Strategies For Controlling Contagious Mastitis

Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

Taking Mastitis Control to the Next Level

Pamela L. Ruegg, DVM, MPVM University of Wisconsin Madison, Wisconsin, USA

Introduction

The dairy industry has been extremely successful in producing safe and nutritious food and for the most part, our industry has been spared the controversy associated with many other animal associated food products. Although there are naysayers, dairy products are widely perceived as nutritious and necessary in the US diet, and for the last 30 years, per capita consumption of most dairy products has remained stable or slightly increased (USDA, 2009) (Figure 1).

Figure 1. Per Capita Commercial Disappearance of Dairy Products, 650 1975-2007 USDA ERS Data 200

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f 160 r

r 550 o P a

s y e 140 d b Y

500 n r r u a e 120 o e s P

P 450 Y e

n r r t 100 o e o n s p r g

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v o a i r 350 s C u r e 60 q e P

t 300 r c 40 a e u F p d

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Milkfat Equivalent Butter cheese ice cream other dairy The highly nutritious nature of milk creates conditions that are ideally suited for growth of pathogenic organisms. While consumption of raw milk remains a well-identified risk factor for disease, pasteurization has been highly effective in ensuring the safety of dairy products (Headrick et al., 1998). The generally favorable reputation of dairy products is due in part to many years of government regulation that has resulted in only a few incidents of diseases associated with consumption of dairy products. Even though dairy products are consumed on a daily basis, milk, ice cream and cheese have been identified as the vehicle for less than 1.5% of all foodborne disease outbreaks investigated by the Centers for Disease Control (Bean et al., 1996). The quality & safety of dairy products do vary among countries and this was well illustrated by the widespread melamine contamination of dairy products in China (CDC, 2008). Government regulations are meant to protect consumers from foodborne diseases but they are not meant to protect producers from changing societal expectations. The continued prosperity of the US dairy industry is dependent on maintaining the overall reputation of our product and continuing to meet a variety of evolving consumer expectations. The purpose of this paper is to discuss the changing definition of milk quality and review some key practices that characterize producers that are already achieving the next level of excellence. Evolving Societal Indicators of Quality Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

According to the Merriam-Webster dictionary, the word “quality” has a number of definitions including: “a distinguishing characteristic” or “a degree of excellence.” Quality assurance is defined as “a program for the systematic monitoring and evaluation of the various aspects of a project ….to ensure that standards of quality are being met.” Both definitions infer that there is widespread societal agreement about standards. For many years, standards for milk quality were fairly consistent, defined solely for product characteristics and were enforced by state regulatory officials. In most regions the primary quality standards included somatic cell count (SCC), total bacterial count and zero tolerance for antibiotic residues violations (Anonymous, 2009b). These regulatory programs have been considered successful. In fiscal year 2007, only 0.028% of bulk milk tank samples were positive for antibiotic residues (Anonymous, 2009a) and since 1995, the average SCC has decreased about 3% each year (Norman, et al., 2009). In spite of this progress the dairy industry cannot disregard changing consumer expectations. Today, consumers expect that food is not only 100% safe and cheap but also produced using practices that meet their expectations for animal care and environmental sustainability. A number of well-funded advocacy groups publicize and oppose issues such as genetic modification of crops and animals (clones), the presence of “hormones” in milk, care of animals (especially on larger farms), and environmental impact of animal production practices. A search of youtube.com (http://www.youtube.com/watch?v=cMNkDKySDdU; http://www.youtube.com/watch?v=EknmfiZ2Ya4; http://www.youtube.com/watch?v=0jpQr4CZ0iQ) reinforces that the internet age allows widely varying images about farming to be rapidly distributed. To maintain the reputation of dairy products it is vitally important that dairy producers recognize and respond to these trends by adopting practices that redefine the concept of quality.

Herd Level Indicators of Mastitis Control & Quality

Distinguishing characteristics of high quality milk are not difficult to define. In 2008, the average SCC of all DHIA herds was 262,000 cells/ml, 22% of all herd test days exceeded 400,000 cells/ml and as a population, smaller herds had higher SCC (Figure 2, from Norman et al., 2009). Somatic cell counts are the most recognized measure of milk quality and the highest performing herds should consistently sell milk and have 85% of the cows with <200,000 cells/ml.

