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ARS Home » Plains Area » Miles City, Montana » Livestock and Range Research Laboratory » Research » Publications at this Location » Publication #110802
Title: EFFECTS OF SEASON OF CALVING AND WEANING AGE ON COW AND CALF PRODUCTION THROUGH WEANING

Author
item Grings, Elaine
item Short, Robert
item Heitschmidt, Rodney

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2000
Publication Date: 6/1/2000
Citation: GRINGS, E.E., SHORT, R., HEITSCHMIDT, R.K. EFFECTS OF SEASON OF CALVING AND WEANING AGE ON COW AND CALF PRODUCTION THROUGH WEANING. JOURNAL OF ANIMAL SCIENCE SUPPLEMENT. 2000. v. 78(Suppl. 2). p. 117.

Interpretive Summary: 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.

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.