a distinctive groove. The hind quarters are usually larger than the fore “…She shall then milk the cow boldly, and not quarters and may secrete 25 to 50% more milk leave stretching and straining of her teates, till than the fore quarters with the ratio between one drop of milk more will come from them; back and fore quarters being 60 to 40%. for the worst point of housewifery that can be, is to leave a cow halfe milkt; for besides the The udder is attached to the body by the losse of milk it is the only way to make the cow following ligaments: dry, and utterly unprofitable for the dairy. The milkmaid, whilst she is milking, shall do nothing 1. The medial suspensory ligament, which rashly or suddenly about the cow which may divides the udder into a right and left half afright or amaze her; but as she came gently, (Figure 48.1), and so with all gentleness she shall depart.” From C. 2. The lateral suspensory ligaments, which Markham (1660). The English housewife – a way form a fibrous layer around the outside of to get wealth. the glands joining the medial suspensory ligaments on the lower surface of the The same principles still apply for present-day glands. dairies using modern equipment. The lateral suspensory ligaments are chiefly Anatomy of the udder fibrous, whereas the medial suspensory ligaments are more elastic fibres. Filling the The udder of a mature dairy cow normally udder therefore stretches the medial ligaments weighs about 10 to 25 kg and consists of four to enlarge the storing capacity of the udder. individual glands, also referred to as quarters. When these ligaments weaken, the udder Each quarter is drained by a teat at the bottom tends to separate from its close adherence to of the quarter. There is no flow of milk between the abdominal wall and the udder is described quarters. The total milk storage capacity of the to be breaking away. Connective tissue udder may be as high as 35 kg. penetrates and traverses each quarter, thus giving shape and further support to the udder. The udder is a skin gland connected to the A big udder may contain a large volume of abdominal cavity through the inguinal canal. connective tissues and little gland tissue; udder Blood and lymph vessels, as well as nerve fibres, size is, therefore, not always a true indication enter the udder from the abdominal cavity of the productive ability or capacity of a cow. through this canal, which forms a tube about 10 cm long.

241 Skin

Median suspensory ligament

Lamellae

Lateral suspensory ligament

Figure 48.1. The suspensory apparatus of the udder of a dairy cow

The udder should ideally shrink during the milking canal, which is 0.5 to 1.0 cm long, prevents process and must therefore be completely dirt entering the udder and milk escaping elastic when empty. before milking commences. The diameter of the streak canal and the tonus of the sphincter It is important for the udder to extend well muscle determine the ease of milking a cow. forward for the maximum utilisation of the At the upper end of the streak canal loose space available underneath the body. This folds of tissue, called the Furstenberg’s Rosette, feature is essential, since the udder must be press down against the opening of the streak large enough to contain all the milk that may canal and assist in preventing the escape of be secreted between milking sessions. This milk from the udder. results in the udder expanding, i.e. becoming larger, by about one-third of its normal size. This The teat cistern has a diameter of about 1 expansion increases the milk-carrying capacity cm with a capacity of 30 to 50 mℓ of milk of the udder by approximately 60%, while the immediately above the teat opening. In the remaining 40% of the milk secreted can be teat cistern, several fairly well-defined circular accommodated in the natural storage spaces membranes are found. This may sometimes of the udder. form a septum across the teat, preventing the flow of milk. If this happens, the septum has to The shape and size of the teats that drain the be pierced with a special needle to enable four glands are independent of the shape normal milk flow. and size of the udder. In addition to the four normal teats, about 40% of cows have one The udder cistern, also called the lactiferous or more supernumerary teats, usually without cistern, with a capacity of 100 to 400 mℓ of the presence of glandular tissue. These teats milk, follows immediately beyond the teat usually occur behind the rear teats. cistern and is situated in the udder. There is no definite separation between these two cisterns Milk collecting system resulting in their being more or less continuous. From the gland cistern five to 20 large milk The teat opening, or streak canal, is situated collecting ducts branch and rebranch into in the lower end of the teat and is surrounded very small collecting tubules, each eventually by a sphincter muscle. This muscular walled ending in an alveolus (Figure 48.2).

242 Section 5 | Chapter 48

Alveoli Lobe Lobule containing alveoli

Connective tissue Major duct Ducts

Gland cistern

Teat cistern

Teat meatus

Figure 48.2. The milk collecting system

An alveolus consists of a single layer of milk tissue) and vascular (blood-vessel) network producing cells attached to the inside of a surrounds the alveolus (Figure 48.3). Each spherical basement membrane. This cell layer lumen drains into a small milk-collecting tubule. of epithelial cells surrounds the lumen, the These small tubes flow together forming larger hollow inside of the alveolus into which the milk milk ducts. is excreted. A dense myoepithelial (muscle

Arteriole

Myoepithelial cell Lumen Capillary Epithelial cell

Venule Ducts

Figure 48.3. The alveolus

The alveoli occur in large numbers in the udder and have a diameter of 0.1 to 0.3 mm. They are grouped together in lobules by connective tissue; each lobule containing about 200 alveoli. All the lobules draining into the same milk duct are described as a lobe.

243 Milk secretion secretory products fill the interior spaces of the cells before leaving through the walls of the Each alveolus is surrounded by a dense apex to fill the lumen with milk. network of fine blood-vessels which provide the milk synthesising cells with a continuous supply About 500 kg of blood pass through the udder of nutrients for the synthesis of milk. There are during the production of one kg of milk. Some three phases identified during milk secretion: milk constituents move unchanged from the blood to the milk, while others are synthesised • Synthesis by the cells of the alveolar by the epithelium. Casein and lactose, for epithelium; example, are found only in milk, while milk fat • Discharge from the epithelial cells into the comprises glyceride combinations not found alveolar lumen; and elsewhere in the body. • Storage in the alveolar, ducts, and cisterns. Udder pressure and secretion rate Directly after milking, the lumina are almost empty, the epithelium folded, and the cells Changes in the secretion rate and themselves are largely devoid of any secretion. intramammary pressure in the udder during As the producing cells draw the raw materials milk secretion as affected by milking interval for milk synthesis from the blood, synthesised are shown in Figure 48.4.

(a) (b)

FigureFigure 48.4. 48. The4. The decrease decrease in in milk milk secretion secretion rates rates (a)(a) and increaseincrease in in udder udder pressure pressure (b) (b) as as affected by the length ofaffected the milking by the interval length of the milking interval

MilkMilk is continually is continually synthesised synthesized atat aa raterate of ofabout about 1 to 224 m ℓhours./g glandular After tissueabout per 36 day. hours, At thewhen aboutcompletion 1 to 2 mℓ/g of milking, glandular when tissue all available per day. milk At hasudder been removed,pressure maypressure be withinas high the as teat about cistern 7 kPa the iscompletion at atmospheric of milking,levels, but when within all an available hour after milkingabove , atmosphericpressure within pressure, the udder increasesmilk secretion by milkabout has 1been kPa removed,as milk re siduepressures fill withinthe collapsed the stops teat andaltogether. udder cisterns. Thereafter, pressure teatinitially cistern increasesis at atmospheric slowly for levels, 5 to 6 but hours, within and then more rapidly at 2 to 4 kPa at the end of an hournormal after milking milking, intervals. pressure The within pressure the at udder this stage There depends are on theindications length of thethat interva thel betweenapparent increasesmilking by session abouts, 1udder kPa ascapacity milk residues, and the fill yield the of declinecows. The in pressuresecretion in therate udder of most is also of greater the milk collapsedin the hind teat quarters and udder than in cisterns. the front Thereafter, quarters, as wellconstituents, as in early lactation.as the milking increases, is due to pressure initially increases slowly for 5 to 6 hours, their absorption during storage, rather than a andMilk then is more secreted rapidly at an at inverse 2 to 4 ratekPa to at mammary the end pressure.true decline This relain secretiontionship is, rate. however, virtually of normallinear for milking the first intervals. 10 hours. The Thereafter, pressure atwith this an extension of the interval, the rate of synthesis stageslows depends down, showing on the alength marked of reduction the interval after aboutOnce 24 hours.the rate After of about milk 36 secretion hours, when has udder been betweenpressure milking may sessions,be as high udder as abocapacity,ut 7 kPa and above depressed atmospheric by pressure,delaying milk milking, secretion it does stops not the altogether.yield of cows. The pressure in the udder is immediately revert to normal when milking also greater in the hind quarters than in the resumes. For example, the yield obtained in front quarters, as well as in early lactation. an 8-hour interval following a 24-hour interval, There are indications that the apparent decline in secretion rate of most of the milk constituents, is 25% less than when the 8-hour interval was Milkas is secretedthe milking at increases, an inverse is ratedue to mammarytheir absorption preceded during storage, by another rather normal than a t8-hourrue decline interval. in pressure.secretion This rate. relationship is, however, virtually linear for the first 10 hours. Thereafter, with an extensionOnce the of rate the of interval, milk secretion the rate has of been synthesis depressed by delaying milking, it does not immediately slowsrevert down, to normalshowing when a marked milking reduction resumes. afterFor example, the yield obtained in an 8-hour interval 244 following a 24-hour interval, is 25% less than when the 8-hour interval was preceded by another normal 8-hour interval.

Milking frequency and milk production Long intervals between milking sessions cause the udder pressure to increase to high levels, slowing down the secretion rate. By shortening milking intervals, an increase in daily production is possible.

The interval between milking sessions is a critical element of dairy management as both the number of milking sessions in a 24-hour day and the duration of the intervals between milking sessions are important. At high milk yields and lower storage capacity in the udder, milk must be Section 5 | Chapter 48

Milking frequency and milk production increase is mainly due to better feeding and overall management. Long intervals between milking sessions cause the udder pressure to increase to high levels, Milking cows only once a day throughout the slowing down the secretion rate. By shortening lactation reduces lactation milk yield by 5 to milking intervals, an increase in daily production 10% in comparison to twice a day milking. is possible. Once-a-day milking is often applied under pasture-based conditions when pasture The interval between milking sessions is a critical production is limited or when cows are at the element of dairy management as both the end of the lactation period when milk yield is number of milking sessions in a 24-hour day and at a low level. the duration of the intervals between milking sessions are important. At high milk yields and The milk let-down reaction lower storage capacity in the udder, milk must be removed more frequently from the udder The largest percentage of milk in the udder is to avoid a reduction in the milk secretion rate. stored in the lumen of the alveoli and in the Intervals longer than 12 hours between milking small milk ducts. Due to the small diameter sessions should be avoided. of these ducts, capillary forces prevent the drainage of the milk. In South Africa, at least 90% of cows are milked twice a day. Milking at exactly equal intervals Milk in the alveoli and ducts cannot be of 12 hours is ideal, but is rarely practiced removed from the udder using normal means because of the unsocial hours which it imposes without the cooperation of the cow. Only the on the milkers and management. The average small quantity of milk present in the teat and intervals for large herds are usually about 14 udder cisterns and in the larger milk ducts can and 10 hours, i.e. at 05:00 and 15:00 per day. be removed. This milk is described as the fore- However, based on research results, a ratio milk and is only a small percentage of the total even as wide as 16 to 8 hours does not reduce milk stored in the udder. milk yield by more than 4%. This means that the lower milk yield could be weighed up against At the commencement of milking, only the milking at more sociable hours, for instance to fore-milk is therefore immediately available. start milking at 07:00 and 15:00 every day. Hereafter an interruption of milk flow usually occurs. This is especially noticeable in cows Milking cows three times instead of twice a that have not been stimulated correctly before day increases milk yield by 5 to 25%, provided milking has started. Before the initiation of the cows are fed adequately. When no extra feed main milk flow, i.e. before milk let-down occurs, is provided to compensate for the higher milk the nervous system of the cow must first be yield, cows will lose body condition (live weight), stimulated to let milk down. which would affect the milk yield of cows in the following lactation negatively. Increasing The nervous reflex responsible for milk let- the number of times cows are milked per day, down begins with the stimulus produced by results in higher production increases in older the suckling of the calf, or the presence of cows in comparison to first lactation cows. A milkers, or the sounds of the milking machine. In decrease in udder pressure is often only partly normal milking routines, udder washing at the responsible for the higher milk yield, because beginning of the milking process usually serves better feeding and management may also as the stimulus for milk let-down. contribute. The teat base, i.e. where the teat joins the No conclusive proof is available that milking udder, is richly supplied with nerve centres and frequency influences the composition of milk a massage (when being washed) or suckling produced daily. Some research showed a slight action on this area produces a strong stimulus. decline in fat percentage in milk when cows The nerve impulse travels to the hypothalamus are milked thrice instead of twice a day. This is of the brain, which activates the pituitary probably because of the higher milk yield. gland to release the hormone oxytocin into the blood which carries it to all parts of the Milking cows four times per day may lead to an body. When it reaches the udder, it causes the increase in milk yield of 5 tot 10% higher than myoepithelial cells surrounding each alveolus that of cows milked three times per day. This to contract, decreasing the size of the lumen of 245 the alveolus, forcing milk out of the ducts. The of cow stimulating cows increases the level of small ducts also shorten and widen to facilitate oxytocin which reaches a peak concentration the movement of milk from the alveoli into the of about 25 μU/ml within two minutes. The larger ducts. As a result of the above, the teat peak concentration may vary considerably, and udder cisterns, as well as the larger milk e.g. from 11 to 65 μU/ml between cows. After ducts, become distended with milk, resulting in peak, the concentration of oxytocin declines the hardening of the udder and teats and an sharply, reaching pre-stimulation levels within increase in intra-mammary pressure. Milk let- about four minutes. down has occurred and the cow can now be milked. A period of 45 to 60 seconds elapses The maximum concentration obtained and the between the time when oxytocin is released time required to reach this peak is dependent into the bloodstream and when it arrives in the on the following factors: udder. • Type of stimulus About 15% of the initial milk volume cannot be Hand stimulation, e.g. a 30-second udder removed from the udder during a thorough, wash, is a strong stimulus and results in normal milking process and is known as residual maximum oxytocin levels in the blood within milk. Removal of residual milk is, however, 1 to 2 minutes. The normal pulsator action of possible by the injection of oxytocin. This the milking machine causes a more gradual procedure is of no practical use as the residual increase and a lower peak concentration. milk does not affect the daily milk yield of cows. The peak is obtained in about double the time than with hand stimulation (Figure 48.5). Oxytocin levels in blood serum • Breed of cow The average oxytocin level in the blood serum of Holstein-Friesian cows are easier to stimulate dairy cows is about 8.0 ± 0.11 μU/ml. As a result than Jersey cows.

Figure 48.5. The oxytocin concentration before, during and after manual (■) and milking machine Figure 48.5. The oxytocin concentration before,(□) stimulation during and after manual (■) and milking machine (□) stimulation

OxytocinOxytocin concentration concentrationand and milkability milkability is required for the complete removal of milk. During the 1960’s, researchers in New Zealand found thatSince hand the-stimulated oxytocin cows, levels i.e. ain 40 the-second blood and udderDuring wash the immediately 1960’s, researchers prior to machine in New-milking, Zealand resulted udder in 16%pressure more start milk toand decline 32% more within fat minutes yieldsfound than that cows hand-stimulatednot stimulated by handcows,. Low i.e. produc a aftering Jersey stimulation, cows were it is usedaccepted in the thatstudy. to ensure These40-second results contributed udder wash to the immediately conclusion that prior high to oxytocin optimal levels, milk as flow a result that of the the strongmilk process milk should letmachine-milking,-down reaction, also resulted cause ina 16%high morepressure milk in and the udderstart withinwhich oneis required minute for after the stimulation. complete removal32% more of milk. fat Sinyieldsce the than oxytocin cows levelsnot stimulated in the blood and udder pressure start to decline within minutesby hand. after Lowstimulation, producing it is acceptedJersey cowsthat to were ensure Theoptimal results milk of flow more that therecent milk research,process using shouldused start in the within study. one Theseminute results after stimulation. contributed to high performing Holstein cows, showed that the conclusion that high oxytocin levels, as production increases because of hand- Thea resultresults of of the more strong recent milk re let-downsearch, using reaction, high performingstimulation, Holstein to be cowsabout, showed0 to 2%. that This small productionalso cause increases a high becausepressure of in hand the -udderstimulation which, to bebeneficial about 0 to 2%.effect This smalldoes beneficial not contradict the 246 effect does not contradict the necessity of stimuli and circumstances contributing to a strong milk let-down reaction. It is, however, evident that the degree of stimulation necessary to ensure complete milking is dependent on factors such as breed, production level and stage of lactation. The conclusion is that in the case of a modern, high genetic merit, high producing dairy cow, the stimuli from the normal milking parlour routine are sufficient to ensure a satisfactory milk let- down reaction and that deliberate stimulation would not be required.

Reasons for this change in emphasis on the necessity for the specific stimulation action include the following:

• High producing dairy breeds and cows are stimulated more easily.

• Due to the culling of cows from the herd on the basis of milk production, it follows that those cows which do not respond adequately to the particular milking parlour routine for a specific dairy will be culled because of low milk yields. The evolution of modern milking machines and methods thus resulted in the selection for animals requiring a minimum of stimulation. Section 5 | Chapter 48 necessity of stimuli and circumstances Effect of time interval between stimulation and contributing to a strong milk let-down reaction. milking on milk characteristics It is, however, evident that the degree of stimulation necessary to ensure complete High oxytocin levels are maintained in the milking is dependent on factors such as breed, blood for only a short period. The duration of production level and stage of lactation. The the milk let-down reaction is therefore also conclusion is that in the case of a modern, high short. Research has shown that the half-life of genetic merit, high producing dairy cow, the oxytocin is about 3 minutes. Because optimum stimuli from the normal milking parlour routine milkability is only obtainable when both are sufficient to ensure a satisfactory milk let- oxytocin levels and udder pressure are high, it down reaction and that deliberate stimulation is important that the milking unit is attached to would not be required. the udder before the oxytocin concentration in the blood starts to decline, which is usually Reasons for this change in emphasis on the within one minute after stimulation. When necessity for the specific stimulation action the interval between stimulation and the include the following: attachment of the milking unit is delayed, milk characteristics are adversely affected (Table • High producing dairy breeds and cows 48.1). are stimulated more easily. Even short delays between stimulation and the • Due to the culling of cows from the herd start of milking may have the following results: on the basis of milk production, it follows that those cows which do not respond adequately • a decrease in milk yield, to the particular milking parlour routine for a • a higher stripping volume, specific dairy will be culled because of low • a longer machine-on time, milkHigh yields. oxytocin The levels evolution are maintained of modern in the milking blood for• only a decreasea short period. in the The maximum duration of milk-flow the milk rate, machineslet-down reactionand methods is therefore thus alsoresulted short. inResearch the • hasa shownlonger thattime the to reachhalf-life peak-flowof oxytocin rate, is selectionabout 3 minutes.for animals Because requiring optimum a minimummilkability of is only• obtainablea lower fat when percentage both oxytocin in milk, levels and and stimulation.udder pressure are high, it is important that the milking• shortening unit is attached the lactation to the udder period before because the of oxytocin concentration in the blood starts to decline, whichearlier isdryingusually up. within one minute after stimulation. When the interval between stimulation and the attachment of the milking unit is delayed, milk characteristics are adversely affected (Table 48.1). Table 48.1. Milking characteristics caused by delays between Table 48.1. Milkingpre-stimulation characteristics and thecaused startby of delaysthe milking between process pre-stimulation and the start of the milking process

Delay (min) Parameters 0 3 15 Total milk yield (kg) 11.2 10.7 10.5 Stripping (kg) 0.2 0.2 0.4 Total machine-on time (min) 7.6 7.7 7.8 Peak-flow rate (kg/min) 2.7 2.4 2.4 Time to reach peak flow rate (min) 1.9 2.1 2.5

Even short delays between stimulation and the start of milking may have the following results:

Inhibition• a ofdecrease milk let-down in milk yield response, the adrenal gland to liberate the hormone • a higher stripping volume, adrenaline (epinephrine) into the blood Inhibition• a lofonger the machine milk let-down-on time, response has stream. The mechanism by which adrenaline been• observeda decrease in in athe number maximum of milk species-flow rateas , causes the inhibition is not absolutely clear. It the result• a lofonger emotional time to reach disturbances, peak-flow ratesuch, as is, however, known that adrenaline causes the cows• beinga lower frightened,fat percentage in pain, in milk anger,, and etc. constriction of the blood vessels in the udder. The immediate• shortening cessation the lactation of period the milk-flow because of isearlier Another drying possibility up. is that adrenaline prevents caused as a result of a nerve stimulus causing the release of oxytocin. Inhibition of milk let-down response Inhibition of the milk let-down response has been observed in a number of species as the result of emotional disturbances, such as cows being frightened, in pain, anger, etc. The immediate cessation of the milk-flow is caused as a result of a nerve stimulus causing the adrenal gland to liberate the hormone adrenaline (epinephrine) into the blood stream. The mechanism by which 247 adrenaline causes the inhibition is not absolutely clear. It is, however, known that adrenaline causes the constriction of the blood vessels in the udder. Another possibility is that adrenaline prevents the release of oxytocin.

Blood circulation through the udder The quantity of blood in the body of cows varies from 5.8 to 8.5% of live weight. In young cows and dry cows, the percentage is lower than in older cows and in cows in milk. It is known that for each 1 kg of milk secreted, 150 to 500 kg of blood must pass through the udder.

To maintain a high secretion rate, an adequate vascular system supplying and draining blood to and from the udder is essential. All the blood vessels to and from the udder occur in pairs, one vessel for each half of the udder. The arteries carrying blood to the udder include the following:

• The external pudic artery This is the most important artery carrying blood to the udder. It enters the udder through the inguinal canal and is then known as the mammary artery. Blood circulation through the udder The blood leaves the udder through the following veins: The quantity of blood in the body of cows varies from 5.8 to 8.5% of live weight. In young cows • The external pudic vein and dry cows, the percentage is lower than in This leaves the udder through the inguinal older cows and in cows in milk. It is known that canal for each 1 kg of milk secreted, 150 to 500 kg of blood must pass through the udder. • Subcutaneous abdominal vein This vein flows from the udder under the To maintain a high secretion rate, an adequate abdomen and enters the body cavity vascular system supplying and draining blood through the milk-well, posterior to the to and from the udder is essential. All the blood sternum. vessels to and from the udder occur in pairs, one vessel for each half of the udder. The Elements of the milking routine arteries carrying blood to the udder include the following: An efficient and fixed milking routine, which is understood by the milkers and which cows are • The external pudic artery used to, is a very important component of milk This is the most important artery carrying production. Low milk yields, low fat tests, short blood to the udder. It enters the udder lactations and the spread of mastitis, often through the inguinal canal and is result from an inefficient milking routine. then known as the mammary artery. The basic steps in the milking routine are as • Perineal artery follows: This artery reaches the udder through the pelvis and supplies blood to the posterior i) Washing the udder dorsal part of the udder. Proper washing of teats and udders before milking (Figure 48.6) serves a three-fold purpose -- controlling bacterial contamination of the milk, -- stimulating milk let down, and -- protecting against mastitis.

Figure 48.6. Hand washing of the udder and teats using running water

Dirt and manure clinging to the cow’s udder before milking. Water at room temperature, and teats contain many millions of bacteria per luke-warm water (approximately 40°C) or, gram of dirt. To prevent this dirt and bacteria preferably, water containing a disinfectant, from being washed into the milk during milking, should be used for this purpose. The following it is essential that the lower part of the udder, methods could be used: and especially the teats, are thoroughly washed 248 - Bucket method: This is a method commonly used in small-scale dairies but is, from both a hygienic and a convenience point of view, not recommended to be used. The disadvantages are that, unless individual washing-cloths are being used for each cow, both Section 5 | Chapter 48 the washing-cloth and water in the bucket become a source of bacterial contamination, -- Bucket method: This is a method commonly -- Automated udder washing: This can increasing the possibility of spreading mastitis among cows. used in small-scale dairies but is, from both be done either in the milking-parlour or a hygienic and a convenience point of in a preparation stall. A water sprayer view,- notHose recommended with spray nozzle to be: This used. method The is hygienic,located convenient on the floorand practical, or a preparation especially in stall disadvantagesmilking parlours.are that, The unless washing individual action can eitheris automatically be done with turnedthe bare on ha ndby or the with cow a washing-clothssingle-servi arec ebeingwashing used-cloth for(one each cloth perentering cow). Devices the stall. which measure disinfectant cow, bothinto thethe washing-clothwater-line are available. and water in the bucket become a source of bacterial The effectiveness of udder washing is affected contamination,- Automated increasing udder washingthe possibility: This ofcan by:be done either in the milking-parlour or in a spreadingpreparation mastitis amongstall. A cows. water sprayer located on the floor or a preparation stall is automatically turned on by the cow entering-- thethe stall. thoroughness of dirt removal from the -- Hose with spray nozzle: This method is teats and lower part of the udder, hygienic,The effectiveness convenient of udder wandashing practical,is affected by:-- preventing the unnecessary wetting of the especially in milking parlours. The washing upper parts of the udder as well as the groin action- canthe thoroughness either be done of dirt with removal the frombare the teatsarea and of lower the partcow, of and the udder , hand- orp reventingwith a thesingle-service unnecessary wettingwashing- of the-- upperdrying parts the of theteats udder and as well udder as the groinbefore cloth (onearea cloth of the percow cow)., and Devices which commencement of milking, preferably with measure- d ryingdisinfectant the teats into and the udder water-line before arecommencement a single-service of milking, paper preferably towel with (Table a single 48.2).- available.service paper towel (Table 48.2).

Table 48.2. The effect of different udder washing procedures on the bacterial content of Table 48.2. The effect of different udder washing procedures on the bacterial content of milk milk

Bacteria per mℓ of milk Washing procedure Clean udders Very dirty udders Average Range Average Range None 5120 1010 – 16900 7530 1550 – 28350 With water, no drying 8840 1550 - 28350 18540 1750 – 111000 Water and drying 3 160 750 – 15000 14400 2660 – 54000 Disinfectant, no drying 2 150 405 – 18750 11250 825 – 64200 Disinfectant and drying 750 172 – 4605 1930 115 – 15740

Udder washing usually serves as a stimulus for the milk let-down reaction and should begin Udderabout washing one minute usually before serves applying as a stimulusthe milking for machine.ii) Testing for mastitis the milk let-down reaction and should begin This involves squeezing a small quantity of milk about one minute before applying the milking from each teat, either onto a stip cup or into ii) Testing for mastitis machine. the paddle which is used for performing the This involves squeezing a small quantity of milk from each teat, either onto a stip cup or into the California Mastitis Test (CMT). This action allows paddle which is used for performing the California Mastitis Test (CMT). This action allows the the milker to ensure that the teat orifice is not milker to ensure that the teat orifice is not blockedblocked and toand check to check for mastitis, for mastitis, blood andblood other and abnormalities in milk (Figure 48.7). other abnormalities in milk (Figure 48.7).

