Polymorphism of the prolactin gene and its association with reproductive traits in F2 local crossed chickens

Background and Aim: Reproductive traits are crucial for genetic improvement in chickens. Prolactin (PRL) is a gene involved in a complex hormonal network that regulates reproduction in chickens. In this study, three local chicken breeds werecrossed and had been produce a second filial (F2) generation, referred to as the F2 local crossed chicken. This study aimed to evaluate reproductive traits, identify single-nucleotide polymorphisms (SNPs), and assess genetic variation in the PRL gene of F2 local crossed chickens.

Materials and Methods: Data on reproductive traits, including body weight (BW) at first egg laying, total egg production (EP) at the first 90 days of laying eggs, egg weight (EW), egg length (EL), and egg width (EWd), and blood samples from 60 hens of F2 local crossed chicken (Merawang × Kampung Unggul Balitbangtan [KUB], n= 30; Murung Panggang × KUB [MP × KUB], n= 30) were collected. SNPs within PRL gene were identified using BioEdit version 7.0. Genetic diversity was calculated using Popgen 1.32. Statistical analysis of reproductive traits and its association with genotypes were assessed using Statistical Product and Service Solutions version 20.

Results: Crossing patterns had no significant effect on reproductive traits (p > 0.05), except for EWd (p < 0.05). Five polymorphic SNPs were identified in exon 5 of the PRL gene: 8052T>C, 8113G>C, 8187C>T, 8188G>A, and 8321C>T. Observed and expected heterozygosity range from 0.15–0.52 and 0.14–0.38, respectively. All SNPs were in the Hardy-Weinberg equilibrium based on Chi-square test (χ2
<3.841), except for SNP 8052T>C in F2 crossing of MP × KUB. SNP 8052T>C was significantly associated with BW (p < 0.05), with TT genotype chickens showing higher BW. SNP 8187C>T was associated with EW and EL (p < 0.05), with CT genotype chickens having higher values for both traits.

Conclusion: This study demonstrates the significant role of the PRL gene in influencing reproductive traits in F2 local crossed chickens. While crossing patterns showed limited impact, specific SNPs in exon 5 of the PRL gene were associated with BW, EW, and EL. The findings highlight PRL gene polymorphisms as valuable markers for improving reproductive traits in poultry breeding programs.