J. Anim Sci.
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J. Anim Sci. 1981. 53:1193-1197.
© 1981 American Society of Animal Science
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Effects of Early Weaning Calves from First-Calf Heifers on Calf and Heifer Performance1,2,

K. S. Lusby, R. P. Wettemann and E. J. Turman2

Abstract

Sixty-three Angus X Hereford calves from first-calf heifers were assigned at birth to remain with their dams until weaning (NW) at 7 months or to be early weaned (EW). Calves were born between February 18 and April 17 and those assigned to be EW were weaned every 2 weeks at 6 to 8 weeks of age. EW calves were raised in drylot and self-fed high concentrate diets until July, when one-half of the calves were moved to pasture and creep-fed. Heifers with EW calves and heifers with NW calves were bled at weekly intervals between 6 and 13 weeks postpartum for plasma progesterone analysis. All heifers were exposed to Angus bulls from May 29 to July 31. NW calves weighed 169.3 kg, at 7 months of age, compared to 169.8 kg for EW calves. Moving calves to pasture with creep feed reduced (P<.05) gains of EW calves by 20 kilograms. Conception rate was greater (P<.05) among EW (96.8%) than among NW heifers (59.4%) during the 64-day breeding season. The average interval from parturition to conception was reduced (P<.05) from 90.5 to 73.0 days by early weaning. Ovarian activity, as indicated by progesterone levels greater than 1 ng/ml, was initiated by 85 days postpartum in 90.3% of the EW heifers, compared to 34.3% of the NW heifers (P<.005). EW heifers gained more rapidly (P<.05) during the summer.

Footnotes

1 Journal Article 3867 of the Agr. Exp. Sta., Oklahoma State Univ., Stillwater 74078.

2 Anim. Sci. Dept






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