Traditional Technologies in the Yak Farming System of the Qinghai-Tibetan Plateau, China

Blackwell Science, Ltd http://www.paper.edu.cn Milking and milk processing: traditional technologies in the yak farming system of the Qinghai-Tibetan Plateau, China

S K DONG,1,3* R J LONG2,3 and M Y KANG1 1Key Laboratory of Natural Disaster and Environmental Change, Ministry of Education, Institute of Resources Science, Beijing Normal University, Beijing, 100875, P. R. China, 2Northeast Plateau Institute of Biology, Chinese Academy of Science, Xining, 810001, P. R. China and 3Grassland Science College, Gansu Agricultural University, Lanzhou, 730070, P. R. China

Yak milk and its products are widely consumed by local herders and are regarded as the resources of economic income by the households on the Qinghai-Tibetan Plateau. Yak raisers have developed their own milking skills and milk-processing technologies through a long history of yak keeping. All of these traditional skills and technologies have their own characteristics. In this paper, the methods and procedures of milking and milk processing in yak farming systems are reviewed. Keywords Dairy yak, Milk collection, Milk products.

*Author for correspondence. E-mail: [email protected] management and milking regime, averaging 0.9 kg INTRODUCTION to 2.6 kg daily within around 180 days of lactation, Yaks are found extensively on China’s Plateau, there are many of them (around 100 head per which is an alpine and subalpine region at altitudes household), so the total quantity produced is sub- ranging from 2000 to 4500 m with a cold, semihu- stantial.7 Moreover, the quality of yak milk is good. mid climate. The area of yak distribution extends The total dry matter is around 17–18% during the from the Himalayas in the south to the Altai in the main lactating period, the fat content varies at north, and from Pamir in the west to the Minshan around 6.5%, protein and lactose are each around mountains in the east, centring on the Qinghai- 5.5%, and ash 0.8%. The proportion of essential to Tibetan Plateau.1 There are 13 million head of yaks nonessential amino acids is around 0.8 : 1.10 This in China, and they play crucial roles in the animal dense and sweetish milk is greatly liked by the husbandry economy of this area. They provide local people and is processed into various prod- milk, milk products, meat, hair and hide for ucts, such as milk tea, butter, cheese, milk residue, Tibetan herders. They are also used as pack ani- milk cake, milk skin and yoghurt (sour milk), by mals and for draught purposes. Without yaks, it is Tibetan households.11 This paper aims to provide doubtful whether man could survive on the harsh, basic information on the traditional technologies of high-altitude grazing lands of the Plateau.2 milking and processing in the yak farming systems Although yaks are multipurpose animals, they of the Qinghai-Tibetan Plateau. are raised mainly for milk production on the Qinghai-Tibetan Plateau of China.3,4 Milk and milk MILKING products are the major ingredients of the daily diets of Tibetan herders, particularly weak, ill and old Machine-milking is limited in the yak farming sys- people and children in areas where yaks graze on tems of the Qinghai-Tibetan Plateau by the poor the alpine meadows and mountain pastures.4 infrastructures on the summer pastures; pastures Because of a shortage of vegetables, yak milk is a near the herders’ houses are kept for winter graz- vital source of vitamins for Tibetan herders;5 butter ing, those far from the herders’ houses are kept for and cheese are two of the major sources of nutri- summer grazing, and the yak herds are normally tion.6 Milk and milk products are also used for milked on the summer pastures.4 Hand milking is many purposes other than food, such as fuel for more practical in these low-labour cost, low- family lamps by herders and holy lamps by Lamas producing yak farming systems, irrespective of or as a lubricant to assist hand milking.7 With a milking regimes and herd management. *Author for good market price, milk products contribute correspondence. E-mail: greatly to the family income of local herders Milking regime [email protected] besides beef, hair and hide.8,9 Three milking regimes exist in different localities: © 2003 Society of Although the milk yield of an individual yak once-daily milking in the mountain areas of the Dairy Technology female is low under the traditional feeding Northern Plateau, twice-daily milking on the

