|Kehrli Jr, Marcus|
Submitted to: Proceedings of the California Animal Nutrition Conference
Publication Type: Proceedings
Publication Acceptance Date: May 1, 2014
Publication Date: May 9, 2014
Citation: Kehrli Jr, M.E. 2014. Immunological dysfunction in periparturient cows: Evidence, causes and ramifications. Proceedings of the California Animal Nutrition Conference, May 14-15, 2014, Fresno, California. p. 11-29. Technical Abstract: With a $35.7 billion Gross Domestic Value for milk produced in the U.S. during 2007, the dairy industry was the single largest component of the 2007 U.S. animal agriculture economic engine. The value of milk produced in 2007 represented 30.2% of the total value of animal agriculture production; this figure had grown from $21-23 billion/year a decade ago. The 2007 NAHMS Dairy Study reported that during 2006, 23.6% of cows were culled from operations, 26.3% and 23% were removed for reproductive and udder health problems respectively. In addition, 16.5% of cow mortalities were due to mastitis. Clearly, the economic value of controlling mastitis pathogens is immense. Most economic analyses of the cost of mastitis cite a 10% production loss as only one part of the overall cost of the disease. A majority (65 to 70%) of losses are associated with decreased milk yield resulting in lower production efficiency; the remaining costs are attributed to treatment. In addition to these direct losses, mastitis causes significant problems in milk quality control, dairy manufacturing practices, quality and yield of cheese, nutritional quality of milk, antibiotic residue problems in milk, meat and the environment, and genetic losses due to premature culling. These additional costs are very significant and are not always included in economic analyses of mastitis costs. Because of the need for a safe, economical and stable supply of food, those of us serving the livestock health industry must be prepared to provide the best quality advice and care in managing our Nation’s dairy herd. For dairy producers, the critical factor in providing a low somatic cell count milk supply is keeping cows free from mastitis. Mastitis is anything causing inflammation of the mammary gland, and infectious mastitis is caused by a plethora of microbial agents . Nearly half of the Nation's herd of dairy cows will experience at least one episode of mastitis during each lactation. Research has already resulted in genetic selection for cows with lower somatic cell counts by the incorporation of this trait into the A.I. sire summary ranking indices. This approach mainly serves to reduce the normal increase in mastitis incidence that occurs as milk production goes up. Coliforms and environmental streptococci are the most common etiologic agents isolated from clinically severe mastitis cases on well-managed dairy farms [2, 3]. Clinical trials and experimental studies have demonstrated repeatedly no benefits of antibiotic therapy in cattle with clinical or subclinical coliform mastitis [4-6]. Hence, the advent of the Escherichia coli J-5 and other endotoxin core mutant vaccines in veterinary medicine many years ago provided us a tool to reduce the incidence and severity of clinical coliform mastitis [7-10]. However, there remains an unmet veterinary medical need of new ways to prevent or treat mastitis caused by environmental pathogens. For several years, research at the USDA’s National Animal Disease Center in Ames, IA undertook a two-fold approach for improving the dairy cow’s resistance to mastitis - immunomodulation and genetic selection for superior immune systems. In this paper, we will focus on the evidence for immune suppression in periparturient dairy cows, how this sets the cow up for infectious diseases such as mastitis, metritis and retained placental membranes, and some of the early research on immune modulation of the transition dairy cow and how that impacted resistance to mastitis.