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 cal ves in Colorado beef herds was investigated as part of a prospective l ongitudinal observational study. A total of 2609 calves born in nine p articipating herds during the 1990 and 1991 calving seasons were monit ored for disease events and subsequently weighed at weaning as a measu re of performance. Morbidity outcomes of interest and their observed i ncidence rates were: general neonatal (to 45 days) morbidity, 2.6%; ne onatal diarrhea, 1.0%; neonatal respiratory disease, 1.0%; and motheri ng 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 ne onatal period resulted in a 15.9 kg reduction (P < 0.01) in calf weani ng weight. When morbidity was investigated as more specific disease co nditions, calves that were classified as mothering problems/weak calve s (i.e. calves that experienced maternal neglect, abandonment, or star vation, and weak calves) weighed 24.4 kg less (P < 0.01) at weaning th an did non-afflicted calves. Respiratory conditions and diarrhea durin g 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 occurr ence during the early life of the calf had a detrimental effect on wea ning weight.