The effects of weaning on cow calf production efficiency and cattle production economics.

摘要

Over a three-year period 240 spring-calving cows (mean +/- SD: age 5.9+/-0.04 years, body weight (BW) 605+/-8 kg; body condition score (BCS) 2.6+/-0.06 (scale 1--5); calving date: (May 1+/-12d) were used to compare very early (VEW: 72+/-12d) with early (EW: 132+/-12d), and normal weaning (NW: 192+/-12d) on cow and calf performance. Heifer calves were backgrounded on pasture and steers split between pasture (VEWP, EWP) and feedlot (VEWF, EWF) until the time of NW. After NW all calves were moved into feedlot. From the time of parturition cow BCS and BW increased as weaning age decreased (P<0.05). Two out of the three years VEW and EW cows had significantly (P<0.05) greater BCS and BW than NW cows. Conception rates, calving intervals and calf birth weights were similar (P>0.05) for all treatments; but culling rates were lowest (P<0.05) for VEW. Heifer ADG from VEW to the time of NW were lower (P<0.05) for VEW heifers (0.8 kg/d) and marginally (P<0.10) lower for EW heifers (0.9 kg/d) than for NW heifers (1.0 kg/d). Through the backgrounding period treatment differences in ADG for heifers were negligible (P>0.05). Results for cyclicity pooled over years (74% of VEW, 85% of EW and 95% of NW cycling at 13 months of age) suggested that weaning treatment had an effect on sexual maturity. Steer ADG from July 9th to Sept. 9th was lowest (P<0.05) for VEWP (0.9 kg/d); intermediate for VEWF and EWP (1.1 kg/d) and greatest for EWF and NW (1.2 kg/d). ADG in the feedlot was not affected by treatment (P>0.05), however from birth to slaughter the VEWP steers had lower ADG (P<0.05) than the EWP, EWF and NW steers, while VEWF steers were intermediate. Days on feed and carcass traits for quality and yield grades were not affected by weaning treatment. Carcass weight, ribeye area (REA) and back fat depth were lower for VEWP and VEWF (P<0.05) compared to the EWP, EWF and NW steers. When REA was expressed as a ratio with carcass weight, there were no differences (P>0.05) among treatments. Feed to gain ration was greatest for VEWP (6.7:1); intermediate for VEWF and EWF (6.3 and 6.4:1) and least for EWP and NW (6.0 and 6.1:1). Net income for the cow/calf systems indicated that EW and backgrounding the calves on pasture until Nov. 9th generated the most net income.