Effect of intensive or extensive systems on buffalo heifers performances: onset of puberty and ovarian size.

Twenty six prepubertal 8-mo-hold buffalo heifers weighing a mean of 134 kg, were used to determine the effect on onset of puberty and on ovarian size of intensive feeding (n=13; IF group) or pasture system (n=13; PS group) . The heifers were weighed monthly and starting from 13th month of age blood samples were collected every 10 days to determine the concentration of plasma progesterone by RIA. Heifers achieved puberty and cyclic ovarian activity when plasma progesterone levels exceeded 1 ng/ml for two consecutive samples with a low value interval. After two cycles, the heifers were naturally mated. Transrectal ultrasonography was performed every twenty days to follow changes in size of ovaries and in follicles number. Significantly higher (P<0.001) gains were obtained by IF system (870 g/d) than PS one (620 g/d) but the mean age at puberty was the same in both groups (599 d vs 610 d, respectively). Within 21 months 8 (IF group) and 10 heifers (PS group) showed cyclic ovarian activity. Ovarian size increased with age in both groups; however, length of right (P<0.05) ovary and the number of follicles >3 mm and <3mm tended to be higher in IF vs PS.