Association between umbilical hernias and genetic line in a swine multiplication herd and methods to differentiate the role of sire in the incidence of umbilical hernias in offspring

Abstract

Objectives: To determine the existence of a link between genetic line and incidence of umbilical hernias in nursery pigs and whether this incidence differs among sires, and to develop a model to identify sires with a high incidence of umbilical hernias among offspring. Materials and methods: Gilt and boar progeny from 8276 litters of a genetic multiplier that used four dam lines and five sire lines were observed for umbilical hernias by 11 weeks of age. Hernias were attributed to birth litter. Odds of umbilical hernia development were calculated using logistic regression and rates were calculated using Poisson regression. Negative binomial models using sire as a random effect were used to predict incidence of hernias and hernia-positive litters from maternal-line sires with ≥ 25 single-sire litters. Results: Odds of umbilical hernia-positive litters were different among sire and progeny lines (P < .01). Rates of umbilical hernias were significantly different between genetic lines. The rate of umbilical hernias in pure maternal-line products was nearly twice that in out-crossed lines (P < .001). For individual-sire predicted hernias compared to observed umbilical hernias, R2 was 0.960, and for individual-sire predicted hernias per litter compared to observed hernias per litter, R2 was 0.816. Implications: Umbilical hernias may be influenced by a genetic component. Progeny testing using 25 single-sire litters identifies potentially heritable defects that occur at a rate twice that in the normal population. Negative binomial models can effectively predict rates of event occurrence.