The effect of calf age at weaning on cow and calf performance and feed utilization by cow-calf pairs11A contribution of the University of Nebraska Agricultural Research Division, supported in part by funds provided through the Hatch Act and the Dr. Kenneth and Caroline McDonald Eng Foundation

The effect of calf weaning age on cow and calf performance and feed utilization was investigated over 2yr. Multiparous, crossbred, lactating beef cows (n=156) with summer-born calves were blocked by prebreeding BW, stratified by calf age, and assigned randomly to 1 of 4 treatments within strata. The experiment was a randomized complete block design with a 2×2 factorial arrangement of treatments with 3 replications (pens) per treatment per year (total n=24). Factors were (1) location—Agricultural Research and Development Center (ARDC) or Panhandle Research and Extension Center (PHREC)—and (2) calf weaning age—early weaned (EW) at 91±18 d of age or conventionally weaned (CW) at 203±16 d of age. All cows and calves were fed a common diet from early to conventional weaning time within each year and location. Cows with weaned calves were limit fed (6.9kg of DM/cow daily), and EW calves were offered ad libitum access to feed (4.0kg of DM/calf per day). Nursing pairs were fed an equivalent amount of DM (10.8kg/ pair per day). Initial cow BW and BCS were similar (P≥0.26), but BW change from early to conventional weaning was 17kg greater (P≤0.01) for EW cows. Cow BCS and conception rates were not affected (P≥0.38) by weaning. Calf BW at conventional weaning was greater (P≥0.05) for CW than EW at ARDC but greater (P≥0.05) for EW than CW calves at PHREC. Calf ADG per unit of total feed energy intake was greater (P≥0.05) for nursing pairs at ARDC but not different between EW and CW at PHREC, indicating early weaning may have minimal effect on reducing feed energy requirements.