Comprehensive analysis of inbreeding depression across growth, fertility, and survival traits in Limousine beef...

The Italian Limousine cattle population, with approximately 100 000 registered animals in the national herd book, plays a crucial role in the country's national beef industry, being one of the most widely spread breeds in Italy. Maintaining genetic diversity is essential to prevent the negative consequences of inbreeding, which can reduce animal performance for economically important traits such as growth, fertility, and longevity. Traditional pedigree-based inbreeding estimates have been previously used, but genomic tools offer the possibility of greater precision. This study evaluated the effects of inbreeding and inbreeding depression on key performance traits in Limousine cattle, considering both pedigree- and genomic-based inbreeding coefficients. Phenotypic comparisons between animals with low and high inbreeding levels revealed a negative effect of inbreeding on growth traits, including birth weight, weaning weight, yearling weight, and average daily gain. These effects were observed regardless of the inbreeding estimation method. Fertility traits were largely unaffected, except for age at first calving, which increased with higher inbreeding. Longevity, measured by the probability of survival across parities, was significantly reduced in inbred animals. Genomic inbreeding showed a greater impact on animals' fertility and longevity. Notably, when separating recent and ancient genomic inbreeding, the former had a more pronounced effect on growth traits. Similarly, recent inbreeding primarily impacted animal longevity. Genomic inbreeding coefficients provided more granular insights into inbreeding depression, allowing for a better identification of individuals at higher risk of performance reduction. The results highlight the detrimental effects of inbreeding on growth, fertility, and longevity in Limousine cattle, which could have implications for herd productivity and genetic diversity. The study underscores the importance of genomic tools to monitor and manage inbreeding levels. Implementing strategies to control inbreeding accumulation is vital for maintaining genetic variability and ensuring the long-term sustainability of beef cattle populations.