Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/20/2000
Publication Date: 6/20/2000
Citation: GRINGS, E.E., SHORT, R., HEITSCHMIDT, R.K. EFFECTS OF SEASON OF CALVING AND WEANING AGE ON COW AND CALF PRODUCTION THROUGH WEANING. WESTERN SECTION OF ANIMAL SCIENCE PROCEEDINGS. 2000. v. 51. p. 125-127. Interpretive Summary: Selection of the optimal times to calve and wean are important decisions for cow/calf producers. The production data reported here will be useful to producers in this decision process. As calving occurred earlier in the year, pregnancy rates were not affected, but weaning weights on a given date increased because calves were older and gained faster. This increase in productivity may be offset by increased production costs. Weaning age affected cow traits more than calf traits.
Technical Abstract: Cows were bred to calve (n=575) in February (F), April (A), or June (J) to determine effects of season of calving (SOC). Cows and replacement heifers were rebred (n=781) so as to have the same SOC the next year. Calves were weaned (early and late) at 6 or 8 mo for F and A calves and at 4 or 6 mo for J calves. There were small but significant (P<.05) effects of SOC on birth weight of calves (36.7, 35.6, and 37.8 kg for F, A, and J, resp.), and there were no significant effects (P>.05) on rebreeding pregnancy rates (86.3, 85.2, and 87.1% for F, A, and J, resp.). Calf weight at a standard age (190 d) was decreased (P<.05) as SOC became later (226, 214, and 191 kg for F, A, and J, resp.), and for J calves at 190 d, late weaned calves were heavier than early weaned (196 vs 186 kg). Calf gains from 1st to 2nd weaning decreased (P<.05) as SOC became later (45, 41, and 30 kg for F, A, and J, resp.) with the main effect being due to J calves, and J calves that were late weaned gained more (P<.05) than early weaned (33 vs 26 kg). Cow weight change from 1st to 2nd weaning decreased (P<.05) as SOC became later and with late weaning (early weaned; 38.7, 14.7, and 9.9 kg vs late weaned; 10.7, -5.5, and -15.7 kg; both F, A, and J, resp.). Cow body condition score was mainly affected by weaning age of the calf with late weaned cows having a greater (P<.05) loss in condition than early weaned cows for each SOC (early weaned; -.04, -.03, and -.30 vs late weaned; -.54, -.51, and -.64; both F, A, and J, resp.). Conclusions are that SOC does not affect rebreeding, but it does have dramatic effects on age constant weight and weight gains of calves. Age of calf at weaning has effects on weight and condition score changes of cows but little effect on calves.