Culling – killing animals in a herd who are no longer productive – is a common farming practice. In the dairy industry, cows are often culled when they can no longer produce sufficient quantities of milk. This paper, published in the Journal of Dairy Science, the official journal of the American Dairy Science Association, investigated causes for low milk production and subsequent culling. While the primary aim of the paper is to provide farmers with information that will help them identify and prevent production-related diseases, the authors express hope that their findings can also be used to improve the health and welfare of dairy cattle.

The study authors examined 1,461 cows slaughtered over a period of three days at a commercial abattoir in the Great Lakes region of the United States. Their team of researchers looked for abscesses in the liver, rumen, and lungs, as well as bruising on the outside of the body. Results showed that 32% of cattle had liver abscesses, over half of which were classified as severe, and 35% of cattle had some kind of abnormality in the tissue lining the rumen.

Both conditions are indicative of subacute ruminal acidosis, a metabolic disease often brought on by two common large-scale farming practices: 1) rapidly changing a cow’s diet during different stages of production, and 2) feeding cows high-energy diets to increase milk production. The authors note that antimicrobial feed additives for correcting the disease are currently available for cows raised for meat, but not dairy. They also state that the prevalence of liver abscesses in their study was 570% more than that identified by the National Beef Quality Audit. However, they point out that the animal health community does not currently perceive of liver abscesses as a prevalent problem in dairy cattle.

Results from lung examinations showed that 33.8% of cattle had pulmonary lesions associated with bovine respiratory disease (BRDC), a condition normally seen in younger cattle due to weaning, transportation, and close physical proximity to other cattle. While not a production-related disease, the authors also found that bruising was present on 54.1% of carcasses. They speculate that the high incidence of bruising may be the result of mass transportation methods. In double-decker aluminum “cattle pots,” or trailers, cows often cannot move without “striking their hips and backs.” The authors recommend investigating how to improve the design of these high-capacity trailers to limit injuries.

In conclusion, the authors contend that pulmonary lesions, which are indicative of BRDC, and ruminal acidosis appear to be prevalent conditions among dairy cattle. They recommend further investigation to validate their findings as well as to explore intervention strategies. Advocates should note that the medical conditions the authors identified are associated with common factory farming practices involving the feeding, housing, and transportation of cows. Advocates could also compare this data, the result of from academic research, to claims made by industry groups about the prevalence of disease among dairy cattle.