CONCLUSION

This study provides the first comprehensive characterization of TGFβ2 gene polymorphisms in KUB chickens and demonstrates their association with growth performance and meat quality in response to multienzyme supplementation. Three TGFβ2 genotypes (CC, TC, and TT) were identified, with allele frequencies of 0.48 (C) and 0.52 (T). Significant associations between genotype and BW, CW, and FCR indicate that TGFβ2 contributes to growth efficiency in this indigenous breed. In addition, dietary phytase and protease supplementation improved meat quality by reducing CL, increasing WHC, and enhancing meat color characteristics, while two novel exon SNPs (c.103C>T and c.99G>A) were identified in KUB chickens. Functional enrichment analyses further implicated extracellular matrix-receptor interaction, metabolic pathways, and muscle development processes, supporting the biological relevance of TGFβ2 in regulating productive traits.

From a practical perspective, these findings provide valuable molecular evidence for integrating TGFβ2 polymorphisms into MAS programs and highlight the potential of combining genetic selection with precision nutritional strategies to improve growth performance and meat quality in indigenous tropical chicken populations. Such an integrated approach could enhance production efficiency while preserving the desirable adaptive characteristics of KUB chickens, thereby contributing to sustainable poultry production and food security in tropical production systems.

A major strength of this study is the integration of molecular genotyping, growth performance evaluation, meat quality assessment, and bioinformatics analyses within a nutrigenetic framework, providing a comprehensive understanding of genotype–nutrition interactions. However, the study is limited by the relatively small sample size, evaluation of a single indigenous breed, and the absence of functional validation of the identified polymorphisms or direct gene expression analyses across genotypes. These limitations restrict the generalizability of the findings and preclude definitive conclusions regarding the biological mechanisms underlying the observed associations.

Future studies should validate these associations in larger, genetically diverse chicken populations, investigate the functional effects of the identified polymorphisms using transcriptomic and proteomic approaches, and evaluate genotype-specific nutritional responses under commercial production conditions. Such investigations will facilitate the development of genomic selection tools and precision feeding strategies for indigenous poultry breeding programs.

Overall, TGFβ2 represents a promising candidate gene for improving growth performance and meat quality in KUB chickens. The findings establish an important foundation for future genomic breeding initiatives and support the application of molecular genetics and precision nutrition to enhance the productivity, sustainability, and competitiveness of indigenous poultry production systems.