Epsilon Open Archive

Abstract

Regrouping of weaned sows gives rise to stressful situations during the critical time when the sows must resume oestrous activity after lactation. The aim of these studies was to simulate the social stress seen after regrouping through repeated injections of synthetic ACTH during oestrus in the sow. The period of treatment lasted for about 48 h from the onset of standing oestrus. The following reproductive events were studied and compared between the ACTH-treated sows (ACTH group) and the control sows (C group): duration of standing oestrus, time of ovulation, hormonal patterns, the number of spermatozoa and their morphology as well as the intraluminal environment of the uterine tubal junction (UTJ) and of isthmus shortly after ovulation, oocyte/embryo transport in the oviduct, and embryo development at 48 or 60 h after ovulation. The sows in the ACTH group stopped displaying signs of standing oestrus sooner after ovulation than the C group, but no effect was found on the time of ovulation. Cortisol and progesterone concentrations were elevated significantly in jugular blood samples taken after the ACTH injections. There were minor differences in oestradiol and LH concentrations between the groups. Overall, inhibin α concentrations were significantly higher during the treatment period in the ACTH group than in the C group. There was a tendency towards a larger number of spermatozoa in the UTJ and oviduct among the sows in the ACTH group. A majority of sows in the ACTH group had moderately to exaggerated amounts of mucus in the intraluminal environment of the sperm reservoir. The ACTH injections had no effect on embryo development. However, fewer oocytes/embryos were retrieved from the ACTH group than from the C group and there was a tendency towards faster embryo transportation to the uterus. In conclusion, simulated stress caused significant loss of oocytes and embryos, shortened the duration of standing oestrus and changed the hormonal pattern of progesterone, and possibly of inhibin α, oestradiol and LH. There were also tendencies towards an altered intraluminal environment in the oviduct and UTJ and augmented transportation of spermatozoa and embryos through the female genital tract in the ACTH-treated sows.