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Western Section, American Society of Animal Science
Vol. 56
D. G.Landblom1, H. H.Patterson2, P. Johnson2, R. Gates2 and S. Paisley3
1North Dakota State University - Dickinson Research Extension Center, Dickinson, ND 58601
2South Dakota State University - West River Agricultural Center, Rapid City, SD 57702
3University of Wyoming - Animal Science Department, Laramie, WY 82071
Weaning calves early from spring calving cows can have multiple impacts on beef production systems. The objective of this three-state study was to evaluate the effects of mid-August (AW) versus early-November weaning (NW) on cow and calf production traits and forage utilization. Three hundred-seventeen cow-calf pairs from the NDSU-Dickinson Research Extension Center (DREC; n=88), SDSU-Antelope Research Station (ANT; n=136) and the University of Wyoming Beef Unit (UW; n=93) were stratified by BW and body condition score (BCS) and assigned to either AW (calves weaned at approx. 140 d of age) or NW (calves weaned at approx. 215 d of age). Cows grazed native range between the two weaning dates. At AW date, a subset of cows from each treatment at DREC were randomly assigned to six 20-ha. pastures (three pastures/treatment) to measure biomass disappearance between AW and NW dates. Steer calves at ANT and DREC were weaned and backgrounded 7.3 wk and finished in a commercial feed yard. Steers at UW were backgrounded 42 d and finished on site. Treatment by location interactions were detected for cow BW change, BCS change, calf ADG, and gain:feed. At each location, AW cows lost less weight (P<0.01) between weaning dates than NW cows. Similarly, cow BCS change was improved (P<0.01) for AW vs. NW at DREC (0.39 and -1.20), ANT (0.34 and -0.02), and UW (-0.05 and -0.78). Forage biomass disappearance, between weaning dates, was reduced by 27.7% (P=0.15) when calves were AW. AW steers at DREC had higher (P<0.01) ADG during backgrounding than NW, and AW steers at DREC and ANT were more efficient (P<.01) during backgrounding. During finishing, AW steers grew slower (P<.01), were less efficient (P<.01) at ANT, and overall were 31 days younger, but required 61 more days on feed to reach harvest endpoint. Weaning spring-born calves at 140 d compared to 215 d reduced forage utilization, improved cow BCS change, and resulted in similar calf performance.
Key Words: Early Weaning, Cow Performance, Forage Disappearance
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