Figure 48.7. Testing of fore-milk for mastitis before attaching clusters on the teats 249 iii) Attaching the teat cups (or milk cluster) wears off within minutes, and if the cow is not The teat cups should be attached as soon after completely milked within this time, the volume udder preparation as possible (Figure 48.8). of residual milk will increase. After stimulation, the milk let-down reaction

Figure 48.8. Attaching the teat cups on the teats

iv) Stripping stripping, usually achieved by downward This is the term given to the methods used to pressure on the claw and by massaging the remove more milk after normal milk flow has udder (Figure 48.9). ceased. Hand stripping gave way to machine

Figure 48.9. Stripping of milk from the udder

The purpose of stripping is to ensure that all 6.8% more milk and 9.2% more fat per lactation the available milk is removed from the udder. than the unstripped halves of the udders. Various research reports have indicated that a higher yield is obtained when stripping The necessity and advantage of stripping is included in the milking routine. In a trial depend largely on the thoroughness of conducted in Germany, in which only the right stripping cows after milking. Complete milking- half of the udders of first lactation cows were out is largely dependent on: stripped after milking, those halves produced 250 Section 5 | Chapter 48

-- effectiveness of stimulation, v) Removing the milking unit -- timely utilisation of milk let-down reaction, The milk clusters can be removed once the and milk-flow rate has dropped to below about 20 -- efficiency of the milking machine. mℓ/min. This is done by cutting off the vacuum from the clusters and by gently drawing To cease machine stripping does not normally the teat-cups off the udder (Figure 48.10). have a detrimental effect on udder health, Continuing to milk cows after the milk flow although air rushing in when machine stripping has dropped results in over-milking with the is done, may increase the risks of mastitis. following disadvantages:

Stripping, being time-consuming, is often -- increases the erosion of the teat orifice, not done at the end of the milking routine. -- this may increase the number of new The responsibility to ensure that the cows are mastitis infections, while thoroughly milked out should, however, not be -- available machine-time is wasted. neglected.

Figure 48.10. Removal of the milking cluster from the teats vi) Rinsing the milking units for example, with water at 85°C for 5 seconds, Although very often omitted from the milking or by back-flushing with either cold or hot water routine, the milking units, in an effort to minimise which may or may not contain a disinfectant, the spread of mastitis organisms from cow to such as hypochlorite or iodine. cow, may be rinsed between cows. This can either be done by dipping the teat cups first Indications are that back-flushing, even in a pre-rinse (water) and then in a sanitising with cold water, reduces new infection rate solution, or by back-flushing with water which as caused by streptococcal but not by may contain a disinfectant. staphylococcal mastitis. There is, however, also evidence that inter-cow cluster pasteurisation, The effect of cluster flushing on new mastitis which is much more effective than any type infection rates is not clear. It is, however, known of cluster flushing, will only give moderate that the bacterial population on liners can be reductions in new infection rates when teat reduced, although not eliminated, by flushing, disinfection is practiced.

251 vii) Teat disinfection -- assists in the prevention and healing of teat The most effective single element in the control lesions, particularly when emollients such as of new udder infection among lactating cows glycerol are included in the formulation. is teat disinfection immediately after milking (Figure 48.11). Teat dipping (disinfection) can This practice can reduce new mastitis cases by be done by either dipping the teats or by approximately 50%. A range of disinfectants, spraying the disinfectant on the teats. including sodium hypochlorite, iodophors, chlorhexidine, dodecyl benzene, sylphonic Teat dipping has the following advantages: acid and others, are employed for this purpose. -- destroys bacteria left on the teat at the end of milking, -- eliminates and prevents colonisation of the teat orifice by pathogenic bacteria, and

Figure 48.11. Teat disinfection using a spray method after milking and the removal of the milking clusters

As with teat dipping, the amount of disinfectant In closing used and the efficiency of teat coverage by spraying depend primarily on the skill of the Milk production is a continuous process in the operator. If care is taken to cover the teats, the udders of dairy cows until all the alveoli and time to spray teats will be longer, while using ducts are filled up. Removal of milk by milking more disinfectant than teat dipping. cows initiates milk synthesis. The milk let-down is affected by the release of oxytocin, while it is The effectiveness of germicidal teat blocked by the secretion of adrenaline. Treating dips in reducing new infections caused cows calmly before and during milking will result by Streptococcus agalactiae and in high milk let-down and milk production. The Staphylococcus aureus is well-documented. interval between udder stimulation and milking The majority of these teat dips are, however, unit attachment should be within one minute, not very effective in eliminating new coliform as high oxytocin levels are maintained in the infections. The use of latex teat dips, which blood only for a short period. High producing were designed to form a physical barrier over dairy cows are stimulated more easily. First the teat opening to prevent environmental lactation cows not adapting well to the milking bacterial contamination between milking parlour management will be culled early as sessions, may be more effective against the their milk yields will be affected negatively. latter organism. A reduction of for example 76% was found in the number of new coliform infections when an acrylic latex teat dip without germicide was used.

252 Section 5 | Chapter 49 CHAPTER 49 THE COMPOSITION OF MILK CHAPTER 49

THE COMPOSITION OF MILK Variation is the only constant characteristic of milk composition Variation is the only constant characteristic of milk composition

Introduction milking session, e.g. such as morning and Introduction evening milking, as well as the total milk from Milkilk is is defined defined as the as undiluted, the undiluted, fresh lacteal fresh secretionday to obtainedday. The by variation the complete in milk milking composition of one or lactealmore healthy secretion cows, excludingobtained colostrum by the, which is a is resultsecreted of within the influence 15 days before of and a aboutlong list5 of Mdayscomplete after calving milkingdown . of one or more physiological, inherited, and environmental healthy cows, excluding colostrum, which is factors. secretedBulk withinmilk obtained 15 days from before different and sources about may5 differ widely in composition. Even milk from an days individualafter calving cow down. may vary from one to another milkingThe gross session, composition e.g. such as of morning milk basedand even oning a milking, as well as the total milk from day to day.large The numbervariation ofin milkmilk compossamplesition collectedis a result from of Bulk milkthe influenceobtained of from a long different list of physiological, sources may inherited a variety, and environmentalof sources andfactors. including different differ widely in composition. Even milk from an breeds is presented in Table 49.1. individualThe gross cow compositionmay vary from of milk one based to another on a large number of milk samples collected from a variety of sources and including different breeds is presented in Table 49.1.

Table Table49.1. The 49.1. gross The composgross compositionition of cow’s of milk cow’s milk

Component Content (%) Total solids (%) Solids not fat (%) Water 87.2 - - Fat 3.7 3.7 - Proteins 3.5 3.5 3.5 Lactose 4.9 4.9 4.9 Minerals 0.7 0.7 0.7 Total 100.0 12.8 9.1

The components, other than water, are known as the total solids (TS) and the total solid minus the fat content is the solids-not-fat (SNF). In average milk, these two groups of components amount The components,to about 12.8% other TS thanand 9.1% water, SNF. are All known milk containsamount the to sameabout gross 12.8% components TS and ,9.1%although SNF. inAll as thevarying total solids proportions (TS) and(Table the 49.total2). solid minus milk contains the same gross components, the fat content is the solids-not-fat (SNF). In although in varying proportions (Table 49.2). average milk, these two groups of components

Table 49.2. The average composition of the milk of various mammals Table 49.2. The average composition of the milk of various mammals

Species Water (%) Fat (%) Protein (%) Lactose (%) Minerals (%) Woman 87.4 3.8 1.6 7.0 0.2 Cow 87.2 3.7 3.5 4.9 0.7 Goat 87.0 4.3 3.5 4.3 0.9 Ewe 80.7 7.9 5.2 4.8 0.9 Buffalo 82.8 7.4 3.6 5.5 0.8 Camel 87.6 5.4 3.0 3.3 0.7 Mare 89.0 1.6 2.7 6.1 0.5 Ass 89.0 2.5 2.0 6.1 0.4 Reindeer 63.3 22.5 10.3 2.5 1.4

253 Since different batches of milk may differ The concentration of soluble salts, mainly lactose noticeably as it is affected by a number of and chloride, in the watery phase, determines biological factors, and to ensure that buying the freezing point of milk. The freezing point of and selling of milk in the trade is conducted milk varies between - 0.512 to - 0.541°C is the on an equitable basis, the composition of most constant physical property of milk. The any batch of milk should be known. Knowing secretory processes of the mammary gland the composition of milk is important for the are such that the osmotic pressure of milk is following reasons: kept in equilibrium with that of the blood. Any depression of the synthesis of lactose, e.g. in • The composition of milk determines the mastitic udders, is compensated by increases yield and composition of manufactured in the sodium and chloride contents in milk. dairy products. For example, the Cheddar Adulteration of milk by the addition of water cheese yield from 100 kg milk containing lowers the concentration of soluble salts and 3% fat is about 8 kg in comparison to causes the freezing point of milk to increase about 10 kg from milk containing 4% fat. above - 0.512°C.

• Milk in the so-called fresh-milk trade The freezing point of milk is therefore a reliable must comply with specific minimum and convenient method for the determination requirements. Although these may vary, of the adulteration of milk with water. Each depending on the controlling authority, 0.001°C increase in the freezing point above the minimum requirements for full-fat fresh - 0.512°C is equivalent to the addition of about milk according to the Act on Agricultural 0.2% water. Product Standard (Act 119 of 1990) should be: Milk fat

-- Fat : minimum 3.3% a. Physical characteristics -- SNF : minimum 8.3% The percentage fat in bulk milk varies between -- Protein : minimum 3.0% (on fat- 3 to 5%, although the variation may be wider in free basis) the milk of individual cows. The fat in milk exists in the form of small globules, averaging in size • The composition of milk is a component from about 0.001 to 0.005 mm in diameter. in the breeding programme of a dairy The surface of these globules is coated with herd. Total milk production is negatively an absorbed layer of phospholipids and correlated to fat and protein percentages. proteins. This layer is commonly known as the This means that fat and protein percentages fat globule membrane and plays an important decrease when milk yield increases. While role in preserving the individual identities of the it is important to increase the total milk globules. About 1.5 to 3.0 billion of these tiny yield of dairy cows, the ultimate aim in globules may occur in 1 mℓ of milk. The size of breeding should be to increase the fat and the globules is dependent on the following protein yield per lactation of dairy cows. factors:

• In most quality payment schemes, the fat • Breed of cow: The fat globules in the milk of and protein content of milk determines dairy breeds with higher fat percentages, about 80% of the farm-gate price. like Jersey and Guernsey, are larger than those in the milk of breeds with lower fat The individual milk components percentages like Holstein-Friesians. The average fat globule in Guernsey milk is 80% Water content larger than that of Holstein milk. Variation in globule size does not cause the daily variation Milk is a natural liquid food containing about in the fat test of the milk of individual cows. 86 to 88% water. Water gives bulk to milk and is the medium in which all the components • Stage of lactation: Cows later in lactation of milk are dissolved or suspended. A small have smaller fat globules in their milk. The fat percentage of the water in milk is hydrated to globules are usually the largest during the the lactose and salts and some is bound in the first two weeks of the lactation with the most proteins. rapid rate of decline occurring during the next two months of the lactation. Thereafter, the rate of decline is slow, although 254 Section 5 | Chapter 49

continuing to the end of the lactation. This Due to the difference in the specific gravity decline in globule size is an important factor (SG) of milk fat (SG of 0.93) and skim milk (SG of as late lactation milk is more susceptible 1.036), the globules in undisturbed milk will, with to the development of a rancid taste. time, rise to the surface to form a cream layer on top of the milk. Due to this, it is of utmost • Individual cows: The size of globules from importance to stir milk thoroughly before a different cows from the same breed may sample of bulk milk is collected for analysis. vary to a great extent. Sampling from a bulk tank should be preceded by at least five minutes of stirring. Fat globules float around in the milk in a true oil-in-water emulsion with the fat being the b. Chemical composition dispersed phase. Fat globules are kept apart Milk fat, like the majority of animal fats, by: consists chiefly of triglycerides of fatty acids. • The viscosity of milk. It also contains varying quantities of other • The fat globule membrane – this membrane components as indicated in Table 49.3. has to be removed or broken before two fat globules can unite. Agitation, as in churning, breaks the membrane and the globules coalesce to form butter granules. • A negative electric charge that is present on the globules.

Table 49.3. The componentsTable 49.3. ofThe milk components fat of milk fat

Components Content in fat(%) Table 49.3. The componentsTriglycerides of milk fat 98 - 99 Phospholipids (lecithin) 0.2 - 1.0 Sterols (cholesterol) 0.2 - 0.4 Components Content in fat(%) Free-fatty acids Trace amounts Triglycerides 98 - 99 Fat-soluble vitamins Trace amounts Phospholipids (lecithin) 0.2 - 1.0 Sterols (cholesterol) 0.2 - 0.4 A triglyceride can Freebe -definedfatty acids as an ester (combination)Trace ofamounts one glycerol molecule with three A triglyceridemolecules of can fatty beacids.Fat - definedsoluble A triglyceride vitamins as can an thus ester bethree representedTrace molecules amounts as follows: of fatty acids. A triglyceride (combination) of one glycerol molecule with can thus be represented as follows: AGlycerol triglyceride + fatty can acid be 1 defined+ fatty acidas an 2 +ester fatty (combination)acid 3 = triglyceride of one + glycerolH2O molecule with three molecules of fatty acids. A triglyceride can thus be represented as follows: Glycerol + fatty acid 1 + fatty acid 2 + fatty acid 3 = triglyceride + H O At least 18 different major fatty acids, some of which are shown in Table 49.4, are2 found in milk Glycerolfat. + fatty acid 1 + fatty acid 2 + fatty acid 3 = triglyceride + H2O At least 18 different major fatty acids, some of which are shown in Table 49.4, are found in milk fat. At Table least 49. 184.differentThe chemical major fatty formula, acids, meltingsome of pointswhich areand shown content in ofTable some 49. major4, are foundfatty acidsin milk in fat.milk fat in comparison to soy beans

TableTable 49. 49.4.4. The The chemicalchemical formula, formula, meltingMelting melting points points and and content content of of s omesome major major fatty fatty acids acids in Fatty acid Formula Content in milk fat (%) Content in soybeans (%) milkin milk fat fatin comparisonin comparison to soy to soybeans beanspoint Butyric C3H7COOH - 8°C 2.9 - Capric C7H15COOH 16°C 0.8 - Melting FattyStearic acid C17FormulaH35COOH 69°C Content in15.0 milk fat (%) Content in soybeans- (%) point Oleic C17H33COOH 14°C 31.9 25 Butyric C3H7COOH - 8°C 2.9 - Linoleic C17H31COOH - 31°C 4.5 55 Capric C7H15COOH 16°C 0.8 - Stearic C17H35COOH 69°C 15.0 - ButyricOleic acid (CH3C -17(CHH33COOH2)2 - COOH)14is°C an example of 31.9a volatile fatty acid. Being25 volatile, it is partlyLinoleic responsible Cfor17H the31COOH pleasant aroma- 31° Cgiven off when 4.5butter is heated. 55

ButyricStearic acidacid (CH(CH33 -- (CH(CH22))216- -COOH)COOH)isis an an example example of of a avolatile saturated fatty long acid.-chain Being fatty volatile acid ,andit isis partlydescribed responsible as a hard for fat the with pleasant a melting aroma point given of 69off ° whenC. butter is heated.

StearicOleic acidacid (CH(CH3 3- -(CH(CH2)27)16- CH=CH- COOH) - is(CH an2 )example7 - COOH) of hasa saturated the same long amount-chain of fatty carbon acid atoms and isas describedstearic acid as ,abu hardt contains fat with 2 a hydrogen melting point atoms of less.69 ° C.It is therefore classified as an unsaturated fatty acid and has a lower melting point (14 °C) and is thus a soft fat. 255 Oleic acid (CH3 - (CH2)7 - CH=CH - (CH2)7 - COOH) has the same amount of carbon atoms as stearicLinoleic acid acid, bu(CHt contains3 - (CH 2) 5hydrogen- CH=CH atoms - (CH less.2)2 - CH=CHIt is therefore - (CH 2classified)5 - COOH) as, similaran unsaturated to stearic fatty and acidoleic and acids, has aalso lower contains melting 18 point carbon (14 atoms°C) and, but is thushas 4a softhydrogen fat. atoms less than stearic acid, as well as two unsaturated bonds. Because this type of fatty acid contains more than one double Linoleicbond, it acidis termed(CH3 -a(CH poly2)-5unsatur- CH=CHated -fatty(CH 2acid.)2 - CH=CH Linoleic - (CHacid2 has)5 - ,COOH)because, similarof its unsaturation, to stearic and a oleicvery acids,low melting also contains point and 18 is carbon therefore atoms classified, but has as a4 veryhydrogen soft fat. atoms less than stearic acid, as well as two unsaturated bonds. Because this type of fatty acid contains more than one double bond,Any threeit is termedfatty acids a pol, ory- unsatureven threeated molecules fatty acid. of Linoleic the same acid fatty has acid, beca, mayuse combineof its unsaturation, with a single a veryglycerol low meltingmolecule point to form and isa thereforetriglyceride. classified A wide as varietya very soft(theoretically fat. 183 = 5832) of different triglycerides may thus appear in milk fat. All different triglycerides would be in an individual Anymilk three fat globule. fatty acids , or even three molecules of the same fatty acid, may combine with a single glycerol molecule to form a triglyceride. A wide variety (theoretically 183 = 5832) of different triglyceridesThe fat percentage may thus in milkappear is currentlyin milk fat. determined All different by means triglycerides of infra -wredould analyzers. be in an This individual method milkis based fat globule. on the absorption of the infra-red light by specific chemical bonds in the triglycerides.

The fat percentage in milk is currently determined by means of infra-red analyzers. This method is based on the absorption of the infra-red light by specific chemical bonds in the triglycerides. Butyric acid (CH3 - (CH2)2 - COOH) is an example and oleic acid, resulting in Jersey cows of a volatile fatty acid. Being volatile, it is partly producing fat that is usually firmer than that responsible for the pleasant aroma given off of Holsteins. when butter is heated. • Feed: Feeds, like green pasture and linseed oil, containing a high percentage of low

Stearic acid (CH3 - (CH2)16 - COOH) is an melting point fatty acids, e.g. oleic and example of a saturated long-chain fatty acid linoleic acid, result in a soft fat, whereas dry and is described as a hard fat with a melting roughages produce a firm fat. point of 69°C. • Stage of lactation: Fatty acids are affected by lactation stage, e.g. butyric acid has a

Oleic acid (CH3 - (CH2)7 - CH=CH - (CH2)7 - maximum value during the first month of COOH) has the same amount of carbon atoms lactation and decreases during succeeding as stearic acid, but contains 2 hydrogen atoms months, reaching a minimum at the end of less. It is therefore classified as an unsaturated the lactation. Stearic and oleic acids are fatty acid and has a lower melting point (14°C) high in early lactation, while it decreases and is thus a soft fat. until mid-lactation and increases again to the end of the lactation period.

Linoleic acid (CH3 - (CH2)5 - CH=CH - (CH2)2 -

CH=CH - (CH2)5 - COOH), similar to stearic and Higher levels of low melting point fatty acids in oleic acids, also contains 18 carbon atoms, but milk result in softer fat, thereby improving the has 4 hydrogen atoms less than stearic acid, spreadability of the butter made from such as well as two unsaturated bonds. Because milk. this type of fatty acid contains more than one double bond, it is termed a poly-unsaturated c. The precursors of milk fat fatty acid. Linoleic acid has, because of its unsaturation, a very low melting point and is Propionic acid is indirectly the main glycerol therefore classified as a very soft fat. precursor. In cows, it is converted into glucose outside the mammary gland. The glucose Any three fatty acids, or even three molecules is converted into glycerol inside the gland. of the same fatty acid, may combine with a Fatty acids may result from the following three single glycerol molecule to form a triglyceride. sources: A wide variety (theoretically 183 = 5832) of different triglycerides may thus appear in milk • Short chain organic acids: Acetic acid fat. All different triglycerides would be in an makes the most important contribution to individual milk fat globule. the synthesis of fatty acids in the mammary gland. Acetic acid results from the The fat percentage in milk is currently fermentation of digestible carbohydrates, determined by means of infra-red analysers. e.g. hemi-cellulose which occurs in high This method is based on the absorption of the concentrations in fibre-rich feeds in the infra-red light by specific chemical bonds in rumen. A certain amount of roughage the triglycerides. in the diet is required to stimulate this fermentation process and to maintain It is important to indicate that the fatty acids the normal fat percentage in milk. in normal milk are chemically bound to the glycerol molecule and thus do not contribute • Fat depots in the animal body: this is a to the acidity of milk. When milk, however, turns major source when cows are underfed. rancid, fatty acids are hydrolysed (set free) from the glycerol molecule by the enzyme lipase. • Ingested fats: Fats in the diet contribute Free fatty acids responsible for the rancid taste approximately 25% of the milk fatty acids. then appear in the milk contributing, although to a very minor extent, to the acidity. d. The role of milk fat in milk and milk products

The percentage of the different fatty acids in Fat is probably the most important component milk differs as a result of the following factors: in milk. Its effect is seen mainly in four categories, i.e. the economy of milk production, human • Breed: In the milk of breeds producing high nutrition, food flavour, and the physical fat milk there is a smaller percentage of properties of milk products. low melting point fatty acids, e.g. butyric 256 Section 5 | Chapter 49

In the past, most payment systems for milk were 1. Milk protein based largely on the fat content of milk. In South Africa, payment for protein was incorporated The average protein content of bulk milk is intoMilk the paymentfat, as with scheme other fats, in 1983.is a rich Since source milk of fat energ abouty, yielding 3.5%, approximatealthough varyingly 9 Kcal/gram between (1 2.8 cal and is still= 4.185relatively Joules). expensive Secondly compared, it serves as to a carrierother of4.0%. the fatThe soluble variation vitamins in the A, D,protein E and content K, and of milkthirdly, components, milk fat containsit is obvious significant that the amounts cost of of themilk, so on-called a daily essential basis, fatty is muchacids less i.e. ,thanlinoleic that of dairyacid products and arachidonic depend acid. on their fat contents. fat. The protein to fat ratio in bulk milk in high fat producing breeds varies from approximately Milk fat, as with other fats, is a rich source of 0.8 to 1.0, while for lower fat producing breeds, The most distinctive role that milk fat fulfills in dairy products concerns the flavour of foods. energy, yielding approximately 9 Kcal/gram the ratio may be almost 1 to 1. (1 calMilk = fat4.185 is responsibleJoules). Secondly, for the rich,it serves pleasing as a flavour of many dairy products such as butter, carriercheese, of andthe icefat cream.soluble On vitamins the other A, hand, D, E it and is also Proteins notable thatare thepolymers milk fat ofis significantamino acids. in many Certain K, flavour and thirdly, problems milk, such fat as containsrancidity and significant oxidized flavoursessential, which amino may acids, occur such in dairy as tryptophanproducts. and amounts of the so-called essential fatty acids lysine, cannot be synthesised in the human i.e.,The linoleic fine body acid and and texture arachidonic in most dairyacid. products isbody. determined These, in manyhowever, instances are byall milkpresent fat. in milk proteins. Of the 20 amino acids occurring in The2. mostMilk distinctiveprotein role that milk fat fulfills in proteins, all are found in milk protein. dairy products concerns the flavour of foods. MilkThe fat average is responsible protein content for the of bulkrich, milk pleasing is about 3.5%Milk contains, although a varying number between of protein 2.8 andcomponents 4.0%. flavourThe variation of many in dairythe protein products content such o f asmilk butter,, on a whichdaily basis differ, isin muchcomposition less than and that properties. of fat. The The cheese,protein and to fat ice ratio cream. in bulk On milk the in other high fathand, producing it major breeds groups varies are from indicated approximately in Table 0.8 49.5.to 1.0, is alsowhile notable for lower that fat theproducing milk fat breeds, is significant the ratio mayin be almost 1 to 1. many flavour problems, such as rancidity and oxidisedProteins flavours, are polymers which of amino may acids. occur Certain in dairy essential amino acids, such as tryptophan and products.lysine, cannot be synthesized in the human body. These, however, are all present in milk proteins. Of the 20 amino acids occurring in proteins, all are found in milk protein. The fine body and texture in most dairy products is determinedMilk contains in amany number instances of protein by componentsmilk fat. which differ in composition and properties. The major groups are indicated in Table 49.5.

