Growth hormone and growth hormone receptor genes diversity in Egyptian rabbits and their association with body weight

Abstract

Rabbit meat is a highly nutritious, easily digestible protein source with low cholesterol and caloric content, offering considerable health benefits. This study investigated polymorphisms in the growth hormone (GH) and growth hormone receptor (GHR) genes and their association with body weight in the Native Middle Egypt Rabbit (NMER) breed and two synthetic lines, Egy-line and S-line, developed by crossing NMER with Giant Flander and Spanish V-line rabbits. Body weights were recorded at 5, 8, 12 and 20 wk of age. Genotyping was performed using polymerase chain reaction (PCR), single-strand conformation polymorphism (SSCP) and DNA sequencing, followed by bioinformatics and statistical analyses. The PCRSSCP analysis revealed substantial polymorphism in GH exon 1, with two genotypes detected in NMER, six in Egy-line and four in S-line, indicating greater genetic diversity in the synthetic lines. In contrast, GHR exons 1 and 3 were monomorphic and highly conserved across all three breeds. The synthetic Egy-line and S-line exhibited significantly higher body weights at 12 and 20 wk compared to the NMER breed, demonstrating the effectiveness of crossbreeding in developing high-growth lines. Association analysis showed that specific GH exon 1 genotypes were significantly linked to higher body weight. In NMER, genotype I in the high litter size group (4–6 kits/doe) and genotype II in the low litter size group (1–3 kits/doe) were superior. In Egy-line, genotypes IV and V were shown in the high and low litter size groups, respectively, while in S-line, genotypes VI and V were superior in the high and low litter size groups, respectively. These findings indicate that GH exon 1 polymorphisms are promising molecular markers for marker-assisted selection (MAS) to improve growth rate in rabbits.