Major genes increasing litter size were identified in certain sheep breeds. These genes include BMPR‐1B, BMP15, GDF9 and B4GALNT2, FecX2. Polish Olkuska sheep is a high‐fecundity sheep breed; while some animals might give birth to just one or two lambs, there are Olkuska ewes which have six or even seven lambs/lambing. Fertility of this breed is caused by mutation in the major gene FecXO (BMP15 gene), but analysis of polymorphism at the locus GDF9 revealed presence of four polymorphisms: G447A (L159L), A978G (G326G), G994A (V332I) and G1111A (V371M). Substitutions V371 and V332I are missense mutations found in the sequence encoding active GDF9 protein. V371 polymorphism has also an effect on litter size in Olkuska breed ewes. Study of genes associated with litter size in Olkuska sheep is of high importance, as they could be used in breeding programmes as selection markers for increasing production efficiency.
Part of the book: Genetic Polymorphisms