Reproductive response to male joining with ewes with different allelic variants of the MTNR1A gene.

The aims were to evaluate the reproductive response to ram placement with Sarda ewes with different allelic variants at position g.15099485 A > G of the MTNR1 A gene. Ram placements occurred between the early and late spring and there was analysis of whether this polymorphism is associated with other nucleotide substitutions. In each of the eight farms where the study was conducted (named F1-F8), 150 ewes (50 with A/A, A/G and G/G genotypes) were selected. In each group of 150 ewes, eight males were joined with ewes on the following dates: 25 March (T1) for F1-F2, 15 April (T2) for F3-F4, 5 May (T3) for F5-F6, and 1 June (T4) for F7-F8. The lambing dates and number of new born lambs were recorded until 220 days after joining rams with ewes. The ewes with G/G or A/G genotypes had a greater fertility rate compared with those with A/A in T1, T2 (P < 0.01), and in T3 and T4 (P < 0.05). The duration of time in days from the time of ram joining with ewes to lambing was less in the ewes with G/G and A/G compared with those with A/A (P < 0.01). The g.15099485A>G variation was always associated with that at position g.15099391G>A. Results indicate there is a positive effect of the g.15099485A>G variant on reproduction when males were joined with ewes in March or April. The association that was ascertained in this study between the g.15099391G>A and g.15099485A>G polymorphisms for the MTNR1 A gene, could provide new insights to clarify the mechanism of action of melatonin.