Estimates of genetic parameters for growth traits to develop a genetic evaluation system in Mexican Hampshire sheep

Context The estimation of genetic parameters is an essential component when developing genetic evaluation systems for livestock. A genetic evaluation was conducted for Mexican Hampshire sheep by using a pedigree of 16,478 animals. Aim We estimated genetic parameters for growth traits and investigated the current genetic trends and the potential advantage that estimated breeding values would provide selection for growth. Methods Performance records and pedigree were provided by the Mexican Sheep Producers Association from Mexican Hampshire sheep flocks. Weight traits at birth (BWT), weaning (WWT), 120 (W120), 150 (W150), and 210 (W210) days of age were analysed using a series of univariate and multivariate models. Model development included testing the merit of including a sire by flock effect. Key results The direct heritability estimates from base and sire by flock effect models across the weight traits ranged from 0.18 to 0.45 and from 0.12 to 0.14 respectively, which are consistent with estimates presented across the literature for comparable populations. The direct heritability for BWT, WWT, W120, and W150 was higher in base models than when the sire by flock effect was fitted. Genetic and phenotypic correlations were positive and moderate to very high among weight traits. Validation analyses conducted to study the predictability of sire estimated breeding values on progeny performance found that fitting the sire by flock interaction improved prediction for WWT, W120 and W150. On the basis of current genetic trends, Mexican Hampshire breeders have achieved 72–82% of the potential genetic gain available from phenotypic selection. Conclusions The economically important growth traits were found to be heritable and strongly correlated in the Mexican Hampshire. Whereas historically, there have been favourable genetic gains in growth, this study has conducted the first across-flock genetic evaluation of the Mexican Hampshire breed. It is expected that the rate of genetic gain can be improved through increased accuracy of selection by using estimated breeding values developed from a national data set. Implications Mexican Hampshire breeders are in a strong position to improve genetic gains in growth traits if the methods, demonstrated by this study, are adopted to estimate breeding values from a national genetic evaluation system and used in breeding programs.