Reproduction Abstracts

Introduction: Low piglet birth weight has severe consequences for neonatal and adult development that cannot be remedied post-natally. It is hypothesised that impaired foetal growth occurs due to inadequate placental vascularisation.

Methods: Endometrial and placental tissues supplying small and normal-sized foetuses were collected from Large White x Landrace gilts at gestational days (GD) 30 (n=5), 60 (n=7) and 90 (n=5) for immunohistochemical staining of the endothelial cell marker, CD31.

Percentage staining (PS) of the chorioallantoic membrane (CAM) was determined on GD 60 and 90. GD60 placental stromal analyses included quantification of PS, number of blood vessels (BV) and internal and external blood vessel diameters. The number of BVs, glands and PS were quantified in endometrial samples (GD 30 and 60).

Results and Discussion: PS was increased in the GD60 CAM associated with small foetuses (mean±SEM; 4.58±1.13%) compared to those supplying normal-sized foetuses (2.17±0.37%; FPr=0.037). This difference was also significant when comparing small and normal-sized males (P≤0.05), but not females. No differences in CAM PS at GD90 were detected.

Stromal PS at GD60 was increased (FPr=0.010) in placentas supplying small foetuses (0.61±0.12%) compared to their normal littermates (0.30±0.04%). No differences in the number of BV present in the placental stroma (GD60) were detected. Internal (P=0.029) and external (P=0.085) BV diameters were increased in placentas associated with small males compared to normal-sized males.

A decrease in the number of glands (FPr<0.001) and blood vessels (FPr<0.001) present in the endometrial samples was observed between GD 30 and 60. No differences were detected in any other parameters investigated in the endometrium.

These findings suggest that the vasculature of placentas supplying small foetuses is altered at GD 60 and 90. Small males have the most striking alterations, highlighting the presence of a potential compensatory mechanism.

(Funding: BBSRC and Edinburgh University).