ASSOCIATION OF THE MTNR1A GENE POLYMORPHISMS AND SEASONAL REPRODUCTION IN SHEEP

Seasonal reproduction in sheep greatly limits the possibilities of continuous year-round production and equitable supply of sheep products on the market. The begging of breeding season in sheep is associated with melatonin secretion under the darkness influence. Melatonin, through specific G protein coupled receptors, MT1 and MT2, affects target tissues and organs. MTNR1A gene is located on 26th chromosome and has two polymorphic sites in sheep. The presence of polymorphism (M/M, R/R) is related to non-seasonal presence of estrus, while absence of polymorphism (m/m, r/r) is related to seasonal estrus presence. Individuals with "M" or "R" allele in homozygous or heterozygous form are characterized by more successful reproduction during long photoperiod or outside the usual breeding season