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Postinflection Growth in Straightbred and Crossbred Cattle, II, Relationships among Weight, Height and Pubertal Characters

Texas A&M University and Texas Agricultural Experiment Station, College Station 77843

Abstract

Weights and hip heights collected quarterly from 9 through 66 mo of age on reproducing cows in a five-breed diallel, which included the Angus, Brahman, Hereford, Holstein and Jersey breeds and all possible two-breed crosses, were analyzed using correlation and regression techniques. The overall correlation between mature weight (AW) and maturing rate for weight (kW), as determined by Brody's equation Y_t = A-Be^-kt fitted to each of the 397 cows, was negative (r = –.25, P<.01), as was that between mature height (AH) and maturing rate for height (kH) (r = –.15, P<.01). Correlations between AW and AH (r = .77) and between kW and kH (r = .39) were positive (P<.01). Correlations within breeds or crosses tended to agree with the overall correlations. The overall weight-on-height regression coefficient was 10.54 kg/cm, although a comparison of models indicated that within-breed and cross regression gave a better (P<.05) fit. The allometric equation W_t = bH_tq fitted the weight-height data well, although examination of residuals indicated a Systematic bias at either extreme of the height scale. Overall heterosis was negative (P<.05) for age at puberty and positive (P<.01) for weight and height at puberty. When data were grouped into two levels of nutrition and two types of breeding (straightbred vs crossbred) and analyzed by least-squares analysis of variance, the level of nutrition X type of breeding interaction was significant (P<.05) for age and weight (but not height) at puberty; for weight:height ratio at puberty, and for weight and height at puberty, each expressed as a proportion of its respective mature value (P<.01).

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