Postpartum ovarian activity and uterine involution in non-seasonal Shiba goats, with or without nursing

Postpartum ovarian activity, uterine involution, and the relationship with hormonal profiles were studied in non-seasonal Shiba goats, with or without nursing of their kids. After parturition, does were allocated to one of two groups, with either weaning on the day of parturition (n = 3; non-nursing group) or weaning at 7–10 weeks after parturition (n = 4; nursing group). Blood sampling (starting 7 days prior to expected day of parturition) and transrectal ultrasound evaluations (starting 2 days after parturition) were conducted every other day or daily to monitor the follicular dynamics, uterus size, and the levels of plasma progesterone, blood glucose, and insulin concentration until at 3 weeks following the first postpartum ovulation. In the nursing group, blood samples were also collected every 10 min for an 8 h period on the day before weaning, 2 and 6 days after weaning, for the analysis of the pulsatile patterns of LH release. In all animals, the blood glucose concentrations increased transiently on the day before parturition and were significantly (p < 0.05) higher than those on the day of parturition (mean of 144 ± 48.8 mg/dl vs 63 ± 11.2 mg/dl). In the non-nursing group, the first postpartum ovulation was observed 9.3 ± 3.2 days after parturition, while in the nursing group, no ovulation occurred before weaning in any of the goats. Here ovulation was observed 18.8 ± 5.0 days after weaning, which was significantly (p < 0.05) later than in the non-nursing group. After first ovulation, all animals in both groups showed early luteal regression. No significant difference in the time required for the completion of uterine involution was recorded between the non-nursing and nursing groups (18.3 ± 4.2 days vs 19.3 ± 3.6 days, respectively), nor in the plasma LH pulse frequency obtained before (1.3 ± 0.5 pulses/8 h), 2 (1.3 ± 1.0 pulses/8 h) and 6 days (2.0 ± 0.8 pulses/8 h) after parturition, in the nursing group. It can be concluded that no ovulation occurs during nursing postpartum, suggesting that nursing is a determinant of the resumption of ovulation in these non-seasonal goats. Ultrasonic observations of the ovary suggest that uterine involution was not influenced by nursing or suckling.