Metabolic adaptations to pregnancy and lactation in German Blackheaded Mutton and Finn sheep ewes with different susceptibilities to pregnancy toxaemia

The metabolic adaptations for pregnancy and lactation were evaluated in ewes with a higher and a lower risk of being affected by pregnancy toxaemia. Plasma concentrations of glucose, insulin, non-esterified fatty acids (NEFA) and β-hydroxybutyrate (β-HB) were determined in 7 pregnant, 4.5- to 6.5-year-old German Blackheaded Mutton ewes (higher risk = HR) and 5 pregnant, 2.5-year-old Finn sheep ewes (lower risk = LR) 8 and 2 weeks ante partum (mid- and late pregnancy), peripartal, as well as 2 weeks post partum (lactation) and 2 weeks after weaning. The maternal body weight was monitored at all the reproductive stages mentioned. To compare the reproductive performance and the rearing success of the groups, the number and the body weight of the lambs born alive and the ADG of the suckling lambs were recorded. In contrast to the ewes of the HR group, the LR sheep showed a significant body weight increment of 49% during late, compared to mid pregnancy, and maintained their body weight after parturition. The reproductive performance and the rearing success did not differ between HR and LR groups (lambs born alive per dam: HR: 2.0 ± 0.2, LR: 2.3 ± 0.7; ADG of the lambs: HR: 265 ± 19 g, LR: 249 ± 23 g). In both groups, the plasma glucose and insulin concentrations were significantly lower during late gestation, compared to lactation. In the HR ewes, the insulin values were also lower in late, compared to mid-pregnancy. Blood NEFA values were identical during all gestational stages in the LR sheep, while values were significantly increased during late pregnancy and lactation in the HR ewes. The NEFA concentrations during late pregnancy were significantly higher in the HR compared to the LR ewes. In both groups, the β-HB levels were elevated during late pregnancy, peripartal and during lactation, compared to the dry period and mid-pregnancy (HR ewes only). Significantly different glucose, insulin and β-HB plasma levels between HR and LR sheep were recorded after parturition. In conclusion, the absence of maternal body weight gain, the decreased insulin secretion and the increased lipolysis at the end of pregnancy indicate that late pregnancy requires more metabolic adaptations in the HR, than in the LR ewes. This high demand may contribute to the development of pregnancy toxaemia.