Variation in frequency of alleles in the MTNR1A gene with possible impact on ability of ewes to show oestrus out of season

Sammanfattning: In Swedish sheep industry it is desired to have lambs slaughtered evenly distributed over the year. Swedish sheep are generally seasonal breeders with lambs born in the spring and slaughtered in the autumn. Some of the breeds, e.g. Swedish Finewool and Roslag sheep breeds have shown ability to lamb out of season. For increased knowledge on the possibilities to breed for out-of-season lambing in Swedish sheep breeds, the aim of this master thesis is to study the variation in frequency of two alleles in the MTNR1A gene in the three breeds; Gotland, Swedish Finewool, and Roslag sheep. This master thesis is divided into two parts. The first part is a literature review with emphasise on reproduction physiology, methods for heat synchronisation and induced out-of-season reproduction, selection for out-of-season reproduction and description of different methods for DNA analyses. Many of the investigated studies have shown a connection between out-of-season breeding and an increasing amount of C alleles in the polymorphic position C606T and G alleles in the polymorphic position G612A on the MTNR1A gene. Another study has also detected a relatively high frequency of the favourable MTNR1A alleles but on seasonal breeds. In the second part of the thesis the allele frequency and genotypes of nucleotide position 606 and 612 in the MTNR1A gene for three different Swedish sheep breeds were investigated. Blood was sampled from around 30 animals of each breed. DNA was extracted from the blood and the sequence containing both SNPs of the MTNR1A gene, was analysed. The three breeds had a similar allele frequency for both positions and the assumed seasonal Gotland ewes had a high frequency (0.87) of the G allele in position G612A. The results indicate that the SNPs investigated are not good markers to decide the Swedish breeds’ ability for out-of-season breeding.