Egg Production Characteristics and Adaptive Traits of F₁ Backcross Progenies Derived from Normal-Feathered, Naked-Neck, and Frizzle Crossbred Chickens under Humid Tropical Conditions
Poultry production in humid tropical environments is constrained by chronic heat stress, which adversely affects reproductive performance, egg quality, and overall adaptability of laying birds. The incorporation of adaptive major genes such as naked-neck (Na) and frizzle (F) into crossbreeding programmes offers a promising strategy for enhancing productivity under such climatic stress. This study evaluated egg production characteristics, egg quality traits, and adaptive performance of F₁ backcross progenies derived from normal-feathered (NF), naked-neck (Na), and frizzle (F) indigenous chickens crossed with an exotic broiler breeder strain (Anak) under humid tropical conditions. The experiment was conducted at the Poultry Unit of the Teaching and Research Farm, Michael Okpara University of Agriculture, Umudike, Nigeria (05°29′N, 07°33′E; 122 m above sea level), characterised by high ambient temperature (27–36°C), relative humidity (57–91%), and annual rainfall of approximately 2,177 mm. Ninety (90) parental birds comprising 45 indigenous genotypes (NF, Na, and F) and 45 exotic breeders were used to generate F₁ progenies through main and reciprocal crosses using artificial insemination. The laying trial lasted 90 days following attainment of point-of-lay at 18 weeks. Data were analysed using a Randomised Complete Block Design with genetic group as fixed effect and hatch as a block, and means were separated using Duncan’s Multiple Range Test at P < 0.05. Significant (P < 0.05) genotypic differences were observed in body weight at first egg (BWFE), age at first egg (AFE), average weight of first egg (AWFE), and short-term egg number (EN₉₀). Reciprocal crosses consistently outperformed main crosses, highlighting the importance of maternal and non-additive genetic effects. The frizzle × exotic (F × E) reciprocal cross recorded the highest BWFE (2000 g), earliest maturity (146 days), and superior egg weight at first lay (47.55 g), while Na × E also demonstrated early maturity and high egg output. Short-term egg production was highest in Na × E (40.70 eggs) and F × E (41.02 eggs), indicating improved laying intensity under thermal stress conditions. External and internal egg quality traits were likewise significantly influenced by genotype. F × E birds exhibited superior egg weight, shell weight, shell thickness, albumen weight (21.72 g), yolk weight (15.45 g), albumen height (8.98 mm), and Haugh unit (155.17), reflecting enhanced structural and internal egg quality. Correlation analyses revealed strong positive associations between egg weight and most egg quality traits, suggesting that selection for egg weight would concurrently improve albumen and yolk yield. Positive correlations between BWFE and egg production traits indicate that heavier pullets at sexual maturity tend to exhibit improved early laying performance, although some genotype-specific trade-offs were observed. The results demonstrate that incorporation of naked-neck and frizzle genes through reciprocal crossbreeding significantly enhances reproductive performance, egg quality, and adaptive capacity under humid tropical conditions. The superiority of F × E and Na × E reciprocal crosses underscores the combined influence of adaptive major genes, maternal effects, and heterosis. Strategic exploitation of these genotypes can contribute to the development of climate-resilient laying chickens suited to tropical production systems, thereby improving productivity, profitability, and sustainability of poultry enterprises in hot–humid environments.
Keywords: F₁ backcross; naked-neck gene; frizzle gene; egg production; egg quality; humid tropics; adaptive traits; reciprocal crossbreeding; poultry genetics.
