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Abstract: This study investigated whether injections of ACTH for 48h, from the onset of the second standing estrus after weaning, had any impact on time of ovulation and patterns of progesterone, estradiol, luteinizing hormone (LH), and inhibin α. The studied sows (n =15) were fitted with jugular vein catheters and randomly divided into a control (C group) and an ACTH group. From the onset of standing estrus, the sows were injected (NaCl or synthetic ACTH, 5μg/kg) every 4h; blood samples were collected immediately before and 45min after each injection. Ovulation was monitored using ultrasonography. The ACTH-group sows stopped displaying signs of standing estrus sooner after ovulation in their second estrus, but no impact was found on time of ovulation. There were no significant differences in the intervals between LH peak, estradiol peak, and the onset of standing estrus between the C and ACTH groups. The cortisol and progesterone concentrations were significantly elevated (p <0.001) in samples taken 45min after ACTH injection. There were minor differences in estradiol and LH concentrations between the groups. Overall inhibin α concentrations were significantly higher during the treatment period in the ACTH than in the C group, but there were no significant differences between samples taken either 45min or 4h after injection. In conclusion, injections of synthetic ACTH during estrus in the sow apparently disturb the duration of signs of standing estrus and the hormonal pattern of progesterone, and possibly of inhibin α, estradiol and LH. [Copyright &y& Elsevier]

Abstract: The hormonal interactions of the hypothalamic–pituitary–ovarian–uterine axis are accountable for a normal reproduction in female pigs. It is of importance to have knowledge of estrous symptoms and hormonal profiles around ovulation. The introduction of the transrectal ultrasonography in sows has given us the possibility to study ovarian activity in conscious animals and relate the timing of estrus to ovulation. Combining this technique with measuring of several hormones like luteinizing hormone (LH), follicle-stimulating hormone (FSH), inhibin, estradiol, progesterone, insulin-like growth hormone I (IGF-I), prostaglandin F2α (PGF2α) metabolite, oxytocin, facilitate our knowledge about the sequence of ovarian events. Evidence suggests that activation of the hypothalamic–pituitary–adrenal axis may hamper the normal gonadotropin secretion and in consequence, the ovarian function. The metabolic status during lactation, weaning of piglets and social stress might affect onset of ovarian activity and the related estrous behavior. The role of seminal plasma, artificial insemination and presence of the boar might also be included as factors regulating the temporal kinetics of ovulation, corpus luteum development, uterine function and steroid production in the ovary. Studies using a simulated stress by means of adrenocorticotrophic hormone (ACTH) administration or food deprivation are tools in understanding how the ovary is susceptible to impairment. The intention of this paper is to review current knowledge concerning the endocrine aspects of normal and stress-influenced ovarian function in pigs. [Copyright &y& Elsevier]