EFFECTS OF CONCURRENT PREGNANCY AND LACTATION IN RABBIT DOES ON THE GROWTH OF FOLLICLES IN DAUGHTERS' OVARIES

The aim of this experiment was to study the effects of concurrent pregnancy and lactation in the mother on follicular development in daughter rabbits. Young females from mothers lactating (group PL) or not (group P) during gestation were sacrificed on days 29 (nPL = np =5), 49 (nPL = np =5) or 70 (nPL = 4, np = 5) and one ovary was taken from each. Follicles were divided into size bands according to their diameter. The P and PL group counts in each band were similar at 29 and 49 days, but at 70 days the number of larger growing follicles (diameter > 241 µm) was lower in the PL than in the P does (83 vs. 155; P<0.05). A mathematical model for follicular development was fitted to the size-class frequencies for animals in both groups and showed that the duration of the first growth phase was longer in the PL than in the P group (26.6 days vs. 14.9 days; P<0.001). These results suggest that concurrent lactation during pregnancy in primiparous does significantly affects early follicular development and delays the appearance of larger ovarian follicles in the daughters.