100% Figure 2. Percent of Herd Test Days > 400,000 cells/ml by Herd Size

, 80% 0 0 4 l

m 60% a / h s l t l r e e c

t 40% a e r G 20% % 0% <50 50 100 150 200 300 500 1000 2000 >3000 Number of Cows per Herd

Almost all US farms easily achieve the US regulatory goals for bacteriological quality of bulk milk (standard plate count (SPC) <100,000 cfu/ml) and most processors enforce much more Presented at the NMC Regional Meeting, Harrisburg PA, May 2009 rigorous standards that measure more than just SPC. In a study that monitored SPC of all dairy farms (n = 235) in Prince Edward Island (PEI) Canada every 2 weeks for 1 year, 50% of the tests were less than 4,900 cfu/ml for SPC, 12,000 cfu/ml for preliminary incubated count (PIC), 12 cfu/ml for laboratory pasteurized count (LPC) and 5 cfu/ml for coliform count (CC) (Elmonslemany and Keefe, 2008). The PEI farms were small farms that had traditional housing & milking equipment. A Wisconsin study evaluated bulk milk quality of large dairy farms (Pantoja., Ruegg & Reinemann, unpublished). Most of the 16 large farms enrolled in that study, shipped tankers of milk at least daily and bacteriological quality was evaluated for most of the milk shipments for 1 year. Of >7000 tests each, 50% of SPC were <3,000 cfu/ml; 50% of LPC were < 120 cfu/ml and 50 % of coliform counts were <50 cfu/ml. The highest performing herds were characterized by the least variation in counts. For example, “Highest Performer Herd A’ experienced only 5% of SPC > 8,000, 7% of CC> 160 and 2% of LPC >310 cfu/ml whereas the values that exceeded the same thresholds for “Lowest Performer Herd B” were 72% of SPC, 62% of CC and 24% of LPC. Goals for high performing herds are set by processors and are not uniform across the industry but SPC of <10,000 cfu/ml and LPC of < 200 cfu/ml are reasonable goals for high performing herds.

Defining goals for milk quality is easier than defining goals for clinical mastitis. The clinical case rate is strongly influenced by case definition, detection intensity, age of the herd and herd policies regarding how to deal with recurrent cases. Most cases of clinical mastitis are mild to moderate in severity and are treated on the farm without any veterinary involvement. Severity scoring systems have been developed (Wenz et al., 2001). Use of a 3-point scale based on clinical symptoms is practical, easily understood, simply recorded and can be an important way to assess detection intensity. When using a 3-point scale, most herds should expect that severity score 3 cases will not exceed about 20% of total clinical cases (Table 1). Herds that have bulk tank SCC <250,000 cells/ml should expect to detect about 4-6 cases of clinical mastitis per 100 cows per month and only about 5 to 20% of the cases should be severity score 3.

Table 1. Expected severity scores for clinical mastitis Severit Coliform y Score Clinical Symptom Study 11 Study 22 Study 33 cases only4 N = 686 N = 169 N = 212 N = 144 1 Abnormal milk only 75% 57% 52% 48% 2 Ab.milk & abnormal udder 20% 20% 41% 31% 3 Ab.milk, Ab. Udder & sick 5% 23% 7% 22% cow 1Nash et al., 2002; 2Oliveira & Ruegg, 2008; 3Rodrigues et al., 2008; 4Wenz et al., 2001 (different but equivalent scoring system used)

Traditional milk quality standards have not taken into account changing societal values about animal well-being and environmental stewardship. Herds that achieve the next level of milk quality will likely have demonstrated that they value individual animal well being and are aware of societal concerns about sustaining rural environments. Like previous quality indicators (such as SCC and SPC) if the dairy industry doesn’t self-regulate, it is likely that governmental regulations will be imposed. Regulations about environmental impact are already in place in many regions and regulations about animal management are increasingly debated by state and Presented at the NMC Regional Meeting, Harrisburg PA, May 2009 federal legislative bodies. While most dairy farmers care deeply about these issues, the highest performing dairy farmers are already creating ways to measure and demonstrate that they are achieving high levels of animal care and environmental stewardship.

