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Abstract
Records of birth weight (BW), weaning weight (WW), gestation length (GL), calving difficulty (CD) and survival (SW), of calves produced in a crossing experiment involving originating with Hereford, Angus, Pinzgauer, Brahman, Tarentaise and Sahiwal bulls mated to Hereford and Angus cows were used in this study. The research presented here was divided into three parts: (1) Comparison of first cross dams mated by natural service to Red Poll (n = 415), Simmental (n = 1879), and Longhorn and Red Poll (n = 86 and 81 respectively), or Charolais (n = 398) bulls. (2) Estimates of differences among specific crosses resulting from reciprocal back crosses, of 2-way F$\sb2$ and 4-way F$\sb1$ progeny with known sires used artificially. Genetic variances and covariances among traits were also estimated with sire and dam models. (3) Estimation of differences due to parental inheritance for direct and maternal effects, estimation of differences in direct and maternal heterosis effects between Bos taurus x Bos taurus and Bos taurus x Bos indicus crosses, and estimation of (co) variance components among traits with an animal model and a sire and dam model. There were significant differences among breed groups for most traits studied. Generally breed groups characterized by higher birth weight and more calving difficulty were also heavier at weaning. Lowest birth and weaning weights involved Sahiwal x Angus and Sahiwal x Hereford inheritance. The largest maternal effects on birth weight involved fraction of Pinzgauer, Hereford, and Angus inheritance. The largest direct effects on birth weight involved fraction of Brahman inheritance.
Ranking of breeds based on regression on breed fractions for maternal effects on weaning weight was Pinzgauer, Brahman, Sahiwal, Angus and Hereford with Pinzgauer and Brahman significantly larger than others. Direct breed effects ranked similarly except ranking of Angus and Hereford was reversed. The difference in heterosis due to effects of Bos taurus x Bos taurus and Bos indicus crosses was significant for direct and maternal effects at weaning. These results suggest that Bos indicus breeds can make a significant contribution to beef production in temperate climatic zones.
Gestation length was longer for calves with most European, breed inheritance. Analyses for survival at weaning indicated that crossbred calves with Hereford, Angus and Pinzgauer inheritance had the poorest rates of survival to weaning.
Most of the estimates of variance components were similarly consistent for the animal and sire models. In most cases the pattern of estimated correlations among traits and heritability estimates were what might be reasonably expected in agreement with previous reports.
