Rodrigo de Almeida Teixeira

Interação genótipo-ambiente em cruzamentos de bovinos de corte

Data from Hereford and Nelore breeds and their crosses were used to estimate the effect of genotype and environment interaction on weaning and yearling weights. The statistical analyses were performed by the least-squares method using models that included region, contemporary group within region, month of birth and sex of the calf, linear and quadratic effects of age of the calf and age of the cow, both nested within sex, and the genetic group and genetic group × region interaction effects. In general, genetic groups were influenced by the region effect. Differences in performance between regions decreased as the proportional contribution of zebu increased. All genotypes increased performance in the less restrictive environment. Crossbreeding systems should consider keeping fitness of dams and their products to environmental conditions.

Efeitos ambientais que afetam o ganho de peso pré-desmama em animais Angus, Hereford, Nelore e mestiços Angus-Nelore e Hereford-Nelore

66.035 records from Nellore, Hereford, Angus and Nellore x Angus and Nellore x Hereford crossbred calves were analyzed to estimate the influence of cow age, age at weaning and the julian birth date on average daily gain from birth to weaning. The statistical analysis indicated that these three covariates had significant effects on this trait. Furthermore, the linear adjustment for age at weaning was not enough to remove this effect on the average daily gain. These results show that these environmental effects can be an important variation source for this trait in animal improvement programs.

Heteroses materna e individual para ganho de peso pré-desmama em bovinos Nelore × Hereford e Nelore × Angus

Data on 62.985 Nellore, Hereford, Angus and Nellore × Angus and Nellore × Hereford crossbred calves were analyzed to estimate maternal and individual heterosis for preweaning daily weight gain (PWD). The individual and maternal heterosis of average daily weight gain showed improvements of 6.2 and 11.2% for PWD of F1 calves and for calves borne from F1 dams. Maternal heterosis corresponded to 64.5% of total heterosis. Bos taurus × Bos indicus crossbred cattle have a PWD larger than the average of purebred cattle.

Avaliação histológica dos testículos de ovinos da raça Santa Inês nascidos em diferentes estações do ano

Four groups of Santa Ines male sheep born in four seasons in the Distrito Federal were analyzed to evaluate the age and body weight at puberty, at which point were castrated. Histological measurements were carried out on the testicles to evaluate cellular parameters and size measurements of the seminiferous tubules. The effect of the group on cellular parameters was significant (P<0.01). Animals born in the dry season were more precocious than the others, but showed the worst histological profile of the testis. The histological traits of the testis of the Santa Ines rams were influenced by the season. The end of the rainy season was shown to the best season for births of sheep in the Central region of Brazil, with histological testicular traits at puberty being superior to the other groups.