Effects of ACTH injections during estrus on concentrations and patterns of progesterone, estradiol, LH, and inhibin α and time of ovulation in the sow

This study investigated whether injections of ACTH for 48 h, 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, 5 μg/kg) every 4 h; blood samples were collected immediately before and 45 min 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 45 min 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 45 min or 4 h 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.