Table 49.5. TTablehe distribution 49.5. The ofdistribution protein in of bulk protein milk in bulk milk

Protein fraction Content in milk (%) Average of total N (%) Casein 2.7 76 - 79 Albumin 0.3 9 Globulin 0.1 3 Proteose-peptone 0.1 4 Non-protein nitrogen 0.2 5 Total protein 3.5 100

2. Casein Casein is precipitated in milk by:

Casein is defined as the protein fraction • Acids: This usually happens when the that precipitates from skim milk when the pH normal pH of milk of about 6.6 sours to a pH decreases1. Casein by acidification to a pH of 4.6 to 4.7. level of 5.2 to 4.5. It is this precipitation of the casein that causes sour milk to thicken TheCasein casein is definedcontent as in th milke protein varies fraction from that2.3 precipitatesto or coagulate.from skim milk when the pH decreases 3.8%.by Itacidification is the main to protein a pH of fraction 4.6 to 4.7. of milk and is • Alcohol: When milk and 68-70% alcohol are not produced anywhere else in nature. In milk, mixed in a 1:1 ratio, the casein precipitates caseinThe caseinoccurs content as a fine in milk colloidal varies fromsuspension 2.3 to 3.8%.in Itif is acid the maindevelopment protein fraction has already of milk occurred.and is combinationnot produced with anywhere calciumels ande in is nature. often termedIn milk, caseinThis occurs is the as basis a fine for colloidal the well-known suspension alcohol in calciumcombination caseinate. with Thecalcium colloidal and is particles often termed have calcium (Alizarol) caseinate. test The by colloidal which rawparticles milk haveis graded a a diameterdiameter ofof approximatelyapproximately 0.0001 0.0001 mm, mm, being being 10 times beforesmaller beingthan the picked fat globules up on in the milk. farm. 10 times smaller than the fat globules in milk. • Rennin: The enzyme rennin used in cheese- making coagulates milk at a normal pH- level within a short time frame. • Heavy ions: The presence of an excess of 257 heavy ions, e.g. Ca++ and Mg++, causes fractions are identical to the protein of blood. the coagulation of casein. These are transferred directly from the blood to the milk. The other whey proteins are, however, Casein, being a high quality protein as it synthesised in the udder. contains all the essential amino acids, is very much in demand in the food industry. Dairy 5. Lactose (milk sugar) products, such as cheese and milk powder, contain a high percentage of casein. Lactose is found in high concentrations in milk only while very low levels appear also in blood Casein also has a number of non-food uses and urine. Lactose is the only carbohydrate in and is being used in the paper coating, glue, milk. Milk from some mammalian species, such plastic, paint, textile, and leather industries. as sea lions and some seals, does not contain any lactose. 3. Albumin and globulin Lactose is a disaccharide, being a compound These two proteins are in true solution in milk consisting of a molecule each of galactose and are not precipitated by rennet or by and glucose. The average percentage of normal acidification to a pH level of 4.7. During normal cows’ milk generally ranges from 4.6 to the cheese-making process, they are thus not 5.2%. This usually amounts to about 50% of the coagulated and remain in the whey. For this total solids in skim milk. reason these proteins are called the soluble or whey proteins. Their total percentage in milk is The osmotic pressure of milk is essentially about 0.5 to 0.7%. similar to that of blood and is maintained by the balance of concentration of lactose Both albumin and globulin are precipitated by and soluble mineral matter, mainly chlorides. heat (about 68°C or higher). This is the reason Thus any variation in lactose concentration is why colostrum, which may contain up to 10% counterbalanced by one in sodium chloride of these proteins, thickens when it is heated. (NaCl) in the opposite direction. The smaller molecular weight of NaCl and its complete Immunoglobulin (IG), a fraction of globulin, is dissociation means that a slight increase in present in normal milk in low concentrations, chloride concentration is counterbalanced while occurring in colostrum in much larger by a much greater decrease in the lactose quantities. These proteins are of unique content of milk. importance for the new-born calf, because they are absorbed into its circulation In a mastitis-infected udder, the permeability system where they fulfill temporarily the of the epithelium cells increases with the result immunological functions of blood gamma- that more blood substances enter the lumen globulin. Immunoglobulins (or antibodies) can and thus the milk. As the chloride content of be absorbed through the intestinal wall only blood (about 0.3%) is about three times that during the first 24 to 36 hours of life, with the of milk, the chloride content of mastitis milk maximum amount being absorbed during the increases from about 0.09 to 0.14%, whereas first hour. After calving, the concentration of the lactose content of milk decreases from IG in colostrum declines sharply, i.e. from 130 about 4.9 to 4.6%. Low lactose values in milk mg/mℓ of milk at 2 hours to 26 mg/mℓ of milk samples from individual cows are, therefore, a at 24 hours. For these reasons, it is of utmost fair indication of a mastitis infection. importance that a new-born calf should receive about 5% of its birth weight in colostrum Lactose fulfills an important role in nutrition within the first half-hour after birth. as it serves as a source of energy providing 4 kCal per gram of milk, while it aids in calcium 4. Precursors of milk proteins and phosphorus assimilation and also in the intestinal synthesis of vitamins, e.g. vitamin D in Casein does not occur in the blood but is some species. synthesised in the udder mainly from the free amino-acids which are absorbed from the The primary uses of lactose are the following: blood. Some of the non-essential amino acids • As an ingredient in infant foods and in are, however, also synthesised in the udder. special dietary products; • In the formulation and standardisation of The immunoglobulins and certain albumin pharmaceuticals, tablets and pills; and 258 Section 5 | Chapter 49

• In the production of caramelised dairy The precursor of lactose is blood glucose. Some products. glucose is converted in the udder to galactose and with both sugars present, lactose is formed. Lactose is fermented by bacteria to lactic acid and is therefore of utmost importance in The contents of the main milk constituents, the manufacturing of fermented and ripened namely, milk fat, total protein and lactose, dairy products. It also plays an important role are currently determined by means of infra- in the texture, taste, and solubility of a wide red analysers. The principle on which these range of dairy products. analysers operate is based on the absorption of infra-red light by specific chemical bonds in the milk constituent to be determined.

6. Minerals (milk salts)

The minerals that occur in milk are listed in Table 49.6.

Table 49.6. The mineral content of normal milk

Minerals Content in milk (%) Calcium (Ca) 0.12 Magnesium (Mg) 0.01 Phosphorus (P) 0.09 Sodium (Na) 0.06 Potassium (K) 0.14 Chloride (Cl) 0.11 Sulphur (S) 0.03 Citric acid 0.16 Total 0.72

Although the mineral content of milk is less than 1%, minerals have a marked effect on the nutritiveAlthough value, the heatmineral, and contentalcohol stabilityof milk ofis milkless . Mineralsuspendeds also (colloidal) affect the combinations.age, thickening of evaporatedthan 1%, mineralsand condensed have milk,a marked the feathering effect onof cream in coffee, the coagulation of milk by rennetthe nutritive, and the value, clumping heat, of theand fat alcohol globules stabilityduring homogenization. In addition to the elements that occur in milk of milk. Minerals also affect the age, thickening in relatively large proportions, there are a Potassium,of evaporated sodium andand chloridecondensed are entirely milk, inthe solution. large Phosphate,number ofcalcium, elements magnesium usually andmeasured citricfeathering acid are of partly cream in insolution coffee, and the partly coagulation in suspended in (colloidal)parts percombinations. million (ppm) or micro-grams per of milk by rennet, and the clumping of the fat ℓ. These are referred to as trace elements (see Inglobules addition during to the homogenisation. elements that occur in milk in relativelyTable 49.7).large proportionsThe fact that, there they are area large present in number of elements usually measured in parts per millionvery (ppm) small oramounts micro-grams does pernot ℓ detract. These arefrom their referredPotassium, to assodium trace andelements chloride (see areTable entirely 49.7). inThe importance fact that they since are presentmany inof verythese small elements amountssolution. doesPhosphate, not detract calcium, from their magnesium importance and since aremany known of these to elementshave remarkable are known tophysiological, have remarkablcitric acide physiological,are partly in catalytic solution, andand nutritional partly in qualities. catalytic, and nutritional qualities.

259 Table 49.7. The trace element content (microgram/litre,Table 49.7. The trace mg/ℓ) element of standard content milk (microgram/litre, mg/ℓ) of standard milk Elements Concentration (mg/ℓ) Aluminum 460 Arsenic 50 Boron 270 Cadmium 26 Chromium 15 Copper 130 Iodine 43 Iron 450 Lead 40 Manganese 22 Molybdenum 73 Nickel 27 Rubidium 2000 Selenium 40 Silver 47 Strontium 171 Zinc 3900

It isIt well-acceptedis well-accepted thatthat more more trace trace elements elements occur 7.in milk.Vitamins The inminerals milk and their concentration occurvalues inin Tablemilk. 49.The7 have minerals been selected and to givetheir a general indication of their proportions in milk. concentrationA higher intake values rate of in most Table of these49.7 haveelements been should Milk increase is a theirgood content source in milk. of a number of selected to give a general indication of their vitamins, such as riboflavin (vitamin B2), while proportionsVitamins inin milkmilk. A higher intake rate of most contributing significantly to vitamins A and B1 of these elements should increase their content requirements. Milk has inadequate levels of in milk. vitamin C (ascorbic acid) and is a poor source Milk is a good source of a number of vitamins, such as riboflavin (vitamin B2), while of vitamin D. The most important vitamins in contributing significantly to vitamins A and B1 requirements. Milk has inadequate levels of vitamin C (ascorbic acid) and is a poor source of vitaminfresh milkD. The are most shown important in Table vitamins 49.8. in fresh milk are shown in Table 49.8.

TableTable 49.8. The49.8. most The mostimportant important vitamins vitamins in fresh in freshmilk milk

Vitamin Content (mg/mℓ) Characteristics • Precursor is carotene which occurs in certain plants • Promotes growth and health • Prevents night blindness and hardening of epithelium A 136 - 176 tissue (e.g. in the respiratory and reproductive tracts) • Heat stable • Prone to oxidation • Prevents beri-beri B1 (Thiamine) 0.02 - 0.08 • Partially destroyed by pasteurisation • Sustains normal growth and skin health B2 (Riboflavin) 0.08 - 0.26 • Destroyed by direct sunlight • Prevents scurvy C (Ascorbic acid) 1.57 - 2.75 • Promotes healthy teeth, bones and blood vessels • Destroyed by heat and sunlight

260 Section 5 | Chapter 49

8. Gasses that is insufficient to damage the creaming ability of milk, e.g. 72°C for 15 seconds, Milk directly from the udder contains about generally pasteurisation. Any residual 8% (by volume) of dissolved gasses. When activity remaining after pasteurisation coming in contact with the atmosphere, and as indicated by the phosphatase the percentage of carbon dioxide (CO2) test, indicates inadequate pasteurisation. decreases, while there is a gain in oxygen (O2) and nitrogen (N2). Milk, as delivered to the • Lipase: consumer, contains about 0.5% O2, 1.3% N2, Lipase plays an important role in milk in that and 4.5% CO2 by volume. it hydrolyses the triglycerides to set the fatty acids free which result in a rancid taste in 9. Enzymes milk.

Milk contains a number of enzymes as they are In closing components and products of the mammary gland. Certain enzymes can, however, result Milk has some distinctive features containing from bacterial growth in milk. The main enzymes food sources such as fat, protein, lactose, natural to milk include catalase, phosphatase, minerals and water. These components vary lipase and reductase: according to breed. The total solid content of milk is about 13% while the solids-no-fat may be • Catalase: about 9%. The production of milk is a biological It decomposes hydrogen peroxide as process and a considerable number of factors follows: affect the composition of milk. This may result in the composition of milk varying from day to

2H2O2 + catalase+ catalase = 2H2O += O22H2O + O2 day. The fat in milk consists of a number of fatty acids which have different effects on human Mastitic milk is rich in this enzyme and health, Because milk has a natural creaming

the release of O2 from H2O2 is used effect, e.g. fat molecules moving upwards as a diagnostic tool for mastitic milk. in the milk and forming a layer on top of the milk, the way in which milk is sampled for the • Phosphatase: analysis of its fat, protein and lactose content The phosphatase enzyme in milk is used in the may affect milk prices. Milk has to be stirred for phosphatase test to determine whether milk at least five minutes before milk sampling can has been properly pasteurised. The enzyme be done. is inactivated by heat treatments that are sufficient to destroy pathogenic bacteria such as Mycobacterium tuberculosis but

261 CHAPTER 50 CHAPTER 50 FACTORS AFFECTING THE COMPOSITION OF MILK FACTORS AFFECTING THE COMPOSITION OF MILK

A cow is a peculiar animal, sometimes she reacts, sometimes not and other times even less A cow is a peculiar animal, sometimes she reacts, sometimes not and other times even less.

IntroductionIntroduction less when a large number of cows contribute to Milk does not have the same composition at all timethes becausesample. it Even is a biological in large herdsproduct the resulting chemical from ilka number does not of havechemical the sameprocesses composition in the udder. composition The chemical of composition bulk-milk may of milk vary also significantly varies becauseat ofall environmentaltimes because and it physiological is a biological factors. from In theday case to ofday. a single The cow,most theimportant composition factors Mof herproduct milk may resulting differ considerably from a number over short of periods,affecting e.g. milk from composition one milking are to another.as follows: The chemicalextent of processes the variation in the of udder. a bulk The milk chemical sample would be less when a large number of cows compositioncontribute toof the milk sample. also Evenvaries in becauselarge herds of the 1.chemical Breeds composition and breeding of bulk-milk may vary environmentalsignificantly andfrom physiological day to day. The factors. most In important the factors affecting milk composition are as casefollows: of a single cow, the composition of her Milk yield and milk composition are hereditary milk may differ considerably over short periods, characteristics and are influenced markedly e.g.1. fromBreeds one milking and breeding to another. The extent of by breed (Table 50.1). theMilk variation yield andof a milk bulkcomposition milk sample are would hereditary be characteristics and are influenced markedly by breed (Table 50.1). Table 50.1. The average lactation milk yield and milk composition of all grade and Tableregistered 50.1. dairy The cowsaverage in milk lactation recording milk in yieldSouth andAfrica milk for thecomposition period 1 Marchof all 2006grade to and28 registeredFebruary 2007dairy (4% cows FCM in milk= fat recordingcorrected in milk: South (0.4 Africa x kg milk)for the + (15period x kg 1 fat)March 2006 to 28 February 2007 (4% FCM = fat corrected milk: (0.4 x kg milk) + (15 x kg fat)

Number of Protein:Fat Breeds Milk (kg) 4% FCM (kg) Fat (%) Fat (kg) Protein (%) Protein (kg) lactations ratio Holstein 60429 8260 7133 3.80 255 3.23 217 0.85 Jersey 49601 5596 5823 4.68 239 3.75 191 0.80 Ayrshire 6773 6200 5918 3.95 229 3.33 193 0.84 Guernsey 1099 5978 5778 4.28 226 3.46 183 0.81

From the data in Table 50.1, it seems that for dairy cow breeds, an increase in milk yield is accompanied by a decrease in fat and protein percentages in milk. Breeds producing less milk Fromhave the higher data fat in andTable protein 50.1, percentages.it seems that Although for • thisIt isincreases a major fat andfactor protein in determiningyields, breeds the dairyproducing cow breeds, a higher an volume increase of milk in havemilk yieldhigher is lactation producer’s fat and protein milk yields. price. When the unit accompanied by a decrease in fat and protein price between these two components percentages in milk. Breeds producing less differs significantly, it may affect breeding The fat to protein ratio in the milk of different breeds differ considerably, being 1 : 0.90, 1 : 0.91, milk have higher fat and protein percentages. strategies. Although1 : 0.81 thisand increases1 : 0.83 for fat Friesians, and protein Ayrshires, yields, Guernseys and Jerseys, respectively. breeds producing a higher volume of milk • In the milk of a single herd, this may indicate haveThe higher fat to proteinlactation ratio fat is andimportant protein with yields. respect to the dietfollowing: deficiencies with regards to roughage and energy contents. The fat• toIt protein determines ratio the in composition the milk of of different dairy products . breeds differ considerably, being 1 : 0.90, 1 : Both milk yield and milk composition are 0.91, 1• : 0.81It is and a major 1 : 0.83 factor for in Friesians, determining Ayrshires, the producer’s hereditary milk price.and Whencan thethus unit be price affected between by Guernseysthese and two Jerseys, components respectively. differs significantly, breedingit may affect and breeding selection strategies. programmes. As the heredity of milk characteristics is correlated, The fat• to Inprotein the milk ratio of is a important single herd, with this respect may indicate a change diet defi inci enciesthe breeding with regards programme to roughage may to the following:and energy contents. affect all milk traits (Table 50.2).

• It determines the composition of dairy products.

262 Both milk yield and milk composition are hereditary and can thus be affected by breeding and selection programmes. As the heredity of milk characteristics is correlated, a change in the breedingBoth programme milk yield may and affect milk all composition milk traits (Table are hereditary 50.2). and can thus be affected by breeding and Section 5 | Chapter 50 selection programmes. As the heredity of milk characteristics is correlated, a change in the Table 50.breeding2.Table The programmegenetic 50.2. The correlations geneticmay affect correlations between all milk milktraits between traits(Table 50.milk2). traits

TableTraits 50.2. The genetic Milkcorrelations(kg) betweenFat (kg) milkProtein traits(kg) Fat (%) Fat (kg) 0.88 - - - Protein (kg) 0.95 0.93 - - Fat (%) Traits - 0.20 Milk (kg) 0.24 Fat (kg) - 0.01Protein (kg) - Fat (%) Protein (%)Fat (kg) - 0.19 0.88 0.04 - 0.06 - 0.49 - Protein (kg) 0.95 0.93 - - Fat (%) - 0.20 0.24 - 0.01 - From Table 50.2 it Proteinseems (%) that the genetic- 0.19 correlation 0.04between milk0.06 yield and fat0.49 and protein Fromyields Table are highly50.2 itpositive seems (more that thanthe 88%) genetic, while wouldon the otherincrease hand fat the andcorrelation protein between yields, milkthough correlationyield andFrom betweenfat andTable protein 50.milk2 percentages ityield seems and that is fat negativethe andgenetic (aboutreducing correlation -20%). the Thereforebetween fat and ,milk breedingprotein yield forpercentages and more fat milkand protein of protein yields are highly positive (more milk. would increaseyields are fat highly and protein positive yields (more, though than 88%)reducing, while the onfat theand other protein hand percentages the correlation of milk. between milk than 88%), while on the other hand the yield and fat and protein percentages is negative (about -20%). Therefore, breeding for more milk correlation between milk yield and fat and In Table 50.3 the effect of selecting for specific In Tablewould 50.3 increase the effect fat andof selecting protein yields for specific, though characteristics reducing the fat over and aprotein period percentages of 20 years of ismilk. proteinshown. percentages is negative (about characteristics over a period of 20 years is -20%). Therefore, breeding for more milk shown. In Table 50.3 the effect of selecting for specific characteristics over a period of 20 years is Table 50.shown.3. The milk yield and milk composition as affected by breeding for specific traits over a 20 year period (*Income per lactation based on fat = R7.93/kg and protein = R11.87/kg)TableTable 50.3. 50.3. The The milk milk yield yield and and milkmilk compositioncomposition asas affectedaffected by by breeding breeding for for specific traits specificover a 20 traits year periodover a( * Income20 year per period lactation (*Income based on per fat lactation = R7.93/kg basedand onfat= protein = Traits R7.93/kgR11.87/kg) and proteinMilk = R11.87/kg)(kg) Fat (%) Protein (%) Income* (R) Milk (kg) 5168 4.3 3.6 3971 Fat (kg) 4622 4.9 3.8 3881 Protein (kg)Traits 5126 Milk (kg) 4.5 Fat (%) 3.8 Protein (%) 4141Income* (R) Fat (%) Milk (kg) 3677 5168 5.8 4.3 4.0 3.6 3437 3971 Protein (%)Fat (kg) 4300 4622 5.4 4.9 4.1 3.8 3934 3881 MaximumProtein difference (kg) (%) 43 5126 45 4.5 14 3.8 20 4141 Fat (%) 3677 5.8 4.0 3437 Protein (%) 4300 5.4 4.1 3934 Maximum difference (%) 43 45 14 20 The lactose and ash content of milk are also affected by breed, although to a lesser degree, lactose being 4.87, 4.81, 4.96 and 5.00%, respectively, for Holstein, Ayrshire, Guernsey and Jersey milk. The ashThe content lactose for andthese ash breeds content was of 0.68, milk 0.68,are also 0.74 affected and 0.70 by% breed,, respectively. although to a lesser degree, lactose The lactosebeing and 4.87, ash 4.81, content4.96 and of5.00%, milk respectively are milk, forcomposition. Holstein, Ayrshire, Milk Guernseyproduced and Jerseyduring milk. also2. affectedTheStage ashby of content breed,lactation for although these breeds to a was lesser 0.68, the0.68, first0.74 and 4 0.70to % ,5 respectively. days after calving is called degree,The stage lactose of lactation being 4.87,has a 4.81,marked 4.96 and and recognisable colostrum, effect which on differsboth milk markedly yield fromand milknormal 5.00%,composition. respectively,2. MilkStage produced offor lactation Holstein, during theAyrshire, first 4 to 5milk. days Colostrum after calving contains is called high colostrum levels, whichof most Guernseydiffers Theandmarkedly stageJersey fromof milk. lactation normal The ash hasmilk. content a markedColostrum for andof contains recognisablethe milk high components effectlevels onof both mostexcept milk of theforyield lactosemilk and milk thesecomponents breedscomposition. wasexcept 0.68, for Milk 0.68,lactose produced 0.74 and and potassium.during 0.70%, the firstTheand 4fat to potassium.perce 5 daysntage after isThe calvingusually fat percentage ishigher called, although colostrum is usually it, which respectively.may varydiffers considerably.markedly fromThe proteinnormal contentmilk. Colostrumofhigher, milk, althoughespeciallycontains ithigh themay albuminlevels vary considerably.of and most globulin of the The milk contents,components is initially veryexcept high for, decreasinglactose and within potassium. aprotein few daysThe content fatback perce to ofnormalntage milk, is levelsespecially usually (Table higher the 50. albumin,4). although it 2. Stage ofmay lactation vary considerably. The protein contentand globulinof milk, especiallycontents, theis initiallyalbumin very and high,globulin decreasing within a few days back to normal contents, is initially very high, decreasing within a few days back to normal levels (Table 50.4). The stage of lactation has a marked and levels (Table 50.4). recognisable effect on both milk yield and

TableTable 50.4. 50.4. The The progressive progressive change change of colostrum intointo milk

Time after Total solids (%) Protein (%) Albumin + globulin (%) Lactose (%) Chlorides (%) Fat (%) calving 0 h 27.0 17.6 11.3 2.2 0.15 5.1 6 h 20.5 10.0 6.3 2.7 0.16 6.8 36 h 12.2 4.0 1.0 4.0 0.16 3.6 4 days 11.9 3.8 0.8 4.7 0.13 2.8 7 days 12.1 3.3 0.7 5.0 0.11 3.5

Milk yield Following the colostrum period, daily milk yield usually increases sharply to reach peak production at about 4 to 10 weeks after calving. During this period, both the fat and protein percentages of milk decrease reaching minimum levels at about the same time as when maximum 263 daily milk yield is reached. At this stage, the fat percentage of milk may be 0.2 to 0.6 percentage points lower than the fat percentage at the start of the lactation. The decline in protein percentage is usually less than that of fat, also reaching minimum levels at about the same time as maximum milk yield (Figure 50.1).

Figure 50.1. The effect of lactation stage on the milk yield (─), fat (■) and protein (□) percentage of dairy cow milk

Peak milk yield is, among other factors, dependent on the genetic merit for milk yield in dairy cows. It is also affected by body condition at calving, feeding strategy in terms of the late dry and early lactation stages, as well as udder health.

Maximum milk yield usually continues for a few weeks after reaching peak milk yields after which the daily milk yield of cows gradually declines. This decline in milk yield continues until the end of the lactation period and accelerates until after the 30th week of the lactation. A useful approximation is that from peak milk yield, the rate of milk yield decline should not exceed 2 to 2.5% per week.

Fat percentage After reaching a minimum level at around peak milk yield, the fat percentage of milk stays relatively constant for a few weeks before gradually starting to increase. This increase continues 2.1 Milk yield when maximum daily milk yield is reached. At this stage, the fat percentage of milk may be Following the colostrum period, daily milk 0.2 to 0.6 percentage points lower than the fat yield usually increases sharply to reach peak percentage at the start of the lactation. The production at about 4 to 10 weeks after decline in protein percentage is usually less calving. During this period, both the fat and than that of fat, also reaching minimum levels protein percentages of milk decrease reaching at about the same time as maximum milk yield minimum levels at about the same time as (Figure 50.1).

Figure 50.1. The effect of lactation stage on the milk yield (─), fat (■) and protein (□) percentage of dairy cow milk

Peak milk yield is, among other factors, higher than at the start of the lactation period. dependent on the genetic merit for milk Cows being milked until very close to calving yield in dairy cows. It is also affected by body often show a decline in fat percentage. condition at calving, feeding strategy in terms of the late dry and early lactation stages, as The difference between maximum and well as udder health. minimum fat percentages in milk over the lactation period may be about 0.6 percentage Maximum milk yield usually continues for a few points and is often higher in breeds producing weeks after reaching peak milk yields after milk containing high fat levels. During first which the daily milk yield of cows gradually lactation, the fat percentage of milk is relatively declines. This decline in milk yield continues low at the beginning of the lactation period, until the end of the lactation period and while reaching higher levels at the end of the accelerates until after the 30th week of the first lactation than in subsequent lactations. lactation. A useful approximation is that from peak milk yield, the rate of milk yield decline 2.3 Protein percentage should not exceed 2 to 2.5% per week. The protein percentage of milk is affected by stage of lactation following a similar lactation 2.2 Fat percentage trend as for milk fat percentage. The variation in protein percentage in milk is, however, less, After reaching a minimum level at around usually about 0.3%. After the decline in early peak milk yield, the fat percentage of milk lactation, a minimum level is reached at the stays relatively constant for a few weeks before time of peak milk yield or shortly thereafter. gradually starting to increase. This increase Protein percentage then remains fairly constant continues until the end of the lactation period, up to 2 to 5 months after the cow has been when the fat percentage of milk is usually inseminated after which protein percentage 264 Section 5 | Chapter 50 continues to increase. This increase in protein remains relatively constant while increasing percentage during late lactation is often not during the last three months of the lactation noticeable in non-pregnant cows. period. During late lactation, the sodium and chloride contents of milk may increase sharply. 2.4 Lactose percentage 3. Age of the cow The lactose percentage of milk tends to follow the trend for milk yield. Lactose percentage Cows produce more milk as they get older. reaches a maximum level at about the 7th The milk yield of mature cows in 4th lactation week after calving. After peak, the lactose is about 25% higher than that in first lactation percentage slowly decreases until mid- cows. However, with consecutive lactation lactation, after which the decline becomes periods, fat, protein and lactose percentages more pronounced. The difference between of cows decrease by about 0.03, 0.01 and maximum and minimum lactose percentages 0.04 percentage points, respectively. After may be about 0.4% percentage points. 5th lactation, these decreases level off considerably. Due to the higher milk yield in 2.5 Minerals later lactations, the fat and protein yield of older cows also increase (Table 50.5). The mineral content of milk varies during the lactation period in a similar way as the The higher milk, fat and protein yields of cows protein percentage in milk. The calcium and in later lactation are related to an increase in phosphorus contents decrease during the first body size (for a higher feed intake) and udder month of the lactation period, after which it capacity.

