PSI-21 - The role of n-carbamylglutamate supplementation during last third of gestation in nutrient restricted twin-bearing ewes.

Abstract: Nutrient restriction in sheep during pregnancy normally occurs in Patagonia with negative effects on ewe body condition (BCS) and reproductive performance. N-carbamylglutamate (NCG), an analogue of N-acetylglutamate, is postulated to improve urea recycling, nitrogen utilization and antioxidant capacity in ruminants. The objective of this study was to evaluate the effect of oral NCG supplementation in naturally nutrient restricted grazing twin-bearing ewes, on maternal body weight (BW) and body condition score (BCS), serum biochemical indexes and antioxidant capacity in mid-late gestation. Ten twin-bearing ewes were orally dosed once-daily with 60 mg/kg BW NCG in a water carrier from 100 to 140 days of gestation (dg) and were compared to unsupplemented controls (CON; n=8). Maternal BW, and BCS were recorded every 10 days, from 100 until 140 dg. Blood samples were collected at the same timepoints to evaluate plasma metabolites (NEFA, urea, total protein, albumin, globulin, Ca, P, Mg, Cholesterol, ASAT, CK, GGT, GLDH, total bilirubin and triglycerides), antioxidant status (malondialdehyde (MDA)), and total antioxidant capacity (TAC). Ewes were managed as a single mob in a paddock with natural pasture (3.3% CP, 1.9 Mcal/kg ME), supplemented with alfalfa hay (600 g/day/ewe; 13% CP and ME 2.2 Mcal/kg ME) from 130 dg, with a stocking rate of 0.9 ewes per hectare and a dry matter availability of 525 kg per hectare, representative of Patagonian prairie conditions. The effect of treatment on ewe BW, BCS and plasma metabolites were analysed using REML analysis in R using lme4 R package with time (dg) and treatment (and their interaction) as fixed effects and animal as the random effect. Ewe BW increased (P< 0.0001) and BCS decreased (P=0.005) with advancing gestation, but there was no effect of treatment. There was a tendency for a treatment effect (P=0.07) on plasma urea with ~10% lower concentrations in NCG than CON ewes at 130 dg (P=0.08) and 140 dg (P=0.04). There was a treatment by time interaction for total bilirubin (P=0.005), phosphorus (P=0.02), and a similar trend for albumin (P=0.09). Ewes supplemented with NCG had~10% lower concentrations of bilirubin at 100 (P=0.01) and 120 dg (P=0.04), lower concentrations of phosphorus (P=0.003) and albumin (P=0.02) at 140 dg compared to CON ewes. No other effects of treatment on blood metabolites or antioxidant status or capacity were observed. Collectively these results suggest that supplementation of nutritionally-restricted ewes with 60 mg/kg BW from 100 to 140 dg did not influence BW or LWT but may have some effects on liver function, protein metabolism, urea recycling, feed intake and/or feed efficiency which warrant further investigation.



*Funded by FONDECYT Project N°1221042; AgResearch Strategic Science Investment Fund.