Estudios realizados y situación actual de la variante génica prolífica ROA (FecXR) de la raza ovina Rasa Aragonesa

In the present work we present the main productive studies carried out to characterize ROA sheep (R+, Rasa Oviaragon®), ewes of the Rasa Aragonesa breed carrying in heterozygosity a natural genetic prolific variant found in 2007 (FecXR allele, BMP15 gene). Its effect on prolificacy leads to an increase of 0.35 lambs/lambing ewe when compared with non-carrier ewes, with an additive effect over the standard hormonal treatments used in farms. In artificially inseminated ewes, an increased fertility was also found in a set of farms (71.1 vs. 59.5 %; p<0.01) as well as an advanced puberty (around 30 days). On the contrary, no differences between genotypes were found in male’s fertility. The studies on the preovulatory LH peak did not show differences between genotypes, which allows for the application of the same protocols used in non-carrier ewes concerning Artificial Insemination (AI) at fixed time. The increased ovulation rate of R+ ewes could be related with the smaller size of their ovarian follicles, with no further influence on fertility, as sown in farms as well as on in vitro embryo production studies. Regarding lamb marketing, the presence of the FecXR allele does not affect morphology, lamb growth or the characteristics of the carcass or meat quality of their offspring. Finally, it has been observed that the productive advantages of the FecXR (ROA) variant result in an increase in profitability of farms that use this variant, which confirms its interest for most farmers.