Table Table50.5.50.5. The 50. 5. averageaverage The average production production production of of registered registered of registered Holstein Holstein-Friesian Holstein-Friesian-Friesian cows cows in cows in the the in1985/86 1985/86 the 1985/86 milk milk recordingmilk recordingrecording year year year

Milk Milk Fat Fat Protein Protein LactationLactation number number (kg) (kg) % % kg kg % % kg kg 1 1 4746 4746 3.61 3.61 171 171 3.24 3.24 154 154 2 2 5336 5336 3.56 3.56 190 190 3.24 3.24 173 173 3+ 3+ 5802 5802 3.54 3.54 205 205 3.20 3.20 186 186

The higherThe highermilk, fatmilk, and fat protein and protein yields yieldsof cows of in cows later in lactation later lactation are related are related to an increase to an increase in body in body size (forsize a higher(for a higherfeed intake) feed intake) and udder and capacity.udder capacity. 4. Interval between milkings yield at the morning milking is higher than the milk yield in the afternoon. The fat percentage 4. Interval4. Interval between between milkings milkings When the interval between milking sessions is in the milk is, however, higher in milk following When the interval between milking sessions is unequal, the milk yield of cows is less after the unequal, theWhen milk the yield interval of cows between is less milking after the sessions the shorteris unequal, interval the milk (Table yield 50.6). of cows is less after the shortershorter interval.shorter interval. It isinterval. for It isthis for Itreason thisis for reason thisthat reason thatthe themilk that milk the yield milk atyield the morningat the morning milking milking is higher is higherthan the than the milk yieldmilk in yield the inafternoon. the afternoon. The fat The percentage fat percentage in the inmilk the is, milk however, is, however, higher higherin milk in following milk following the shorterthe shorter interval interval (Table (Table 50.6). 50.6). Table 50.6. The milk yield and milk composition Table Table50.6. The50.6. milk Theof Jersey yieldmilk andyieldcows milk andas affected compositionmilk composition by milking of Jersey of interval Jersey cows ascows affected as affected by milking by milking intervalinterval

PrecedingPreceding milking milking interval interval (hours) (hours) ParametersParameters 5 5 7 7 12 12 Milk (kg)Milk (kg) 15.0 15.0 17.0 17.0 29.0 29.0 Fat (%) Fat (%) 6.63 6.63 6.53 6.53 3.93 3.93 Fat (kg)Fat (kg) 1.10 1.10 1.10 1.10 0.99 0.99 Solids notSolids fat (kg)not fat (kg)9.43 9.43 9.48 9.48 9.59 9.59

On aOn fat-free a fatOn-free abasis, fat basis,-free milking milkingbasis, milkinginterval interval interval has littlelittle haseffect littlesay on effectat the 06:00 onprotein the and protein percentage 18:00, percentage the in milk milk. yieldinWhen milk. is usuallyWhencows cows effectare on milked theare protein milked twice percentageatwice day ata dayequal at in intervals,equal milk. intervals,When say at highersay06:00 at and 06:00at 18:00,the and morning 18:00,the milk the milking, yieldmilk is yield usuallyalthough is usually higher at highera cowsat are the milked morningat the morningtwice milking a daymilking, although at equal, although at aintervals, lower at a fatlower percentage.lower fat percentage. fat percentage.

5. Water5. Water intake intake 265 LactatingLactatingcows requirecows require 3 to 5 3litres to 5 oflitres water of forwater each for kg each of milkkg of produced. milk produced. Therefore Therefore, restricting, restricting the amountthe amount and quality and quality of water of waterfor dairy for cowsdairy resultcows resultin a lower in a lowermilk yieldmilk, yieldas well, a s aswell fat as fat percentage.percentage. Cows Cowshaving hav freeing access free accessto fresh to waterfresh producewater produce about 7%about more 7% milkmore and milk 6% and more 6% more fat thanfat cows than having cows having access accessto water to onlywater two only to twothree to times three pertimes day. per day.

6. Mastitis6. Mastitis Udder Udderinfection infection, or mastitis, or mastitis, has a, markedhas a marked and characteristic and characteristic effect effecton the on milk the yield milk andyield milk and milk compositioncomposition of dairy of cows dairy(Table cows (Table 50.7). 50.7). Table Table50.7. The 50.7. effect The ofeffect somatic of somatic cell count cell count(SCC) (SCC) on the on milk the yield milk of yield dairy of cowsdairy cows

SCC x 1000/mSCC x 1000/mℓ ℓ DegreeDegree of mastitis of mastitis Milk lossMilk (%) loss (%) Below 200Below 200 Slight Slight 2.7 2.7 201 - 500201 - 500 MiddlingMiddling 4.1 4.1 501 - 1000501 - 1000 Bad Bad 6.4 6.4 More thanMore 1001 than 1001 Severe Severe 8.8 8.8

Udder Udderinfection infection affects affects all the allmajor the majormilk components milk components which whichtend to tend decrease to decrease in concentration in concentration, , althoughalthough whey protein,whey protein, sodium sodium (Na) and (Na) Chloride and Chloride (Cl) show (Cl) anshow increase an increase (Table (Table 50.8). 50.8). Table 50.5. The average production of registered Holstein-Friesian cows in the 1985/86 milk recording year

Milk Fat Protein Lactation number (kg) % kg % kg 1 4746 3.61 171 3.24 154 2 5336 3.56 190 3.24 173 3+ 5802 3.54 205 3.20 186

The higher milk, fat and protein yields of cows in later lactation are related to an increase in body size (for a higher feed intake) and udder capacity.

4. Interval between milkings When the interval between milking sessions is unequal, the milk yield of cows is less after the shorter interval. It is for this reason that the milk yield at the morning milking is higher than the milk yield in the afternoon. The fat percentage in the milk is, however, higher in milk following the shorter interval (Table 50.6).

Table 50.6. The milk yield and milk composition of Jersey cows as affected by milking interval

Preceding milking interval (hours) Parameters 5 7 12 Milk (kg) 15.0 17.0 29.0 Fat (%) 6.63 6.53 3.93 Fat (kg) 1.10 1.10 0.99 Solids not fat (kg) 9.43 9.48 9.59

5. Water intake 6. Mastitis On a fat-free basis, milking interval has little effect on the protein percentage in milk. When cows Lactatingare milked cows twicerequire a day 3 toat equal5 litres intervals, of water say atUdder 06:00 infection,and 18:00, orthe mastitis,milk yield has is a usually marked higher and for eachat the kgmorning of milk milking produced., although atTherefore, a lower fat characteristicpercentage. effect on the milk yield and milk restricting the amount and quality of water for composition of dairy cows (Table 50.7). dairy cows5. resultWater in intake a lower milk yield, as well as fat percentage.Lactating co wsCows require having 3 to free5 litres access of water to forUdder each kginfection of milk produced.affects Thereforeall the ,majorrestricting milk fresh waterthe amount produce and aboutquality 7%of morewater milkfor dairyand cowscomponents result in a whichlower milktend yield to, adecreases well as fatin 6% morepercentage. fat than Cowscows havhavinging free access access to towater fresh waterconcentration,produce about although 7% more whey milk protein, and 6% sodium more only twofat thanto three cows times having per access day. to water only two to(Na) three and times Chloride per day. (Cl) show an increase (Table 50.8). 6. Mastitis Udder infection, or mastitis, has a marked and characteristic effect on the milk yield and milk composition ofTable dairy 50.7. cows The(Table effect 50. 7)of. somatic cell count (SCC) on the Table 50.7. Themilk effect yield of of somatic dairy cows cell count (SCC) on the milk yield of dairy cows

SCC x 1000/mℓ Degree of mastitis Milk loss (%) Below 200 Slight 2.7 201 - 500 Middling 4.1 501 - 1000 Bad 6.4 More than 1001 Severe 8.8

Udder infection affects all the major milk components which tend to decrease in concentration, although whey protein, sodium (Na) and Chloride (Cl) show an increase (Table 50.8).

Table 50.8Table. The milk50.8. compositionThe milk composition of cows as ofaffected cows asby affectedmastitis by mastitis

Composition (%) Milk component Effect Normal milk Mastitic milk Fat (%) Decrease 3.8 3.6 Protein (%) Slight decrease 3.6 3.5 Casein (%) Decrease 2.8 2.3 Whey protein (%) Increase 0.8 1.2 Lactose (%) Decrease 4.9 4.4 Sodium (Na+) Increase 0.05 0.08 Chloride (Cl-) Increase 0.10 0.18 Calcium (Ca++) Decrease 0.13 0.09

• The loss in fat yield may be as high as 6 kg/cow/year for each increase of 250 000 cells in somatic cell count above 200 000 cells/mℓ of milk. • The lactose content decreased markedly. A lactose content of less than 4.6% in the milk • The loss in fat yield may be as high as 6 kg/ concentration was 0.26% lower in mastitic of an individual cow is an indication of mastitis. To maintain the osmotic pressure of cow/year for each increase of 250 000 cells milk (SCC more than 1 x 106/mℓ of milk) than in somaticmilk, the cell decrease count inabove lactose 200 concentration 000 cells/ is counteredin normal by an milk increase (SCC in below sodium 500 chloride 000/mℓ of mℓ ofcontent. milk. milk) • The• lactoseThe total content protein decreasedcontent remains markedly. relatively • constantMastitic because milk theshows decrease a greaterin casein enzyme is A lactosecountered content by an ofincrease less than in the 4.6% albumin in the and globulinactivity. percentages. The catalase activity may be milk• ofMainly an individual due to the cow decrease is an inindication the fat and of lactosedouble percentages, that of the normal total solids milk. and solids- mastitis.not- Tofat maintaincontent thedecrease osmotic in pressuremastitic ofmilk. A study showed that the total solids milk, concentrationthe decrease was in lactose 0.26% lower concentration in mastitic milk7. Variation(SCC mo rein thanmilk 1 composition x 106/mℓ of milk) during than a is counteredin normal milkby an(SCC increase below 500 in 000/m sodiumℓ of milk single) milking chloride• Mastitic content. milk shows a greater enzyme activity. The catalase activity may be double that of • The totalnormal protein milk. content remains relatively It is well known that the fat content of milk constant because the decrease in casein increases continuously during the milking 7.is counteredVariation by in an milk increase composition in the during albumin a single process, milking i.e. the fore milk has a very low fat It andis well globulin known percentages.that the fat content of milk increasescontentcontinuously while stripped during the milk milking at the process, end of the • i.e.Mainly the fore due milk to has the a decreasevery low fat in contentthe fat while and strippedmilking milk process at the endhas ofthe the highestmilking processfat content haslactose the highest percentages, fat content (Tablethe total 50.9 ).solids The fatand content (Table of the 50.9). final The 5% fatof milkcontent may beof asthe high final as 5% of 10%.solids-not-fat content decrease in mastitic milk may be as high as 10%. milk. A study showed that the total solids 266 Table 50.9. The effect of the stage of the milking process on the fat percentage of milk

Milk portion Proportion of total yield (%) Fat (%) First 15 1.9 Middle 58 2.3 Last 27 6.8 Composite 100 3.1

The magnitude of this effect differs greatly among cows, i.e. being more pronounced in high producing cows. From this, it follows that incomplete milking would result in the production of milk containing less fat. When the udder is subsequently milked normally, the fat content of the milk should be higher. When milking is incomplete for several successive days, the fat percentage is markedly less only on the first day of incomplete milking.

The solids-not-fat content, estimated as a proportion of the fat-free milk, does not change during the milking process. Milk yield lost due to incomplete milking, especially in high-producing cows, are normally not fully recovered. Table 50.8. The milk composition of cows as affected by mastitis

Composition (%) Milk component Effect Normal milk Mastitic milk Fat (%) Decrease 3.8 3.6 Protein (%) Slight decrease 3.6 3.5 Casein (%) Decrease 2.8 2.3 Whey protein (%) Increase 0.8 1.2 Lactose (%) Decrease 4.9 4.4 Sodium (Na+) Increase 0.05 0.08 Chloride (Cl-) Increase 0.10 0.18 Calcium (Ca++) Decrease 0.13 0.09

• The loss in fat yield may be as high as 6 kg/cow/year for each increase of 250 000 cells in somatic cell count above 200 000 cells/mℓ of milk. • The lactose content decreased markedly. A lactose content of less than 4.6% in the milk of an individual cow is an indication of mastitis. To maintain the osmotic pressure of milk, the decrease in lactose concentration is countered by an increase in sodium chloride content. • The total protein content remains relatively constant because the decrease in casein is countered by an increase in the albumin and globulin percentages. • Mainly due to the decrease in the fat and lactose percentages, the total solids and solids- not-fat content decrease in mastitic milk. A study showed that the total solids concentration was 0.26% lower in mastitic milk (SCC more than 1 x 106/mℓ of milk) than in normal milk (SCC below 500 000/mℓ of milk) • Mastitic milk shows a greater enzyme activity. The catalase activity may be double that of normal milk.

7. Variation in milk composition during a single milking It is well known that the fat content of milk increases continuously during the milking process, i.e. the fore milk has a very low fat content while stripped milk at the end of the milking process has the highest fat content (Table 50.9). The fat content of the final 5% of milk may be as high as Section 5 | Chapter 50 10%. Table 50.9. The effect of the stage of the milking process on the fat Table 50.9percentage. The effect of of the milk stage of the milking process on the fat percentage of milk

Milk portion Proportion of total yield (%) Fat (%) First 15 1.9 Middle 58 2.3 Last 27 6.8 Composite 100 3.1

The magnitude of this effect differs greatly among cows, i.e. being more pronounced in high The producingmagnitude cows. of Fromthis effect this, it differsfollows greatlythat incomplete Exercise milking aids wouldin the result digestion in the productionof feed andof amongmilk cows,containing i.e. lessbeing fat . moreWhen thepronounced udder is subsequently coupled milkedwith an normally, increased the fatfeed con tentintake, of the milk in highmilk producing should be cows.higher. From When this, milking it follows is incompleteyield may for be several maintained, successive even days, while the the fat fat that percentageincomplete is markedlymilking lesswould only result on the infirst the day percentageof incomplete increases.milking. production of milk containing less fat. When the udderThe solids is subsequently-not-fat content milked, estimated normally, as a proportionthe 9. Climate of the fat-free milk, does not change during fat contentthe milking of the process. milk should Milk beyield higher. lost due When to incomplete milking, especially in high-producing milkingcows, is areincomplete normally notfor fully several recovered. successive 9.1 Season days, the fat percentage is markedly less only on the first day of incomplete milking. The seasonal influence on the milk of a single herd is dependent on factors, such as seasonal The solids-not-fat content, estimated as a calving, environmental temperature, and proportion of the fat-free milk, does not seasonal related feeding strategies. change during the milking process. Milk yield lost due to incomplete milking, especially in In South Africa as a whole, milk production high-producing cows, are normally not fully is high from September to February and low recovered. during the winter months. Fat and protein percentages follow a reverse pattern and are 8. Exercise low during the months of high milk production (Figure 50.2). Excessive exercise has a marked decreasing effect on milk yield. As a result of the lower milk volume, fat percentage increases. The nett result is a slight reduction in fat yield.

Figure 50.2. The (a) average daily milk yield (litres x 1 000) and (b) fat (■) and protein (□) percentage of milk as affected by month of the year

9.2 Ambient temperature The adverse effect of high temperatures is enhanced by long periods of exposure, the Ambient temperature is usually the most absence of air movement, and high humidity. important single climatic factor affecting the milk yield of dairy cows. The magnitude of the Milk breeds, which originated in the cold effect of temperature is dependent on factors, to temperate climate of Europe, are better such as breed, air movement, air relative adapted to low than to high temperatures. humidity, period of exposure, and individual The approximate lower and upper critical cows. temperatures for Holstein-Friesian and Jersey cows are shown in Table 50.10. 267 8. Exercise Excessive exercise has a marked decreasing effect on milk yield. As a result of the lower milk volume, fat percentage increases. The nett result is a slight reduction in fat yield.

Exercise aids in the digestion of feed and coupled with an increased feed intake, milk yield may be maintained, even while the fat percentage increases.

9. Climate 9.1 Season The seasonal influence on the milk of a single herd is dependent on factors, such as seasonal calving, environmental temperature, and seasonal related feeding strategies.

In South Africa as a whole, milk production is high from September to February and low during the winter months. Fat and protein percentages follow a reverse pattern and are low during the months of high milk production (Figure 50.2).

(a) (b) Figure 50.2. The (a) average daily milk yield (litres x 1 000) and (b) fat (■) and protein (□) percentage of milk as affected by month of the year

9.2 Ambient temperature

Ambient temperature is usually the most important single climatic factor affecting the milk yield of dairy cows. The magnitude of the effect of temperature is dependent on factors, such as breed, air movement, air relative humidity, period of exposure, and individual cows.

The adverse effect of high temperatures is enhanced by long periods of exposure, the absence of air movement, and high humidity.

Milk breeds, which originated in the cold to temperate climate of Europe, are better adapted to low than to high temperatures. The approximate lower and upper critical temperatures for Holstein-Friesian and Jersey cows are shown in Table 50.10. Table 50.10. Critical temperatures for Holstein-Friesian Table 50.10. Criticaland Jerseytemperatures cows for Holstein-Friesian and Jersey cows

Critical temperatures (°C) Breed Low High Holstein-Friesian - 12 27 Jersey - 1 30

High ambientHigh temperatures ambient temperatures (above 27°C)(above for 27 °C)production,for short periods, than on e.g. low for producing only one day,cows. while short periods,night e.g. temperatures for only one are day, low, while may night only have a slight effect on the production performance temperaturesof aredairy low, cows. may Heat only stress have has a a slightmore markedThe effect influence on high produc of inghigh cows , especiallyenvironmental effect on theduring production peak production, performance than onof dairylow produc temperaturesing cows. on the physiology of the cow is cows. Heat stress has a more marked effect on given in Table 50.11. high producingThe influencecows, especially of high environmental during peak temperatures on the physiology of the cow is given in Table 50.11.

TableTable 50.11. 50.11 .TheThe respirationrespiration rate,rate, rectal temperature,temperature, hay hay intake intake and and milk milk yield yield as affected as affectedby increasing by increasing ambient temperatureambient temperaturess

Respiration rate Hay intake Milk yield Ambient temperature (°C) Rectal temperature (°C) (breaths/min) (kg/day) (kg/day) 10 17 38.3 13 20 21 42 38.5 12 20 27 56 38.7 11 18 33 88 39.2 7 11

During cold weather, milk yield and protein percentage may decrease slightly. An increase in fat percentage may occur (Figure 50.3). During cold weather, milk yield and protein percentage may decrease slightly. An increase in fat percentage may occur (Figure 50.3).

(a) (b) Figure 50.3: The effect of ambient temperature on (a) milk yield and (b) milk composition (a) of dairy cows (b) Figure 50.3: The effect of ambient temperature on (a) milk yield and (b) milk composition of dairy These variations are more noticeablecows when the ambient temperature approaches the critical levels. Wind and a low-energy diet increase the negative effects of low These variationstemperature are mores. noticeable when the When the critical temperature is exceeded, ambient temperature approaches the critical milk yield, protein and lactose percentages levels. Wind Theand optimum a low-energy ambient diettemp increaseerature for dropdairy sharply,cows range whiles between the fat 4 percentageand 21 °C. As usually the the negativetemperature effects of lowincreases temperatures. within this range,increases the fat percentage because usuallyof the decrease reductions by in0.1 milk – 0.2% per 6 °C. Between 21 and 27 °C,yield.the milk yield slowly starts to decrease and the The optimumdecre ambientase in fat temperature percentage becomes for dairy more noticeable. cows ranges between 4 and 21°C. As the The detrimental effect of high environmental temperature increases within this range, the temperatures may be partly eliminated by When the critical temperature is exceeded, milk yield, protein and lactose percentages fat percentage usually decreases by 0.1 – 0.2% measures such as providing shade (Table drop sharply, while the fat percentage usually increases because of the reduction in milk per 6°C. Between 21 and 27°C, the milk yield 50.12), spray cooling and the cooling of the slowly starts yieldto decrease. and the decrease in drinking water. fat percentage becomes more noticeable. The detrimental effect of high environmental temperatures may be partly eliminated by measures such as providing shade (Table 50.12), spray cooling and the cooling of the 268 drinking water. Section 5 | Chapter 50

TableTableTable 50.12. 50. 50.121 .The 2The. The effect effect effect ofof of providingprovi providingding shadeshade shade toto to dairydairy dairy cowscows cows

ParametersParameters ShadeShade provided provided NoNo shade shade AmbientAmbient temperature temperature (°C) (°C) 28.428.4 36.736.7 MilkMilk yield yield (kg (kg/day)/day) 16.616.6 15.015.0 FatFat (%) (%) 3.83.8 3.43.4 NumberNumber of ofm astitismastitis infections infections 9 9 1919 ConceptionConception rate rate (%) (%) 7979 6060

10.10. DryDry period period and and body body condition condition 10. Dry periodTheThe length lengthand ofbody ofthe the drycondition dry period period and and the the body body conditionregenerate condition of of cowssecretory cows at atcalving calvingtissueare inare therelated. related. udder. Cows Cows Cows must must calving down in a good condition usually havehave a drya dry period period of ofabout about 60 60 days days to toreplenish replenish their their body body supplies supplies and and to toregenerate regenerate secretory secretory The length of the dry period and the body produce more milk with higher fat and protein tissuetissuein inthe the udder udder. . condition of cows at calving are related. percentages in the following lactation period Cows mustCows have calving a dry down period in a ofgood about condition 60 usuallyin comparison produce moreto thin milk (lower with higbodyher fatcondition and protein days to Cowsreplenish calving their down body in asupplies good condition and to usuallyscore) produce cows (Tablemore milk 50.13). with higher fat and protein percentagespercentages in inthe the fo llowingfollowing lactation lactation period period in incomparison comparison to tothin thin (lower (lower body body condition condition score) score) cowscows (Table (Table 50. 50.131).3). Table 50.13. The effect of the condition score of cows at calving down on TabletheTable milk 50. 50. 1yield31. 3The. Theand effect effectmilk of composition of the the condition condition of score cows score of during of cows cows theat atcalving first calving 16 down downweeks on on ofthe thethe milk milk yield yield and and milklactationmilk composition composition period of of cows cows during during the the first first 16 16 weeks weeks of of the the lactatio lactation periodn period

ConditionCondition score score ProductionProduction parameters parameters 2.52.5 3.53.5 TotalTotal feed feed intake intake (kg (kgDMDM/day)/day) 16.316.3 15.915.9 PeakPeak milk milk yield yield (kg/day) (kg/day) 27.827.8 29.829.8 MeanMean m ilkm ilkyield yield (kg/day) (kg/day) 23.623.6 25.725.7 FatFat (%) (%) 3.863.86 3.953.95 ProteinProtein(%)(%) 3.193.19 3.063.06 LossLoss in inlive live weight weight (kg/day) (kg/day) - 0.04- 0.04 - 0.10- 0.10 MilkMilk yield yield (kg/lactation) (kg/lactation) 5 0965 096 5 7185 718

In Inanother another study study, the, the milk, milk, fat, fat, and and protein protein yield yield during during the the first first five five months months of ofthe the lactation lactation In anotherperiod periodstudy, increased increasedthe milk, by fat,by 122 122 and, 8, and8protein and 4 kg4 kg,yieldrespectively,, respectively, slightly forafter for each each peak 30 30 kgproduction, kg increase increase in which inlive live weight increasesweight during during during the first five months of the lactation period and maintains persistency. Cows calving down thethe dry dry period. period. increased by 122, 8 and 4 kg, respectively, for in autumn experience the spring flush too late each 30 kgAn increase increase in milklive weightyield is duringobtained the with indry the periods lactation of up toperiod appro xtoimately affect 60 milk days. yield Increasing to dry period.An increase in milk yield is obtained with dryany periods extent. of up to approximately 60 days. Increasing thethe dry dry periods periods from from 20 20 to to40 40 and and 40 40 to to60 60 days, days, incr increaseseasesin inmilk milk yield yield of ofapproximately approximately 13 13 and and 3.5 %, respectively, can be expected. An increase3.5 % ,inrespectively, milk yield can is beobtained expected. with 12. Feeding dry periods of up to approximately 60 days. Increasing11. 11.theSeason Seasondry ofperiods of calving calving from 20 to 40 The effect of feeding on milk production and and 40 toParPar 60ticularlyticularly days, in increasesinregionsregions where inwhere milk cows cows yield are are offed fed acomposition drya dry ration ration during duringis complicated.winter winter and and go go onto Aonto greenfew green basicgrazing grazing approximatelyduringduring spring,13 spring, and the 3.5%,the season season respectively, of ofcalving calving willcan will influence influenceprinciples their their apply: milk milk yield yield per per lactation. lactation. In Inthe the UK, UK, the the be expected.effecteffect of ofthe the so so-called-called spring spring flush flush (with (with regards regards to tothe the change changeto topasture pasture feeding), feeding), increases increases the the milkmilk yield yield of ofcows cows by by 10 10 to to15 15%,%regardless, regardless12.1 at atwhich whichComposition stage stage of of the ofthe lactation ration lactation curve curve pasture pasture feeding feeding 11. Seasonstarts.starts. of calvingFor For the the spring spring calv calvinging cows cows, peak, peak production production increases increasesfollowedfollowed by by a asubsequent subsequent rapid rapid declinedecline in inmilk milk yield. yield. The The effect effect on on winter winter calvA calv cow,inging cows to cows produce is ismost most beneficial,at beneficial, an optimum because because level the the withinincrease increase Particularlyin in milkin milk regionsyieldyield wherethen then occurs cowsoccurs slightly areslightly fed after aafter herpeak peak genetic production production potential,, ,whichwhich needs increases increases various and and nutrients. maintains maintains dry rationpersistency persistencyduring winter. Cows. Cows andcalving calving go down ontodown in green inautumn autumn Anexperience experience ideal ration the the springshould spring flush contain:flush too too late late in inthe the lact lactationation grazing duringpeperiodriod spring,to toaffect affect the milk milk season yield yield toof toany calving any exten exten willt. t. influence their milk yield per lactation. In the • 16% CP (crude protein), UK, the effect12.12. FeedingofFeeding the so-called spring flush (with • 10 – 11 Megajoules (MJ) digestible energy regards ThetoThe the effect effect changeofof feeding feeding to onpasture on milk milk production feeding),production and and composition percomposition kg DM, is iscomplicated. complicated. A Afew few basic basic principles principles increasesapply theapply :milk: yield of cows by 10 to 15%, • 0.6% Ca (calcium), regardless at which stage of the lactation curve • 0.4% P (phosphorus), and pasture feeding starts. For the spring calving • At least 15% CF (crude fibre). cows, peak production increases followed by a subsequent rapid decline in milk yield. The Over and above these guidelines, factors such effect on winter calving cows is most beneficial, as protein and fibre quality, mineral and vitamin because the increase in milk yield then occurs status should also be taken into account. 269 12.2 Energy intake percentage of the milk. However, when the level of dietary fat exceeds about 7%, the milk A high energy intake usually results in a higher fat percentage, and maybe also the protein milk yield and higher protein percentage, but, content in milk may decrease. due to the higher milk yield, fat percentage may decrease. Broadly, it can be accepted that all fats and oils, particularly unsaturated fats such 12.3 Protein intake as soya and maize oil, included in rations high in concentrates, decreases butter fat Underfeeding protein affects milk yield percentage. negatively and may also depress protein percentage during early lactation. By 12.5 Roughage-to-concentrate ratio increasing protein intake while maintaining energy levels, the protein percentage in the The roughage-to-concentrate ratio in the milk may increase. The response is, however, ration has a distinct effect on the ratio of acetic dependent on the rumen degradability of the to propionic acid produced in the rumen. protein in the ration. To ensure a high protein percentage in milk, it is advisable that the ration Acetic acid, the precursor of milk fat, is should contain at least 4% non-degradable produced when fibre is digested in the rumen. protein, such as fish meal or oil cake. Propionic acid is derived from the degradation of carbohydrates and promotes the synthesis 12.4 Fat supplements of lactose, which encourages milk production. Propionic acid serves as an important source of Including rumen-protected fats in rations energy during the synthesis of protein by rumen usually increases the fat percentage of milk. microbes, resulting in higher protein levels in milk. Rations containing high concentrate The addition ofin mosthigher types protein of fatslevels and in oilsmilk. to Rationsa levels containing increase high the concentrate milk yield levels and increase protein the fat-free or low-fatmilk ration,yield and e.g. protein to a rationpercentage very of percentagecows, while diets of cows, high in while fibre diets increases high milk in fibre fat rich in fibre percentage(1% or less (Table fat), 50. 1 4increases). the fat increases milk fat percentage (Table 50.14).

