Etiology and Prevention of Fatty Liver and Ketosis in Dairy Cattle

According to the most recent National Animal Health Monitoring System for dairy cattle (National Animal Health Monitoring System, 2008), leading causes of morbidity in dairy cattle are clinical mastitis, lameness, infertility, retained placenta, milk fever, reproductive problems, and displaced abomasum. Of cows removed from herds, about 53% leave for one or more of the above reasons. Additionally, the rate of mortality of cows in U.S. dairy herds is nearly 6%, with 43% of these related to periparturient health issues, and likely a large portion of those classified as “unknown” (25%) occurring as a result of complications from the above. Overall, 16.2% of the cows that are permanently removed from a dairy herd are removed before 50 days in milk (DIM). These cows represent losses before the most profitable period of lactation. The relationship of the above disorders to excess prepartal body condition score (BCS) has been documented by numerous researchers and extensively reviewed (Bewley and Schultz, 2008). Briefly, cows with excessive body condition at calving, or excessive weight loss after calving, demonstrate overall decreased reproductive performance and increased likelihood of dystocia, retained placenta, metritis, milk fever, cystic ovaries, lameness, and mastitis as well as metabolic disorders, fatty liver, and ketosis. An epidemiological study by Gillund et al. (2001) found 20% of cows in surveyed herds to experience ketosis, and cows with BCS > 3.5 at calving to be 2.5 times more likely to become ketotic. Cows that became ketotic lost more body weight (BW) during early lactation, and the likelihood of conceiving at first insemination was decreased by 37%. Thus, the relationship of BCS, fatty liver, and ketosis has enormous economic impact on health and reproductive performance of dairy cows.