THE INFLUENCE OF THE PROLIFICACY GENE FEC-B ON THE REPRODUCTIVE-BIOLOGY OF 3 4-ROMNEY-MARSH X 1/4-MERINO-BOOROOLA EWES/

Some aspects of estrous were evaluated during the reproductive season in 72 3/4 Romney Marsh x 1/4 Merino Booroola ewes. Daily distribution of onset of estrous, length of estrous and incidence of anovulatory cy cles for carrier and non carrier females of the prolificacy gene FecB was studied. For these parameters the genotypes were statistically sim ilar. Ovulation rate was greater in FecB gene carriers than in non car riers. This shows that the Fec gene acts mainly on the ovulation rate, without changing aspects of estrous behavior.