Table 50.14.50.14 The. The effect effect of roughage-to-concentrateof roughage-to-concentrate ratio ratio on the on milk the yield milk and yield fat and fat percentageof of milk milk

Percentage Milk yield Fat Roughage Concentrate (kg/day) (%) (kg) 45 55 24.1 3.51 0.85 60 40 23.9 3.58 0.85 75 25 22.2 3.71 0.82

12.6 Physical 12.6structurePhysical and quality structure of and qualityMilk of roughageyield, fat and protein percentages may roughage increase when roughage is fed as silage Finely ground (less than 1.0 - 2.5 cm) insteadand pelleted of hay. roughages The reason move for through this is thatthe rumen forage at Finely grounda (lessfaster thanrate than 1.0 long- 2.5 hay cm). Th eandresult ofcrops this isare that usually cows ruminateharvested less earlier(chewing for the silage cud) pelleted roughagesand therefore move producingthrough the less rumen saliva whichthan fornormally hay. This buffers increases the rumen the energy resulting content in less at a faster rateacetic than acid long being hay. produced. The result This of thismay affectof the the roughage, fat percentage while in milk maintaining negatively. itsFeeding fibre is that cows ruminatea small quantity less (chewing of ungrounded, the cud) coarse content, hay may helpwhich to isovercome more digestible this situation. as it contains and therefore producing less saliva which less hemi-cellulose and lignin. normally buffersFeeding the roughagesrumen resulting containing in lesshigh energy levels, such as early-cut silage or hay, acetic acid beingincrease produced.s milk and Thisprotein may yield, affect while 12.7 decreasing Level fatof feedpercentage intake in milk. the fat percentage in milk negatively. Feeding a small quantityMilk of yield, ungrounded, fat and protein coarse percentage hay Thes maymilk increaseyield of when cows roughage increases is fedby asfeeding silage may help to overcomeinstead of thishay. situation.The reason for this is largerthat forage quantities crops ofare the usually same harvested diet, although earlier the for silage than for hay. This increases the fatenergy percentage content of may the roughage decrease., while The maintaining net result Feeding roughagesits fibre contentcontaining, which high is m oreenergy digestible mayas beit contains a decrease less hemi in fat-cellulose yield. and lignin. levels, such as early-cut silage or hay, increases milk and protein12.7 yield,Level while of feed decreasing intake fat percentage in milk. 270 The milk yield of cows increases by feeding larger quantities of the same diet, although the fat percentage may decrease. The net result may be a decrease in fat yield.

12.8 Frequency of feeding

When high concentrate rations are fed, the milk fat depression could be overcome by more frequent feeding, i.e. feeding more times per day.

12.9 Feeding of supplements

Milk fat depression as a result of rations low in fibre or in which the roughage is finely ground, may be reduced by feeding pH buffers, such as sodium bicarbonate, magnesium oxide, or sodium bentonite. The optimum level of intake is about 150 to 200 g sodium bicarbonate per cow per day or either 1 % sodium bicarbonate or 0.5% magnesium oxide in the concentrate.

13. Milk sampling For milk analysis, the value of the final results is dependent on the representativeness of the milk sample collected of the total volume of the product to be tested. It is therefore very important that Section 5 | Chapter 50

12.8 Frequency of feeding cow per day or either 1% sodium bicarbonate or 0.5% magnesium oxide in the concentrate. When high concentrate rations are fed, the milk fat depression could be overcome by 13. Milk sampling more frequent feeding, i.e. feeding more times per day. For milk analysis, the value of the final results is dependent on the representativeness of the 12.9 Feeding of supplements milk sample collected of the total volume of the product to be tested. It is therefore very Milk fat depression as a result of rations low in important that a representative sample for fibre or in which the roughage is finely ground, testing is collected. This is very important in the may be reduced by feeding pH buffers, such case of milk as creaming takes place when as sodium bicarbonate, magnesium oxide, or milk is not stirred during storage (Table 50.15). sodium bentonite. The optimum level of intake is about 150 to 200 g sodium bicarbonate per

a representative sample for testing is collected. This is very important in the case of milk as creaming takes place whenTable milk 50.15. is not The stirred effect during of creaming storage (Table 50.15). on the fat content in the top 25% of Table 50.15. The effectunstirred of creaming milk on the fat content in the top 25% of unstirred milk

Time (h) Fat content (%) 0 5.25 ½ 5.36 1 6.06 3 12.00 5 13.40

The risingThe fat risingglobules fat globulesserve as serve a filter as acarrying filter carrying Factors bacteria such andas lipolysissomatic (rancidity),cells to the topchurning, layers of bacteriamilk. and Thesomatic latter, cells upon to creaming, the top layerswill thus of alsoand be bacteriologicalconcentrated in the deterioration upper milk layer. may Therefore affect , milk. The tlatter,horough upon agitation creaming, of milk will isthus required also be before the milkaccuracy sampling of chemicalis done to analysis.ensure homogeneity As these . concentratedHowever, in the agitation upper ofmilk milk layer. should Therefore, not be excessive influences to prevent are enhancedthe churning by of temperature, fat. it is thorough agitation of milk is required before advisable to store milk samples prior to analysis milk samplingWhen isa singledone sampleto ensure from homogeneity. several containers at is a to temperature be compiled, offor belowexample, 10°C. to determine To facilitate the fat However,content agitation in the milkof milk of a shouldherd over not a 24 be h period,thorough a sub -mixingsample of eacha sample container before should analysis, be taken excessivein to proportion prevent theto thechurning quantity of fat.of milk in theit is spadvisableecific container. that the The bottles sub- samplesshould beshould of a be combined and, if necessary, mixed and resampleconvenientd to obtain size a suitableand not sample be filled volume. to more than When a single sample from several containers 75% of their capacity. is to be compiled,Factors such for as example,lipolysis (rancidity), to determine churning, and bacteriological deterioration may affect the the fat contentaccuracy in of the chemical milk of analysia herds. over As these a 24 influencesh 14. Diagnosing are enhanced problems by temperature, with regards it is advisable to to period, astore sub-sample milk samples of each prior container to analysis should at a temperature low milk of solidsbelow content 10 °C. To facilitate thorough be taken in proportion to the quantity of milk in mixing of a sample before analysis, it is advisable that the bottles should be of a convenient size the specific container. The sub-samples should In Figures 50.4 to 50.6 flow diagrammes are and not be filled to more than 75% of their capacity. be combined and, if necessary, mixed and presented to identify possible problems resampled to obtain a suitable sample volume. with regards to low fat, protein and lactose 14. Diagnosing problems with regardspercentages to low milk in solidsmilk. Thesecontent diagrammes can In Figures 50.4 to 5.6 flow diagrammes are bepresented used to to identify identify problemspossible problems quickly. with regards to low fat, protein and lactose percentages in milk. These diagrammes can be used to identify problems quickly.

271 Low fat percentage

No Is milk yield high? Yes

Is roughage intake Are many cows in Yes less than 35%? early lactation?

No Yes

Breeding may be Effect of lactation Possible reproductive suspect stage problem

Use high genetic Action merit bulls for fat Action Action percentage

Use milk recording

Cull poor Apply selective Spread calving Pregnancy check performing cows breeding pattern

Action

Increase fibre Feed pH-buffers Feed concentrates Feed rumen inert Restrict feeding of

intake (NaHCO3) in smaller portions saturated lipids unsaturated lipids

Action

Feed more Feed a total mixed Feed a high forage Feed better quality roughage ration concentrate roughage

Figure 50.4. A flow diagramme to determine problems with regards to a low fat percentage in milk

272 Section 5 | Chapter 50

Low protein percentage

Are many cows in Yes No early lactation?

Effect of lactation Is energy intake Breeding suspect stage sufficient?

Action No Unknown Action

Change calving Change breeding Action down pattern policy - use bulls with high genetic merit for protein %

Feed additional grains Analyze feed and or concentrates evaluate total diet

Action No Satisfactory?

Figure 50.5. A flow diagramme to determine problems with regards to a low protein percentage in milk

273 Low lactose percentage

Is SCC higher than Yes No 0.5 mil/mℓ of milk?

Are many cows in late Are fat and protein % lactation? low?

Yes No Yes No

Determine Improbable Effect of lactation freezing point Probably mastitis stage Positive results? Action

Consider drying off Thorough Action Action cows investigation

Find source of added water

Consult a Apply preventative Evaluate milking veterinarian measures machine efficiency

Treat infected Cull cows with quarters harmed quarters

Figure 50.6. A flow diagramme to determine problems with regards to a low lactose percentage in milk (SCC = somatic cell count)

274 Section 5 | Chapter 51 CHAPTER 51 MILKING PARLOUR HYGIENE

Hygiene is a way of life

Introduction 1.3 Sweet curdling and ropiness

ilk, in addition to being a nutritious food Bacteria responsible for these defects in milk source, presents a favourable physical are capable of increasing the viscosity of the Menvironment for the growth and milk without significant acid production. The increase in the number of micro-organisms. responsible bacteria are often contaminants Being a metabolic product, it is subjected to from stagnant water. Examples include the widely different production conditions and is following bacteria: normally contaminated by a broad spectrum of • Alcaligenes viscosus from stagnant water, micro-organisms. Although bacteria dominate and in fresh milk, molds, yeasts, and viruses may • Bacillus subtilis from hay and dust. also occur. 1.4 Proteolytic bacteria 1. Micro-organisms associated with milk Proteolytic bacteria decompose the casein in From the viewpoint of the dairy producer milk, causing faecal odours and bitter flavours. and dairy technologist, it would be sensible Because of the proteolysis of proteins in milk, it to group different bacteria according to the appears to be watery. specific changes they bring about in milk Example: Clostridium butyricum. and dairy products, or according to their temperature-related characteristics. Important 1.5 Psychrotrophic bacteria groups, based on these characteristics, are the following: Psychrotrophic bacteria are capable of multiplying at temperatures between 2 and 1.1 Acid-producing bacteria 10°C and therefore often become the dominant population in milk that is stored at below 10°C Acid-producing bacteria ferment lactose for 2 days or longer. During the first 24 hours’ mainly into lactic acid. As a result of the acid cold storage, the percentage psychrotrophic production, the pH of fresh milk drops from bacteria in milk may, for example, increase about 6.66 to as low as 4.6. At a pH of about 5.2 from 15 to 80% of the total population. and lower, casein in milk coagulates and milk thickens. These bacteria are usually mesophilic, Pseudomonas spp., mainly P. fluroescens, usually i.e. growing best at moderate temperatures, account for about 50% of the psychrotrophic neither too hot nor too cold, typically between bacteria in milk and are capable of producing 20 and 45°C. They are the dominant population heat resistant enzymes which easily survive in milk that has been inadequately cooled. pasteurisation. Examples of such bacteria are Streptococcus lactis and Lactobacillus bulgaricus. Due to the proteolytic activity of these enzymes, they are often responsible for the bitter flavours 1.2 Gas-forming bacteria that may develop in pasteurised and sterilised milk. These bacteria ferment lactose to produce gas (CO2 and H2) in milk and dairy products. Off-flavours which may develop in UHT (long- Well-known examples include: life) milk are often caused by these enzymes. • coliform bacteria, e.g. Escherichia coli (E. coli) causing early blowing of cheese, and • Clostridium butyricum, which is an anaerobic spore-forming bacteria causing late blowing of cheese. 275 1.6 Mesophilic bacteria in brilliant green broth at 44°C and indole in tryptone water (Eijkman test). The presence of Mesophilic bacteria can grow at temperatures E.coli in water usually indicates recent faecal ranging from 5 to 45°C with an optimum growth contamination. temperature of about 25 to 37°C. The majority of bacteria occurring in nature, and thus also 1.10 Total viable count in milk, falls within this group. The total viable or standard plate count Example: indicates the total number of viable micro- • Streptococci, e.g. S. lactis – lactic acid organisms present in 1 mℓ of milk as determined fermenter, by the colony plate count method. The total • Micrococci, e.g. M. pyogenes – mastitis, viable count is often confused with the total and count, which is determined microscopically • Staphylococcus areus – mastitis. and includes both viable and dead microbial cells. Raw milk sold in South Africa for further 1.7 Thermoduric bacteria processing, is usually classified according to bacterial quality as follows: Thermoduric bacteria can survive, but do not grow, at pasteurisation temperatures. -- Class A = less than 50 000 bacteria/mℓ of Examples of temperature-time combinations milk, for the pasteurisation process are: -- Class B = 50 000 to 200 000/mℓ of milk, and -- Class C = more than 200 000/mℓ of milk. • 75°C for 15 seconds, or • 62.8°C for 30 minutes. 2. The bacterial content of freshly drawn milk 1.8 Spore forming bacteria Milk drawn aseptically from a healthy udder Spore forming bacteria are capable of usually contains less than 1 000 bacteria/mℓ producing endospores (internal) which can of milk. There is a considerable variation in the survive a heat treatment of 80°C for 10 minutes. numbers of organisms found in milk at different stages of the milking process. The foremilk Typical examples are: contains the highest number of bacteria, for • Bacillus cereus which causes bitty cream, example, from 1 000 to 10 000/mℓ. After the • B. subtilis which causes ropiness, and first few streams of milk, the count in bacteria • Clostridium butyricum which is responsibile decreases sharply and thereafter more for late (butyric) blowing of cheese. gradually until a minimum of 100 to 200/mℓ is reached in stripped (last) milk. Bacteria present 1.9 Coliform organisms inside a healthy udder are mostly micro- cocci, which are inactive and do not have a Coliform bacteria have the capacity to significant influence on the hygienic quality or produce both gas and acid from lactose at keeping quality of milk. 30°C. The incidence of coliforms in raw milk has received considerable attention due to Mastitic infected quarters may excrete the following reasons: fluctuating numbers of organisms in their milk. The counts may vary, for example, from a few • their association with contamination of thousand per mℓ in milk from sub-clinical cases faecal origin (Escherichia coli), to more than 10 million/mℓ in milk from clinically • the off-flavours that they produce in milk, infected quarters. Where bulk milk has a total and bacterial count of more than 50 000 bacteria/ • the ease at which their presence can be mℓ, mastitis is often the reason for the high indicated. count.

Coliforms readily multiply on moist dairy Milk secreted by infected cows/udders may utensils, especially in the presence of milk convey the following pathogens (disease residues. Poorly cleansed utensils are often the causing) bacteria to the consumer: main source of contamination. Escherichia coli (E. coli) may be distinguished from the rest of the group due to their ability to produce grass 276 Section 5 | Chapter 51

• Tuberculoses – Mucobacterium tubercolusis, 3.1 Contamination from the exterior udder and • Contagious abortion Brucelloses – Brucella teats abortus, • Anthrax – Bacillus anthrax, Between milking sessions, udders and teats of • 3.FoodSources poisoning of contamination – Staphylococcus aureus cows may become soiled in different ways, (mastitis), and e.g. dung, mud, and bedding material. Such • DuringSore throatmilk harvesting, – Streptococcus bacteria from pyogenes the external dirt part may of thecontain udder, many environment, millions ofand bacteria milking per utensils(mastitis). gain entry into the milk. The result is thatgram. at the If end not of removed the milking beforehand, process, milk the may dirt on contain from 10 000 to several hundred thousand bacteriathe teats, per mtogetherℓ of milk .with the large number of 3. Sources of contamination bacteria associated with it, may be washed 3.1 Contamination from the exterior udder andinto teats the milk during milking, resulting in an During milk harvesting, bacteria from the increase in the bacterial count of the milk externalBetween part of milking the udder,sessions environment,, udders and teats and of cowsaccordingly may become (Table soiled 51.1). in different ways, e.g. milkingdung, utensils mud gain, and entry bedding into material.the milk. SuchThe result dirt may contain many millions of bacteria per gm. If is thatnot at theremoved end beforehand,of the milking the process,dirt on the milk teats, together with the large number of bacteria may contain from 10 000 to several hundred associated with it, may be washed into the milk during milking, resulting in an increase in the thousand bacteria per mℓ of milk. bacterial count of the milk accordingly (Table 51.1).

Table 51.1. TheTable effect 51.1. of Thehousing effect and of teathousing washing and onteat the washing bacterial on content the bacterial of bulk tank milk content of bulk tank milk

Housing Teats Bacteria per mℓ of milk Bedded on sand Unwashed 31 700 Washed 15 500 On pasture Unwashed 4 250 Washed 3 530

To minimize contamination from external sources, it is essential to wash the teats thoroughly To minimise contamination from external 3.3 Water supplies sources,before it milkingis essential start s.toIt iswash also importantthe teats to dry teats using a disposable paper towel before thoroughlyattaching before the milking milking clusters. starts. It is also Water used in the process of milk production important to dry teats using a disposable paper should be of bacteriologically potable quality. towel 3.2beforeAerial attaching contamination the milking clusters. Using water with a high bacterial load for washing would increase the bacterial count 3.2 AerialThe contaminationnumber of organisms contaminating milkof from milk the through air is normally contamination. not high. BacterialWater from counts on air in milking-sheds should not exceedstorage 200 tanks, bacteria boreholes, per litre. wellsUnder and normal dams, The numberconditions of organismsthe levels of contaminating contamination frommilk thisinadequately source are negligible protected in comparisonfrom rodents, to that birds from thederived air is normallyfrom teats, not utensils, high. Bacterial and surfaces. counts and dust, may be contaminated with bacteria on air in milking-sheds should not exceed 200 from faecal origin. This type of contamination bacteriaBecause per litre. of the Under severe normal conditions conditions existing the in themay atmosphere, not only increase most of tthehe organismstotal bacterial coming count levels fromof contamination this source are comparativelyfrom this source resistant. are Theyof the are milk,often butresponsible may also for be specific harmful defects and in even negligiblemilk inand comparison dairy products. to that For thisderived reason from, and becausepathogenic. the number Examples of micro of-organisms such pathogens in the teats, airutensils, is largely and dependent surfaces. on the dust load, pollutioninclude of the the air following:with dust, especially immediately before milking, should be kept to a minimum. Because of the severe conditions existing in the • Eschericia coli, atmosphere,Examples: most of the organisms coming • Pseudomonas, from this •sourceBacillus are cereus comparatively – bitty cream, resistant. and • Faecal streptococci, and They are often responsible for specific defects • Bacillus spores. • Bacillus subtilis – sweet curdling. in milk and dairy products. For this reason, and because the number of micro-organisms When water quality is under suspicion, it in the3.3 airWater is largely supplies dependent on the dust would be a good practice to delay chemical load, pollution of the air with dust, especially disinfection of milking equipment until just immediatelyWater used before in the milking, process should of milk be production kept to beforeshould bethe of nextbacteriologically milking and potable to merely quality. drain a minimum.Using water with a high bacterial load for washingthe woulddisinfectant increase solution the bacterial from count the equipmentof milk through contamination. Water from storage tanks,before boreholes, milking. wells and dams, inadequately Examples:protected from rodents, birds and dust, may be contaminated with bacteria from faecal origin. • Bacillus cereus – bitty cream, and • Bacillus subtilis – sweet curdling. 277 Chlorination, by dosing with hypochlorite, washing of utensils. Rubber, having an is a common practice to improve the absorbent surface that may become very bacteriological quality of water. Chlorinated porous due to maltreatment and corrosion, rinsing water should contain between 1 to may, for this reason, be a major source 3 parts of active chlorine per million parts of of bacterial contamination. In a study on water. farms producing milk of unsatisfactory bacteriological quality, it was found that 3.4 Milking equipment as a source of bacterial the rubber-ware of the milking machines contamination added 10 to 120 times the number of contaminants normally contributed by the Inadequately cleansed and disinfected metal and glass parts. milk contact surfaces are major sources of bacterial contamination of milk. During the • Time and conditions under which utensils usual cleaning process, it is impossible to are stored: eliminate all the bacteria on these surfaces. A Bacterial growth is largely dependent on survey of 350 milking machines showed that in temperature and moisture. When utensils 91% of cases, the total bacterial count on milk are stored under humid conditions, or contact surfaces was higher than 100 bacteria not properly drained after cleaning, the per cm2. For smooth surfaces, such as glass bacteria that survived the cleaning process and stainless steel, which are relatively easy may multiply rapidly to large numbers in the to clean, bacterial counts less than 5 bacteria interval between milking sessions. per cm2 would be satisfactory. On more porous or coarser surfaces, such as rubber, equipment • Sanitation of utensils immediately prior to in poor physical condition, or where milkstone use: layers occur, the bacterial count may run into The bacteria that survive the initial cleaning many thousands per cm2. process may multiply considerably in the interval between milking sessions. To The number of bacteria occurring on milk limit contamination from this source, it is contact surfaces depends, amongst others, on advisable to rinse, immediately prior to use, the following factors: all milk contact surfaces with a sanitiser. Such sanitisers may be a chlorine solution • The effectiveness of the washing process: containing 100 to 150 ppm available chlorine. When milk residues, such as fat, protein and minerals, are not completely removed Even by rinsing utensils with clean water, during the washing process, the following depending on the vigorousness of the rinse, may result: 50% and more of the bacteria may be removed from the utensils. • large numbers of bacteria surviving in the residues, and • Construction of utensils • protein residues, especially, reacting Milking equipment is seldom uniformly with sanitising agents, such as chlorine, contaminated. Bacteria and residues decreasing the effectiveness of the accumulate in difficult-to-clean areas and latter. in parts of badly designed components. In any specific milking installation, these Milking equipment should be washed problem areas should be identified, shortly after being used. When milk residues regularly inspected, and, if necessary, are allowed to dry on contact surfaces, a routinely cleaned by hand. A few examples film, i.e. milkstone, forms. Milkstone consists of trouble areas include the following: of protein and milk salts. It is a hard film and difficult to wash off. Milkstone may also form -- all rubber to metal connections, when milk is rinsed from utensils by very hot -- sample cocks at measuring jar outlets, water. -- dead-ends in pipes, -- vacuum to milk line connections, • The condition of utensils used: -- bulk tank outlet taps, and Corroded or roughened surfaces, milkstone -- rubber seals such as between lids of deposits, open seams, etc. not only containers such as on some measuring jars increase the surface on which bacteria and milking machine buckets. can settle, but also impede effective 278 Section 5 | Chapter 51

3.5 The vacuum line as a source of Milk residues may enter the vacuum lines contamination through overfilling of containers, cracked inflations, or due to evaporation of warm In some milking systems, vacuum lines, which milk under vacuum and condensation of are not cleaned during the normal circulation the moisture in the vacuum system. Bacteria of detergents, open together with milk lines multiplying in these residues may constitute into the same receptacle, for example: a major source of contamination and for this reason, the vacuum system should be cleaned • where the vacuum line, as such or through on a routine basis or whenever milk was sucked a pulsator, enters the bucket of a milking into the system. system, and • in most releasers.

