THE INFLUENCE OF NEONATAL HEALTH ON WEANING WEIGHT OF COLORADO, USA BEEF-CALVES

The effect of morbidity during early life on the weaning weight of calves in Colorado beef herds was investigated as part of a prospective longitudinal observational study. A total of 2609 calves born in nine participating herds during the 1990 and 1991 calving seasons were monitored for disease events and subsequently weighed at weaning as a measure of performance. Morbidity outcomes of interest and their observed incidence rates were: general neonatal (to 45 days) morbidity, 2.6%; neonatal diarrhea, 1.0%; neonatal respiratory disease, 1.0%; and mothering problems/weak calves, 0.4%. Mean calf weaning weight was 244 +/- 46 kg. Weaning weight data were adjusted by multiple regression for the effects of the herd, year, age of the calf, age of the dam, calf sex, frame size of the dam, and twin birth. General morbidity during the neonatal period resulted in a 15.9 kg reduction (P < 0.01) in calf weaning weight. When morbidity was investigated as more specific disease conditions, calves that were classified as mothering problems/weak calves (i.e. calves that experienced maternal neglect, abandonment, or starvation, and weak calves) weighed 24.4 kg less (P < 0.01) at weaning than did non-afflicted calves. Respiratory conditions and diarrhea during the neonatal period resulted in 16.5 kg (P < 0.01) and 10.7 kg (P < 0.05) reductions in weaning weight, respectively. Thus, disease occurrence during the early life of the calf had a detrimental effect on weaning weight.