GROWTH PATTERNS OF FIRST-CROSS COWS UNDER TWO ENVIRONMENTS

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Abstract
Growth patterns of 1000 first-cross females produced by mating Charolais, Limousin, and Simmental sires with Angus. Hereford, and Shorthorn dams were compared on 503 females under extensive range conditions at Manyberries, Alberta, and 497 females under semi-intensive farm conditions at Brandon, Manitoba. Three input groups born in 1970, 1971, and 1972 were involved. Hereford × Angus (HA) females. 75 at each location, served as a control population. Location difference in initial weight (12 mo of age) and in final weaning weight taken in 1979 were negligible and all input groups at each station were equivalent in weight at 7.5 yr of age. However, large annual fluctuations occurred in weights at Manyberries with breeding weights in 1974 averaging 86, 93, and 99% of those taken 24 mo previously for females born in 1970, 1971, and 1972. Females at Brandon gained weight during gestation and usually lost weight during nursing. Those at Manyberries invariably gained weight during nursing with substantial gestation weight losses in 3 yr. Nursing status of the female had large effects on weight changes, with barren years providing the opportunity for large compensatory gains. Ranking of the females by their breed of sire was Charolais > Simmental = Limousin > HA for annual breeding and weaning weights at both locations (P < 0.05). Average rankings by breed of dam’s dam were Shorthorn > Hereford > Angus > HA at Brandon and Hereford > Shorthorn > Angus > HA at Manyberries. However, the only consistently significant differences (P < 0.05) were those between the HA control and the other crosses. These breed rankings were not affected by nursing status of the dam.