Polymorphisms of the melatonin receptor 1A (MTNR1A) gene affect sexual performance of Rasa Aragonesa rams without changing their social dominance

Abstract The aim of this study was to investigate whether a specific genotype of the MTNR1A gene influences social dominance and reproductive performance in rams. Thirty-one rams were genotyped for Rsal and Mnll polymorphism of the gene: CC (n = 19), CT (n = 5), and TT (n = 7), and GG (n = 20), GA (n = 6), or AA (n = 5), respectively. Social behavior was recorded by direct observations, and rams were tested in individual serving-capacity tests. The genotypes did not differ in the numbers of aggressions that they performed or received, and their active and passive behaviors were similar. For the Rsal and Mnll polymorphism, TT and GG rams were responsible for 54% and 56% of the total number of recorded sexual events (P < 0.05), respectively. Results of this study confirm that the best sexual performance of rams was among those that carried certain genotypes of the MTNR1A gene, but it was not correlated with differences in social dominance.