Vol 56, No 2 May 2003 http://www.paper.edu.cn grasslands of the Central Plateau and three-times to 0800 h, and are then allowed to graze freely and daily milking along the valleys of the Eastern Pla- have access to water at a short distance from the teau.12 This diversity in the milking regime campsite. The calves are tethered at the campsite, depends not only on the geographical difference or are tied together in pairs and allowed to graze but also on the herders’ custom and labour availa- near the camp from around 0800 to 1300 h. The bility and the condition of the animals.13 cows are driven to the campsite for a second milk- Although 30–50% more milk is obtained by ing (without tethering) from around 1300 to milking yaks two or three times a day rather than 1500 h. The calves are then allowed to graze with just once a day, the fat percentage in the milk their mothers away from the campsite from around declines with the increased milk yield (quantity).14 1500 to 1900 h. Grazing is ended at around 1900 h, Moreover, according to research by Zhang and and the calves are separated from their mothers and Pu15 on Tianzhu White yaks, milk yield was nega- tethered to a long rope at the campsite. The cows tively correlated with the total dry matter content are milked for a third time from around 1900 to and the amino acid content of the milk. 2100 h. The calves remain tethered overnight, and In addition to milk composition, the milking the cows may either be tethered or free, depending regime can affect the growth of the calves. The on the topography of the land and the ease with weight gain of the newborns under once-daily which they can be driven back to the campsite in milking can be double that from twice-daily milk- the morning.13 ing.16,17 This is a consequence of differences in Regardless of which kind of milking regime is milk intake by the calves. When the cows are used by the herders, the calves must be separated milked once a day, the calves are kept apart from from the cows at milking and for night grazing. If their mothers for a relative short period of time the calf is tethered, the cow will be tied up too, but only, and they get ample opportunity to suckle. not if the calf is kept in a closed corral. However, calves of cows milked twice a day have Tethering is usually done by hitching a neck rope perhaps only 4–5 h with their mothers, and their to a 40–50-cm wooden peg that, in turn, is attached chances of suckling are lower (see later). The to a long rope with many rings (Figure 1).21 As reproductive rate of the cows also fell significantly described by Zhang,10 the tethering site is square when they were milked twice or three times a day.18 with a wooden pole at each corner and enclosed by Frequent milking reduced the cows’ time on graz- several circles of ropes made from yak hair or skin ing and forage selection,19 and their poor body (Figure 2). There is a distance of around 2 m condition resulting from intake deficiency (both between two yaks and 5 m between two layers of quantity and quality) led to lower proportions of ropes. Normally, 1-year-old calves are tethered to cows in oestrus and pregnancy.20 the centre rope, 2-year-old calves to the second, dehorned cows to the third and horned cows to the Herd management fourth layer. First-calving cows are not usually Grazing and tethering (fencing) are two important milked, but are tethered to the sides of the outer aspects of herd management, and grazing manage- layer far from the tents. ment is related to the milking regime. Milking takes places where the cows are teth- In the once-daily milking regime, the cows are ered. After a short time, the cows ‘remember’ the recalled from their night grazing to the campsite, position along the rope where they are to be tied, where they are mustered without tethering (or with and they quickly learn a new position if given one tethering when the calves are tethered) from after a move to a new campsite.12 around 0500 to 0700 h They are milked from In some areas, milking also takes places in stalls. around 0700 to 0900 h. The calves are released The milkers calls to the yaks using the charming, from their overnight wooden closure (tethering) to eloquent names given to them at first milking. A little graze with their mothers and suckle from around barley powder mixed with salt may be used as a 0900 to 1800 h. The herds are then brought to the further incentive to tempt the cows into the stall campsites and the calves are fenced in a wooden (with left and front stone walls about 100–120 cm corral (or are tethered to a long rope) from around long, 60–80 cm wide and 60–80 cm high and the 1800 to 2000 h. The yak cows are allowed to graze other side open). Once there, the cows are hitched freely on the pasture near the campsite from around by their neck ropes to wooden poles and milked by 2000 to 0500 h.7 the milkers.13 In the twice-daily milking regime, grazing man- The labour requirements and divisions are dif- agement of herds is very similar to that of the once- ferent under the various milking regimes. One daily milking herds, but the cows are milked twice, adult (usually a Tibetan woman) can usually finish with first milking around 0700 to 0900 h and sec- grazing, tethering and milking a herd of 40–50 ond milking around 2000 to 2100 h.19 cows in a once-a-day milking system. For a twice- In the three-times daily milking regime, the a-day milking regime, a child is responsible for cows are milked for the first time from around 0500 grazing and tethering the herds of both cows and

