Genotype at the MTNR1A locus and response to melatonin treatment in Sarda lambs

With the aim to evaluate the effect of melatonin treatment and melatonin receptor 1A (MTNR1A) genotype on advance of puberty, 423 Sarda lambs were chosen. On June 26th, they were divided into three groups, each of 141 animals (groups 0, 1, and 2), on the basis of live weight. On June 30th, animals in group 1 received a single implant (18 mg melatonin), while group 2 received two implants. Group 0 was untreated. Thirty-five days after treatment (August 4th), rams were introduced and after 40 days they were removed. From January 1stto February 10thlambing dates were recorded. Genomic DNA was extracted and subjected to PCR for the amplification of exon II and then digested with enzymes MnlI and RsaI and placed into +/+, +/−, or −/− group for MnlI and C/C, C/T, or T/T group for RsaI. Samples were cloned and sequenced. Data obtained were subjected to χ2test in order to evaluate the difference in fertility among groups and the link between genotype and reproductive activity. Genotype +/+ and C/C showed the highest incidence. Treated groups showed a higher number of lambing at 10thFebruary compared to control group (P<0.04). Melatonin treatment results more efficient in +/+ genotype.