Dams representing diverse breed types were evaluated during eight breeding cycles. Those that survived were removed from the experiment at 10 years of age. O f the 301 original dams, 34.2% died or were removed from the herd because o f injury, serious illness, or poor reproductive performance. Breed differences in measures of longevity were statistically significant. Percentages of Hereford, Red Poll, Hereford x Red Poll, Red Poll x Hereford, Angus x Hereford, Angus x Charolais, Brahman x Hereford and Brahman x Angus dams that survived until the eighth mating season were 48.5, 71.4, 52.8, 71.4, 73.2, 67.5, 90.0 and 79.5,respectively. Lifetime total number of calves weaned by dams in these breed categories were 4.54, 5.45, 4.45, 5.49, 5.98, 5.57, 6.96 and 6.22, respectively. Brahman-cross (P <.01) and Angus x Charolais (P<.10) dams exceeded Hereford dams in lifetime total number of calves weaned but did not differ from Angus x Herefords. There was no evidence of heterosis in longevity of Hereford x Red Poll crosses.

C. M Bailey

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XIV. Dairy cattle genetics and breeding, adaptation and conservation., , 327–329, 1990
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