Modeling and genetic evaluation of growth latent variable in Kermani sheep

The present research aims to construct the latent variable of growth in Kermani sheep, and to evaluate the measurement model and genetic evaluation by applying pedigree and data information collected from 1993 to 2013 in the Breeding Station of Kermani sheep, Shahre Babak, Kerman Province. The records of body weights at birth (BWT), weaning (WWT), six months (SIXWT), nine months (NINEWT), and twelve months (YWT) of age were used to construct a growth latent variable. Fitting the measurement model considered for constructing the latent variable of growth was done by applying confirmatory factor analysis and was evaluated by using goodness of fit statistical measures including root mean square error of approximation (RMSEA), Tuker-Lewis index (TLI), and confirmatory fit index (CFI). The values of RMSEA, TLI, and CFI were obtained at 0.05, 0.99, and 0.99, respectively, implying the construct adequacy for assessing the latent variable of growth in Kermani sheep. An estimate of 0.34 was obtained for latent variable of growth. Positive estimates of genetic, phenotypic, and environmental correlations between the latent variable of growth and any of the investigated body weight traits were obtained. Furthermore, Spearman's rank correlations between estimated breeding values of the latent variable of growth with any of the investigated body weights were positive and high, implying the selection of superior animals for the latent variable of growth may result in the selection of superior animals for investigated body weights except for BWT.