Follicular Development in Lactating,Post Weaning and Anoestrous Primiparous Sows

The ovarian follicular system was studied in 4 lactating sows (6 or 8 weeks lactation period), 4 post weaning sows (2 or 4 days after weaning) and 5 post weaning anoestrous sows (22 days after weaning) by macroscopical and microscopical examinations. Blood sampling was performed daily in the post weaning anoestrous sows. The results showed that none of the sows had ovulated during lactation and after weaning. Only small and medium sized follicles were present in the ovaries of the sows. The blood levels of oestradiol-17β and progesterone were low throughout the post weaning period in the anoestrous sows. Microscopical examination showed that all sows had more normal than atretic follicles. In the lactating sows all follicles were below 5 mm in size, the majority being small (1.00–2.99 mm in diameter). The post weaning sows had follicles up to 5.00–5.99 mm and 23–24% of the follicles were medium sized (3.00–5.99 mm in diameter). The post weaning anoestrous sows had no follicles above 5 mm in diameter but many normal medium sized follicles.