Milk yield persistency and its relationship with health problems in Holstein dairy cows supplemented with different levels of ruminally protected methionine and choline
Abstract. Forty Holstein dairy cows in their first and second lactation were used in a lactation study from 4-week prepartum through 14-week postpartum to investigate the potential effect of feeding different levels of ruminally protected methionine and choline on milk yield persistency of Holstein dairy cows. Cows were randomly assigned to receive one of the following treatments: 18 g/d of rumen-protected methionine (RPM), 60 g/d of rumenprotected choline (RPC), 18 g/d of RPM + 60 g/d of RPC, or neither supplement (control). The use of polynomial equations revealed that the polynomial coefficients of regression were closer (P<0.05) to zero for RPM+RPC-fed cows than for other cows. Therefore, RPM+RPC-fed cows had a more persistent (P<0.05) early-lactation milk yield than did other cows. Cows fed RPM+RPC had the lowest health problems compared with other groups. The treatments significantly affected actual milk yield (P<0.05), 4 % fat-corrected milk (FCM) (P<0.01) and energy-corrected milk (ECM) (P<0.01) across lactation weeks. The treatments significantly affected average dry matter intake (DMI) for the first 14 week postpartum (P<0.05). Also, treatments significantly affected lactose percentage of milk across lactation weeks (P<0.01). In general, it was expected that RPM+RPC-fed cows with greater persistency of lactation would be healthier because the incidence of metabolic and reproductive disorders and negative energy balance that originate from the physiological stress of high milk yield would be lower.