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Title: IMPACT OF CALVING SEASON ON STOCKER AND FEEDLOT PERFORMANCE

Author
item Phillips, William
item Grings, Elaine
item Short, Richard
item Heitschmidt, Rodney
item Mayeux Jr, Herman

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2006
Publication Date: 9/28/2006
Citation: Phillips, W.A., Grings, E.E., Short, R.E., Heitschmidt, R.K., Mayeux Jr, H.S. 2006. Impact of calving season on stocker and feedlot performance. Professional Animal Scientist. 22:392-400.

Interpretive Summary: Cow-calf producers may alter the season of calving from late winter to late spring to reduce cow herd feed cost. In the fall, when calves are weaned, older calves had greater body weight and gross returns than younger calves. However, transportation cost to the next production point was less for younger calves than older calves, because more young calves could be transport on each truck. Calving season had no affect on rate of gain when calves were on pasture, but younger calves gained weigh at a greater rate than older heavier calves in the feedlot. In vertically integrated beef production systems, changing the calving date allows producers to shift the production of calf body weight gain from the cow-calf component to the feedlot component to take advantage of lower cost of gain.

Technical Abstract: Cow-calf producers using native rangelands may manipulate the season of calving to alter the match-up of forage resources with animal nutrient demands and to impact time and amount of labor resources. In environments were cool-season forages are the major forage resource, shifting calving season from winter to spring may reduce feed cost, but produces a calf with less BW at weaning. The objective of this experiment was to determine the impact of calving season and age at weaning on stocker and subsequent feedlot performance of calves produced in the northern Great Plains and shipped to the southern Great Plains for growth and finishing. Cows were assigned to late winter (LW), early spring (ES) or late spring (LS) calving seasons. Steers in the LW and ES groups were weaned at 190 and 240 d of age. Steers in the LS group were weaned at 140 and 190 d of age. Steers were shipped to Oklahoma for a 120- or 196-d stocker period before being fed a high energy diet for finishing. Delaying the calving season reduced the age of the calf at entry into the stocker and feedlot phases. Younger calves had less (P < 0.01) BW at the beginning of the stocker period and less winter ADG but gained BW more rapidly ( P < 0.01) in the spring than older calves. As a result, differences in BW among the three calving seasons at the beginning of the finishing phase were similar to those at the beginning of the stocker phase. Regardless of calving season, steers gained 146 kg over a 196-d stocker period and 88 kg over 120-d grazing season. Younger steers were in the feedlot longer (P < 0.01) and had greater (P < 0.10) ADG than older steers. Carcass traits were not different among steers born in LW, ES or LS. Delaying the calving season decreased calf BW at weaning, but did not reduce the amount of BW gained as a stocker. In a vertically integrated enterprise, delaying the calving season resulted in more of the BW gain being achieved in the feedlot. Key Words: Calving Season, Age at Weaning. Wheat Pasture, Growth, Beef Cattle.