Association of PIT1 genotypes with growth traits in Canchim cattle

Abstract

Use of genetic markers can aid on the identification of animals with highest breeding values in beef cattle. The PIT1 gene codes for the Pit-1 transcription factor is essential for the activation of prolactin, growth hormone and PIT1 genes. This research is an investigation of the effect of PIT1-HinfI polymorphism on growth traits of 509 Canchim animals, from two lineages, GG1 and GG2. PIT1 genotypes were identified through PCR-RFLP. Genotype effect on phenotypic values for birth weight (BW), standardized weaning weight (W240), weight at 12 months of age (W365), and the average daily weight gain from birth to weaning (AGBW), and from weaning to 12 months of age (AGW12) were analyzed by the least squares method. Effects of the interaction between the animal's genetic group and PIT1 genotype for W240, AGBW and AGW12 were observed (P < 0.05). Differences between means of HinfI (-/-), HinfI (+/+) and HinfI (+/-) genotypes for W240 and AGBW were observed in GG2 (P < 0.05), revealing superiority of (-/-) genotype for those traits. Means for genotypes (+/+) and (+/-) for W240 and AGBW, did not differ from one another, suggesting a dominance effect of the HinfI (+) allele. The HinfI (-) allele had a favorable effect on W240 and AGBW in GG2, when present in homozygosis. The difference between PIT1 behavior observed in the two genetic groups may suggest the action of a quantitative trait locus linked to PIT1, segregating only in GG2 population.