Trait association of genetic markers in the growth hormone and the growth hormone receptor gene in a White Leghorn strain

Abstract

Alleles of the growth hormone (GH) gene and GH receptor (GHR) gene were analyzed for association with juvenile body weight (HBWT), age at first egg (AFE), the hen-day rate of egg production (HDR), egg specific gravity (SPG), and egg weight (EWT) in a strain of White Leghorns. The particular strain segregated at near equal frequencies for two GH alleles defined by differences at three restriction fragment length polymorphisms (RFLP) and for two GHR alleles defined by a single RFLP. The GH genotype was significantly associated with AFE (P < or = 0.04) as well as HDR from 274 to 385 d (P < or = 0.04) and 386 to 497 d (P < or = 0.0003). The GHR genotype (haploid in female chickens) had trends for association with HBW (P < or = 0.06) and HDR from AFE to 273 d (P < or = 0.07). The effects on the egg quality traits SPG and EWT were not significant. Regression analysis revealed that HDR was associated negatively with AFE and positively with HBWT. The slope of the regression line of HDR on AFE varied with the GH genotype, with the effect that the differences in HDR between GH genotypes was relatively small in chickens with early AFE and large in chickens with late AFE. Similarly, the slope of the regression of HDR on HBWT varied between GHR genotypes, with the result that the effect of the GHR genotype on HDR in chickens with low HBWT was opposite to its effect in chickens with high HBWT. The complex relationship between genotypes and traits may reflect gene interaction and indicates that simple models based on additive gene effects may not be adequate for the dissection of the genetic architecture of quantitative traits.

A study of association between genetic markers in candidate genes and reproductive traits in one generation of a commercial broiler breeder hen population

“…Owing to the likely role of the GH-IGF1 system in producing polyfollicular ovaries at the onset of lay, a possible association between GHR with the number of eggs produced in the first two months was also examined, but without success. Feng et al (1997) demonstrated a significant association with age at first egg and alleles of GHR that may be worth investigating along with other components of the GH-IGFI system. Studies seeking correlations between alleles of candidate genes and quantitative traits have frequently used single-generation comparisons (eg Feng et al, 1997(eg Feng et al, , 1998Nagaraja et al, 2000).…”

Identification and characterization of single nucleotide polymorphisms in 12 chicken growth-correlated genes by denaturing high performance liquid chromatography

“…In the chicken GH gene, several SNP in introns have been identified and reported to be associated with growth, egg production and disease resistance [11,13,20]. Sex-linked dwarf chickens are just due to a mutation at an exon-intron splicing site of the GHR gene [17].…”

“…Sex-linked dwarf chickens are just due to a mutation at an exon-intron splicing site of the GHR gene [17]. Another SNP that led to the presence or absence of a poly (A) signal in intron 2 was found to influence ages at first egg and egg production from 274 to 385 days [11,12]. Two SNP in the IGF-II gene were significantly related to growth and feeding traits [3].…”

“…In chickens, certain SNP of GH [11], GHR [11,12], IGF-I and -II genes [3,41] have been reported to be associated with chicken growth, feeding and egg laying traits. The SNP in the porcine pituitaryspecific transcription factor-1 (PIT-1) gene are also significantly related to carcass traits [33].…”

Association of chicken growth hormone polymorphisms with egg production

“…These polymorphic sites were located in intron 1, intron 3, and intron 4, respectively. The authors suggested that the alleles that were located within the introns might have been selected for several reasons, such as an array of egg production traits, resistance to Marek's disease, or resistance to avian leukosis Feng et al, 1997). Nie et al (2005) used denaturing high-performance liquid chromatography to investigate 4 chicken breeds, and identified 283 SNPs from 12 genes of the somatotropic axis that differed in growth and reproductive characteristics.…”