TableTable 51. 51.2.2. The The relative relative importance importance of theof the different different sources sources of contamination of contamination

Source of contamination Contribution to bacterial count/mℓ of bulk milk Internal healthy udder 300 to 4 000 Mastitic udder Up to 25 000 and more External udder 500 to 15 000 Air (hand-milking) 100 to 1 500 Milking equipment Up to 500 000

4. The washing and cleaning of milk utensils 4. The washing and cleaning of milk of proteins. Due to the low concentration of utensils 4.1 Types of cleaning agents available chlorine, the presence of milk solids, and the high pH of the solution, the bactericidal effect 4.1 Types ofDifferent cleaning types agents of compoundsavailable are formulatedof chlorine to serve may a bespecific questionable. purpose in the cleaning process. The best known cleaners available to the dairy industry are: Different types of compounds are formulated Advantages: to serve a4.1.1 specificDetergents purpose in the cleaning • Dissolves both fat and protein. process. The best known cleaners available to • Relatively low corrosiveness. the dairy industryDetergents are: are formulated to remove organic residues, such as milk fat, protein and mineral deposits. These compounds as such usuallyDisadvantages: have very little, if any, bacterial influence. 4.1.1 Detergents • The continual use of alkaline detergents, especially when used together with Two main types of detergents are available. Detergents are formulated to remove organic hard water, tends to cause a build-up of residues, such as milk fat, protein and mineral mineral layers (milkstone). To prevent this, deposits. These4.1.1.1 compoundsAlkaline detergents as such usually it is advisable to alternatively use an acid have very little, if any, bacterial influence. detergent once a week. Alkaline detergents are the oldest and most• commonlyCorrosive used on aluminum. dairy cleaner. Normally, they are Two main typesmixtures of detergents of inorganic are alkalines, available. such as: 4.1.1.2 Acid detergents 4.1.1.1 AlkalineSodium detergents carbonate - Na2CO3 Sodium bicarbonate - NaHCO3 Acid detergents usually contain nitric, Alkaline detergentsSodium phosp arehate the oldest- Naand3PO most4.12H20 phosphoric, or sulphamic acid. Their principal commonly Sodiumused dairy hydroxide cleaner. Normally,- NaOH they function, in a balanced cleaning programme, are mixtures of inorganic alkalines, such as: is to prevent the accumulation of mineral Formulations to improve detergency maydeposits include (milkstone).additives, such as wetting agents, water

Sodium carbonatesofteners and chlorine.- Na2 COChlorine3 is included at a concentration of about 100 ppm available Sodium bicarbonatechlorine to assist -in NaHCO the remo3 val of proteins.Advantages: Due to the low concentration of chlorine, the Sodium phosphatepresence of milk -solids Na3PO, and4.12H the20 high pH• of Removethe solution, or theprevent bactericidal the effectformation of chlorine of Sodium hydroxidemay be questionable. - NaOH organic layers.

FormulationsAdvantages to improve: detergency may Disadvantages: include additives, such as wetting agents, • Acid detergents have little effect on fat • Dissolves both fat and protein. water softeners and chlorine. Chlorine is and protein containing organic residues. • included at a concentrationRelatively low corrosivenessof about 100. • Normally more corrosive than alkaline ppm available chlorine to assist in the removal detergents. Disadvantages: 279 • The continual use of alkaline detergents, especially when used together with hard water, tends to cause a build-up of mineral layers (milkstone). To prevent this, it is advisable to alternatively use an acid detergent once a week. • Corrosive on aluminum.

4.1.1.2 Acid detergents 4.1.2 Sanitisers flavours in milk, • long acting, for example, up to 8 hours, and The purpose of sanitisers is to destroy micro- • at recommended concentrations, it is organisms. The best sanitisers used in the dairy not corrosive on stainless steel, tin-coated industry include the following: surfaces or aluminium, but may corrode rubber. 4.1.2.1 Chlorine 4.1.3 Detergent-sanitisers Active chlorine, especially in a slightly acid medium, is an effective sanitiser. A Detergent-sanitisers are compounds disadvantage is that it is readily inactivated by containing both detergents and sanitisers. organic material, such as fat and protein, and The advantage of such a compound is that is usually unstable above about 50°C. the cleaning operation is simplified. The disadvantage is that the effectiveness of the When sodium hypochlorite as such is to be sanitiser being applied in the presence of milk used as a sanitiser, it is recommended that the residues is usually impaired. solution temperature should not exceed 50°C and that the concentration should be between Examples of this type of compound are: 150 to 200 ppm, with the contact time being • Chlorine containing alkaline detergents. about 5 to 10 minutes. In this case the chlorine content of the working solution is about 200 ppm. 4.1.2.2 Iodine • Iodofors. Iodine together with a wetting agent. Iodofors usually contain phosphoric Active iodine solutions are excellent sanitisers, acid. relatively stable in storage and in the presence • Quaternary ammonium compounds are of organic material. The brown colour serves as in themselves good wetting agents and an indication of solution strength and the low therefore have a built-in detergency. pH prevents the formation of inorganic layers. Cleansing agents, especially alkaline Due to its volatility, the temperature of working detergents, are available in powdered, as well solutions should not exceed 50°C. as in liquid form. Foaming and non-foaming formulations are also available for manual and 4.1.2.3 Quaternary ammonium compounds circulation cleaning respectively. (QAC’s) 5. Cleaning procedures These agents are very stable during storage at high temperatures. They are also effective The cleaning process has as purpose: against many types of organisms, non-odorous • to remove organic and inorganic residues, and non-colouring. Their rinse ability is usually and relatively low, which is a decisive disadvantage. • to destroy as many of the remaining bacteria as practically as possible. 4.1.2.4 Hydrogen peroxide acetic acid 5.1 Five-stage system This type of sanitiser has been available since the 1980’s. Bacterial activity is dependent The traditional procedure for the cleaning of on the presence of peroxi acetic acid and the dairy utensils, both in manual or circulation- hydrogen peroxide. Characteristics are: in-place (CIP) systems, consists of the following five stages: • effective at room (low) temperature (high temperatures will result in the breaking up • Pre-rinse of the active chemicals and should be The function of the pre-rinse, which is avoided), done with water at a temperature not • kills a broad spectrum of microbes, exceeding 45°C, is to remove as much • has a fast action, of the milk residues as possible. In CIP • effective at a low concentration (0.25 to systems, rinsing water is not circulated 0.40%), but run to waste until free of milkiness. • residues, viz. water, oxygen and acetic acid, are non-toxic and do not cause off- 280 Section 5 | Chapter 51

To prevent the formation of a film of milk 5.2 Three-stage system solids which, at a later stage, will be difficult to remove, pre-rinsing should be done as By developing detergent-sanitisers, it became soon as possible after utensils have been possible to combine the cleaning and sterilising used. Hot water is not recommended for processes. This has led to the well-known three pre-rinsing as it encourages the formation stage method, which consists of the following of milkstone. stages:

• Wash • pre-rinse, The purpose of the washing process is to • circulate hot detergent-sanitiser solution, remove all remaining residues. Wash with a and hot (60 to 80°C) alkaline detergent solution. • final rinse. Solution strength is usually about 0.5% and the minimum circulation time in CIP systems, In both the 3- and 5-stage cleaning procedures, about 10 minutes. For manual washing, an acid detergent, at about one tenth of the the temperature should be above 40°C. normal concentration, can be used to acidify To prevent the build-up of milkstone, the the final rinsing water. By reducing the pH of alkaline detergent has to be alternated, the rinsing water to less than 4.5, the build-up say once a week, with an acid detergent. of milkstone and the multiplication of bacteria is largely prevented. • Intermediate rinse Clean water is used to remove the soiled 5.3 Acidified boiling water (ABW) system detergent wash. The rinsing allows the sanitiser to act on surfaces free of organic This system was developed for the cleaning of residues. pipeline milking machines and consists of only two stages: • Sanitising Circulate a sanitiser solution containing, • pre-rinse to remove milk residues, and for example 150 to 200 ppm active • the flushing of the pipelines with water, at chlorine, for at least 5 minutes. a temperature of 90°C or higher, which contains about 0.5% sulphamic or nitric By separating the cleaning and sanitising acid. processes, the sanitiser can be used at its optimum pH for a minimum contact time This method of cleaning can be very effective, and at a lower concentration. This reduces but requires considerable supervision. All inner the risk of corrosion, as well as costs. plant surfaces must come in contact with the diluted acid and a temperature of at least • Final rinse 77°C must be maintained within the cleaning The last step in the cleaning process is to get circuit for at least 2 minutes. Examples of rid of the residues of cleaning compounds, cleaning programmes for milking machines which may tint the milk or corrode the are presented in Table 51.3. utensils. Water of good bacteriological quality, such as chlorinated water containting 1 to 3 ppm chlorine, is used for the final rinsing.

Alternative Instead of sanitising immediately after washing, the sanitiser may also be applied just before the utensils are used. This assures a low number of bacteria on the equipment and prevents the corrosion of stainless steel, which can occur if certain sanitisers are in contact with the metal for a long period of time.

281 • the flushing of the pipelines with water, at a temperature of 90 °C or higher, which contains about 0.5% sulphamic or nitric acid.

This method of cleaning can be very effective, but requires considerable supervision. All inner plant surfaces must come in contact with the diluted acid and a temperature of at least 77 °C must be maintained within the cleaning circuit for at least 2 minutes. Examples of cleaning programmes for milking machines are presented in Table 51.3.

TableTable 51.3. 51.Examples3. Example of cleanings of cleaning programmes programmes for formilking milking machines machines

Programmes Actions 1 2 3 4 1. Pre-rinse with water at ≤ 40 °C Yes Yes Yes Yes

2. Wash with ± 0.5% warm (60 - 80 °C) alkaline detergent Yes Yes Yes -

3. Rinse with water Yes Yes Yes -

4. Sanitize with 150 ppm chlorine, 25 ppm iodine or 0.25% H2O2/Hac, preferably Yes - Yes - before being used 5. Rinse with clean water Yes - - -

6. Rinse with ± 0.15% acidified water with a pH of < 4.5 Yes - -

7. Periodically remove milkstone with 0.3 to 1% acid detergent Yes - - -

8. Wash without circulation using 0.55% acidified water at ≥ 90 °C - - Yes

5.4 Cleaning5.4 Cleaning of bulk of tank bulk tank • Drain detergent from moisture trap. • Repeat with hot acid detergent, starting When theWhen bulk the tank bulk is tanknot cleanedis not cleaned by means by means ofat a theCIP cocksystem, farthest the following from the procedure pump. Drain is of a CIPrecommended: system, the following procedure is trap. recommended: • Rinse with clean water, starting at the cock • Rinse with tap water. farthest from the pump. Drain trap. • Rinse with• tapPrepare water., in a plastic bucket, a chlorinated,• Open foaming all stallalkaline cocks detergent and run at 7the - 10 pump times to • Prepare, inthe a plastic normal bucket,strength. a Close chlorinated, tank outlet, placedry bucket the vacuum containing line. the detergent inside the foaming alkalinetank and detergent thoroughly at brush 7 - 10all timesinside surfaces from the bucket. Let detergent flow from the normalthe strength. tank to theClose bucket. tank Dismantle outlet, outlet6. Factors tap and affecting wash thebrush success in the ofbucket. a Use place bucketdetergent containing from bucket the to detergent wash the outside cleaning of the tank. programme inside •theRinse tank inside and and thoroughly outside with brushtap water. all inside• surfacesRinse inside from with the acidified bucket. water Let (acid The detergent) following at about factors 10% have normal a decisive concentration. effect on detergent flow from the tank to the bucket. the effectiveness of a cleaning programme. • Sanitize before use. Dismantle outlet tap and wash brush in the bucket. Use detergent from bucket to wash 6.1 Quality of the water 5.5 Cleaning the vacuum line the outside of• theOpen tank. all stall cocks and run the pump to dry the vacuum line. • Rinse inside and outside with tap water. The most important characteristics that • Rinse inside• Draw with hot acidifiedalkaline detergent water through (acid eachdetermine stall cock the into quality the vacuum of the line. water Start areat the the 6. Factors affecting the success of a cleaning programme detergent)cock at nearest about the vacuum10% pump.normal Do nothardness, draw more the solution bacteriological into the system quality, than and the the concentration.moisture trap can hold. iron and manganese content. The following factors have a decisive effect on the effectiveness of a cleaning programme. • Sanitise •beforeDrain use. detergent from moisture trap. • Repeat with hot acid detergent, startingWater at the cockhardness farthest is frommeasured the pump. by Drainthe content trap. 6.1 Quality of the water 5.5 Cleaning• Rinse the withvacuum clean line water, starting at the ofcock calcium farthest fromcarbonate the pump. equivalent Drain trap. in mg/litre (Table 51.4). • Draw hot Thealkaline most detergentimportant characteristicsthrough each that determine the quality of the water are the hardness, stall cock theinto bacteriological the vacuum qualityline. Start, and at the the iron and manganese content. cock nearest the vacuum pump. Do not draw moreWater solution hardness into theis measured system than by the the content of calcium carbonate equivalent in mg/litre (Table moisture trap51.4 ).can hold.

Table 51.4. ClassificationTable 51.4. ofClassification water hardness of water hardness

Hardness CaCO3 equivalent mg/ℓ of water Soft 0 to 60 Moderate 60 to 120 Hard 120 to 180 Very hard Over 180

The water softening ability of well-formulated detergents is usually sufficient for moderately 282 hard water. If the hardness is more than 150 mg/ℓ, it is recommended that the detergent concentration should be increased by 10% for each increase of about 50 mg CaCO3/ℓ. For very hard water, special formulations may be required.

Iron and manganese present in concentrations of 0.1 ppm or higher, may, especially in the presence of alkaline detergents, be responsible for a build-up of brown-red or black layers. To prevent this build-up, acid detergents should be used more often in the cleaning programme.

When the water used for the washing of udders or the rinsing of the milking utensils contains large numbers of bacteria, it will have a detrimental effect on the quality of the milk. Water of good bacteriological quality should comply with the standards indicated in Table 51.5.

Table 51.5. The bacteriological standards for water used for washing of udders and rinsing of milking utensils

Criterium Standard Total viable count 21 °C/72 h < 500/mℓ Total viable count 37 °C/72 h < 50/mℓ Coliforms < 50/100mℓ E.coli Negative/100mℓ

6.2 Choice of cleaning compounds and procedure

Cleaning compounds are formulated for a specific purpose (see 4.1) and should be applied accordingly in an effective program (see 5).

6.3 Concentration of the cleaning compound • Open all stall cocks and run the pump to dry the vacuum line.

6. Factors affecting the success of a cleaning programme

The following factors have a decisive effect on the effectiveness of a cleaning programme.

6.1 Quality of the water

The most important characteristics that determine the quality of the water are the hardness, the bacteriological quality, and the iron and manganese content.

Water hardness is measured by the content of calcium carbonate equivalent in mg/litre (Table 51.4).

Table 51.4. Classification of water hardness

Hardness CaCO3 equivalent mg/ℓ of water Soft 0 to 60 Moderate 60 to 120 Hard 120 to 180 Very hard Over 180 Section 5 | Chapter 51

The waterThe watersoftening softening ability ability of well-formulated of well-formulated for detergents a build-up is usually of brown-red sufficient or for black moderately layers. To detergents is usually sufficient for moderately prevent this build-up, acid detergents should be hard water. If the hardness is more than 150 mg/ℓ, it is recommended that the detergent hard water. If the hardness is more than 150 used more often in the cleaning programme. concentration should be increased by 10% for each increase of about 50 mg CaCO3/ℓ. For mg/ℓ, it is recommended that the detergent concentrationvery hard should water, specialbe increased formulations by 10% may for be requiredWhen .the water used for the washing of each increase of about 50 mg CaCO3/ℓ. For udders or the rinsing of the milking utensils very hardIron water, and manganese special formulationspresent in concentrations may be contains of 0.1 ppm large or numbershigher, may, of bacteria, especially it willin the have required.presence of alkaline detergents, be responsiblea for detrimental a build-up ofeffect brown on-red the or qualityblack layers. of the To milk. prevent this build-up, acid detergents should beWater used moreof good often bacteriologicalin the cleaning program qualityme should. Iron and manganese present in concentrations comply with the standards indicated in Table of 0.1 Whenppm orthe higher,water used may, for especiallythe washing in of the udders 51.5. or the rinsing of the milking utensils contains presencelarge of numbers alkaline ofdetergents, bacteria, it be will responsible have a detrimental effect on the quality of the milk. Water of good bacteriological quality should comply with the standards indicated in Table 51.5.

Table 51.5. TableThe b51.5.acterio Thelogical bacteriological standards forstandards water used for waterfor washing used of udders and for washing of udders and rinsing of milking utensils rinsing of milking utensils

Criterium Standard Total viable count 21 °C/72 h < 500/mℓ Total viable count 37 °C/72 h < 50/mℓ Coliforms < 50/100mℓ E.coli Negative/100mℓ

6.2 Choice of cleaning compounds and procedure

6.2 ChoiceCleaning of cleaning compounds compounds are formulated and for a specificWhen purpose the water (see is very4.1) andhard should or the betemperature applied procedureaccordingly in an effective program (see 5). is low, then the concentration of the detergent should be increased. Cleaning6.3 Concentrationcompounds ofare the cleaningformulated compound for a specific purpose (see 4.1) and should be 6.4 Temperature of detergents applied accordinglyBoth economy in an and effective the effectiveness programmeof the compound are influenced by its concentration. The (see 5). recommended concentration is usually theThe optimum effectiveness and should (detergency) be adhered to. ofCleaning any agents, especially those containing chlorine,detergent may lose strengthis largely during dependentthe storage; therefore,on theit 6.3 Concentrationis important of the to limitcleaning the storage time whiletemperature keeping containers of the well washing closed water. and in aUsually, dry area. the compound detergency of washing water is better when the temperature of the water is higher. For When the water is very hard or the temperature is low, then the concentration of the detergent Both economy and the effectiveness of the circulation cleaning of milking machines, the compoundshould are influenced be increased. by its concentration. initial temperature of the detergent should be The recommended concentration is usually about 75 to 80°C (Table 51.6). At the end of the optimum6.4 Tem andperature should of bedetergents adhered to. the circulation time, it should preferably not be Cleaning agents, especially those containing below 45°C. chlorine, mayThe loseeffectiveness strength (detergency)during the storage;of any detergent is largely dependent on the temperature of the therefore, washingit is important water. Usually, to limit thethe detergency storage of washing water is better when the temperature of time while thekeeping water containersis higher. For well circulation closed and cleaning of milking machines, the initial temperature of in a dry area.the detergent should be about 75 to 80 °C (Table 51.6). At the end of the circulation time, it should preferably not be below 45 °C.

TableTable 51. 51.6.6. The The total total viable viable count count on milkingon milking machine machine rinsings rinsings

Initial temperature of detergent (°C) Distribution of bacteria/0.1m2 (%) Less than 10 000 More than 50 000 82 50.2 23.7 45 to 60 20.0 67.8 45 14.3 73.9

6.5 Volume of detergent and circulation speed

The volume must be sufficient to wet all milk contact surfaces. For milking machines with weighing bottles, approximately 8 to 14 litres of solution is required per milking point. 283

For the thorough removal of residues, a flow speed of not less than 3.5 litres/minute/milk point must be maintained.

6.6 Circulation time

Due to the decrease in solution temperature, an extended circulation time may be counter- productive. Circulation for 10 to 15 minutes should be sufficient. The temperature at the end of the washing cycle should preferably not be less than 45 °C.

6.7 Supervision

An important reason why cleaning programs fail is because of the lack of supervision. If the operator adheres to the abovementioned details, success, even using a simple procedure, is obtainable.

7. Cooling and milk quality

The bacteria present in milk at the end of the milking process multiply quickly during storage at room temperature. As the generation time of bacteria is strongly affected by temperature, prompt cooling to a low temperature delays the increase in the number of bacteria in milk. The effect of cooling is, however, dependent on: 6.5 Volume of detergent and circulation 7. Cooling and milk quality speed The bacteria present in milk at the end of the The volume must be sufficient to wet all milk milking process multiply quickly during storage contact surfaces. For milking machines with at room temperature. As the generation time weighing bottles, approximately 8 to 14 litres of of bacteria is strongly affected by temperature, solution is required per milking point. prompt cooling to a low temperature delays the increase in the number of bacteria in milk. For the thorough removal of residues, a flow The effect of cooling is, however, dependent speed of not less than 3.5 litres/minute/milk on: point must be maintained. • storage temperature, • rate of cooling, 6.6 Circulation time • storage time, and • initial bacterial count. Due to the decrease in solution temperature, an extended circulation time may be counter- 7.1 Storage temperature and time productive. Circulation for 10 to 15 minutes should be• sufficient.storage temperature, The temperature at the The generation time, i.e. the time necessary • storage temperature, end of the• ratewashing of cooling, cycle should preferably for a single bacterium to divide into two not be less• thanrate of45°C. cooling, cells, is largely dependent on temperature. • storage time, and • storage time, and A generation time of 30 minutes at 35°C may • initial bacterial count. 6.7 Supervision• initial bacterial count. for example increase to 11 hours at 5°C. The effect of storage temperature and time on 7.1 Storage temperature and time An important7.1 Storage reason temperature why cleaning and programmestime bacterial counts on the bacterial count in milk fail is because of the lack of supervision. If the is presented in Table 51.7. The generation time, i.e. the time necessary for a single bacterium to divide into two cells, is operatorThe generationadheres time,to the i.e. theabovementioned time necessary for a single bacterium to divide into two cells, is largely dependent on temperature. A generation time of 30 minutes at 35 °C may for example details,largely success, dependent even using on temperature. a simple procedure, A generation time of 30 minutes at 35 °C may for example increase to 11 hours at 5 °C. The effect of storage temperature and time on bacterial counts on is obtainable.increase to 11 hours at 5 °C. The effect of storage temperature and time on bacterial counts on the bacterial count in milk is presented in Table 51.7. the bacterial count in milk is presented in Table 51.7. Table 51.7. TheTable increase 51.7. ofThe bacterial increase counts of bacterial as affected counts by storage as affected temperature by and time Table 51.7. The increase of bacterial counts as affected by storage temperature and time storage temperature and time Storage Bacterial count after storage for days temperatureStorage (°C) 0Bacterial count after2 storage for days3 temperature (°C) 0 2 3 5 160 000 430 000 3.1 x 105 5 75 160160 000000 3 430400 000000 193.1 x10x 106 6 107 160160 000000 693 400000 000 23019 xx10 106 10 160 000 69 000 000 230 x 106 7.2 Initial count 7.2 Initial7.2 Initialcount count increase in bacterial count is much higher, The generation time at a specific temperature ise.g. significantly 180%. At affected a higher by thestorage initial temperature,bacterial The generation time at a specific temperature is significantly affected by the initial bacterial The generationcount (Table time 51. 8at). aAt specific a storage temperature temperature ofthe 5 °C increase, the bacterial in bacterial count ofcount fresh ismilk even may higher, count (Table 51.8). At a storage temperature of 5 °C, the bacterial count of fresh milk may is significantlyincrease by affected25% after by 24h, the however, initial bacterial when the e.g. bacterial 250 and count 780%. in fresh These milk increases is higher, in bacterial the increase by 25% after 24h, however, when the bacterial count in fresh milk is higher, the countincrease (Table in51.8). bacterial At a countstorage is much temperature higher, e.g. count 180%. inAt milk a higher would storage have temperature, a major effect the on increase in bacterial count is much higher, e.g. 180%. At a higher storage temperature, the of 5°C,increase the bacterial in bacterial count count of is fresh even milkhigher may, e.g. the250 qualityand 780%. of milk These following increases its ininitial bacterial bacterial increase in bacterial count is even higher, e.g. 250 and 780%. These increases in bacterial increasecount by in milk25% woulafterd have24h, ahowever, major effect when on the count quality and of milk storage following temperature. its initial bacterial count in milk would have a major effect on the quality of milk following its initial bacterial the bacterialcount and countstorage in temperature. fresh milk is higher, the count and storage temperature. Table 51.8. The rate of bacterial growth during storage as affected by initial count TableTable 51.8. 51.8. The The rate rate of of bacterial bacterial growth growth during during storage storage as as affectedaffected byby initialinitial count Bacterial count Storage temperature (°C) Bacterial count Increase % Storage temperature (°C) Fresh After 24 h Increase % 4Fresh 000 After5 000 24 h 25 5 4 000 5 000 25 5 136 000 381 000 180 136 000 381 000 180 4 000 14 000 250 10 4 000 14 000 250 10 136 000 1.2 x 106 780 136 000 1.2 x 106 780 In closing Milk,In closing being a food source, is a ideal medium for the growth of micro-organisms. It naturally Milk, being a food source, is a ideal medium for the growth of micro-organisms. It naturally 284 contains a broad spectrum of such organisms which multiply under specific environmental contains a broad spectrum of such organisms which multiply under specific environmental conditions. Milk contains acid-producing bacteria which naturally ferments lactose in milk to conditions. Milk contains acid-producing bacteria which naturally ferments lactose in milk to lactic acid increasing the acidity levels in milk as indicated by a decrease in the pH level of milk. lactic acid increasing the acidity levels in milk as indicated by a decrease in the pH level of milk. At a pH below 5.2, the casein component in milk coagulates and milk thickens. Mastitis is a At a pH below 5.2, the casein component in milk coagulates and milk thickens. Mastitis is a major problem in dairy cows as mastitic milk contains large number of different bacteria which major problem in dairy cows as mastitic milk contains large number of different bacteria which reduces the feeding value of milk. During milking, or milk harvesting, bacteria from the external reduces the feeding value of milk. During milking, or milk harvesting, bacteria from the external part of the udder, environment, and milking utensils gain entry into the milk. Therefore, the part of the udder, environment, and milking utensils gain entry into the milk. Therefore, the milking process, the operation and maintenance of the milking machine as well as the milking process, the operation and maintenance of the milking machine as well as the environment cows are housed, have a major effect on the occurrence of mastitis in cows and the environment cows are housed, have a major effect on the occurrence of mastitis in cows and the quality of milk. quality of milk. Section 5 | Chapter 51

In closing thickens. Mastitis is a major problem in dairy cows as mastitic milk contains large numbers of Milk, being a food source, is a ideal medium different bacteria which reduces the feeding for the growth of micro-organisms. It naturally value of milk. During milking, or milk harvesting, contains a broad spectrum of such organisms bacteria from the external part of the udder, which multiply under specific environmental environment, and milking utensils gain entry conditions. Milk contains acid-producing into the milk. Therefore, the milking process, bacteria which naturally ferments lactose the operation and maintenance of the milking in milk to lactic acid increasing the acidity machine as well as the environment cows are levels in milk as indicated by a decrease in housed, have a major effect on the occurrence the pH level of milk. At a pH below 5.2, the of mastitis in cows and the quality of milk. casein component in milk coagulates and milk

