Associations between novel polymorphisms at the 5'-UTR region of the prolactin gene and egg production and quality in chickens.

The objective was to characterize polymorphisms at the 5'-UTR region of the prolactin gene, and determine their association with egg production and egg quality traits in White Leghorn chickens. The study was conducted on four strains of White Leghorn chickens, namely IWH, IWI, IWK, and layer control. Overall, there were three alleles (designated A, B, and C) and five genotypes, with genotypic frequencies of 0.09, 0.75, 0.07, 0.02, and 0.07 for AA, AB, AC, BB, and BC, respectively. There were significant differences among genotypes for egg production up to 52 and 64 wk of age, with maximal egg yields for genotypes AA and AC (144.5 ± 5.06 and 143.2 ± 4.67 eggs, respectively). Furthermore, there were significant differences among genotypes for egg quality traits, including egg weight and Haugh unit at 40 wk of age, Haugh unit at 52 wk, and yolk color index and Haugh unit at 64 wk. Birds with AA or AC genotypes had the best egg quality traits. On the contrary, these genotypes had the lowest prolactin expression, whereas this expression was highest in birds with the BB genotype. In conclusion, polymorphisms at the 5'-UTR of prolactin gene were significantly associated with egg production and egg quality traits in White Leghorn chickens.