Evaluate the Relationship between Polymorphism

Remarkable seasonal variations are observed in the reproductive activities of small ruminants living in temperate latitudes (Luridiana et al. 2015). Thus, a great alteration is induced by lamb reproductive seasonality and its consequent meat market price. Alternatively, out-of-season reproduction is induced through a wide use of hormonal treatments in some countries. However, there is a need for a search for some other methods due to the increasing demand for free-hormone products (Martinez-Royo et al. 2012). Nonetheless, identification of informative genetic markers has been suggested to improve selection efficiency for reducing breeding seasonality in sheep (Moradi et al. 2014). In a response to photoperiodism, animals are engaged in the secretion of differential melatonin to regulate their reproductive activities (Saxena et al. 2014). The light signals relayed to the pineal gland by several neurons from the retina, known as photoperiodic information, are translated into the daily cycle of melatonin secretion, the level of The objective of this study was to evaluate the relationship between polymorphism at the MnlI site of MTNR1A gene and production traits of Shal and Romanov crossbreeding. The crossbreeding between Shal and Romanov was done on 600 Shal ewes. For this reason, Shal ewes were laparoscopically and artificially inseminated with the semen of Romanov breed. For the preparation of genomic DNA, a total of 90 ewes, either Shal (n=50) or Shal × Romanov (n=40), were used and an 824 bp fragment of exon 2 of the MTNR1A gene was amplified. In this research, two genotypes MM and Mm were detected in the study Shal population with frequencies of 0.78 and 0.22, respectively, while MM and mm genotypes of the study crossbreeds were detected with 0.125 and 0.0875 frequencies, respectively. However, the mm and Mm genotypes were not detected in Shal and Shal × Romanov crossbreeds, respectively. The MnlI marker site in Shal × Romanov breeds had a significant effect (P>0.05) on body weight after 3 months (BW3) as the ewes with MM genotypes had significantly higher BW3 than mm individuals. However, no significant difference was observed between MM and mm marker sites for birth weight (BW) and 6-month body weight (BW6). The same results were observed for Shal breeds as when MM and Mm genotypes were detected for BW, BW3 and BW6 traits. In conclusion, in this study, mm genotype as a measurement for litter size in sheep breeds was successfully introduced into Shal × Romanov crossbreeds, while their production traits were not affected by MnlI genotypes.