285 CHAPTER 52 CHAPTER 52

MASTITIS AND MILK QUALITY MASTITIS AND MILK QUALITY

IntroductionIntroduction standard level in milk. Udder infection or The quality of milk is described by themastitis solids iscontent the single consisting most importantof fat, protein reason and forlactose he qualitypercentages of milk, as iswell described as the somatic by the cell ancount increasing (SCC) in number milk. The of white SCC bloodof milk cells. refers For to the solids numbercontent of consisting white blood of cells fat, and protein the number this reason,of epithelial an increase cells in milkin the, usually SCC of per milk mℓ is theof milk. and lactoseThe SCC percentages, is used as an as indication well as theof themost level reliable of infection and practicalin the udder way and to identifyis regarded sub- as an somatic cell count (SCC) in milk. The SCC clinical mastitis in the udder of dairy cows. indirect way of describing the level of mastitis in milk. When an infection occurs in the udder, the Tof milk refers to the number of white blood cells body produces a large number of white blood cells to resist the infection. Because of the and the number of epithelial cells in milk, usually The SCC in milk from a healthy udder is usually per mℓ of milk.increasing The SCC number is used of as white an indicationblood cells, especiallybelow 200 neutrophils, 000 per the mℓ SCC of count milk. in A milk positive increases of the levelabove of infection the standard in thelevel udder in milk. and Udder is infectionindication or ofmastitis udder is infection the single (mastitis) most important is usually reason regarded asfor an increasingindirect waynumber of ofdescribing white blood whencells. For the this SCC reason in milk, an hasincrease increased in the SCCto about of milk is the level ofthe mastitis most reliablein milk. and When practical an infection way to identify 400 000sub- clinicalper mℓ mastitisof milk. in As the mastitis udder of may dairy occur cows. occurs in the udder, the body produces a in only one of the four quarters, the SCC of a large numberThe of SCC white in blood milk from cells a to healthy resist the udder single is usually milk belowsample 200 from 000 perall quarters mℓ of milk. must A be positive infection. Becauseindication of of theudd erincreasing infection (mastitis)number isevaluated usually when carefully, the SCC especially in milk has when increase settingd to about of white blood400 000 cells, per mℓespecially of milk. Asneutrophils, mastitis may threshold occur in valuesonly one for of SCC the (Tablefour quarters, 52.1). the SCC of a the SCC countsingle inmilk milk sample increases from aboveall quarters the must be evaluated carefully, especially when setting threshold values for SCC (Table 52.1). Table 52.1. The percentage correct and incorrect Table 52.1.mastitis The percentage classifications correct and when incorrect using mastitis different classifications when using different mathematicalmathematical estimations estimations of thresholdof threshold values values for somaticfor cell count (SCC) for individual cowssomatic cell count (SCC) for individual cows

Threshold value Classification (%) (SCC/mℓ of milk) Correct False negative False positive 100 000 44 0.3 55.9 200 000 69 2.0 29.1 300 000 78 5.1 16.9 400 000 84 9.1 6.8

In dairy herdsIn dairy already herds applyingalready applying the correct the correct mastitisfollowing: control measures, individual cow SCC may mastitis controlbe used measures, as an additional individual source ofcow information 1. Thewith number regards ofto mastitisthe mastitis cases status in the of herd, the herd. SCC may bePossible used advantagesas an additional emanating source from ofregular testing2. The for number mastitis of may mastitis be as cases follows: among first information with regards to the mastitis status lactation cows, of the herd. Possible advantages emanating 3. The lactation stage when udder • An indication of the number of cows to be culled because of chronic infections not from regular testing for mastitis may be as infections occur, and responding to the treatment of mastitis. follows: 4. The effect of herd management on the • An indication of early drying-off cows withincidence the aim of mastitis.treating an infected quarter while • An indication ofthe the cow number is dry. of cows to be culled because• An of early chronic indication infections of infections not whichWhen mayindividual then be SCC treated numbers or to areconduct being bacteriological used to responding to theculturing treatment towards of identifying mastitis. specificdetermine bacteria when that may and respond which cowsdifferently to cull, to drytreatment. off, • An indication• ofBy early grouping drying-off records cows according with toand lactation to treat stage, cows, age thisof cows, may resultetc. valueab in preventivele deductions the aim of treatingcould be an made infected regarding quarter the following: measures being disregarded. This may result in while the cow 1.is dry.The number of mastitis cases inan the increase herd, in the number of mastitis cases in • An early indication2. The numberof infections of mastitis which cases amongthe herd. first Thelactation axiom cows, ‘prevention is better than may then be3. treatedThe lactation or stageto conduct when udder cure’ infections applies occur especially, and with regards to mastitis bacteriological4. Theculturing effect of herd managementtowards management. on the incidence of mastitis. identifying specific bacteria that may respond differently to treatment. Herd somatic cell count (HSCC) • By grouping records according to lactation stage, age of cows, etc. valuable Herd SCC is generally used as a suitable deductions could be made regarding the indicator of the udder health in a dairy herd (Table 52.2). 286 When individual SCC numbers are being used to determine when and which cows to cull, dry off, and to treat cows, this may result in preventive measures being disregarded. This may result in an increaseWhen in individual the number SCC of mastitisnumbers cases are being in the used herd. toThe determine axiom 'whenprevention and which is better cows than to cull, dry cure' appliesoff,especially and to treat with cows, regards this to may mastitis result management. in preventive measures being disregarded. This may result in an increase in the number of mastitis cases in the herd. The axiom 'prevention is better than Herd somaticcure ' cellapplies countespecially (HSCC) with regards to mastitis management. Herd SCC is generally used as a suitable indicator of the udder health in a dairy herd (Table Section 5 | Chapter 52 52.2). Herd somatic cell count (HSCC) Herd SCC is generally used as a suitable indicator of the udder health in a dairy herd (Table TableTable 52.2.52. 52.2. The2). Therelat relationshipionship between between herd herdsomatic somatic cell count cell andcount level and of level mastitis of mastitis

Herd Tablesomatic 52.cell2. countThe relationshipLevel between of mastitis herd somaticMastitis cellinfected count quarters and level in the of herd mastitis (%) Less than 250 000 Good None 250 001 - 500Herd 000 somatic cell countAcceptableLevel of mastitis Mastitis<20 infected quarters in the herd (%) 500 001- 750Less 000 than 250 000 DangerousGood 21 - 40 None More than 750250 001001 - 500 000 Herd problemsAcceptable 40 + <20 500 001- 750 000 Dangerous 21 - 40 It must be keptMore in mind than 750that 001 a high HSCC mayHerd be problems the result of high proportion of40 +subclinical It mastitismust be caseskept in(infected mind that quarters) a high or HSCC a smaller may proportionof clinical of mastitisclinical maycases affectof mastitis. the herdWith SCC beregards the result to Itclinical mustof high becases, keptproportion the in SCCmind inof that individualsubclinical a high HSCCquarters very may maystrongly. be be the high resulter than of 10high million proportion per mℓ of of subclinical mastitismilk. Incases amastitis small (infected herd cases, a singlequarters)(infected or a quarters) orfew a casessmaller or of a clinicalsmaller mastitis proportion may ofaffect clinical the herdcases SCC of mastitis.very With proportionstrongly. regardsof clinical to clinical cases cases, of mastitis.the SCC inWith individual The HSCC quarters of maymilk besamples higher thancollected 10 million monthly per mℓ of regards to milk.clinical In cases,a small the herd SCC, a single in individual or a few casesfrom ofabout clinical 1650 mastitis dairy mayfarmers affect in the the herd Western SCC very quartersThe HSCC maystro of ben gly.milk higher samples than collected 10 million monthly per mℓ from Cape about during 1650 a dairy 12-month farmers period in the is Westernpresented in ofCape milk. during In a small a 12 -herd,month a period single is or presented a few cases in Table Table 52.3. 52.3. The HSCC of milk samples collected monthly from about 1650 dairy farmers in the Western Table 52.Cape3. The during distribution a 12-month of herdperiod somatic is presented cell countsin Table (HSCC) 52.3. for dairy farmers in the Western Cape overTable a 12 52.3.-month The period distribution of herd somatic cell counts Table 52.(HSCC)3. The fordistribution dairy farmers of herd in somaticthe Western cell counts Cape (HSCC) over afor dairy farmers in the HSCCWestern (x 1000/mℓ12-month Cape overmilk period) a 12-monthProportion period of milk samples (%) < 99 2.2 100 – 199 HSCC (x 1000/mℓ milk) Proportion12.7 of milk samples (%) 200 – 299 < 99 20.1 2.2 300 – 399 100 – 199 18.2 12.7 400 – 499 200 – 299 13.8 20.1 500 – 699 300 – 399 16.5 18.2 700 – 999 400 – 499 10.4 13.8 > 1000 500 – 699 6.1 16.5 700 – 999 10.4 Economic implications> 1000 of a high herd somatic cell counts 6.1 It is well-known that mastitis not only affects the appearance and composition of milk, it also results in Economica reduction implications in milk yield. of aAlthough high herd the somatic reduction cell incounts milk yield may not always be noticeable,It itis maywell -beknown responsiblethat mastitis for up not to only80% affectsof the totalthe appearance cost of m astitis.and composition The relationship of milk, it also Economicbetween HSCCimplicationsresults andin a areduction ofreduction a high in herdin milk milk somatic yield. yield Although variesnoticeable, among the reduction itstudies. may be inA responsiblemilkrealistic yield relationship may for upnot to always 80% be cellbetween counts HSCC,noticeable, the percentageit may be responsiblemilk yield loss,for up the ofto amount the80% total of of the milkcost total andof cost mastitis.potential of mastitis. Theincome relationshipThe lost relationship annually isbetween presented HSCC in Table and 52. a 4.reduction in milkbetween yield varies HSCC among and studies.a reduction A realistic in milk relationship yield It is well-knownbetween that HSCC, mastitis the notpercentage only affects milk yield varies loss, among the amount studies. of milk A realisticand potential relationship income lost the appearanceannually and is presented composition in Table of 52. milk,4. it between HSCC, the percentage milk yield loss, also results in a reduction in milk yield. Although the amount of milk and potential income lost the reduction in milk yield may not always be annually is presented in Table 52.4.

TableTable 52.4. 52.4.Milk Milk and andfinancial financial losses becauselosses ofbecause mastitis ofas reflectedmastitis asby herd reflected somatic by herd cell somatic cell counts (HSCC) counts (HSCC)

Monthly loss depending on daily milk yield HSCC Milk yield loss (%) 600 ℓ 1 000 ℓ 2 000 ℓ 540 ℓ 910 ℓ 1825 ℓ 250 000 3 R326 R728 R1 460 1 095 ℓ 1 825 ℓ 3 650 ℓ 500 000 6 R876 R1 460 R2 920 1 825 ℓ 3 040 ℓ 6 080 ℓ 1 000 000 10 R1 460 R2 433 R4 866

Based on another study, the following equation was developed to estimate the reduction in milk yield because of mastitis:

Milk yield loss (%) = 2.39 + 0.01(HSCC/1000) 287 This means that for herd somatic cell counts of 250 000, 500 000 and 1 000 000, milk yield losses are estimated to be 4.9, 7.4 and 12.4%, respectively.

Mastitis in dairy cows also affects milking parlour management. Infected cows have to be milked separately, while the milk from cows under treatment has to be discarded so as to not contaminate milk to be collected by the dairy processors. Furthermore, mastitis also affects the composition of milk (Table 52.5).

Table 52.5. The effect of mastitis on milk composition

Composition (%) Milk component Effect Normal milk Mastitis milk Fat percentage Reduction 3.8 3.6 Protein percentage Small reduction 3.6 3.5 Casein percentage Reduction 2.8 2.3 Whey protein percentage Increase 0.8 1.2 Lactose percentage Reduction 4.9 4.4 Na+ Increase 0.05 0.08 Cl-- Increase 0.10 0.18 Ca++ Reduction 0.13 0.09

Some of the changes in the chemical composition of milk, as indicated in Table 552., reduce the quality of dairy products that are produced from mastitic milk. Examples include a reduction in the curdling of milk and cheese, milk powder dissolving poorly, and sedimentation occurring in ultra-high temperature (UHT) milk.

Mastitis prevention A strategy to reduce the incidence of mastitis in a dairy herd should include the following principles:

1. Treating infected quarters; although this is part of the mastitis prevention strategy, it only treats the symptoms, and not the causes, of mastitis. 2. The prevention of mastitis does not rely on some superior medicine and quick fixes, but largely on a continuing evaluation and adaptation of mastitis control measures. 3. A case of mastitis can only occur after a pathogen has entered the udder through the teat opening. The aim of mastitis management should be to reduce the possibility of such an Table 52.4. Milk and financial losses because of mastitis as reflected by herd somatic cell counts (HSCC)

Monthly loss depending on daily milk yield HSCC Milk yield loss (%) 600 ℓ 1 000 ℓ 2 000 ℓ 540 ℓ 910 ℓ 1825 ℓ 250 000 3 R326 R728 R1 460 1 095 ℓ 1 825 ℓ 3 650 ℓ 500 000 6 R876 R1 460 R2 920 1 825 ℓ 3 040 ℓ 6 080 ℓ 1 000 000 10 R1 460 R2 433 R4 866

Based on another study, the following equation was developed to estimate the reduction in milk yield because of mastitis: Based on another study, the following equation Mastitis in dairy cows also affects milking was developed to estimate the reduction in parlour management. Infected cows have to milk yieldMilk because yield lossof mastitis: (%) = 2.39 + 0.01(HSCC/1000)be milked separately, while the milk from cows under treatment has to be discarded so as to Milk yieldThis loss means (%) = 2.39that for+ 0.01(HSCC/1000) herd somatic cell countsnot of contaminate 250 000, 500 milk 000 toand be 1 collected000 000, milk by theyield losses are estimated to be 4.9, 7.4 and 12.4%,dairy respectively. processors. Furthermore, mastitis also This means that for herd somatic cell counts affects the composition of milk (Table 52.5). of 250 000,Mastitis 500 000in dairy and cows 1 000 also 000, affects milk milking yield parlour management. Infected cows have to be milked losses areseparately estimated, while to bethe 4.9,milk 7.4 from and cows 12.4%, under treatment has to be discarded so as to not contaminate respectively.milk to be collected by the dairy processors. Furthermore, mastitis also affects the composition of milk (Table 52.5).

Table 52.Table5. The 52.5. effect The of effectmastitis of onmastitis milk compositionon milk composition

Composition (%) Milk component Effect Normal milk Mastitis milk Fat percentage Reduction 3.8 3.6 Protein percentage Small reduction 3.6 3.5 Casein percentage Reduction 2.8 2.3 Whey protein percentage Increase 0.8 1.2 Lactose percentage Reduction 4.9 4.4 Na+ Increase 0.05 0.08 Cl-- Increase 0.10 0.18 Ca++ Reduction 0.13 0.09

Some of the changes in the chemical composition of milk, as indicated in Table 552., reduce the Some of the changes in the chemical such a goal should include the following: quality of dairy products that are produced from mastitic milk. Examples include a reduction in composition of milk, as indicated in Table • A mean monthly HSCC of less than 300 the curdling of milk and cheese, milk powder dissolving poorly, and sedimentation occurring in 52.5, reduce the quality of dairy products that 000 per mℓ of milk. are producedultra-high from temperature mastitic (UHT) milk. milk.Examples • A maximum of 35 clinical infected include a reduction in the curdling of milk quarters per 100 cows per year, (35/ and cheese,Mastitis milk prevention powder dissolving poorly, (100*4)) = 8.75%. and sedimentationA strategy to occurringreduce the incidencein ultra-high of mas titis• in90% a dairy of cows herd should should haveinclude SCC the less following than temperatureprinciples: (UHT) milk. 400 000 per mℓ of milk.

Mastitis prevention1. Treating infected quarters; although thisA mastitis is part ofcontrol the mastitis programme prevention should strategy, include it only treats the symptoms, and not the causesthe, offollowing mastitis. principles: A strategy to2. reduceThe prevention the incidence of mastitis of mastitis does not rely on some superior medicine and quick fixes, but in a dairy herdlargely should on includea continuing the evaluationfollowing and1. adaptationA correct of milking mastitis procedure, control measures. e.g.: principles: 3. A case of mastitis can only occur after a pathogen has entered the udder through the teat opening. The aim of mastitis management• Not s houldwetting be theto reduce udder the excessively, possibility of such an 1. Treating infected quarters; although this • Drying teats and udder properly, is part of the mastitis prevention strategy, • Ensuring that a proper milk let-down process it only treats the symptoms, and not the occurs, causes, of mastitis. • Test regularly for mastitis before milking by 2. The prevention of mastitis does not rely on using the strip cup, some superior medicine and quick fixes, • Keeping record of positive quarters (mastitis but largely on a continuing evaluation and can be transferred by milkers by hand adaptation of mastitis control measures. between cows), 3. A case of mastitis can only occur after a • Attach milking clusters correctly, not too pathogen has entered the udder through soon or too long after stimulation, the teat opening. The aim of mastitis • Prevent over-milking in cows, management should be to reduce the • Rinse milking clusters between successive possibility of such an event. For this reason, cows, injuries to the teat opening should be • Milk cows with infected quarters at the end prevented, while the exposure of the teat of the milking process, which is especially opening to pathogens should be reduced. important for Staphylococcus areus and 4. Aiming to maintain a realistic standard of Streptococcus agalactiae infections, and mastitis infection in the herd should be part • Applying teat dip after milking. of a mastitis control system. Examples of 288 Section 5 | Chapter 52

2. A correct milk machine operation, sanitising • Keeping a realistic cull rate of cows suffering and maintenance, e.g.: from recurring incidences of mastitis.

• Prevent air leakages between teat and milk 4. Managing the environment: cluster during the milking process, • Cut vacuum before attempting to remove Provide a friendly, hygienic and dry environment the cluster unit from the udder, for cows in the herd. This specifically refers to: • Efficient milking machine functioning -- Calving down areas, involves the following: -- Holding areas before and after milking, -- Regular servicing and testing of the -- Passage ways at feeding troughs and lanes milking machine, to and from the milking parlour, -- Maintaining the correct vacuum levels -- Avoid wet, saturated pastures, provide (50 kPa), good drainage, -- Maintaining a stable vacuum level in -- Provide correctly designed and built free the cluster which depends on sufficient stalls for cows to lie down in housing systems. vacuum reserve levels (100 + 25 x n) This specifically refers to the length, width of where n = <10, sufficient capacity of free stalls, free stall surfaces areas (avoid the cluster, air flow holes in the milking using saw dust as bedding), well ventilated cluster are open, a short milking tube buildings and high roofs to reduce heat between cluster and milk line (not stress, longer than 1.5 m), and low milk lines. -- Control flies by removing manure and • A correct pulsation rate (60 ± 5 per min), keeping soil surfaces dry, and -- Provide hygienic and a dry area for dry • The correct pulsation ratio (D-value = >15%). cows, and -- Maintain a correct feeding programme 3. Acceptable treatment strategies: with regards to minerals and vitamins, specifically shortages in selenium and • Establish a strategy with regards to the vitamin E may have a negative effect on treatment of mastitis cases during the udder health. lactation period and at the end of the lactation period, at drying off. Dry cow Know the enemy treatment should either be for all cows or only for specific cows. The correct Knowing the specific pathogen causing mastitis treatment of mastitis in lactating cows in dairy herd may go a long way in reducing involves treating cows early using a suitable the herd somatic cell count. For this reason, it is antibiotic while maintaining the treatment important that mastitic milk should be regularly until the infection is cleared up. cultured to identify pathogen causing mastitis. • Using a specific antibiotic treatment should A sterile milk sample from an infected quarter be motivated. should be collected for culturing at a suitable • Keep records of treatments and the success facility for identifying specific bacteria. A rate of treatment. summary of the most important mastitis-causing • Were possible, bacteriological culturing bacteria is presented in Table 52.6. should be done to identify bacteria for a specific treatment.

289 Table 52.6. The most important mastitis causing bacteria affecting dairy cows Table 52.6. The most important mastitis causing bacteria affecting dairy cows

Pathogens Table 52.6. TheSource most of contamination important mastitis causingControl measures bacteria affecting dairy cows 1. Pathogens transferred during milking • Maintain a functional milking machine Pathogens Source of contamination • PreventControl injuries measuresto teats and cross 1. Pathogens transferred during milking contamination • Infected quarters • Maintain• a high milking parlour hygiene • Open wounds on teats Maintain a functional milking machine Staphylococcus areus • Apply teat• dip after milking • Damaged teat openings Prevent injuries to teats and cross • Apply a correctcontamination dry cow treatment • Skin of •theInfected teats and quarters the udder • Cull chronic• Maintain cases a of high S. areus milkinginfection parlour hygiene • Open wounds on teats Staphylococcus areus • Treatment• Apply during teatthe dip lactation after milking period is • Damaged teat openings often unsuccessful• Apply a correct (less than dry cow40%) treatment • Skin of the teats and the udder • Maintain• Cull a functional chronic cases milking of machine S. areus infection • Prevent• crossTreatment contamination during the lactation period is • Maintainoften a high unsuccessful milking parlour (less hygiene than 40%) Streptococcus agalactiae • Infected quarter • Apply teat• Maintain dip after a functionalmilking milking machine • Apply a• correctPrevent dry cross cow contamination treatment • May be• successfullyMaintain a hightreated milking during parlour the hygiene Streptococcus agalactiae • Infected quarter lactation• Apply period teat (> 75%)dip after milking 2. Pathogens from the environment • Apply a correct dry cow treatment • Maintain• May a high be milking successfully parlour treated hygiene during the Occur on a wide spread basis e.g. • Wash andlactation dry teats period before (> milking75%) • in the housing environment, 2. Pathogens from the environment • Provide a clean and dry housing • on the skin surface of cows, Streptococcus uberis environment• Maintain a high milking parlour hygiene • infectedOccur quarters, on a wetwide udders spread basis e.g. • Consider• Wash applying and adry pre teats-milking before teat milking dip and • in the housing environment, • Treatment• Provide during a the cle lactationan and dry period housing and • teat washing• on the cloths skin surface of cows, Streptococcus uberis the dry periodenvironment is often successful • infected quarters, wet udders • Provide• aConsider clean and applying dry housing a pre -milking teat dip • Manure, and environment• Treatment during the lactation period and Different coli-form • Dirty, wet• teat and washing muddy soilcloths • Maintainthe a high dry standardperiod is often of hygiene successful in bacteria such as: surfaces free stalls• Provide a clean and dry housing Escherichia coli • Infected• Manurewater , • Keep teatsenvironment and the udder dry and clean KlebsiellaDifferent spp. coli-form • Dirty milking• Dirty, equipment wet and muddy soil • Apply a• dryMaintain cow treatment a high standard of hygiene in Enterobacterbacteria spp. such as: • Bedding surfacesmaterial such as saw • A post-milkingfree stalls teat dip is not very efficient Escherichia coli dust • Infected water for these• Keeppathogens teats and the udder dry and clean Klebsiella spp. • Dirty milking equipment • Apply a dry cow treatment Enterobacter spp. • Bedding material such as saw • A post-milking teat dip is not very efficient dust It is well known that a wide range of factors, separatelyfor theseand pathogenscomplementary, may It is well knowncontribute that to a the wide occurrence range of mastitisfactors, in abetween dairy herd. herds, Because each of the factor’srelative importancecontribution separatelyof theand Itindividual is wellcomplementary, knownfactors thatthat amay widemay differ range is between difficult of factors, herds, to separately eachquantify. factor’s and The contributiocomplementary, followingn is summarymay contributedifficult to thecontribute tooccurrence quantify. to the The ofoccurrence followingmastitis ofin summary mastitisa (Table in(Table a 52.7) dairy 52. provides herd.7) provides Because an indicationan of indication the relative of ofthe importance the most dairy herd.most Because probableof the of the individualeffect relative of some factors importance of the that factors may probable causingdiffer between new effect cases herds,of of some mastitis. each of thefactor’s factors contributio causingn is of the individualdifficult factors to quantify. that may The followingdiffer new summary cases (Table of mastitis. 52.7) provides an indication of the Table 52.most7. Theprobable most effect probale of some effect of of the different factors causingfactors onnew mastitis cases of mastitis.

