Use of threshold and linear models to estimate variance components and breeding values for disease resistance in Italian heavy pigs

Abstract

The Italian National Pig Breeders Association (ANAS) manages the breeding programs of the Italian Large White (ILW), Landrace (IL), and Duroc (ID) breeds, mainly oriented to the production of PDO hams. ANAS evaluates the inclusion of genetic resistance in its breeding scheme. This study aimed to estimate variance components and breeding values (EBV) using threshold (TM) and linear (LM) models. During the sib test performed at the genetic station of ANAS from 1997 to 2021, 9,595 (respiratory diseases) and 12,046 (enteritis) diagnoses were collected by the veterinary. The trait was recorded as a dichotomous variable: affected animals with 1, whereas healthy with 2. A multi-breed model was applied with the breed, sex, and farm sector as fixed effects and litter, animal, and residual as random effects. The same model was also applied within each breed, removing the breed effect. The limited data size within single breed did not allow to estimate accurate variance components. With the multi-breed model, low heritabilities were estimated for respiratory (0.09) and enteritis (0.15), with TM and LM leading to the same values. The multibreed model led to more precise variance components estimation and to EBV very close to the ones from the single breed analyses. Pearson and Spearman rank correlations between EBV estimated with TM and LM in the multibreed scenario were ≥0.97. Results of this study demonstrated the feasibility of including disease resistance among the breeding goals of ANAS and that both TM and LM could be used to reach this objective.Highlights Genetic selection for disease resistance in heavy pigs is possible Low heritabilities estimated for enteritis and respiratory disorders Threshold and linear models gave similar results.