Ultrasonographic characterization of the ovaries in non-pregnant first served sows and gilts

This study was aimed firstly, to examine the ovaries in non-pregnant first served sows and gilts by transcutaneous ultrasonography and secondly, to evaluate the suitability for this procedure to be performed routinely on farms. Two thousand five hundred and twenty-three females on a 1250-sow unit, synchronized with Regumate (gilts only) and/or gonadotropins (sows and gilts) not detected as returned to estrus by daily boar contact prior to scanning were ultrasonographically tested for pregnancy between days 20 and 114 postinsemination (p.i.). Of 256 sows (S) and 130 gilts (G) found to be non-pregnant the ovaries were visualized in 87.1 and 80.0% of them, respectively. Ovarian findings were: corpora lutea (CL); follicles of 2-6mm (F(2-6)); peri-ovulatory ovarian structures (POS; comprising follicles of 7-8mm and corpora haemorrhagica); single cysts (SC); oligocystic ovarian degeneration (OOD) and polycystic ovarian degeneration (POD). Their incidence was: CL>F2-6>POS>POD ( P<0.05 ) in both S and G. POD and SC plus OOD were more frequently in S ( P<0.05 ). The ovarian findings were related to the intervals of regular (days 18-25 p.i. (R1), 38-46 p.i. (R2)) and irregular service returns (days 26-37 p.i. (IR1), 47-114 p.i. (IR2)). Comparison within intervals: CL tended to be more frequently with P<0.05 only at IR2 in S. Comparison among intervals (R1 to IR2): The percentage of females (1) with CL tended to increase (S and G) and (2) with F2-6 plus POS decreased significantly (S; P<0.05 ) or tendentiously (G). SC plus OOD was higher before R2, POD after IR1 (S and G; P<0.05 ). In conclusion, the results indicate a high heterogeneity of ovarian structures in non-pregnant first served sows and gilts up to day 114 after service and suggest CL as an important cause for a delayed and, rather than POD, a failed service return. The results further demonstrate that transcutaneous ultrasonography is an appropriate and recommended method for examining the ovaries on farm in female pigs with reproductive failures.