Hormonal profiles and embryo survival of sows subjected to induced stress during days 13 and 14 of pregnancy.

Group housing of sows during the mating and gestation period has become the overall common management practice in Sweden. Loose housing is probably less stressful for the animals because it allows them more opportunities to behave naturally, but mixing unfamiliar sows does create a stressful situation due to aggressive interactions, which can lead to food deprivation. The objective of the present study was to investigate and compare the effects of stress in form of food deprivation and ACTH administration at days 13 and 14 of pregnancy (day 1, first day of standing oestrus) in sows. The hormonal secretion of the sows and foetal survival by day 30 of pregnancy was, therefore, studied in 17 crossbred multiparous sows. The sows were randomly allocated into three different groups: one control (C-) group; one food deprived (FD-) group, which was deprived of food from the morning of day 13 of pregnancy until the evening meal on day 14; and a third group (A-), which was given intravenous injections of synthetic ACTH (Synachten Depot), at a dose of 0.01 mg/kg body weight every sixth hour from 6 a.m. on day 13 until 6 a.m. on day 15 of pregnancy. All sows were slaughtered at 30 +/- 2 day of pregnancy and the genital tracts recovered. Total number of corpora lutea (CL), total number of viable or nonviable embryos and foetal survival rates were determined. Samples from the peripheral blood circulation were collected four times a day from day 12 until slaughter, except during days 13-15 when blood was collected every second hour. The blood samples were analysed for cortisol, progesterone, oestrone, prostaglandin F(2alpha)-metabolite, oestrone-sulphate, insulin, free fatty acids and triglycerides. FD-sows had increased levels of cortisol, free fatty acids and progesterone, as well as a lowered level of insulin in the peripheral blood plasma, while A-group sows had increased levels of both cortisol and insulin compared with the C-group. Treatment with ACTH seemed to cause a 2-day delay in the increase of oestrone, from day 19, as seen in the FD- and C-group, to day 21 of pregnancy. At the time of slaughter, there were no significant differences among groups in terms of total number of foetuses and foetal survival rate. The results of the present study suggest a capacity of the sow to compensate for the influence of induced moderate stress at the time of pregnancy when maternal recognition occurs.