Estimação do índice de eficiência reprodutiva e parâmetros genéticos em ovelhas

Abstract

This study aimed to estimate a reproductive efficiency index in ewes based on body weight ratio, and their genetic parameters. Phenotypic and genealogical information was used from the database of the Experimental Station Pedro Arle, of Embrapa Tabuleiros Costeiros, between 1990 and 2018, Frei Paulo, Sergipe, Brazil. The individual reproductive efficiency of the animals was evaluated through the index calculated by dividing the body weight of the litter of lambs by the body weight of the dam at lambing, thus, two indices were calculated using litter weights at birth and at weaning. Dams were separated into two birth types (single and multiple) and three lambing order categories (first, second and third or more) from which they were born. It was evaluated which categories provided the best reproductive index, through a factorial design to test the effects and the comparison of the means by the Tukey test, using the SAS statistical software. For the estimation of the genetic parameters of the index, analyzes were carried out using programs of BLUPF90 family. The variance components were estimated using GIBBS2F90 software and the subsequent means obtained with POSTGIBBSF90. By the factorial test, there was a significant difference (p<0.05) regarding the lambing order of the birth index, with the highest values being from the ewes born from primiparous dams; and regarding the type of birth for the weaning index, with the highest values were from ewes born from multiple birth. The estimated heritability coefficients for the indices showed high magnitudes, as well as high and positive genetic correlation. These results indicated there is a possibility of genetic gain through selection and the birth index can be used as a selection criterion for the weaning index. The high heritability values suggest that phenotypic selection may be promote genetic gain for these traits.