A Contemporary Assessment of Variance Components and Heritability of Reproductive Traits in Andalusian Black Cattle (Negra Andaluza)

The Andalusian Black cattle (Negra Andaluza) is a heritage breed facing severe demographic and genetic threats due to its limited population and marginal economic use. Understanding the genetic basis of reproductive traits is critical for designing sustainable conservation and breeding strategies. This study provides an updated evaluation of the genetic parameters for ten key reproductive traits in this endangered breed, based on a comprehensive dataset and analyzed using MTDFREML methodologies. Additive genetic variance, environmental variance, and permanent environmental (uncorrelated random) variance components were estimated for each trait, including Total Number of Births, Age at First Calving, Birth Interval, Number of Parturitions, Mean Productive Months per Parturition, Total Active Productive Time, Age at Last Parturition, Reproductive Lifespan, Monthly Birth Rate, and Relative Reproductive Efficiency. Heritability estimates ranged from 0.39 to 0.65, indicating moderate to high potential for genetic improvement through selection. Total Number of Births and Age at First Calving exhibited the highest heritabilities (0.65 and 0.59, respectively), suggesting that these traits could serve as effective selection criteria in reproductive management programs. The substantial additive genetic variation found in most traits, despite the breed’s endangered status, supports the feasibility of conserving and enhancing reproductive performance through carefully structured genetic programs. The updated estimates provide refined benchmarks for the design of selection indices and conservation actions aimed at reversing the breed’s genetic erosion. This study underscores the value of incorporating updated genetic evaluations in the management of threatened livestock populations and contributes essential data for the strategic recovery and sustainable utilization of the Andalusian Black cattle. Future efforts should integrate these findings into multi-trait selection programs that balance productivity with genetic diversity conservation.