|Short, Robert - RETIRED ARS|
|Mayeux Jr, Herman|
Submitted to: Proceedings of the National Conference on Grazing Lands
Publication Type: Proceedings
Publication Acceptance Date: November 12, 2006
Publication Date: December 9, 2006
Citation: Grings, E.E., Phillips, W.A., Short, R.E., Mayeux Jr, H.S., Heitschmidt, R.K. 2006. Calving system, weaning age, and post-weaning management impacts on cow and steer calf performance. Proceedings of the National Conference on Grazing Lands, pg 499. Interpretive Summary: Altering times of calving or weaning changes both inputs and outputs in the cow-calf portion of a beef production system. Calving later in the year can result in lighter calf weaning weights and decreased feed costs for cow-calf enterprises in the Northern Great Plains. Steers from these different calving systems perform similarly in growing programs, but consideration should be given to age and weight at entry into finishing programs to produce carcasses of similar quality. Two approaches were taken to raise steers from weaning to harvest. The OK systems made maximum use of grazable forages. Under this approach, movement of steers between individual components, ie growing and finishing periods, was based on date of forage availability. For steers transported from MT immediately after weaning and those transported in May, one goal was to take advantage of wheat pasture in May. All steers were then moved to the finishing programs at the same calendar date, regardless of body weight or age. The MT Growing-Finishing system used harvested forages to grow steers to a given weight before entry to the finishing phase. The two approaches result in different timing of gain. For those systems relying on date-based movements, a greater amount of the weight gain was shifted into the feedlot phase for lighter, younger steers, whereas in the harvested forage system, these younger calves spent a greater amount of time in the growing program and less in the finishing program. This difference may explain some of the varied results between the growing-finishing systems. It appears that steers weaned at younger ages need to be placed into finishing programs at lighter weights and/or younger ages to obtain the same amount of marbling as steers that are older at weaning for harvest at similar weights. Alternatively, steers weaned at younger ages could be slaughtered at heavier weights if similar marbling was desired. Evaluation of other carcass traits indicates that slaughtering these earlier weaned steers at heavier weights would not be detrimental to overall carcass quality.
Technical Abstract: A 3-yr study evaluated late winter (LW), early spring (ES), and late spring (LS) calving systems (average number of cows per calving season year = 168) in conjunction with varied weaning strategies on beef cow and calf performance from Northern Great Plains rangelands and subsequent post-weaning steer performance. Calves in LW and ES systems were weaned at 190- and 240-d of age; LS calves were weaned at 140- and 190-d of age. Breeding by natural service occurred in a 32-d period that included estrous synchronization. Cows were managed through the year as appropriate for their calving season. Cow BW change and BCS dynamics were affected by calving system, but fall pregnancy rate was not. Estimated harvested feed inputs were less for the LS compared to LW or ES systems. Birth weight and overall rate of gain from birth to weaning did not differ for steers from the three calving systems. Calf weaning weight differed by weaning age within calving system (P < 0.001), and steers from the LS calving system and weaned at 190-d of age tended (P< 0.06) to be lighter than the same age steers from the LW or ES calving systems. After weaning, steers were fed in confinement in MT or shipped to OK and either grazed or were fed forage. The impacts of calving systems and weaning age on steer performance during the growing phase depended on the system used and its endpoint. Steers from various pre-weaning systems backgrounded to a common weight endpoint in MT did not differ in grower or finisher ADG. Stocker cattle in OK exhibited no difference in ADG during winter but ADG did differ (P < 0.01) in spring with overall ADG not differing for calving system or weaning age. Steers from the LS calving system were leaner (P < 0.05) whether they were younger (OK finishing) or of similar age (MT finishing) at harvest than steers from LW or ES systems. In a vertically integrated beef production system, calving later in the calendar year shifted more of the body weight gains to the stocker and finishing phases.