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Figure 1 Tethering the cows and calves. (courtesy of Miller, 1998)

the udder and the flank, and rub the udder with a dry, clean cloth to remove all kinds of dirt before milking.24 Sometimes, the udder and teat are washed with fresh, clean water from a bucket, and dried in such a way that no liquid can drip into the milk resulting in contamination. On rainy days, the yak cow is not milked or is milked in the tents to prevent the rainwater flowing from the cow’s body into the milk.13 Figure 2 Sketch map of the tethering sites of yak herd. The milking reflex is stimulated, in the first instance, by the calf poking the udder and being allowed to suck a little until milk let-down occurs. calves, and one adult (woman) is involved in milk- The calf is then tethered to a rope at a short distance ing the cows and processing the milk products. Two but still within sight of the cow, and hand milking adults are involved in the three-times-a-day milk- starts. The reflex has to be restimulated a second ing system: a man takes the responsibilities of time by the same procedure with the calf, after half grazing and tethering the herds, and a woman is in of the milk has been extracted.7 In some cases, imi- charge of milking the cows and processing the raw tation of the calf’s voice by the milker is very effec- milk.22 tive in stimulating milk let-down.25 With the let-down, milking is started as illus- Hand milking trated in Figure 3.7 Normally the milker squats on Temperamentally, yaks are wild yet timid, and the right side of the cow with the pail hung from a cowardly yet aggressive. All these aspects have to hook on a girdle and uses a little butter, which has be taken into account in training yaks to obey com- been spread on the side of the pail, to lubricate the mands, so that one milker can easily milk a large teats. Although a forced rhythmic squeezing with herd. For some skilful milkers, it is not necessary the full hand maintains a strong let-down reflex and to tether the yak cows. They go to the cows, any- is a rapid way of evacuating milk from the udder where on the campsite with bucket in hand and calf without permanent stretching of the teat canal, the in tow, and tie up the forelimbs of the cows with a small teats of the yak cows only allow the teats to short rope and milk.10 be slid between thumb and forefinger.7 Dirt, such as dung, hair and flakes of skin, may The milker usually starts to milk with the fore- easily drop into the milk as a result of the motion quarters and finishes milking with the hindquarters of the udder during milking.23 To prevent dirt fall- at about 80 squeezes a minute.10 For a skilful ing into the milk, the herders often clean the coats milker, two cows can be alternately milked over the of the yak cows and frequently clip the long hair of same time period. She milks the first cow for about

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Figure 3 Milking in progress. (courtesy of Miller, 1998)

6 minutes (with two stimulations by the calf, one at minutes; boiled raw milk is added in the proportion the beginning and one in the middle of milking), required and boiling continues for a further few then tethers the cow to the rope and milks the sec- minutes.11 This is similar to Mongolian milk tea, a ond cow with the same procedure as the first cow. mixture of tea and Mongolia cattle milk.27 After finishing the first milking on the second cow, Some people may add a little salt. Sugar is never she milks the first cow for the second time, lasting added, and the milk itself already has a sweetish around 3 minutes (with two stimulations again by taste. Tibetans often add some roasted oat or barley the calf at the beginning and in the middle of milk- flour, or a mixture of the two, to the brew, making ing). Then she milks the second cow for the second it both a food (Zanba) and a drink for themselves time, a third cow for the first time, and so on.25 and their guests.28 This is a staple part of the diet of When all quarters have been emptied, the milker the herders and their families.29 filters the dirt from the milk through a piece of cloth In the warm season, when there is plenty of milk and pours the milk into a large container (a pot or available, or when given to guests, the brew will bucket) in which all the milk extracted from differ- contain 20% milk or even more; the colour of the ent cows on the same morning, noon or night are drink is yellow. Herdsmen and their families more mixed together. After being milked, the cows and often drink a light tea with only 5% milk added and their calves are released for grazing around the tent.24 the colour then is milky white with a little yellow.11 As the yak cows are very sensitive to new smells Normally, whole milk is used in the tea, but skim and voices, the milkers are not changed frequently milk is also used so as to increase the amount of and they have to keep quiet during milking.7 butter that can be produced from the available milk supply.7 MILK PROCESSING Raw butter Fresh milk is processed immediately by house- There are two main ways of making yak butter prac- holds into a variety of indigenous products capable tised by the local herdsmen in China: either churn- of being stored for long time in the vast ranges of ing the butter in a wooden bucket or squeezing it in the Qinghai-Tibetan Plateau. a bag made of hide.7 Milk separators are coming into use in some areas, but are not popular.25 Milk tea Making butter by churning involves allowing Boiled raw milk, as a drink, is used mainly for the the milk to stand for a day to ferment. The milk is beverage known as ‘milk tea’—a mixture of tea then heated to about 20°C. The warm milk is and yak milk—drunk at all times of the year.26 The poured into a churn set aside for the purpose and milk tea is brewed from tea leaves (cut from a tea varying in size from up to 80 cm high and 60 cm in brick) that are added to water and boiled for a few diameter. A stick for stirring is held in the centre of

