Association between GNRHR, LHR and IGF1 polymorphisms and timing of puberty in male Angus cattle

After weaning, 276 Angus males were measured every month for weight (W), scrotal circumference (SC), sperm concentration (C) and percentage of motility (M). A total of 4 SNPs, two within GNRHR, one in LHR and one in IGF1 were genotyped using the pyrosequencing technique. IGF1-SnaBI SNP was significant associated (P < 0.01) with age at SC 28 cm, but it were not associated with age at M 10% and C 50 million. Genotype CC exhibited an average age at SC 28 cm of 7 and 11 days higher than CT (p = 0.037) and TT (p = 0.012), respectively. This SNP explained 1.5% of the genetic variance of age of puberty at SC28. LHR-I499L, GNRHR-SNP5 and GNRHR-SNP6 were not associated with any of the measurements. However, GNRHR haplotypes showed a suggestive association with age at SC 28 cm.The findings presented here could support the hypothesis that IGF1 is a regulator of the arrival to puberty in male calves and is involved in the events that precede and initiate puberty in bull calves. Given that most studies in cattle, as well as in other mammals, were done in female, the present results are the first evidence of markers associated with age at puberty in male cattle.Among cattle breeds, significant differences have been reported in the age when bulls reach puberty [1-5]. Although the timing of puberty is likely to be a multigenic trait, data from human and mouse indicate that there could be single genes with major effects involved. Despite its economic importance, there are few genetic markers associated with this trait. Recently, gonadotropin-releasing hormone receptor (GNRHR) polymorphisms have been associated with the days to first service after calving in dairy cattle [6], and with age of first corpus luteum in Brahman and Tropical Composite female [7]. Recently, Fortes et al. [8,9], using a system biology approach in Brahman and Tropical Composite dams, identified candidate genes and pathways (e.g. axon guidance, cell adhesion, ErbB signaling, and glutamate activity) that are kno