Polymorphism of growth hormone, growth hormone receptor, prolactin and prolactin receptor genes in connection with egg production in Poltava clay chicken

The molecular assisted selection in animals is based on polymorphism study of desired gene alleles related to economic important traits, particularly productivity parameters. Allelic variants can be a result of different modification of DNA nucleotide composition, i.e. spot mutations leading to a single nucleotide polymorphism (SNP), insertions and deletions (indel), etc. Anyway, targeted selection necessitates detecting gene polymorphism and estimating its relationship with productivity. The genes encoding proteins which are involved in the growth and development regulation, such as hormones, are considered the most perspective and attractive candidates. So far as the physiological ef- fect of any hormone is known to be directly related to its receptor, it is advisable to study gene polymorphism of both hormones and their receptors. In the Ukraine the relationship between poly- morphism of the genes mentioned hereinabove and hen performance was not still studied. Therefore these stipulate the relevance and novelty of our investigation presented in the paper. The genetic structure of Poltava Clay chicken egg-and-meat breed (line 14, n = 98, laboratory population of State Poultry Research Station of the National Academy of Agrarian Sciences of Ukraine) was stud- ied on growth hormone ( GH ), growth hormone receptor ( GHR ), prolactin ( PRL ) and prolactin receptor genes ( PRLR ). Gene polymorphism was determined by PCR-RFLP analysis and by compara- tive analysis of amplified fragment length when studying insertion in the prolactin locus. The growth hormone, growth hormone receptor and prolactin genes were polymorphic. The frequencies obtained were as follows: 0.372 and 0.628 for alleles C and T ( PRL -AluI), respectively, in GH -MspI (in-tron 1) 0.908 for alleles A , 0.020 for B , 0.072 for C ; in GH -SacI (the intron 4) 0.036 for A , 0.964 for B ; in GHR -NspI 0.280 for A , 0.720 for B . The prolactin gene (24 indel) and prolactin receptor gene were monomorphic. The relationship of different genotypes of prolactin, growth hormone, and growth hormone receptor genes with egg productivity was studied. All studied polymorphic loci were in Hardy-Weinberg equilibrium in population of Poltava clay chicken breed. It is shown the signifi- cant differences in the productivity of individuals of different genotypes for the loci of prolactin ( PRL -AluI) and growth hormone ( GH -SacI). The egg production for 12 weeks in the individuals with genotype CC - PRL exceeded that in the individuals with genotype TT - PRL and amounted to 75.38±2.33 and 67.82±1.21, respectively (P < 0.01). Egg production for 40 weeks in the chickens with genotype CC - PRL reached 201.50±8.43, and in TT - PRL hens it was 188.32±3.45. The egg weight at 30 th week of life was 54.80±1.44 g in the individuals with CC - PRL genotype against 50.95±0.54 g in the individuals with CT - PRL genotype (P < 0.05). At the same time the heterozy-gous individuals with genotype AB (SacI +/SacI − ) on growth hormone gene were characterized by a significantly higher egg production during 12 week productive period compared to chickens with genotype BB (SacI − /SacI − ), particularly 72.00±1.67 against 66.98±1.05. Also the differences were shown in the egg weight at the 30 th week of life. Its value reached 55.02±1.52 g in the individuals with genotype AB while in hens with genotype BB it was 51.40±0.42 g (P < 0.05).