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Ovarian follicular changes after weaning in sows
J H Killen1, R K Christenson, J J Ford
1Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933-0166.
Journal of Animal Science
|September 1, 1992
Summary
Weaning in sows triggers changes in ovarian follicular development. Steroid and insulin-like growth factor I (IGF-I) concentrations within follicles shift post-weaning, influencing reproductive cycles.
Area of Science:
- Reproductive Biology
- Animal Science
- Endocrinology
Background:
- Post-weaning anestrus is a significant concern in swine reproduction.
- Understanding ovarian follicular dynamics is crucial for improving fertility in sows.
Purpose of the Study:
- To investigate ovarian follicular development and steroidogenesis in sows following litter weaning.
- To identify early follicular markers associated with the return to estrus after weaning.
Main Methods:
- Three experiments utilized unilateral ovariectomy in sows at various time points post-weaning (0-72 hours).
- Follicular fluid and granulosa cells were analyzed for steroid hormone (progesterone, testosterone, estradiol) and insulin-like growth factor I (IGF-I) concentrations.
- Corpus luteum formation was assessed to track follicular fate.
Main Results:
- Large follicles developed into corpora lutea in 82-72% of sows by 48-72 hours post-weaning.
- Progesterone levels in medium follicles increased initially post-weaning, followed by increases in testosterone and estradiol.
- Insulin-like growth factor I (IGF-I) concentrations were not correlated with key steroid hormones or granulosa cell estradiol production.
Conclusions:
- Ovarian follicular development and steroidogenesis are significantly altered in sows shortly after litter weaning.
- Hormonal changes within follicles post-weaning may influence the interval to the first estrus.
- IGF-I does not appear to directly modulate steroidogenesis in sow follicles during the early post-weaning period.