Fetal and maternal plasma lipids in chronically catheterized mares in late gestation: effects of different nutritional states.

The effects of different nutritional states on plasma lipid concentrations have been examined in pregnant mares and their fetuses. Maternal and fetal arterial catheters were inserted into 12 pony mares between 244-303 days' gestation (term 320-360 days) and observations made from 5 days following the insertion of catheters. After recovery from surgery maternal and fetal arterial samples were withdrawn from 7 mares with normal feeding patterns (Group IA), from four of these mares at the end of a 30 h fast and 3 h later following refeeding (Group IB) and six mares who failed to re-establish normal feeding patterns (Group II). The fatty acid concentrations and composition of the plasma free fatty acid (FFA), triacylglycerol and phospholipid fractions were analysed. Maternal FFA, triacylglycerol and phospholipid concentrations were significantly raised in the fasted (Group IB) and under-fed (Group II) mares. Fetal concentrations of FFA and phospholipid increased significantly in the group of under-fed (Group II) mares but not in the fasted (Group IB) mares. In the fetal plasma the proportions of polyunsaturated fatty acids derived from essential fatty acids in the FFA and phospholipid fractions were much higher than those in the mare. In the fasted (IB) and under-fed (II) groups the relative amounts of the polyunsaturated fatty acids in each fraction remained unchanged (P > 0.05). These results show a short fast or prolonged undernutrition result in raised maternal plasma lipid concentrations which in turn can effect the total amount of lipid in the fetal circulation. However any increases in polyunsaturated fatty acids in the fetus (e.g. in Group II) are unlikely to come from the maternal circulation; likely sources of these fatty acids are the placenta or fetal tissues.