Responses to the backtest as genetic indicators of disease resilience in grow-finish pigs.

Abstract

Behavioral responses to the backtest are heritable and genetically correlated with physiological response to infectious and non-infectious stressors in pigs. This study explored their potential as genetic indicator traits for the resilience of pigs to diseases. A total of 4,095 Yorkshire x Landrace barrows were phenotyped for performance and disease resilience traits before, during, and after their initial exposure to a polymicrobial disease challenge and genotyped for 650K single nucleotide polymorphisms across the genome. Traits recorded included average daily gain, feed intake, feeding duration, feed efficiency traits, subjective health scores, health treatment and mortality rates, antibody- and cell-mediated immune responses, and the carcass traits of carcass weight, dressing percentage, carcass loin depth, lean yield, and carcass backfat. The backtest was performed on 899 of these pigs for 30 s at ∼27 days of age, prior to their initial exposure to the challenge, and recorded responses included the number and intensity of vocalizations and of struggles. Estimates of phenotypic correlations of backtest responses with performance and resilience traits were generally low, ranging from -0.08 to 0.11. Corresponding estimates of genetic correlations with each performance and resilience trait were similar for the four backtest response traits and ranged from -0.92 to 0.58 but with large standard errors. Suggestive estimates, however, indicated that selecting pigs with high backtest responses would result in pigs with higher average daily gain and feed intake and lower mortality rates but more clinical treatments under disease. Inconclusive genetic correlations were observed for backtest responses with health scores, feed efficiency traits, and immune response traits. These results suggest that backtest responses evaluated on young and clinically healthy pigs have potential as genetic indicator traits for performance and disease resilience of pigs, although more data are required to validate the strength of these relationships for more robust applications in the swine breeding industry.