Abstract: There are presented the results of bovine cross breading F1 of seven races of beef cattle with parents of Zebu females taken from a tropical environment. They were handled in a system of rotational shepherding, at night and day. There were confined in corrals and were fed with a kilo of concentrate, molasses 4% (dry matter) and free access urea. The paternal races were: Charolais (Cha), Simmental (Si), Hereford (HE), Brown Swiss (PS), Holstein (Ho), Brahman (BRA) and Indu-Brazil (Id). The parameters were analyzed at birth (PN), weight at weaning (PD), weight at 1 year (PA) and final weight (PF). The statistical model included the fixed effects of weight of the mother, sex of the calf, race of the father, year of birth and the interactions: sex-race of the father, sex at year of birth, race of the father per year of birth and experimental error. The averages for PN, had a range from 29.413-32.655 for the paternal races (Id) and (Si); weight of the mother at birth, weaning, race of father and year of birth had significant effects (p>0.05); in case of PD was found a range of 97.391 for (Id) to 112.895 for (PS); finding significant effects in the weight of the mother, race of the father and year of birth (p<0.05). In case of PA, there were found 154.813 for (BRA) to 196 for (Ho), having significance (p>0.05) for the effects of weight of the mother to weaning, sex of the calf, race of the father, year of birth, father of the calf and for PF were found a range of 243.933 for (BRA) to 243.933 and 295.892 for (Cha), being significant all the effects, only the interactions were not, except with the race of the father for 1 year, which was the expected result. It is confirmed that the climatic and maternal effects are relevant in the tropisc, since in initial parameters of growth the genetic manifestation can get confused due to the fact that the initial parameters are similar. It appears that some races have major sensibility than others at the beginning, but as soon as the genotypes show up with adaptation after weaning, it becomes apparent the capacity of behaviour (p<0.05). This itself can be observed by the effect of sex of the calf. The effect of the paternal race is significantly different in all the parameters. The opposite is the case for the effect of weight of the mother where it was found that it was diminished as the calf was growing up.
R. Sahagun, J.H.V. Medina and I.J. Ruiz, 2009. Estimates of Genetic and Environmental Parameters in Tropical Areas that Influence the Growth Beef Bovine F1. Journal of Animal and Veterinary Advances, 8: 2503-2507.