Postpartum Uterine Involution in Martina Franca Jennies

SIMPLE SUMMARY: The assessment of a normal postpartum course is pivotal to maximize the likelihood to achieve a new pregnancy, especially in equids. However, postpartum (PP) uterine involution was studied in the horse but, to date, very little is known about the donkey, and many aspects of this fine-tuning reproductive phase remain to be clarified. The present study aimed to investigate the PP uterine involution in normal foaling Martina Franca jennies by ultrasonography, histology, and cytology. The results showed that ultrasonographic differences between the post-pregnant and non-post-pregnant uterine horn disappeared by PP Day 7. Endometrial glands area and perimeter showed a significant constant trend of decrease from PP Day 1 to PP Day 28. Epithelial thickness significantly increased from PP Days 1–3 to PP Day 7, and again, concurrently with the foal heat, to PP Day 14. Endometrial cytology showed a marked neutrophil reduction at PP Day 7, and an eosinophil increase from the first 3 days after parturition to the PP Days 7–14. Based on the combined ultrasonographic, histological, and cytological findings, the results of the present study suggest that, in Martina Franca jennies with normal foaling, the PP uterine involution can be considered complete at PP Day 14. ABSTRACT: This study investigated the postpartum (PP) uterine involution in nine multiparous Martina Franca jennies with at term, normal, and singleton foaling. Transrectal ultrasonography performed at Days 1, 3, 7, 14, 21, and 28 showed that the uterine tip diameters did not differ between the post-pregnant (PPH) and non-post-pregnant uterine horns (NPPH), whereas the diameter of the middle PPH was larger than the NPPH until Day 7 (p < 0.05). The diameter of the corpora-cornual junction resulted larger in the PPH than NPPH at Day 7 (p < 0.05). At Day 3, the microcaruncolae were not detected. Endometrial glands (GL) number increased, with the highest value on Day 28. Endometrial GL area and perimeter decreased (p < 0.001) from Day 1 to Day 28. Epithelial thickness increased from Days 1–3 to Day 7 (p < 0.001), and concurrently with the foal heat to Day 14 (p < 0.001), with a decrease at Days 21–28. A marked neutrophils reduction on Day 7 and eosinophil increase from the first three days to Days 7–14 was observed. The results suggest that, in Martina Franca jennies with normal foaling, the PP uterine involution can be considered complete on Day 14.