Postpartum body condition score and results from the first test day milk as predictors of disease, fertility, yield, and culling in commercial dairy herds

The study used field data from a regular herd health service to investigate the relationships between body condition scores or first test day milk dat a and disease incidence, milk yield, fertility, and culling. Path model ana lysis with adjustment for time at risk was applied to delineate the time se quence of events. Milk fever occurred more often in fat cows, and endometri tis occurred between calving and 20 d of lactation more often in thin cows. Fat cows were less likely to conceive at first service than were cows in n ormal condition. Fat body condition postpartum, higher first test day milk yield, and a fat to protein ratio of >1.5 increased body condition loss. Fa t or thin condition or condition loss was not related to other lactation di seases, fertility parameters, milk yield, or culling. First test day milk y ield was 1.3 kg higher after milk fever and was 7.1 kg lower after displace d abomasum. Higher first test day milk yield directly increased the risk of ovarian cyst and lameness, increased 100-d milk yield, and reduced the ris k of culling and indirectly decreased reproductive performance. Cows with a fat to protein ratio of >1.5 had higher risks for ketosis, displaced aboma sum, ovarian cyst, lameness, and mastitis. Those cows produced more milk bu t showed poor reproductive performance. Given this type of herd health data , we concluded that the first test day milk yield and the fat to protein ra tio were more reliable indicators of disease, fertility, and milk yield tha n was body condition score or loss of body condition score.