Growth Performance and Adaptive Traits of F₁ Backcross Progenies Derived from Normal-Feathered, Naked-Neck, and Frizzle Crossbred Chickens under Humid Tropical Conditions
The development of poultry genotypes capable of sustaining high productivity under humid tropical conditions remains a major challenge in sub-Saharan Africa, where elevated temperature and humidity impose chronic environmental stress. This study evaluated the growth performance and adaptive traits 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, characterised by high ambient temperature (27–36°C maximum), relative humidity (57–91%), and annual rainfall of approximately 2,177 mm. A total of 90 parental birds (48 weeks old), comprising 45 indigenous genotypes and 45 exotic broiler breeders, were used to generate F₁ progenies through main and reciprocal crosses using artificial insemination. The resulting crossbreds, each containing 50% exotic genetic background, were reared from day-old to 18 weeks of age under standard management conditions. Growth performance traits (body weight, average daily feed intake [ADFI], feed conversion ratio [FCR], and mortality percentage) and linear body measurements (body length, wing length, keel length, shank length, breast width, drumstick length) were recorded. Data were analysed using analysis of variance in a completely randomised design, with genotype and cross direction as fixed effects. Genotype significantly influenced (P < 0.05) body weight, ADFI, FCR, morphometric traits, and mortality rates across ages. Reciprocal crosses consistently outperformed main crosses in growth performance. At 18 weeks, final body weights were highest in the frizzle × exotic (F × E) reciprocal cross (1666.67 g), followed by normal-feathered × exotic (NF × E) and naked-neck × exotic (Na × E). Main crosses recorded comparatively lower body weights. Average daily feed intake was significantly higher in reciprocal crosses, corresponding with improved growth. Feed conversion ratio values were consistently lower (P < 0.05) in reciprocal crosses, indicating superior feed efficiency, with F × E exhibiting the most favourable efficiency across evaluation periods. Linear body measurements at 18 weeks further confirmed genotype effects. Reciprocal crosses demonstrated significantly greater body length, keel length, wing length, breast width, and drumstick length compared with main crosses. The F × E genotype showed superior musculoskeletal development in both cockerels and pullets, suggesting enhanced meat-type potential under humid tropical conditions. Mortality patterns revealed significant genotype differences. Naked-neck crosses exhibited higher brooding, rearing, and laying mortality rates, indicating reduced early-life viability under the prevailing environmental conditions. In contrast, frizzle-bearing crosses recorded comparatively lower mortality, suggesting improved environmental adaptability, possibly due to enhanced heat dissipation associated with reduced plumage density. Overall, the results demonstrate that both genotype and cross direction exert significant influence on growth performance and adaptive capacity in tropical poultry production systems. Reciprocal crossing, particularly involving frizzle males and exotic females (F × E), produced progenies with superior growth rate, feed efficiency, morphometric development, and survivability. These findings underscore the importance of strategic crossbreeding and gene interaction in developing climate-resilient meat-type chickens suitable for humid tropical environments.
Keywords: F₁ backcross; frizzle gene; naked-neck gene; reciprocal cross; feed efficiency; morphometric traits; humid tropics; poultry breeding; genotype × environment interaction.
