Heterosis effects on growth and egg-laying performance in reciprocal F1 crosses between Fayoumi and two exotic chicken breeds

Heterosis (hybrid vigor) is a powerful genetic phenomenon where crossbred offspring outperform their purebred parents, offering significant potential for improving productivity in animal breeding. This study investigated heterosis effects in reciprocal F1 crosses between the tropically-adapted Fayoumi (FM) and two exotic chicken breeds (Koekoek [KK] and White Leghorn [WL]) for growth, egg production, and egg quality traits. The aim was to identify optimal crossbreeding strategies that combine the Fayoumi’s adaptability with enhanced productivity for tropical poultry production systems. Favorable heterosis was observed for key traits including body weight (BW), body weight gain (BWG), body weight at first egg (BWFE), age at first egg (AFE), egg weight (EW), yolk weight (YW), and yolk height (YH), indicating strong non-additive genetic effects. The FM♂ × KK♀ cross exhibited superior growth performance, while the KK♂ × FM♀ cross showed exceptional egg production potential. Negative heterosis was noted for albumen height (AH) and Haugh units (HU), suggesting genetic incompatibilities affecting internal egg quality. Heterosis patterns for growth and egg quality traits varied with age, declining during later stages of sampling, likely due to increasing additive genetic effects. Reciprocal crosses displayed divergent performance, highlighting the importance of parental line orientation in breeding programs. The study demonstrates the potential of targeted heterosis utilization to develop high-performing chicken genotypes for smallholder poultry systems in tropical regions. The FM♂ × KK♀ and KK♂ × FM♀ crosses were particularly promising, combining improved productivity with the Fayoumi’s adaptive traits. These findings provide practical insights for designing crossbreeding strategies in smallholder poultry production, emphasizing the need to consider trait-specific heterosis, age effects, and reciprocal cross differences. The results highlight heterosis as a valuable tool for sustainable genetic improvement in poultry.