Phenotypic and genetic characteristics of fecundity in sheep. A review

The phenotypic characteristics of animals are result of the complex interaction of a number of genetic and non-genetic factors, which usually act simultaneously and it is difficult to determine the degree of influence of each of them. Early identification of the genetic traits of individuals enables more efficient management of selection. Fertility determins the cost-effectiveness of sheep farming, regardless of productive direction. The individual fertility of the animals is determined by the number of lambs born per sheep. This trait is characterized by a low inheritance rate, hence conventional breeding methods shows slow progress. The introduction of new molecular-based technologies to improve productivity contributes to a greater and faster effect on the realization of animal genetic resources. The assessment of the breeding value of animals at the earliest possible age makes it possible to maximize the effect of the selection and to increase the use of animals with the highest genetic potential. The molecular markers and the application of RFLP-PCR method allow the determination of allelic variants of genes related to the quantity and quality of animal productivity. By identifying the different polymorphic variations and their phenotypic manifestation, a database can be accumulated to manage the genetic progression of economically important traits. Many mutations have been found in sheep that affect fertility and ovulation rates to varying degrees. Large number of mutations which affects ovulation have been found in genes expressing different proteins, such as the BMPR1B or FecB (Booroola gene or the bone morphogenetic protein receptor type 1B), GDF9 or FecG (the growth differentiation factor 9b) and BMP15 or FecX (a bone morphogenetic protein 15).