Stress and Early Pregnancy in Sows Effect on endocrinology, ova transport and embryo development

Razdan, P. 2003. Stress and early pregnancy in sows Effect on endocrinology, ova transport and embryo development Doctoral dissertation. Mixing unfamiliar breeding female pigs creates stressful situations due to aggressive interactions, which can lead to food deprivation of the more submissive animals. The aim of this thesis was to study the type of stress occurring when sows are regrouped into unfamiliar groups and to determine the effect of this type of stress during two different stages of pregnancy in multiparous sows. Ova transport rate, embryo cleavage rate, the number of spermatozoa attached to the zona pellucida and the hormonal patterns were studied in sows subjected to food deprivation or ACTH-stimulation for 48 h, immediately after ovulation in their second oestrus after weaning. In sows subjected to the same treatments during the time of maternal recognition of pregnancy, the effect on hormonal concentrations in the blood plasma and allantoic fluid was examined, as well as the conceptus growth and foetal survival rate at day 30 of pregnancy. Food deprivation decreased ova transport rate, which might be due to an impact of the elevated levels of PGF 2α-metabolite on oviductal motility. Sows stimulated with ACTH had an increased level of cortisol and a decreased baseline level of PGF 2α-metabolite. There was no difference in ova transport rate but ACTH-stimulated sows had decreased embryonic cleavage rate and a lower number of spermatozoa attached to the zona pellucida compared with controls, indicating an alteration in the oviductal environment. Food deprivation and ACTH-stimulation during days 13 and 14 of pregnancy had no effect on embryo survival at day 30 of pregnancy, but both treatments increased the plasma levels of cortisol. ACTH-stimulation caused a two-day delay in the increase of plasma oestrone concentration seen at day 19 of pregnancy in control sows. This delay might reflect an impeded development of the embryos. Plasma levels of cortisol, progesterone, and free fatty acids increased concomitantly with a decrease in insulin in food-deprived sows, indicating an adrenal activation as well as a catabolic metabolism with decreased metabolic clearance rate in the liver. Progesterone concentration in allantoic fluid among food-deprived sows was elevated. This increase in progesterone concentration was positively correlated with the weight of the placentas, suggesting an influence of progesterone on placenta size. Post-ovulatory stress appears to alter the oviductal environment and post-ovulatory food deprivation also induces a decrease in ova transport rate. However, multiparous, well-nursed sows appear …