Variability of growth-related hormones across different chicken (Gallus gallus) genotypes is
crucial for understanding their adaptive capabilities, performance potential, and suitability for
production in the humid region of Nigeria. This study investigated the diversity of growth-related hormones, specifically insulin and thyroid-stimulating hormone (TSH), among four chicken genotypes—Normal Feather (NF), Frizzle Feather (FF), Naked Neck (NN), and ISA Brown (IB)—raised in Nigeria's humid region. A total of 120 chickens, evenly distributed across genotypes and sexes, were sampled at 24 weeks of age. Hormonal levels were analyzed using the Enzyme-Linked Immunosorbent Assay (ELISA) method. Data were analyzed using the General Linear Model and Cluster Analysis of the Statistical Package for Social Sciences (Version 22), the mean difference of the different groups was determined using Two-way Analysis of Variance (ANOVA). Significance level was at P<0.05. Results revealed significant genotype-specific differences in hormone levels. Insulin levels were highest in IB cocks (3.02 ± 0.44) and lowest in NF hens (1.88 ± 0.06), while TSH levels peaked in NN (0.98 ± 0.09) and were lowest in FF cocks (0.64 ± 0.06). Cocks generally exhibited higher insulin levels than hens, whereas TSH levels were consistent across sexes. NN chickens demonstrated a unique hormonal profile, marked by elevated TSH levels, suggesting superior adaptability to environmental stressors. The dendrogram illustrated that FF birds share similarities withthe IB group before clustering with the NF birds. NN birds are the most distinct group, clustering with the others only at a higher rescaled distance, indicating lower similarity compared to other groups. These findings highlight the interplay between genotype, hormonal regulation, and environmental adaptability, offering valuable insights for breeding programs aimed at enhancing poultry productivity in tropical regions.
Keywords: Chickens, Hormones, Genotypes, Growth, Variability
