Genetic parameters for health of the growing pig using medication records

Abstract

The objective of this study was to estimate genetic parameters for health of the growing pig. Pedigree, production and medication records were available for an Australian herd of Large White pigs, which had 812 growing pigs medicated between 2011 and 2016. The number of pigs in the herd was quantified through birth-month contemporary groups using two pedigrees - a reduced pedigree based on available performance records, and a full pedigree, constructed using numbers weaned per litter. Since the full pedigree provides a more precise measure of the number of pigs on-farm, the estimated medication prevalence of 2.2% using the full pedigree is more accurate than the 7.5% estimate using the reduced pedigree. There were minimal pathogenic challenges described in the reasons for medication, and so the herd can be classified as high-health. Genetic parameters for health, which was defined as a binary trait of medicated (case) or not medicated (control), were estimated using the reduced and full pedigree. Significant fixed effects included sex (2 levels; reduced pedigree only) and linear covariate of number of post-weaning deaths in the litter. In this herd, male pigs from litters with a higher number of post-weaning deaths were more likely to be medicated. Genetic parameter estimates were fairly consistent using either pedigree, with heritability estimated at 0.06 ± 0.04 (± SE) using the reduced pedigree, and 0.04 ± 0.03 using the full pedigree. Therefore, the reduced pedigree available from performance recording may be sufficient to derive genetic parameter estimates for health. Further, animals with higher estimated breeding values for growth were less likely to be medicated, which supports the use of growth as an indirect indicator for health. This study highlights the use of on-farm medication records to provide insight into the health status of a herd, and its potential use for the genetic improvement of health in growing pigs.