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Figure 4 Butter making in a churn. (courtesy of Cai and Wiener, 1995)

the churn by the lid (see Figure 4). The herdsman processes. Sour cream is made by adding some rotates the stick until the fat solidifies and it is dif- sour milk in raw butter and fermenting it for half a ficult to churn further. The churning takes between day.30 Pure ghee is made by heating the raw butter 1 and 4 hours depending on the size of the churn to remove protein and water.10 used and the quantity of milk. The herdsman then Raw butter is the principal product from yak removes, by hand, the lumps of milk fat floating on milk and one of the staple foods of the local people. the surface and washes them in water. Next, the Fresh raw butter contains 12–15% water and 1% water is squeezed out and the butter is formed into protein and the rest is fat. and the old butter (made cylindrical or cube-shaped blocks using a small in the previous year) contains about 3% water.7 plank of wood. Finally, the raw butter is wrapped Raw butter production is normally regarded as the with broad tree leaves or clean paper and stored in yardstick to measure the quality of yak milk, and a bag of calf-hide, a yak rumen or a wooden con- herdsmen pay great attention to it.31 tainer. Each block weighs approximately 50 kg. Raw butter is used for a number of foods. It is The butter will keep usable in this way for one or added to milk tea and consumed salted or unsalted two years without going mouldy, but not usually according to the area. When milk is not available, for longer.7 butter is used in tea in some areas in place of raw Squeezing is an alternative way to make butter milk. Some herdsmen, however, drink butter-tea by hand. The milk is first heated, as before, and from choice. Another use is to mix melted butter poured into the bag made of calf- or goat-hide. The with roasted flour in equal quantities to make herdsman blows into the bag to expand it and Zanba. The mixture is then kneaded and stored closes the opening. The bag is then shaken until the until used. When required, this dough is melted fat solidifies into globules, when the contents of the into salted or sugared water and eaten in that way, bag are poured into another container. The rest of or further mixed with seeds, such as peanut, ses- the procedure is similar to that already described.7 ame, walnut, soybean or mixed with Chinese dates. Edible pigments and antiseptics can be added into These ingredients add flavour and make the food a raw butter to make it more colourful and keep it favourite among Tibetan people for welcoming much longer.11 their guests.28 Raw butter can be made into sour cream and Raw butter is also used for many purposes other pure ghee (butter oil) depending on the different than food, such as for tanning and for polishing fur

