Effects of Level of Feeding During Early to Mid-Pregnancy on Placental and Fetal Development in the Sheep

Abstract

Objective: This study was designed to determine the effect of maternal undernutrition during early to mid-pregnancy (i.e. 28 – 80 days gestation; term ≈ 147 days) on placental and fatal development in the sheep. Materials and Methods: Singleton and twin- bearing ewes were malnourished between 28 to 80 days of pregnancy and its effects on both placental and fatal components determined. Malnourished ewes were fed 3.2 - 3.8 MJ day^-1 of metabolisable energy (ME) (~ 60% of ME requirements). Diet comprised of chopped hay and barley-based concentrates. Results: Maternal malnourishment had no effect on total placental weight, but caused a significant increase (P<0.05) in the weight of the fetal placenta of the uterine horn occupied by the fetus in singleton bearing ewes. Fetal development in singletons was not affected, but limb length was significantly reduced (P<0.05). Total placental weight and fetal placental weight were significantly reduced (P<0.05) in the twin-bearing ewes. Undernutrition caused a reduction (P<0.05) in fetal weight in the twins. Maternal malnourishment had no effect on cell development in the maternal placenta of the twin-bearing ewes, but blood supply to the maternal placenta was stimulated. In contrast to the maternal placenta, undernutrition did not only cause a reduction (P<0.05) in cell number in the fetal placenta, but also a reduction (P<0.05) in the supply of blood. Undernutrition had no effect on cell size or blood supply to the maternal liver. Conclusion: These findings demonstrate the differential effects of maternal malnourishment on placental and fetal development in singleton and twin-bearing ewes.

Key words: Feeding level, Early to mid pregnancy, placenta, fetal development, ewe