Cystic ovaries in Intermittently Suckled Sows: follicle growth and endocrine profiles

Studies have shown that 2-6% of culled sows have cystic ovaries (e.g. Heinonen et al. (1998) Anim Reprod Sci 52: 235-244). Little is known about the aetiology of cystic ovaries. Furthermore, most studies examining hormone profiles of sows with cystic ovaries have used ACTH to induce the cysts. The endocrine profile preceding and during the formation of spontaneously developing cysts is not known. In a number of experiments we attempted to induce lactation ovulation by separating sows from their piglets for a number of hours daily during established lactation (IS; Intermittent Suckling). In these studies, sows repeatedly developed cystic ovaries. The aim of this study is to describe the follicle development, hormone levels and oestrus expression of these sows and of their normally ovulating counterparts. Data came from 3 experiments in which IS-sows were separated from their litters for 12h daily from day 14 of lactation onwards. Control sows were fully lactating until weaning at day 21 of lactation. The total number of IS sows included in the studies was 89, of which 52 (58%) ovulated within 8 days after start of IS and 10 (11%) developed cystic ovaries. Of the 36 control sows, 34 (94%) ovulated within 8 days after weaning and 2 (6%) developed cystic ovaries. Differences were evaluated between cystic sows and their normal ovulating counterparts, using SAS-GLM and taking into account Experiment as a fixed effect. At days 1 to 4 after start of IS or weaning, follicle diameter of sows that developed cystic ovaries was similar to the follicle diameter of the sows that ovulated (P>0.10), but follicle diameter was greater for sows developing cysts from day 5 onwards (P0.10), but in sows that developed cysts, E2 levels did not return to basal levels within 48 h after peak E2. LH basal levels were not significantly different, but the increase in LH after peak E2 was significantly lower in sows that developed cystic ovaries (0.4±0.1ng/ml vs. 3.6±0.3ng/ml; P