Impact of maternal body condition on maternal and foal metabolism

Abstract

The maternal environment during gestation can influence foal metabolism. The objective of this study was to investigate the impact of moderate differences in maternal body condition during late gestation on mare and foal metabolism. We hypothesized that differences in maternal body condition would alter dam glucose metabolism and leptin concentrations, and foal leptin concentrations during the early postpartum period. Light breed mares (n = 6) were divided into moderately obese (MO; n = 3) or lean (LN; n = 3) groups based on body condition score (BCS) and cresty neck score (CNS) at 315 (±0.5) days of gestation. Mares were fasted overnight and underwent intravenous (i.v.) glucose tolerance tests at 315 (±0.45) days gestation, and 60 (±0.6) and 119 (±1.3) days postpartum (pp). Mares were administered dextrose i.v. (0.3 g/kg BW) followed by an i.v. insulin infusion (0.3 mU/kg BW) 20 min later. Blood samples were collected from a jugular vein at −30, −15, 0, 2, 5, 10, 15, 20, 25, 30, 45, 60, and 120 min relative to dextrose infusion. Glucose and insulin concentrations were determined by ELISA. Circulating leptin concentrations were analyzed in mares at parturition, and 59 (±0.6) and 118 (±1.3) days pp, and in foals on d 1, 7, 14, 28, 59, and 118 of age by RIA. Differences between groups were tested using a t-test with significance at P ≤ 0.05 and a tendency at 0.05 < P ≤ 0.10. The MO group had greater BCS (6.1 ± 0.3; P = 0.01) and CNS (2.7 ± 0.2; P = 0.01) than LN mares (BCS: 4.3 ± 0.3; CNS: 1.3 ± 0.2). Moderately obese mares tended to have 8% greater glucose area under the curve (AUC) after dextrose (P = 0.10) and 9% greater glucose AUC after insulin infusion (P = 0.10) than LN mares at 315 d of gestation. At d 60 pp, LN mares tended to have 69% greater insulin AUC after dextrose (P = 0.10) and 70% greater insulin AUC after insulin (P = 0.10) infusion than MO mares. At d 119 pp, LN mares had 23% greater insulin AUC before dextrose infusion (P = 0.04) than MO mares. Moderately obese mares tended to have 87% greater leptin concentrations at parturition (13.2 ± 2.8 ng/mL; P = 0.06) and 80% greater leptin concentrations on d 118 pp (7.7 ± 1.4 ng/mL; P = 0.06) than LN mares (parturition: 5.2 ng/mL ± 1.1; d 118: 3.3 ng/mL ± 1.0). There were no observed differences in leptin concentrations among foals born to LN or MO mares. Differences in maternal glucose metabolism and leptin concentrations suggest metabolic differences among lean and moderately obese mares. However, moderate changes in maternal body condition do not appear to affect foal leptin concentrations in the early postpartum period.