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Factors Affecting Net Calf Crop in Beef Cattle^{1, 2,}

United States Department of Agriculture and the Virginia and Louisiana Agricultural Experiment Station

Abstract

Some factors related to failure to conceive and to pre- and post-natal calf losses were studied in Angus, Hereford, and Shorthorn cattle at the Beef Cattle Research Station, Front Royal, Virginia, and in Brahman, Brahman-Angus and Africander-Angus cattle at the Iberia Livestock Station, Jeanerette, Louisiana, in 1956 and 1957. The largest losses in potential calf crop were the result of: (1) failure to conceive or early embryonic death before the first pregnancy check, and (2) death of the calf at or shortly after the time of birth. The proportion of cows conceiving could be increased by: (1) shortening the interval from calving to first estrus, (2) increasing the proportion conceiving at first service, and (3) keeping herds free from Vibrio fetus. The interval from calving to first estrus in cows suckling calves was longer in the younger than in the older cows and shorter in the Angus than in the other breeds studied. The conception rate at first service and for the entire breeding season were lower when yearling bulls were used (all breeds except Brahman), in herds having Vibrio fetus and in dry cows (exceptions were Africander-Angus and Brahman). Losses at or shortly after birth were quite variable between breeds and years.

¹ Contributing to Southern Regional Project S-10.

² Published with the approval of the Directors of Virginia and Louisiana Agricultural Experiment Stations.

³ Beef Cattle Research Branch, Animal Husbandry Research Division, ARS, Agricultural Research Center, Beltsville, Maryland.

⁴ Beef Cattle Research Branch, Animal Husbandry Research Division, ARS, Iberia Livestock Experiment Station, Jeanerette, Louisiana.

⁵ Beef Cattle Research Branch, Animal Husbandry Research Division, ARS, Beef Cattle Research Station, Front Royal,

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