Abstract

At 3 months of age, the ovaries of F+ Booroola lambs [i.e. those heterozygous for the fecundity (F) gene] were lighter (P<0.01) than those of ++ Booroola lambs (i.e. those without the F-gene) which were of similar age and body weight. However, the number of follicles (>/= 1 mm diam.) in the above F+ lambs was 1.5 fold greater (P<0.01) than that in the ++ lambs. In lambs of both genotypes, ovarian follicles were active in synthesising testosterone and oestradiol and of reaching diameters which were similar to those of preovulatory follicles in mature ewes. However, none of the ovaries showed evidence of recent ovulations. In Booroola ewes (4 to 8 years of age), the proportions of small ovarian follicles (0.5 to 1.0 mm diam.) that synthesised progesterone, androstenedione and oestradiol in culture were related (P<0.05) to genotype (homozygous, FF > F+ > ++ ewes). Also in the above ewes, follicles in the FF and F+ animals reached maturity at smaller diameters than in ++ animals, namely 3.4

WH, McMillan

Proceedings of the New Zealand Society of Animal Production, Volume 46, , 225-228, 1986