Inbreeding effects on reproductive traits of pureline colored pig breeds in government pig farm in Bhutan

Abstract

Inbreeding in most cases reduces the performance of animals referred to as inbreeding depression. The objectives of the study were (i) to investigate the increase of inbreeding over time and (ii) to estimate the effects of inbreeding on seven reproductive traits in three pure-line colored pigs at National Piggery Research and Development Centre (NPiRDC) in Bhutan. Farrowing records of 3073 from 694 sows were used to estimate the effects of dam inbreeding, sire inbreeding and litter inbreeding on reproductive traits using a linear mixed model. The inbreeding rate per generation was 2.59% for Duroc, 1.14% for Large Black and 1.06% for Saddleback population. The sire inbreeding showed a significant (p<0.05) effect on gestation length (GL). The litter inbreeding significantly reduced number weaned (NW) by 0.015 piglets and increased pre-weaning mortality (PWM) by 0.174% per 1% increase in litter inbreeding. The linear model of dam inbreeding did not show significant effects on any of the traits analyzed. However, the quadratic model showed a significant (p<0.05) effect of dam inbreeding on PWM, suggesting that the effect of dam inbreeding depend on level of dam inbreeding. The interaction of dam inbreeding and breed was significant (p<0.001) for PWM, suggesting the effect of dam inbreeding differ between breeds on PWM. The effects of dam inbreeding were -0.315% (SE=0.081) in Duroc, 0.390% (SE=0.139) in Large Black and 0.614% (SE=0.124) in Saddleback. Although unfavorable effects of inbreeding were detected on most of the analyzed traits, the inbreeding depressions were not drastic at present. Relatively, the litter inbreeding had stronger effect than dam and sire inbreeding on the traits analyzed. In the future, investigating effects of inbreeding on other traits that were not covered under this study might be useful to understand more on the effects of inbreeding at the farm.