Characteristics of High Performing Herds

There are thousands of US dairy herds that produce high quality milk and achieve excellence in mastitis control. The best of these herds are represented each year by the finalists for the National Dairy Quality Awards (http://www.nmconline.org/ndqa/ndqawin2008.htm). These herds are nominated because of their motivation and success in producing high quality milk. Brief initial nominations are screened and about 40-50 finalists are asked to submit detailed herd information. Since 2005, final applications have been received for about 120 herds. Finalists ranged in size from 20 to 3600 cows and have been located in the East (19%), Midwest (71%) and West (10%). It is interesting to compare the performance of these elite herds to their peers (Table 2). These high performing herds have greater production and lower bulk tank quality indicators as compared to general US dairy herds (represented by the NAHMS data) or WI herds that participated in a milk quality program (“Milk Money”). The NDQA finalists did not achieve their success by culling or using management techniques such as quarter milkers (13% of finalists used on >5% of cows) or drying off quarters (10% of the finalists had >10% of cows with light quarters). Finalists reported greater usage of recommended procedures that are known to result in the production of higher quality milk.

Table 2. Comparison of NDQA Finalists and representative herds from other studies NDQA Finalists WI Milk Money Herdsb All >200 NAHMS SCC SCC > Finalists cows Dairy 2007a <250,000 400,000 Number of herds 120 15 2,194 36 61 Number cows 161 701 Not reported 214 167 RHA milk – lbs 23,000 25,000 20,000 22,000 21,000 (kg) (10,500) (11,400) (9,100) (10,200) (9,600) Yearly SCC (cells/ml) 80,000 88,000 31%<200,000c 198,000 565,000 Highest monthly SCC in year 109,000 111,000 Not reported Yearly SPC (cfu/ml) 2,400 2,100 5,900 19,000 Highest monthly SPC in year 7,000 6,400 Not reported Annual clinical Rate (%) 11% 11% 17% 6% per 10% per month month Annual Cull Rated (%) 22% 22% 30% 32% 52% Have written milking routine 46% 55% Not reported 17% 17% Milkers always wear gloves 78% 91% 55% 86% 55% Use DHIA records 73% 80% 46% Not reported Complete milking routinee 74% 83% 81% 68% Perform bulk tank culture 45% 88% 34% 54% 52% Culture individual cows 87% 82% 43% Not reported aUSDA 2008b; bfrom Rodrigues et al., 2005, cNAHMS studies generally report categorical data; dincludes dead cows, eincludes forestrip, predip, dry and attach without regard to order of procedures. Reaching the Next Level of Quality Performance Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

It is increasingly evident that mastitis control can’t be separated from other key management issues. Problems with housing, biosecurity and animal health management are often associated with increased mastitis problems. Many experienced consultants believe that farms that pay attention to details and care about the cows generally have less mastitis as compared to herds that are less animal oriented. Societal changes dictate that the definition of “quality” will evolve. Farms that reach the next level of performance will likely demonstrate excellence in at least two key areas:

