Individual animal model estimates of genetic correlations between performance test and reproduction traits of landrace pigs performance tested in a commercial nucleus herd

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Abstract
Bivariate individual animal model estimates of genetic and environmental correlations between reproduction traits (number born alive and average piglet weight) and performance test traits (ultrasonic backfat depth, average daily food intake, average daily gain and food conversion ratio) of Landrace pigs were calculated. The estimates were produced using a derivative-free restricted maximum likelihood algorithm to calculate likelihoods for different combinations of covariance parameters. A quadratic approximation to the likelihood surface was used to estimate the maximum likelihood values with respect to the covariance parameters. For all combinations of performance test traits with reproduction traits the resulting genetic and residual correlation estimates were low, with a maximum absolute value of 0·233 for the genetic correlation between food conversion ratio and number born alive. Standard errors of genetic correlation estimates were between 0·11 and 0·15. There is expected to have been little effect upon reproduction traits from the rigorous selection carried out upon performance test traits over the years. When incorporating reproduction data into best linear unbiased prediction analysis procedures it should be possible to analyse performance test and reproduction traits from this population separately, thereby making savings on computer resources and time required for the analysis of all traits.