Changes of vaginal epithelium in creole pigs ovulating during lactation

Abstract

The objective of this study was to identify changes of the vaginal epithelium in Mexican hairless sows, which ovulated during lactation, caused by the effect of the boar presence and the litter withdrawal. In order to determine the oestrus stage, an exfoliative vaginal cytology and 17b estradiol and progesterone determinations were carried out on the 8 day after the onset of lactation out accompanied with behaviour observations. Four groups of sows were used: Group 1 was not stimulated; Group 2, remained with the boar; Group 3 was separated from its litter for 4 h and Group 4 got both stimuli. Vaginal smear samples were collected every 24 h. for 5 days after stimulus. An ANOVA statistical analysis was performed for repetitive samples during the 5 days of the test. Stimuli used in group 4 caused significant modifications (P< 0·001) when compared to Groups 1, 2 y 3. Estradiol levels were higher than 30 pg/ml in Group 4 on day 10 post partum and 4.5 ng/ml of progesterone on day 11 and 12 post partum. It was evident that 100% of the sows in Groups 1, 2 and 3 did not show oestral activity when relating vaginal cytology with the oestral behaviour and hormone determination of the lactating sows, whereas 100% of the sows in group 4 presented oestrus 72 h. after the stimulus and ovulated 24 to 36 h after the oestrus onset, this was corroborated by estradiol and progesterone determinations, respectively.