High performing farms value their cows. Consumers are unfamiliar with animal production practices and many believe that farmers (especially farmers with large farms) care more maximizing profits than maximizing animal well being. Advocacy groups focus on publicizing certain management practices that seem to diminish animal well-being. Management practices that are of special concern include: housing (especially lack of access to outdoors), methods that are perceived to increase milk production and reduce longevity (especially rBST), mastitis, lameness, mutilations (especially tail docking), management of downer cows and separation of calves (Anonymous, 2009). Many dairy farmers have the same concerns and provide environments that exceed the expectations of consumers. Farms that reach the highest level of quality performance are aware of these issues and prioritize individual animal care over other issues. Three key practices of farmers that value cows are: 1. Minimizing animal mortality. Death of adult dairy cows is the most dramatic indication of animal health management failure and should occur rarely. Overall, adult cow mortality has increased from 3.8% in 1996 to 5.7% in 2007 (USDA, 2008a). Important risk factors for death include: mastitis, respiratory disease, lameness, and calving problems (McConnel et al., 2008, USDA, 2007a). High performance farms should routinely investigate and record cow mortalities and few deaths should be attributable to mastitis. If 15% of clinical mastitis cases are grade 3 (severe) and 15% of those result in death (Erskine et al, 2002) then only about 2% of clinical mastitis cases per year should result in death. Herds that exceed these guidelines should review detection and treatment protocols. A diagnosis should always be pursued for cows that die of unknown causes. Herds that have overall mortality rates that exceed 4% should actively implement changes in animal management, disease detection & treatment. 2. Minimizing injuries and lameness. The image of disabled animals is disturbing to both dairy farmers and consumers. According to USDA (2007a& 2007b), the percentage of lame cows on U.S. dairy farms increased from 11% (1996) to 14% (2007) and the percentage of dead cows attributed to lameness increased from 13% (1996) to 20% (2007). The design of housing areas and the frequency of hoof trimming are two important risk factors that impact the frequency of lameness (Espejo and Endres, 2007). Herds that reach the next level of quality performance will should routinely score locomotion (Sprecher et al., 1997) and hocks.(Weary and Taszkun, 2000) and adapt housing, feeding and herd management to minimize injuries and lameness. 3. Minimizing the use of management practices that don’t improve animal care and that can create potentially damaging images for our industry. Tail docking is one example of a common management practice that should be reconsidered. While the dairy industry has enjoyed a generally favorable public image, tail docking is probably one of the most Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

controversial management issues. Advocates for tail docking cite perceived improvements in cow cleanliness, mastitis and worker convenience as reasons to consider tail docking, however many animal welfare advocates consider tail docking to be unnecessary mutilation. Several European countries and some Australian states have prohibited tail docking and both the Canadian and American Veterinary Medical Associations have policy statements which oppose the practice of tail docking for routine management of dairy cattle. Reviews of the research about tail docking have been published (Ruegg, 2004; Stull et al., 2002). Research has shown that the process of tail docking isn’t especially stressful for cows but no benefits in animal cleanliness or health have been documented. Several studies have demonstrated that tail docking does not reduce mastitis (Schreiner and Ruegg, 2003, Tucker et al., 2001) and no benefits to cattle welfare have been associated with tail docking. Herds that reach the next level of milk quality will respond to societal concerns about the practice and use alternatives to tail docking (such as trimming switches). High performing farms, invest in their workers. Dairy farm management can be described as the act of directing and controlling a dairy operation and its employees towards accomplishing a common goal beyond the scope of an individual effort (Hohmann, 2008). Reaching farm goals is dependent on a team effort and the ability to successfully motivate farm employees. Today’s dairy managers increasingly rely upon others to milk their cows. In the absence of a clearly defined monitoring system, it is easy for managers to lose control of the milking process and they are often unaware of the true rate of clinical mastitis. Specialized milking personnel on larger dairies may have an incentive not to detect or report all cases and mild cases of clinical mastitis will not be detected when milking routines do not include forestripping. In a survey of Wisconsin dairy farmers (n = 140 responders), farmers were asked an open ended question that stated: “What is your greatest challenge in maintaining production of high quality milk?” The most common responses were related to employee management (mentioned by 26% of responders) followed by management of the environment of the cow (mentioned by 14% of responders) and maintaining consistency in the milking process (mentioned by 11% of responders) (Hohmann, 2008). On these farms (ranging in size from 20 to 200 cows) milking was performed by twice as many employees as compared to family members. Responders reported that they employed 4 full or part-time non-family members and 2 full or part-time family members to milk cows. Most (56%) responders did not provide employees with a written milking routine or have a written treatment protocol for clinical mastitis (55%). Twenty-five percent of producers never trained milking technicians and 43% only trained when workers were hired. Three key practices that will reduce mastitis and bring farms to the next level of quality performance are: 1. Train and equip your workers. Training and the use of standardized farm practices is associated with farm performance. One study reported that continual training of employees was associated with increased return on equity (Stup, et al., 2006). Data from Wisconsin freestall operations (n = 101) indicate that training of milking technicians has an impact on milking speed and is associated with reduced monthly rates of clinical mastitis (Table 3. Rodrigues et al., 2005). A similar relationship was found for farms that provided written milking routines for workers (Table 3). Table 3. Influence of Milking Routine on Performance for Wisconsin Freestall Farms (from Rodrigues et al, 2005). Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

