Early growth performance of Bos taurus x Bos indicus cattle crosses in Ethiopia:: estimation of individual crossbreeding effects

In an effort to estimate breed differences, heterotic and recombination effects, a total of 4957 birth weight (BWT), 4245 weaning weight (WWT) and 3330 yearling weight (YWT) records collected from 38 crossbred and three purebred genotypes generated from crossing Friesian (F), Jersey (J) and Simmental (S) with the Boran (Bo), Barca (Ba) and Horro (Ho) (Bos indicus ) breeds in Ethiopia were used. Differences between genotypes were significant (p < 0.01) for all traits. Genetic group mean values adjusted for environmental effects ranged from 20 to 30 kg for BWT, 88 to 114 kg for WWT, 122 to 157 kg for YWT and 358 to 492 g for preweaning average daily gain (ADG). The breed additive effect of F as a deviation from the Bo was significant (p < 0.01) and positive for all traits. Relative to the Bo mean, the additional breed additive contributions of the F breed on BWT, WWT, ADG and YWT were 39.3, 16.5, 9.3 and 10.3%, respectively. However, the breed additive effects of the Ho and J breeds were significantly (p < 0.01) negative for all traits. The heterotic effects were significantly negative (p < 0.01) for BWT for all F and S crosses, but positive (p < 0.01) on all other traits for all types of crosses. The average heterosis estimated within the F, J and S breeds were: -2.1 +/- 0.6, 0.2 +/- 0.6 (p > 0.05) and -2.3 +/- 0.6 kg for BWT, 8.82.1, 11.8 +/- 2.3 and 13.7 +/- 2.4 kg for WWT, 60.4 +/- 11.3, 64.8 +/- 12.3 and 90.6 +/- 12.7 g for ADG, and 19.8 +/- 2.6, 19.5 +/- 2.8 and 20.8 +/- 2.9 kg for YWT, respectively. The recombination effects were significant (p < 0.01) for the majority of crosses for all traits. The estimates of the recombination loss were negative in all traits, except for BWT. The average recombination effects estimated within the F, J and S breeds were: 2.6 +/- 0.8, 2.9 +/- 0.9 and 2.4 +/- 1.0 kg for BWT, -13.6 +/- 3.2, -4.2 +/- 3.4 (p > 0.05) and -16.0 +/- 4.0 kg for WWT, -88.0 +/- 17.1, -39.4 +/- 18.4 and -102.2 +/- 21.3 g for ADG, and -14.4 +/- 4.0, -0.1 +/- 4.4 (p > 0.05) and -17.5 +/- 4.9 kg for YWT, respectively. It could be concluded that the breed differences, heterotic and recombination effects seem to be important genetic factors affecting early growth performances in the breed crosses tested.