Genetic trend analysis of performance traits in central Anatolian Merino sheep

This study quantified genetic parameters, trends, and gains for key growth and efficiency traits in Central Anatolian Merino (CAM) sheep using a decade of performance and pedigree records (2013–2023; n = 13.920). Traits analyzed were birth weight (BW), weaning weight (WW), average daily weight gain (ADWG), and Kleiber ratio (KR). After data cleaning and pedigree validation, variance–covariance components were estimated via multivariate animal models including direct and maternal additive effects, using REML (WOMBAT). Fixed effects (year, sex, birth type, dam age) were identified in R. Heritability (h²) estimates indicated moderate genetic control: BW = 0.408, WW = 0.365, ADWG = 0.366, and KR = 0.385. Maternal variance contributed meaningfully across traits and was comparable to direct variance for KR, underscoring the importance of maternal effects. Genetic correlations revealed a very strong positive association between WW and ADWG (rₐ = 0.994), and moderate-to-high correlations of KR with WW (0.674) and ADWG (0.685). BW showed weak, slightly negative correlations with postnatal traits, suggesting largely distinct genetic control. Genetic trend analysis showed clear, positive trajectories from ~2015 onward. Over 2013–2023, total genetic gain was substantial for WW (+0.401 kg, +0.040 kg·year⁻¹) and positive for ADWG (+0.051 kg, +0.005 kg·year⁻¹), whereas KR declined (−0.255 units, −0.026 units·year⁻¹) and BW slightly decreased (−0.058 kg, −0.006 kg·year⁻¹). A transient dip around 2022 coincided with a smaller cohort (n = 850) and likely environmental noise. A multi-trait selection index—retaining positive weights for WW and ADWG while assigning a balancing positive weight to KR—should reconcile growth with feed efficiency, enhancing long-term genetic, economic, and environmental sustainability in CAM flocks.