Influences of melatonin treatment, MTNR1A and KiSS-1 genes polymorphisms on first conception in Sarda ewe lambs.

In order to investigate if the melatonin receptor 1A (MTNR1A) and kisspeptin (KiSS-1) genes influence the
reproductive response to melatonin treatment, 510 Sarda ewe lambs were divided into groups C (control) and M; GroupM
received one melatonin implant (18 mg). After 35 days rams were introduced for 40 days and subsequent lambing dates
and number of newborns were recorded. The MTNR1A gene Exon II and KiSS-1 gene Exon I were amplified and
genotyped by restriction fragment length polymorphism (RFLP) and single-strand conformation polymorphism analysis.
Two single nucleotide polymorphisms (SNPs; C606T and G612A) in MTNR1A and one (G1035A) in KiSS-1 were found.
The most frequent genotypes were G/G (63%) and C/C (53%) for MTNR1A and G/G (92%) for KiSS-1. Treated animals
showed a higher lambing rate (P,0.05) and an advanced lambing date (P,0.05) compared with controls. The three
SNPs did not influence the onset of reproductive activity. The majority of the G/G animals of Group M lambed before
190 days after ram introduction (P,0.05), while in Group C a higher number of G/G animals lambed after this date.
Data revealed the positive effect of melatonin treatment on the time of first conception in ewe lambs and highlighted that
the G/G genotype of the MTNR1A gene is able to influence the reproductive response to melatonin treatment.