Evaluation of Welfare Traits in Hybrids Obtained from Reciprocal Crosses between Anatolian-T and Commercial Broiler Parent Stocks

Abstract

This study aimed to evaluate the effects of genotype, sex, and their interaction on welfare-related traits, morphological characteristics, and developmental stability in reciprocal crosses between Anatolian-T and commercial broiler parent stocks at 3 and 6 weeks of age. Welfare indicators, including tonic immobility (TI) and rectal temperature (RT), were largely unaffected by genotype and genotype × sex interactions at both ages. At 3 weeks, sex had a significant effect on RT, with males exhibiting slightly higher values, suggesting early metabolic differences; however, this effect was not observed at 6 weeks. These findings indicate that early physiological welfare traits are relatively stable and largely independent of genetic background.

Morphological traits, including comb length (CL), comb width (CW), and beak length (BL), were significantly influenced by sex at both ages, with males consistently showing higher values. Genotype effects were not evident at 3 weeks but became significant at 6 weeks, highlighting the increasing influence of genetic background on phenotypic expression as birds approached market age. Reciprocal cross differences suggested potential maternal and sex-linked genetic effects.

Fluctuating asymmetry (FA) and relative asymmetry (RA) analyses revealed that developmental instability was generally low and not significantly affected by genotype at 3 weeks. However, at 6 weeks, genotype, sex, and genotype × sex interactions significantly influenced several traits, particularly in head, tarsometatarsus, and foot measurements. These results indicate that developmental instability increases with age and becomes more sensitive to genetic and physiological factors.

Taken together, the findings demonstrate that early-stage traits are relatively stable across genotypes, whereas later developmental stages show increased variability driven by genotype, sex, and their interaction. These results emphasize the importance of considering age-dependent effects in broiler breeding and welfare evaluation.