Ultrasound examination of the uterine diameter and the uterine blood vessels size in temporarily confined sows in the postpartal period– a pilot study

Abstract Background Prolonged farrowing duration is currently one of the challenges in the swine industry, which leads to postpartum complications by increasing uterine inflammation, and interference with physiological processes after parturition. The aim of the present study was to assess the relationship between uterine involution and uterine vessel size with farrowing duration in temporarily confined sows (during the day of farrowing and for the following 3 days) under tropical climates. Results Fourteen Landrace × Yorkshire sows were included in the study. Uterine diameter and uterine vessel size were measured from 2 to 15 days postpartum using B-mode ultrasonography, a non-invasive technique that enables continuous monitoring of uterine involution and detection of reproductive problems in the same sows throughout the 15-day postpartum period. To determine the relationship between farrowing duration and uterine diameter, sows were categorized into two groups: sows with a farrowing duration of ≤ 300 min (normal) and sows with a farrowing duration > 300 min (prolonged). The mean farrowing duration was 200 ± 128 min, with 28.6% of sows experiencing prolonged farrowing. In the prolonged farrowing group, the diameter decreased from 43.5 ± 9.4 mm to 12.4 ± 0.5 mm, while in the normal group, it decreased from 30.7 ± 1.4 mm to 13.6 ± 0.4 mm. On day 2, sows in the prolonged farrowing group exhibited a higher uterine diameter than the normal group (P = 0.042). There was no significant difference in the size of the uterine blood vessels between the two groups (prolonged farrowing: 7.3 ± 1.3 mm to 2.5 ± 0.1 mm; normal farrowing 6.1 ± 0.7 mm to 2.7 ± 0.1 mm) (P = 0.397). However, the uterine diameter was correlated with the size of the uterine blood vessels in sows with either a normal farrowing duration (r = 0.705, P < 0.001) or a prolonged farrowing duration (r = 0.749, P < 0.001). Conclusions This is the first study to evaluate and provide initial data on uterine vessel size and its correlation with the uterine diameter in postpartum sows. Although no significant differences between uterine vessel size and farrowing duration were detected, a notable increase in uterine size during the initial 2 days postpartum in temporarily confined sows under tropical climates with prolonged farrowing duration was identified.