Vol 56, No 2 May 2003 http://www.paper.edu.cn coats. It is used as a fuel in domestic lamps by separated with a cloth once it is sufficiently firm. herdsman and in holy lamps by Lamas, but also on The curd is then placed in moulds and pressed with family altars. Butter is also used by women on their stone slabs. The block is turned at 15 min, 30 min, skin, as hair grease and as a lubricant to assist in 1 h, 1.5 h and 5 h and after overnight pressing. hand milking. When mixed with different colour- Cheese blocks are brined (22%) for 48 h or ing materials, butter is used to make moulded given a daily salt washing for 3 weeks. They are sculptures.32 then stored for curing at 10–15°C, i.e. at the ambi- ent temperature of the Plateau. The cheese devel- Milk residue ops a good flavour after 5 months, and 6 to 8% of On the Plateau, ‘milk residue’ (as it is called by the the cheese weight is lost. The chemical composi- herdsmen) or dried cheese is normally made from tion of 3-month-old yak cheese is around 68.2% of skimmed milk but occasionally from whole milk. total solids, 49.4% of butter-fat on a dry matter Whichever milk is used, it is heated to 50–60°C basis and 1.37% salt.11 and sour milk added to make the liquid curd. The Cheese is usually served as a snack with the milk mixture is poured into a wicker basket or gauze bag tea28 cooked in dishes or used in sandwiches.35 to allow the whey to run off. The curds are the fresh Herdsmen who graze the animals on the pasture ‘milk residues’, and then they are spread on a cloth often keep cheese as a snack. to be dried.13 Half-dried residue contains about 20–30%, or sometimes 40%, water. Dried residue Sour milk contains little water and can be stored as long as Sour milk (yoghurt) is a favourite among herdsmen 1 year at −4°C.33 The dried milk residue from and their families throughout the year but espe- skimmed milk is white and hard, that from whole cially in the warm season when milk is being pro- milk yellow and brittle. The protein content in the duced. Freshly boiled milk is poured into a pail and former is around 75%34 and the latter 55%.11 when the temperature has fallen to 50°C a little Fresh milk residue is served as a snack with milk sour milk is added and mixed until the temperature tea and is also used in other ways such as fried or has dropped to 40°C. The pail is then covered and eaten with added salt and sugar.28 Half-dried resi- wrapped in wool to keep it warm. Five or six hours due is usually kept as a snack for herdsmen who are later in the warm season, and longer in winter, the out tending the animals on pasture. Dried residue is milk will have soured.13 This product can keep its also mixed with butter to make Zanba. quality for about 3 days in summer and 6 days in winter under the normal conditions of the Qinghai- Cheese Tibetan Plateau, but it can be stored for up to Cheesemaking is not practised extensively on the 14 days at −18°C to −21°C.36 Generally, the fat and Plateau because the quantities of milk available are lactose contents in the product are around 6.5% often small and local herders prefer other products and 7%, respectively.37 to cheese in their diets; only a few Tibetan house- The sour milk can be made from either whole or holds possess the techniques of cheesemaking as skimmed milk—the former having more colour described by Lai et al.35 and taste.11 Continuous fermentation of yoghurt Before making cheese, raw milk is standardized can be stimulated by introducing a culture mix of to around 3.5% fat through cream separation. The Streptococcus thermophillus and Lactobacillus excess cream is churned into butter. The cheese bulgaricus.38 A ratio of 2 : 1 between L. bulgaricus milk is then ‘in-can’ pasteurized at 65°C for 5 min and S. thermophillus can result in good and fast- by immersing the can in boiling water. Milk is then fermenting sour yak milk.37 The sour milk is drunk cooled to 30°C by dipping the can in a trough of alone or sometimes mixed with Zanba. Sugar is cool water. The cheese milk is transferred into a usually added to the sour milk for the guest.12 copper kettle and put on a traditional fire. Then sour milk (starter) is added and stirred for 1 min Milk skin before the milk is allowed to set at 20–30°C; the Milk skin (as it is called by the herdsmen) is the kettle is then covered for about 6 h. special milk product of the yak-raising areas of the As soon as the gel is sufficiently firm, it is cut Plateau; it is usually produced by Muslim and into small cubes of 0.5–1.0 cm that are left undis- Mongolian people.39 Fresh raw milk is poured into turbed for 25 min at 30°C, while the whey is a pot and heated to near boiling (around 85°C), the expelled. Then the curd–whey mixture is heated to heat is slowed down and the milk is stirred with a about 53°C over an open fire, while being stirred ladle. When the dense foam appears, the pot is then for 30 min. Whey is drained off using a cloth, and removed and cooled down. After about 12 h, a the curd is washed several times with water of thick layer of milk skin (around 1 cm thick) is decreasing temperature, e.g. 30°C, 20°C and 10°C, found on the surface of the milk. The milk skin is successively, leaving the curd in contact with the removed from the pail with a knife and a chopstick, water for 10–20 min each time. The curd is and dried for 2–3 days.40 Rice or millet soup (1/3

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to 1/4) is sometimes also added to raw milk to get REFERENCES a low-fat milk skin.13 This product can be made from either whole or 1Lu Z L (1999) Yak resources in China. China Herbivores skimmed milk.39 The milk skin is usually served as 1 42–45. a snack with milk tea, but it is also cooked in dishes 2 Miller D J (1996) Conserving and managing yak genetic or put in sandwiches.12 diversity: an introduction. In Conservation and Manage- ment of Yak Genetic Diversity. Miller D J, Craig S R and Other products Rana G M, eds. Proceedings of a Workshop in ICIMOD, Milk cake is a product mainly of whole milk, October 29–31, 1996, Kathmandu, Nepal International Centre for Integrated Mountain Development (ICIMOD). although sometimes skimmed milk is used. It is 3Verdiev Z and Erin I (1981) Yak farming is milk and similar in production to ‘milk residue’, but is meat production. Molochnoe i Miasnoe Skotovodstvo 2 harder and looks like ‘cake’. 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