The effect of calf-hood pneumonia on heifer survival and subsequent performance

Bovine Respiratory Disease Complex (BRD) is a prevalent and economically important disease in growing cattle. The objectives of this research were to evaluate the effect of year and season of birth on BRD and other disease incidence during the first 6 months of life and to evaluate the effect of BRD and disease incidence at ≤6 months on survival and age at first calving. Additionally, we analyzed the effect of BRD and other disease on lactating dairy cow milk yield and body weight. Health events, cull and mortality records, and calving dates were obtained from Holstein heifer calves (n = 1590) born between January 2000 and April 2015 on the Pennsylvania State University (PSU) dairy herd. There were 1055 cattle included in the cow performance dataset, which yielded 708,162 daily milk yield observations and 560,059 daily body weight observations. Year of birth (P < 0.0001) and season of birth (P = 0.0003) were significant predictors for BRD incidence. Calves born in the fall were most likely to have a pneumonia treatment recorded. Cattle not treated for calf-hood pneumonia had 1.53 greater odds of surviving to 24 months than unhealthy herd-mates. Cattle not treated for any disease in the first 6 months had 1.53 greater odds of surviving to 24 months. There were no differences between healthy and diseased calves for age at first calving (P = 0.46). BRD incidence resulted in lower body weight in early first lactation, but otherwise had no significant effects on milk yield and body weight. There is a challenge to determine the true impact of BRD on future milk production potential because animals with severe BRD are more likely to die or be culled and never enter the milking string. The results, which showed heifers treated for pneumonia left the herd earlier and were significantly less likely to survive to 24 months, raise economic and animal welfare cost to the dairy industry.