Candidate genes for marker-assisted selection for growth, carcass and meat quality traits in rabbits

Growth and meat production are the most relevant targets for animal breeders, there are strong relationships between animal growth regulation, body composition and meat quality. Therefore, it is essential to identify the genetic factors that are controlling growth, carcass, and meat quality traits and to explore the correlations between identified genes of those traits. Identification of candidate genes may shift rabbit breeding from classical to modern approaches, which offer great potential to accelerate genetic improvement plans, especially in developing countries. The current work reviews several genes and mutations affecting growth, carcass and meat quality traits. These candidate genes and mutations can be incorporated into MAS programs to improve rabbit breeds especially local breeds, provided that a reasonable proportion of trait additive genetic variance is explained by the significant marker. Furthermore, we highlighted the indispensable need for more researches investigating candidate genes for different traits.

Identification of nucleotide variation of growth hormone gene in rabbit populations reared in Bulgaria

Five rabbit populations of New Zealand White (NZW), Californian (CAL), crossbred NZW×GW and two generations of the synthetic population – SPF₁ and SPF₂ reared in Bulgaria were included in the present study with the aim of detecting the genetic variability of the growth hormone encoding gene (<em>GH</em>) via polymerase chain reaction with the restriction fragment length polymorphism analysis and direct sequencing. The targeted region of the rabbit <em>GH</em> gene was amplified and a fragment of a total of 231 bp was obtained in all studied populations. Allele identification was determined after enzymatic digestion, where two fragments of 62 and 169 bp correspond to allele C and an undigested fragment of 231 bp corresponds to allele T. Two additional bands of 107 and 124 bp evidenced A/G genetic polymorphism in the rabbit <em>GH</em> gene. Thirtyeight percent of the studied rabbits were carriers of the double mutation (C/T+A/G) in the same locus as the studied <em>GH</em> gene. The sequence analysis revealed two nucleotide substitutions – g.111C&gt;T and g.156A&gt;G in the non-coding region between the regulatory TATA box and 5’ UTR region, and a novel g.255G&gt;A genetic variant in intron 1 of GH gene. The A&gt;G transition was most frequent (40.57%), compared to the other ones, G&gt;A (28.57%) and C&gt;T (10.80%), respectively. The most frequent genotype in the NZW population was homozygous TT (0.93), with a prevalence of the T allele (0.97) over allele C (0.03) for g.111C&gt;T SNP site. The distribution of the allele and genotype frequencies at the sites g.156A&gt;G and g.255G&gt;A in this rabbit group was identical, with the highest value of 0.93 for alleles A and G, respectively. The rabbit populations CAL and NZW×GW showed equal frequencies of the prevalent T allele (0.83) and for homozygous TT genotype (0.67) according to g.111C&gt;T SNP. The highest values were obtained for the allele А (0.83) and for homozygous AA genotype (0.67) at c.33A&gt;G SNP in these rabbit groups. The highest values (0.67, 0.60 and 0.80) for the heterozygous genotypes at g.111C&gt;T, g.156A&gt;G and g.255G&gt;A SNPs, respectively, were detected among the SPF₂ rabbit population, compared to the both homozygous genotypes. The results obtained in the present research indicates a significant degree of genetic variability of the studied polymorphic <em>GH</em> locus in the SPF₂ rabbit group.

Identification of two novel single nucleotide polymorphism sites in the Myostatin (MSTN) gene and their association with carcass traits in meat-type rabbits (Oryctolagus cuniculus)

<p>Two unknown single nucleotide polymorphism (SNP) sites in exons 1 (c.194C&gt;T) and 2 (c.445T&gt;A) of meat-type rabbit <em>MSTN</em> gene were identified in the study. Our objective was to analyse the population genetics structure of the two novel SNP sites in 230 individuals from six breeds and their associations with carcass traits of rabbits. We found that live body weight (BW), cold carcass weight (CCW), reference carcass weight (RCW), CCW percentage (P_CCW) and RCW percentage (P_RCW) of the rabbits with the genotype CC at the c.194C&gt;T of exon 1 or AA at the c.445T&gt;A of exon 2 were significantly higher than those with other genotypes. Diplotype significantly affected BW, RCW, CCW, P_RCW (<em>P</em>&lt;0.01) and P_CCW and P_CM (<em>P</em>&lt;0.05). CC/AA was the advantageous diplotype for BW, RCW, CCW and P_CM, and TT/AA was the advantageous diplotype for P_CCW and P_RCW. In contrast, TT/TT was the negative diplotype for BW, CCW, RCW, P_CCW and P_RCW, and TT/AA was the negative diplotype for P_CM. The results suggest that the two new mutations of <em>MSTN</em> gene significantly affected BW, CCW, RCW, P_CCW and P_RCW of rabbits, and <em>MSTN</em> may be an important candidate gene of carcass traits in meat-type rabbits.</p>