Estimation of Genetic Parameters for Growth and Adaptation Traits in Tropical Poultry Breeds: A Comprehensive Review

The objective of the current review article was to compile estimates of growth and adaptation traits in poultry breeds in the Tropics. Growth traits, including body weight at various ages (BW), average daily weight gain (ADG), feed conversion ratio (FCR), carcass yield (CY), abdominal fat (AF), and shank length (SL), exhibited moderate heritability (h²) and moderate to high repeatability (R), indicating their suitability for genetic selection. In contrast, adaptation traits such as heat tolerance index (HI), disease resistance rate (DR), survivability rate (SR), mortality rate (MR), and feather coverage (FC) showed low to moderate heritability but high repeatability, emphasizing the role of environmental factors. Genetic correlations revealed that selecting for early growth enhances later body weight. At the same time, ADG was positively associated with BW but negatively with FCR, indicating improved feed efficiency in faster-growing birds. The FCR had a strong negative correlation with BW20 and CY, while BW20 showed a moderate positive correlation with AF, necessitating balanced selection strategies. Among adaptation traits, HI correlated positively with DR and SR but negatively with MR, confirming that birds with greater heat tolerance are generally healthier and more resilient. Estimated breeding values (EBVs) indicated genetic improvement potential, with BW ranging from 5 to 70 g, ADG16-20 from 3.5 to 5 g/day, CY from 1.5 to 2.5%, and SL from 1.2 to 1.8 mm. Adaptation traits also exhibited positive EBVs, including HI (0.11-0.15), DR (5-8%), SR (4-6%), and FC (3-4%), while MR showed a negative EBV (-6 to -5%), supporting its reduction through selection. In conclusion, genetic selection is a viable approach to improving growth traits, while adaptation traits require optimized environmental management. Further research on genetic parameters, particularly in tropical poultry breeds, is recommended to improve breeding programs effectively.