The records of 263 Angus (AN) bull calves representing 21 sire families and 270 young Hereford (HE) bull calves representing 26 sire families, born in the spring of 1984,1985 and 1986 were analyzed. Bull calves were feedlot performance tested for 168 days following weaning at Agriculture and Agri-Food Canada Lethbridge Research Station, Lethbridge, Alberta, Canada. Estimates of genetic and environmental determinations for body weight (WT), average daily gain (ADG) and relative growth rate (RGR) measurements in each 28-d period of the 1 68-d gain test were calculated. Estimates of direct heritability (h2,) for WT (0.13 to 0.27) were higher than those of maternal heritability (h2m, 0.02 to 0.20), indicating the body size of a bull calf was influenced more by the genotype of the calf than by the genotype of the dam. The differences between h2, and h2m were not obvious for ADG (0.12 to 0.20 for h2, vs 0.12 to 0.17 for h2J and RGR (0.01* to 0.19 for h2, vs 0.01 to 0.20 for h2J , indicating that it may be worthwhile to utilize the maternal genetic variation for postweaning growth performance. However, the strong negative genetic correlations (r.J between direct and maternal genetic effects (-0.65 to -1.0) would limit the effective utilization of both direct and maternal genetic effects. The residual variance components accounted for over 70% of the phenotypic variances and were the largest components of phenotypic variances of the traits. The influences of residual effects on each of the traits were relatively uniform during the test period, indicating that the management of the animals were constant throughout the test period.

M. F Liu, D. RC Bailey, N. H Shannon

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 214–217, 1994
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