Effects of maternal feed restriction on placental lactogen and its correlation with pregnancy-associated glycoproteins in pregnant ewes

Placental lactogen (PL) and pregnancy-associated glycoproteins (PAGs), secreted by trophoblast binucleate cells, are central to fetal development in ruminants. While nutritional effects on PAGs are documented, impacts on maternal PL and its relationship with PAGs remain unclear. This study examined the effects of maternal feed restriction on ovine placental lactogen (oPL)concentrations and their correlation with PAGs in pregnant ewes. Fifty-nine ewes (singletons or multiples) were pair-matched to a control group (100 % energy requirements) or a feed-restricted group (50 % requirements) from day 24-100 of gestation. Blood was collected on Days 24 (T1), 50 (T2), 80 (T3), 110 (T4), and 140 (T5) to measure oPL, PAGs, and metabolic indicators (NEFA, glucose, total protein). Feed restriction did not significantly affect oPL (p > 0.1). oPL varied with time and litter size (p < 0.001), showing a nadir at T3 and a peak at T5; ewes with multiples had consistently higher levels. In singleton pregnancies, oPL at T5 positively predicted lamb birth weight (p = 0.05). Although oPL and PAGs displayed similar biphasic patterns (decline at T3, peak at T5), no significant correlation was found between them. oPL showed a weak, negative correlation with NEFA at T1 and moderate, negative correlation with total protein at T5; no association was observed with glucose. In conclusion, moderate maternal undernutrition during early gestation does not compromise oPL secretion, highlighting its resilience and role in supporting fetal growth. The similar temporal pattern but absence of correlation between oPL and PAGs suggest distinct regulatory mechanisms, with both hormones acting protectively to ensure fetal well-being.