Genetic parameters and GWAS of maturity trait: an early functional longevity proxy in French Alpine and Saanen goats.

This study investigated the phenotypic expression and genetic architecture of maturity, defined as the ability to maintain or increase milk yield across parities, in French Alpine and Saanen dairy goats. Maturity showed low heritability (around 0.10) and high repeatability (around 0.55) in both breeds and was genetically independent from milk yield routinely evaluated (parity 1 to 10) but positively correlated with milk yields in later parities (parity 2 to 6) and functional longevity. GEBVs correlations between functional longevity and other traits evaluated were calculated. A QTL associated with maturity showed positional coincidence with the CSN1S1 gene. Bucks homozygous for the strong allele at this locus had lower maturity. Bucks with a lower maturity breeding value, have their progeny producing more milk in first lactation but less in later ones, leading to lower lifetime yields and shorter longevity. These results demonstrate that maturity captures individual differences in production trajectories, and that genetic evaluation of maturity can help to select animals that combine long-term production and resilience more quickly than longevity breeding value can. The introduction of maturity into breeding objectives could complement selection for early milk yield and improve overall sustainability of dairy goat systems.