|Mayeux Jr, Herman|
Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2006
Publication Date: 9/1/2006
Citation: Grings, E.E., Phillips, W.A., Short, R.E., Mayeux Jr, H.S., Heitschmidt, R.K. 2006. Post-weaning performance of steers from varying calving and weaning strategies in montana. Professional Animal Scientist 22:386-391. Interpretive Summary: Calves from various calving seasons and weaning strategies may differ in weight at weaning in rangeland-based production systems. Profitability of steer calves from these systems may then be influenced by the length of time in the feedlot and carcass composition. We conducted a three-year study to evaluate the post-weaning performance of steers from rangeland-based cow-calf production systems in the Northern Great Plains. Steers calves born in late winter, early spring, or late spring were weaned at one of two ages and fed until harvest. Calving season and weaning age affected the weight of steers entering the feedlot. The number of days in the feedlot was affected primarily by age of steers at weaning. Carcass weight was impacted by calving season and weaning age. Delaying calving in the Northern Great Plains until late spring, while keeping weaning age at 190-days, resulted in decreased weight of steers going into the feedlot. Calving later in the calendar year without altering weaning time produces lighter calves at weaning that required greater number of days to harvest and have lighter carcasses with less marbling and lower quality grades. It may be desirable to develop altered feeding programs for steers from late spring calving systems in the Northern Great Plains that promote more rapid gains early in the growing period or make use of less expensive feeds while delaying entry into the feedlot.
Technical Abstract: The impact of varied calving and weaning times on post-weaning production of steer calves from the Northern Great Plains was evaluated in a 3-yr study. Steers (n = 220) born in late winter (LW), early spring (ES), or late spring (LS) were weaned at 140- (LS140), 190- (LW190, ES190, LS190), or 240- (LW240, ES240) d of age after grazing with their dams on native range. Steers were pen-fed a growing diet until the weaning group averaged approximately 375 kg. They were then moved to an individual feeding facility and fed a higher energy diet. Steers were allotted to harvest dates based upon visual estimates of fat thickness. Data were analyzed as a completely random design using mixed model procedures. Year and year by treatment were random effects. Non-orthogonal estimates were used to delineate treatment effects. Initial steer weights were affected by calving system and age at weaning, with LS190 steers weighing 24 ± 10 kg less (P < 0.05) than the average of the LW190 and ES190, LW and ES steers weaned at 190-d averaging 26 ± 8 kg less (P < 0.01) than those weaned at 240-d of age, and LS140 weighing 26 ± 11 kg less (P < 0.05) than LS190. There were no treatment differences in ADG during the growing phase or ADG, feed intake, or feed efficiency during the finishing phase. Steers averaged 537 ± 4 kg at harvest and total days to harvest differed between LW and ES steers weaned at 190- versus 240-d of age due to a 37 ± 12 d difference (P < 0.01) in time to reach harvest. Carcass composition was affected by age at weaning in October (240-, 190-, or 140-d of age), with hot carcass weight, marbling score, and quality grade all decreasing as age at weaning decreased. LW steers had greater hot carcass weights, marbling scores and quality grades than EW steers. Differences in post-weaning performance of steers due to calving and weaning strategies should be considered in developing appropriate post-weaning management strategies.