Cows milk per Hour per Milking Monthly Rate of Clinical Variable Technician Mastitis Written Milking Yes 47 5.0% Routine No 36 7.1% Training Frequency Never 34 9.6% At Hiring 42 4.8% Frequently 49 5.8%

2. Ask for help when needed. Dairy farming is a complex process that involves interactions between animals, nature and people. Like other research-based businesses, the growth in knowledge about dairy management practices is extraordinary. Dairy farmers acquire information about animal health from a variety of sources including veterinarians, nutritionists, other producers, dairy magazines and consultants. The use of consultants can help farmers sort through complex issues and make informed decisions. Consultants visit multiple farms, see results from wide variety of management decisions and bring an outside perspective to farm decisions. An increasing use of consultants is the formation of on-farm management teams. On-farm management teams can be formed to troubleshoot specific farm issues or to meet periodically and review farm performance. A properly formed management team can aid the farmer by bringing expertise on narrow issues. Management teams also allow for dialogue between consultants (such as veterinarians and dairy plant personnel) that have shared interest in specific outcomes. The management team format is extremely successful in problem solving mastitis problems. Farms that participated in a team-based milk quality program in Wisconsin, increased adoption of best management practices and improved mastitis control (Rodrigues and Ruegg, 2005). After 4 months of participation, the bulk tank SCC of these herds dropped by 78,000 cells/ml, the standard plate count dropped by 10,000 cfu/ml and the monthly rate of clinical mastitis treatments dropped from 7% to 5% of cows. 3. Improve communication with workers. Many farms employ Hispanic farm workers and few farmers are fluent in Spanish. While the statistics are not available to support it, it is possible that more US cows are milked by Spanish speaking worker than are milked by English speakers. This trend is relatively new and farm managers have not had a chance to learn Spanish. Of WI producers responding to a survey, 53% of farms had employees that speak Spanish as their first language but only 1.5% indicated that they felt that they spoke Spanish well. About 60% of farms that had employees that speak Spanish as their first language used translators to communicate (Hohmann, 2008). A recent survey of farm workers (n = 309) located on 34 dairies in Wisconsin indicated that most were of Mexican origin, originated in the same region and many were related to each other (Dyk, 2007). Only 20% of Hispanic workers considered themselves “good” or “fluent” in English. The educational level of the Hispanic employees was quite different than that of Presented at the NMC Regional Meeting, Harrisburg PA, May 2009

US origin workers on the same farms. Of the Hispanic workers, 6% indicated that they had no education, 43% completed or started primary school, 17% completed or started high school and only 12% had some post high school training. Most responding workers desired training even though 35% indicated that the farm that they worked had not provided it. This oversight becomes especially important because 30% of the employees indicated that they had had a work related injury. Dairy farm workers that milk cows maybe the only employees that actually touch & observe most cows and they may be the only people that have the opportunity to detect mastitis. They are essentially the first responders. High performing farms will hire translators, learn about their workers culture and schedule frequent meetings with farm personnel. Most importantly, high performing farmers will show the workers that they care. Summary

Milk is a special product that is extremely complex to produce. Dairy farmer have to be aware of the needs of cows, the needs of their employees and the changing values of consumers. Ensuring milk quality requires minimizing mastitis and other limitations to animal health and productivity. Farmers that reach the highest levels of performance have implemented systems that allow them to produce exceptionally high quality milk, value their cows and train and equip their workers.

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