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Crossing Beef x Beef and Beef x Brown Swiss: Pregnancy Rate, Calf Survival, Weaning Age and Rate¹

Fort Keogh Livestock and Range Research Laboratory², Miles City, MT 59301

Abstract

October pregnancy rate, calf survival to weaning, weaning age, weaning rate and actual kg of calf weaned/cow exposed were determined in a 4-yr study involving 880 matings of Angus (A), Hereford (H) and Charolais (C) sires to A, H, C and Brown Swiss (BS) dams. Cows were mated in single-sire herds for 45 or 60 d under pasture conditions; heifers were bred to produce their first calf at 3 yr of age. Pregnancy rate of lactating dams was 9.4% higher (P<.01) than for non-lactating dams. Pregnancy rates for straightbred matings were 87.5%, 80.6% and 75.4%, respectively, for A, H and C groups (P<.05). No differences (P>.10) due to sire breed were found for any of the traits studied except for calf age at weaning. Calves from C sires were younger (P<.01) at weaning than calves from H and A sires. Breed-of-dam differences (P<.05 to P<.01) were found for all traits studied except calf survival rate. All BS dams produced crossbred calves and had lower pregnancy and weaning rates (both P<.01), calves were younger at weaning (P<.05), had lower kg of calf weaned/cow exposed (P<.05) than for beef-breed dams producing crossbred calves. Crossbred calves from BS dams were 4.9, 11.0 and 3.4 d younger (P<.05 to P<.01) at weaning, respectively, than crossbred calves from H, A and C dams. The reciprocal crossbreds HA, HC and AC each exceeded the respective parent breeds in all reproduction traits studied. The average heterosis for pregnancy rate, calf survival rate, weaning rate, weaning age and actual kg of calf weaned/cow exposed were 3.8, 1.4, 5.4, .5 and 8%, respectively.

¹ This study was conducted as a contributing project to Western Regional Proj. WRCC-1. Montana Agr. Exp. Sta. Journal Series No. 1387.

² USDA-ARS and Montana Agr. Exp. Sta., cooperating.