|Short, Robert - RETIRED ARS|
|Mayeux Jr, Herman|
Submitted to: Proceedings of the National Conference on Grazing Lands
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 2006
Publication Date: N/A
Technical Abstract: A 3-yr study evaluated late winter (LW), early spring (ES), and late spring (LS) calving systems (avg n . SC-1 . year-1 = 168) in conjunction with varied weaning strategies on beef cow and calf performance from Northern Great Plains rangelands. 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 calves from the three calving systems. Calf weaning weight differed by weaning age within calving system (P < 0.001), and calves from the LS calving system and weaned at 190-d of age tended (P< 0.06) to be lighter than the same age calves from the LW or ES calving systems. After weaning, steers were fed in confinement in MT or shipped to OK and either grazed or 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. When fed to a common date, grower ADG decreased (P < 0.05) as age of entry to the grower program decreased, whether the younger age was due to calving system or weaning age. 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 lighter and 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.