FactorsTableTable 52.7. 52.7. The The most most probale probale effecteffectMost ofprob differentable effect factorson masti onti smastitismastitis Teat dip 50 – 70% less Milking cluster About 20% less ScreensFactor in shorts milking tube About 15%Most less probable effect on mastitis ClustersTeat slipping dip off Significantly50 – more70% less ChangesMilking in vacuum clusterduring milking Little to Aboutsignificantly 20% less more High vacuScreensum levels in short milking tube Mostly moreAbout 15% less Rinsing ofClusters clusters slipping between off cows RelativeSignificantly little value more IncorrectChanges pulsation in vacuum during milking IncreasesLittle to significantly more IncorrectHigh cluster vacu removalum levels IncreasesMostly more Over-milkingRinsing of clusters between cows UncertainRelativeto probably little value IncompleteIncorrect milking pulsation VaryingIncreasesresponse SeparatingIncorrect infected cluster cows removal Result inIncreases fewer cases Pre-milkOver teat- dippingmilking No to littleUncertain effect to probably Incomplete milking Varying response Separating infected cows Result in fewer cases From this it seemsPre-milk that teat some dipping factors require more emphasisNo to than little effectothers, e.g. teat dipping after milking is more important than pre-milking. Similarly rinsing clusters between cows seem to From this it seems that some factors require more emphasis than others, e.g. teat dipping after milking is more important than pre-milking. Similarly rinsing clusters between cows seem to

290 Section 5 | Chapter 52

From this it seems that some factors require blood cells causes the SCC count in milk to more emphasis than others, e.g. teat dipping increase above the standard level in milk. after milking is more important than pre-milking. Udder infection or mastitis is the single most Similarly rinsing clusters between cows seem to important reason for an increasing number of have relative value as the water quality may white blood cells. For this reason, an increase be questionable. High vacuum levels mostly in the SCC of milk is the most reliable and increase the probability of mastitis. practical way to identify sub-clinical mastitis in the udder of dairy cows. A wide range of In closing factors, separately and complementary, contribute to the amount of mastitis cases The fat, protein and lactose contents as well in a dairy herd. The relative importance of as the SCC of milk indicate the quality of individual factors differs between herds. milk. The SCC is used as an indication of the Factors affecting mastitis include the following: number of white blood cells and epithelial a correct milking procedure, a correct milking cells in milk which is an indirect indication of machine operation using correct sanitising and the mastitis infection in milk. This is because maintenance procedures, correct treatment when some infection occurs in the alveoli, the strategies and providing a clean and hygienic body produces white blood cells to combat environment for cows. the infection. Increasing the number of white

291 CHAPTER 53 MILKING PARLOURS FOR MODERN DAIRIES

Introduction should allow cows, milk, and waste water to be handled effectively and efficiently. Decisions ike most businesses, dairy farming has concerning the milking centre are some of the to be profitable. Part of the financial most complicated decisions a dairy farmer success is the consumer demand for has to make. Milking procedures, herd size, the dairy farm’s products, namely, milk expansion plans, milking interval, and the Land beef. Dairy farms require a large capital equity position of a producer influence these outlay which consists mostly of cows, feeds, decisions. One specific milking parlour would heavy equipment like tractors, trucks, feed not meet the requirements of all dairy farmers. mixing equipment, and various buildings. This includes the milking machine, bulk tanks, Past milking systems milking parlour and associated structures, such as holding areas, feeding silos, crushes, a Looking at the world production and herd size scale for weighing cows, etc. Cows are usually figures, one can see that average herd size milked at least twice a day for every day of the has increased dramatically, with the number year. As the labour input of milking cows is a of dairy farms decreasing in proportion. In major factor, it is of utmost importance that the South Africa, the average herd size, in the milking parlour is suitable for the operation. This late 1990s, was 90 lactating cows. Currently, is mainly determined by the number of cows this figure is estimated to be about 130 to 200 being milked every day. Milking cows must be lactating cows with the number of large herds an easy operation as this is mostly reliant on (in excess of 500 cows) increasing. This means people doing the physical work. The labour that the management on dairy farms is getting force milking cows each day has a major more and more important, and many crucial effect on the quality of milk recovered from decisions have to be made every day on the cows before being processed, as well as the farm. survival or longevity of cows. Which milking system to use? This is why it is important that the harvesting of milk, being the most important income Dairy farmers wishing to upgrade existing on a dairy farm, is done professionally and milking parlours should consider the following correctly. This must be done with the greatest factors before selecting a specific system. care without affecting the welfare of cows, These factors also apply to new farmers as this may have a large negative effect on wanting to start up a dairy. Factors to take in their longevity and the eventual financial account include the following: sustainability of the farm. The genetic level of the herd and the quality of feed being used 1. How many cows are to be milked daily in on a daily basis are important factors affecting the milking parlour? the total milk output of the herd. However, the 2. Which milking procedure will be used milking process is a major factor in extracting (minimal or full)? the milk from cows, as this is the major product 3. If a full milking routine is to be used, how that is produced on a dairy farm. much contact time is required (strips per teat)? A milking parlour on a dairy farm is a specialised 4. Which milking routine is to be used building, or section of a building, designed to (sequential, grouping or territorial)? milk cows and handle milk. The milking parlour 5. Would the milking parlour accommodate must be designed, constructed and managed expansion in the future? with the goal of providing a safe and enabling 6. Are there major structural changes to environment for cows and workers. The be made to the existing parlour, or is a milking system and its operation must ensure a completely new building the preferred continuous daily collection and storage of high option? quality milk. A well-designed milking centre 7. Which feeding system is being used, e.g. 292 2. Which milking procedure will be used (minimal or full)? 3. If a full milking routine is to be used, how much contact time is required (strips per teat)? 4. Which milking routine is to be used (sequential, grouping or territorial)? 5. Would the milking parlour accommodate expansion in the future? 6. Are there major structural changes to be made to the existing parlour, or is a completely new building the preferred option? 7. Which feeding system is being used, e.g. pasture-based, total mixed ration (TMR) or Section 5 | Chapter 53 mixed system. pasture-based, total mixed ration (TMR) or • Prep time - time taken to manually clean mixed8. Aresystem. the facilities around the parlour, like holding(wash yards, using races running, and pens water), adequate and fordry the teats 8. Are thechanges facilities, especially around when the an parlour, expansion like of the herdand is udder. envisaged? holding9. Is yards,in-parlour races, concentrate and pens, feeding adequate being considered • Contact? time - the actual time spent for 10.theWhat changes, level of automation especially is requiredwhen inan (and outside)washing the andparlour? drying teats also stimulating expansion11. Is milk of recordingthe herd tois envisaged?be conducted, i.e. using approvedfor the milk release meters? of oxytocin to enable milk 9. Is in-parlour12. What is concentratethe maximum milkingfeeding time being per day available?let-down. considered? • Prep-lag time – the time between the start 10. OptionsWhat level for ofm ilkingautomation procedures is required and routines in (and in parallelof teat and preparation herringbone toparlours the application of Itoutside) is essential the thatparlour? dairy producers develop accurate timethe budgets milking forclusters. the milking procedures and 11. routinesIs milk recording they select. to Before be conducted, the options i.e. for using milking •procedures Milking proceduresand routines can- the be individualdiscussed, theevents followingapproved terms milk must meters? be defined: (i.e. strip, pre-dip, wipe, attach) required to 12. What is the maximum milking time per day milk a single cow. Prepavailable? time - time taken to manually clean (wash using• runningMilking water)routines and - definesdry teats andhow udder. an individual Contact time - the actual time spent washing and dryingmilker teats oralso a stimulatinggroup of milkersfor the releasecarry outof a Options foroxytocin milking to procedures enable milk letand-down. routines in given milking procedure (minimal or full) parallelPrep- lagand time herringbone– the time parlours between the start of teat preparationover multiple to the cows. application of the milking clusters. It isMilking essential procedures that dairy- the producersindividual eventsdevelop (i.e. strip,The actualpre-dip, time wipe, required attach) requiredfor individual to mil kevents a accurate singletime cow. budgets for the milking during the milking process is shown in Table proceduresMilking r outinesand routines- define theys how select. an individual Before milker53.1. or a group of milkers carry out a given the options for milking procedures and routines milking procedure (minimal or full) over multiple cows. can be discussed, the following terms must be defined: The actual time required for individual events during the milking process is shown in Table 53.1.

TableTable 53.1. 53.1. Time Time (seconds) (seconds) required forfor individual events ofof thethe milking milking procedure.procedure

Procedure Event Minimal* Full Full with 10 sec contact time Strip (seconds) 4 - 6 4 - 6 10 Pre-dip (seconds) - 6 - 8 6 - 8 Wipe (seconds) 6 - 8 6 - 8 6 - 8 Attach (seconds) 8 - 10 8 - 10 8 - 10 Total (seconds) 12 - 18 24 - 32 30 - 36 *Strip or wipe and attach

Some of the advantages and disadvantages of minimal and full milking procedures are listed Somebelow of. the advantages and disadvantages 2. Advantages and disadvantages of a full of minimal and full milking procedures are milking procedure listed1. Advantagesbelow. and disadvantages of a minimal milking routine »» Maximises teat sanitation and milk let-down. 1. Advantages Compromises and disadvantages teat skin sanitation of a . »» Uses 4 separate procedures or can combine minimal Successful milking routine when cows enter the milking parlourinto clean two and or drythree. procedures. »» Use when maximum milk quality results are »» Compromises teat skin sanitation. the goal. »» Successful when cows enter the milking »» Minimises “machine on-time”. parlour clean and dry. »» Results in lower cow throughput or higher »» “Machine on-time” may be prolonged. labour cost compared to “minimal” or »» Steady unit throughput is increased. “none”. »» Time required to milk the herd may be »» Requires milker training to maximise results. decreased (total milking time). »» May require milkers to decide when extra cleaning of dirty teats is required. »» Can cause lower milk quality and higher mastitis when compared to “full hygiene”.

293 Milking routines attaching clusters. Full milking procedures affect the number of cows per stall per hour Correct and proper managed routines in the in parallel, herringbone, and rotary parlours. In parlour are of crucial importance. A proper large parallel and herringbone parlours cows routine is required to milk out cows completely. per stall per hour are 5.2 - 6.5 cows per unit per Anything outside the normal routine practice hour when minimal milking procedures are used in the parlour adds to higher stress levels in and 4.4 - 6.0 cows per unit per hour when full cows, usually resulting in under-milking (not milking procedures are used. These figures will, completely milked out) of cows. There are of course, be affected by the level of training many negative factors that can disturb the and other management procedures to be daily routine, e.g.: followed by milkers. In rotary parlours, cows per • Faulty settings of the milking machine, like stall per hour would mainly be determined by the teat-end vacuum, or problems related the rotation speed of the milking platform and to pulsation and vacuum levels, the routine to be followed. • Abnormal noises, • Change of milking times, In large parallel and herringbone milking • Change in the handling of the cows prior to parlours, milking procedures have a large entering the parlour, effect on the number of milking units one milker • Stray voltage (a cow reacts negatively to is able to handle. When a full milking procedure any stray voltage higher than 2 - 5 Volts), is used, a milker should be able to operate 10 and units on one side and 17 units on another side • Non-regular visitors in the parlour. when using minimal milking procedures. These recommendations are based on allowing 4 - 6 When a proper routine is followed and the seconds to strip a cow and attaching all the stimulation of the cow’s milk let-down hormone units on one side of the parlour in 4 minutes. is done efficiently, it is expected to milk-out In recent years, several milking management cows completely. specialists have been recommending stripping 2 - 3 squirts per teat (in 8 - 10 seconds) when In parallel and herringbone parlours, there stripping cows to increase stimulation and are three milking routines, namely, grouping, improve milk let-down. sequential, and territorial. The reason for this is that unit-on-time is 1. Grouping milking routine - In a grouping reduced by increasing udder stimulation. The routine, the milker performs all the individual sequencing of the individual events of the tasks of the milking procedure on 4 to 5 cows. milking procedure is critical. Research has Once these tasks have been completed shown that an ideal prep-lag time is 1 minute for a group of cows, the milker then moves and 18 seconds. Prep-lag times of 1-1.5 minutes on to the next group of available cows. seem to be accepted as optimal for all stages of lactation. Producers will have to decide 2. Sequential milking routine – Milkers using which milking procedure they will use and the a sequential routine split up the individual amount of stimulation that is required. tasks of the milking procedure between milkers and work as a team. Milkers work as a team following each other, performing Selecting parlour type their individual tasks. Dairy farmers usually have a personal 3. Territorial milking routine - Milkers are preference for a certain parlour type. Often assigned a number of milking units (clusters) this personal preference conflicts with the on both sides of the parlour and only number of cows to be milked, length of the operate the units assigned to them. When milking shift, anticipated milk quality, udder a territorial routine is used, milkers are not health results, and financial resources. The dependent on other milkers to perform selection of a milking parlour is affected by specific tasks. the initial herd size, expansion plans, economic impact on the dairy, and the ability to train The standard milking procedures for the minimal and manage employees. Dairy producers system include stripping milk, wiping teats, and should visit as many types of milking parlours as attaching clusters, while the full system include possible and make a final decision after having pre-dipping, stripping milk, wiping teats, and an opportunity to review all types, which may 294 Section 5 | Chapter 53 not necessarily be the fastest or latest milking Parallel and herringbone parlours have an machine and design. advantage over rotary parlours which cannot be expanded in steps. Total hours of use One vs. two milking parlours (double pit A milking parlour sized to be used for only 4 to parlours) 6 hours a day, will be more expensive to build and operate per cow than when the parlour Some research has indicated that two smaller operates 20 to 21 hours per day. For example, milking parlours are more efficient than one a 250 - cow dairy, milking twice a day could larger milking parlour. Building two separate be milked in a double-4 herringbone parlour parlours also allows producers to construct the in a 6-hour shift, or milked in a double-10 dairy in phases, while increasing the number of herringbone in a 3-hour shift. Fewer hours of use groups of lactating cows. may be desirable if farm personnel also have other duties, such as crop production, feeding, Training and monitoring milkers animal health, and raising replacements. However, a larger return on investment will Providing training and monitoring milkers are be realised when the milking parlour can be constant challenges for dairy producers. In used 20 to 21 hours a day to milk cows. Dairy parallel and herringbone parlours with multiple farmers often have to make a choice between milkers, to improve parlour performance, the number of cows that can be milked and it becomes very important to train teams which milking procedure they can use under of milkers to work together. In parallel and these conditions. If not careful, milk quality and herringbone parlours, operators are mobile and udder health may suffer with negative effects able to perform multiple tasks (e.g. stripping, on milk yield. pre-dipping, wiping teats, and attaching clusters) as compared to rotary parlours where Number of milkers operators are fixed in one location and can only perform one or two tasks at this location. The number of milkers may be affected by the To maximise the performance of multiple availability of personnel, milking procedure, or operator parallel and herringbone parlours, herd size. Most small herringbone and parallel milkers have to work together to perform the milking parlours (double-4 to double-12) could milking procedures over multiple cows using be operated by 2 to 3 milkers for the bigger of a grouping or sequential milking routine. After the two milking parlours. One-person parlours milker training has been completed, the dairy are more efficient in the number of cows per farmer will have to monitor the performance labour hour. Two-or-more-operator parallel of individual milkers and parlour performance. or herringbone parlours have the advantage of continuous operation, even during group Evaluating parlour performance change, when one operator is late for the milking shift, or when a short emergency Milking parlour performance has been requires one operator to leave the parlour. evaluated by time and motion studies to The disadvantage is that it is more difficult for measure steady-state throughput (cows per the owner to assess operator performance or hour). Steady-state throughput does not quality standards, and the number of cows include time for cleaning the milking system, per labour hour will be less. However, many maintenance of equipment, effects of group producers are able to achieve the same changing, and milking the hospital strings. labour efficiency in multiple operator parlours These studies also allow for the opportunity to as single operator parlours with training and determine the effect of different management monitoring programmes. variables on milking parlour performance. Historically, this information has been used Initial herd size and expansion plans to size milking parlours towards meeting the requirements for dairy farmers. Dairy farmers should consider their current herd size along with plans to increase the Sizing milking parlours herd size in the future. When a producer wants to grow the herd size in steps, parallel or As dairy herds increase in sizes, the sizing of herringbone parlours should be constructed to milking parlours becomes more complicated. allow for expansion as the herd size increases. Many dairy farmers choose to use a so-called 295 hospital parlour (for cows under treatment for the cleaning and maintenance of the parlour. mastitis, etc.), thereby reducing the pressure of The facilities or cow groups are determined cow through-put in the main parlour. Some dairy based on milking one group in 60 minutes farmers are also milking healthy cows in these when milking twice a day, 40 minutes when hospital parlours to increase the number of milking three times a day, and 30 minutes when cows to be milked. Some dairies are increasing milking four times a day. Group sizes of cows the number of daily milkings from three to even are adjusted to be divisible by the number of five times a day, especially during the first 21 stalls on one side of the milking parlour. Having - 42 days of the lactation period, after which as many occupied stalls as possible per cycle the number of daily milkings is reduced to two maximises parlour efficiency. or three times per day. Such factors have a dramatic impact on how the milking parlour is The number of cows that will be milked per sized. hour can be calculated using the following formulae: Typically, milking parlours are sized so that the herd can be milked once in 10 hours when Total number of stalls x turns per stall per hour = milking twice a day, 6.5 hours when milking cows milked per hour (CPH) and three times a day, and 5 hours when milking four times a day. Using these criteria, the Number of milking cows = CPH x milking shift milking parlour will be sized to accommodate length (hours)

Figure 53.1. An example of utilisation of labour with minimum routine, 4 operators, 72 unit rotary parlour

Sizing rotary parlours Theoretical throughput assumes that the parlour never stops, cows are milked out in 1 Entry time (seconds/stall), number of empty rotation and a new cow occupies every stall at stalls, number of cows which go around a entry. In reality, there are empty stalls (about 4 second time, entry and exit stops, and the size at any time, between getting on the table and of the parlour (number of stalls) influence the getting off the table), cows that go around a performance of rotary parlours. The entry time second time, and times when the rotary table will determine the maximum number of cows is stopped. that can be milked per hour. For example, if the entry time is 10 seconds, the maximum In Table 53.2, rotary parlour performance throughput will be 360 cows per hour (3600 at different percentages of theoretical seconds per hour / 10 seconds per stall = 360 throughput is shown. As the number of empty cows per hour). This is referred to as theoretical stalls, cows making a second trip around, and throughput. number of stops increases, the percent of theoretical throughput is reduced. 296 Section 5 | Chapter 53

Table 53.Table2. The 53.2. number The number of cows of per cows hour per in houra rotary in a parlour rotary parlour

Percentage of theoretical number of cows per hour (%)

100 90 80 70 60 Time (sec/stall) 8 450 405 360 315 270 9 400 360 320 280 240 10 360 324 288 252 216 11 327 295 262 229 196 12 300 270 240 210 180 13 277 249 222 194 166 14 257 231 206 180 154 15 240 216 192 168 144 16 225 203 180 158 135

The numberThe number of stalls of stalls or size or ofsize the of rotarythe rotary parlour parlour shown. affects Athe rotary available parlour unit- muston-time. be Inlarge Table enough 53.3, affectsavailable the available unit-on-time unit-on-time. for different sizesIn Table of rotary to parloursallow approximately at different rotation 90 percent times is of shown the cows. A 53.3, rotaryavailable parlour unit-on-time must be large for enough different to allowsizes approximatelyto be milked 90 out percent in one of trip the around cows to the be milkedparlour. of rotaryout in parlours one trip ataround different the parlour. rotation times is

Table 53.3. Available unit-on-time estimated for rotary parlours at different rotation times*Table 53.3. Available unit-on-time estimated for rotary parlours at different rotation times*

Revolution time Available unit on time Number of Entry time stalls (sec/stall) Seconds per Minutes per Seconds per Minutes per revolution revolution revolution revolution 40 8 320 5:20 240 4:00 40 10 400 6:40 300 5:00 40 12 480 8:00 360 6:00 40 15 600 10:00 780 7:30 60 8 480 8:00 400 6:40 60 10 600 10:00 500 8:20 60 12 720 12:00 600 10:00 60 15 900 15:00 750 12:30 72 8 576 9:22 496 8:16 72 10 720 12:00 620 10:20 72 12 864 14:24 744 12:24 72 15 1080 18:00 930 15:30 80 8 640 10:40 560 9:20 80 10 800 13:20 700 11:40 80 12 960 16:00 840 14:00 80 15 1500 20:00 1050 17:30 *Assumes 5 stalls for entry and exit, 3 stalls for pre-milking hygiene, and 2 stalls to detach

In reviewing the data available today, rotary parlours should be sized at an 11-12 seconds per In reviewingstall rotation the data and 81%available of theoretical today, rotarythroughput. stalls, The respectively parlour should (Table be 53.4).large enoughMilking toparlours allow parloursnine should minutes be of sized available at an unit 11-12-on-time. seconds When sizingwith 60 rotary stalls parlours or larger on are a steady able stateto increase throughput the per stallbasis, rotation approximately and 581% and 5.8of cowstheoretical are milked number per stall of per rotations hour for per milking hour parloursand still withmaintain less throughput.than 54 andThe 60parlour stalls, respectiv shouldely be (Table large 53. 4).adequate Milking parlours time to with milk 60 cows stalls orcompletely larger are ableout, enoughto increaseto allow the nine number minutes of rotations of available per hour without and still some maintain cows adequate going aroundtime to milka second cows unit-on-time.completely When out ,sizingwithout rotary some parlours cows going on around time. a second It is critical time. that It is rotarycritical parlours that rotary be parlour sized tos steadybe state sized throughputto accommodate basis, some approximately expansion because accommodate they are very difficultsome expansion to expand. because they 5 and 5.8 cows are milked per stall per hour are very difficult to expand. for milkingTable parlours 53.4. Results with lessfrom than a survey 54 and conducted 60 in the USA showing the performance of different sized rotary milking parlours using a full milk procedure 297

Number of milking parlour stalls Parameters 24 - 40 48 - 54 60 - 80 Number of milking parlours 8 5 7 Average number of stalls 36 51 72 Average number of cows/hour 181 258 420 Average number of milkers 2.6 2.7 5.41 Average number cows labour/hour 82 98 77 Average milk yield (kg/day) 32 34 33 Average rotation/stall/hour 5.42 5.42 6.16 Average cows/stall/hour 5.01 5.06 5.82

Impact of automatic take-offs Research showed that when automatic cluster remover settings were increased, average milking duration was reduced by 10.2 to 15.6 seconds per cow. Higher automatic cluster remover settings Table 53.3. Available unit-on-time estimated for rotary parlours at different rotation times*

Revolution time Available unit on time Number of Entry time stalls (sec/stall) Seconds per Minutes per Seconds per Minutes per revolution revolution revolution revolution 40 8 320 5:20 240 4:00 40 10 400 6:40 300 5:00 40 12 480 8:00 360 6:00 40 15 600 10:00 780 7:30 60 8 480 8:00 400 6:40 60 10 600 10:00 500 8:20 60 12 720 12:00 600 10:00 60 15 900 15:00 750 12:30 72 8 576 9:22 496 8:16 72 10 720 12:00 620 10:20 72 12 864 14:24 744 12:24 72 15 1080 18:00 930 15:30 80 8 640 10:40 560 9:20 80 10 800 13:20 700 11:40 80 12 960 16:00 840 14:00 80 15 1500 20:00 1050 17:30 *Assumes 5 stalls for entry and exit, 3 stalls for pre-milking hygiene, and 2 stalls to detach

In reviewing the data available today, rotary parlours should be sized at an 11-12 seconds per stall rotation and 81% of theoretical throughput. The parlour should be large enough to allow nine minutes of available unit-on-time. When sizing rotary parlours on a steady state throughput basis, approximately 5 and 5.8 cows are milked per stall per hour for milking parlours with less than 54 and 60 stalls, respectively (Table 53.4). Milking parlours with 60 stalls or larger are able to increase the number of rotations per hour and still maintain adequate time to milk cows completely out, without some cows going around a second time. It is critical that rotary parlours be sized to accommodate some expansion because they are very difficult to expand.

TableTable 53.4. 53.4 Results. Results from from a survey a survey conducted conducted in the in USAthe showingUSA showing the performance the performance of ofdifferent different size sizedd rotary rotary milking milking parlours parlours using using a a full full milk milk procedure procedure

Number of milking parlour stalls Parameters 24 - 40 48 - 54 60 - 80 Number of milking parlours 8 5 7 Average number of stalls 36 51 72 Average number of cows/hour 181 258 420 Average number of milkers 2.6 2.7 5.41 Average number cows labour/hour 82 98 77 Average milk yield (kg/day) 32 34 33 Average rotation/stall/hour 5.42 5.42 6.16 Average cows/stall/hour 5.01 5.06 5.82

Impact of automatic take-offs Impact of automatic take-offs control devices. Computer programmes Research showed that when automatic cluster remover settings were increased, average milking that help with daily decisions like calving duration was reduced by 10.2 to 15.6 seconds per cow. Higher automatic cluster remover settings Research showed that when automatic cluster data, lactation data, milking records, cow remover settings were increased, average performance figures and historical data to milking duration was reduced by 10.2 to 15.6 name only a few, make management easier seconds per cow. Higher automatic cluster for the dairy farmer. One should remember remover settings did not have a negative impact that a management programme is as useful on the milk yield of cows. The average milk as the data that is put into it. Computerised flow per minute also increased. The conclusion management systems are becoming a very was that increasing automatic cluster remover important tool for many dairy farmers on which settings represents an opportunity to increase to base daily management decisions. parlour performance. The basic norms for modern milking machines Herd size and feeding practice determine the level of automation A large volume of information is available on this topic, and international standards are In essence, there are four parlour lay-out available to assist the manufacturers of milking choices for medium to large scale dairy equipment to ensure that machines will be fully farming: operational once installed. The international • Rotary parlours (internal or external ISO standards are widely used as the correct configuration) norm for this purpose, and many aspects • Big Bore or swing-over herringbone parlours are dealt with in these norms. Important • Double sided herringbone parlours aspects covered in the ISO standards that are • Parallel or rapid exit parlours researched continuously, and that may affect the milk harvesting process negatively, include The choice is very much determined by herd the following: size and the cow throughput that is required, and varies from farm to farm. Management • Milk and vacuum line design for different style, personal preference and finance size machines, available are some of the most important • Cleaning capacity design, factors that will decide on the choice made. • Pulsator characteristic design, The number of milking units will be determined • Vacuum drops between different points in by the milking time available, as well as by the the milking machine that are allowed, and herd size and feed practice. • The important aspect of teat end vacuum level specification, which is surely the Level of automation required most important measurement to do to secure that damage to the cow’s teats is The level of automation in the milking parlour eliminated. It should be between 32 and is largely affected by the management level 40kPa according to ISO norms, and can required for the dairy. Usually this includes only be tested with specialised equipment. equipment like electronic milk meters, automatic cluster removers, and milk flow 298 Section 5 | Chapter 53

Robotic milking – a future option In closing

Hundreds of dairy farmers world-wide are The choice of milking equipment and the type milking their cows by robotic or voluntary of parlour depends on the level of automation milking systems. In such systems, cows decide and information that is required for the daily when they want to be milked (most of the management of the dairy herd. Together with times cows visit the milking parlour 4 to 6 these choices, the availability of services and times per day), and during milking, various spares on an ongoing basis will aid the decision parameters like teat end condition compared making process. The welfare of cows should be to previous milkings, milk quality evaluation, considered when considering different milking cleaning and drying of each teat, the milking parlour options. Milk is produced from fewer, of each quarter individually, the cleaning of but higher yielding cows. Structural changes the teat cups after milking and post dipping, have caused a decrease in number of dairy are recorded automatically. This information farms, while they have increased in size and is then included in the herd management use of technology. This high technology has programme. In some cases specific information become an ordinary tool for the dairy farmer. can be sent to a mobile phone. The limitation It should be kept in mind that milking is not only of the voluntary milking system is the number of a procedure where the milk is drained from the cows that can be milked per station. Currently, teats, it is an event where many physiological 60 - 70 cows can be milked with one machine. mechanisms are activated in the body of In the near future, robotic milking machines will the lactating cow, events which influence be improved, which should make them more mechanisms regulating production capacity, affordable. Adaptations to current parlour milk composition, feed intake and animal configurations should also follow towards more behaviour. automation.

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