Postweaning Behavior and Growth Performance of Early and Conventionally Weaned Beef Calves

Forty beef cow-calf pairs (rotational grazing system) were used in each of 2 yr to evaluate postweaning stress, behavior, and growth of calves that varied in weaning age and in immediate postweaning proximity to their dams. The cow-calf pairs were blocked by cow and calf BW, age, breed, and calf sex, and allotted to one of four treatments (n = 10): early weaned (X¯ = 4 mo) with dams removed from (EWR) or stayed on (EWS) the same farm and conventionally weaned (X¯ = 7 mo) with dams removed from (CWR) or stayed on (CWS) the farm. An additional group of calves (n = 20) were weaned (X¯ = 7 mo) and immediately relocated to a feedlot. Behavioral observations (feeding/grazing, movement, resting, socializing, vocalizing, agnonistic activities) were made beginning at 1500 h on the weaning day and continued for 6 d. Individual and group observations were recorded at sunrise and sunset (for 1-h intervals) by two observers; group observations were recorded at 1200 h by one observer. The early weaned (EW) calves had greater frequency of stress vocalization (P<0.01) and pacing (P<0.02) than calves weaned at 7 mo. Calves of either age that remained within visual and auditory proximity of their dams (EWS and CWS) had greater frequency of stress vocalizations (P<0.01) than calves of either age isolated from their dams (EWR and CWR). However, these differences were reduced (P<0.01) after only 3 d. Calves of either age that were isolated from their dams continued to demonstrate distress behavior at the end of the 6-d observation period. Early weaned calves had a lesser total BW gain (P<0.05) from birth to relocation to the feedlot because of less ADG postweaning (4 to 7 mo; P<0.05) than CW calves. Calves weaned and relocated immediately to the feedlot had a lesser postweaning 28-d ADG (P<0.05) than calves on pasture with limited concentrate feeding postweaning. White blood cell counts (WBC) and neutrophil:lymphocyte ratios (N:L) were not significantly different among treatments. These data indicate that weaning behavioral stress is minimized when calves are weaned at conventional (7 mo) weaning ages. Regardless of weaning age, postweaning stress (behavioral but not physiological) levels were reduced if dams remained within visual and auditory proximity after 3 d.