Polymorphisms in luteinizing hormone receptor and hypothalamic gonadotropin-releasing hormone genes and their effects on sperm quality traits in Chinese Holstein bulls.

Genes of hypothalamic-pituitary-gonadal axis play a key role in male reproductive performance. This study evaluated the polymorphisms of luteinizing hormone receptor (LHR) and hypothalamic gonadotropin-releasing hormone (GnRH) genes and their effects on sperm quality traits including semen volume per ejaculate (VOL), sperm density (SD), fresh sperm motility (FSM), thawed sperm motility (TSM), acrosome integrity rate (AIR), and abnormal sperm rate (ASR) collected from 205 Chinese Hostein bulls. The study bulls consisted of 205 mature Chinese Holstein, 27 Simmental, 28 Charolais, and 14 German yellow cattle. One single nucleotide polymorphism (SNP) (A883G) in exon 2 of GnRH and two SNPs (A51703G and G51656T) in intron 9 of LHR were identified in 274 bulls. Analysis of variance in 205 Chinese Holstein bulls showed that age had significant effect on both SD and FSM (P < 0.01), and ASR (P < 0.05). With regards to genotype and its interaction with age, only the SNP of G51656T in LHR gene had significant effect on SD (P < 0.05, P < 0.01; respectively). The association result showed that bulls with AG genotype had higher FSM than bulls with AA and GG genotype in LHR at 51,703 locus (P < 0.10), and bulls with GG genotype had higher SD than bulls with TT genotype in LHR at G51656T locus (P < 0.10). Phenotypic correlation among the traits revealed that significant negative correlations were observed between ASR and AIR (r = -0.736, P < 0.01), ASR and AIR (r = -0.500, P < 0.01). There were moderate positive correlations between VOL and SD (r = 0.422, P < 0.01), as well as FSM (r = 0.411, P < 0.01). In conclusion, LHR may be a potential marker for sperm quality of SD and FSM.