PSIX-19 Leucine supplementation alters immune responses and blood metabolites of lambs exposed to endotoxin

Abstract This study evaluated effects of supplemental Leu on immune responses and blood metabolites of 29 wether lambs (43.8±10.7 kg) exposed to lipopolysaccharide (LPS). Lambs were fed (1.8% BW daily) a diet of 70% alfalfa hay and 30% corn-based supplement in equal portions twice daily. Lambs were adapted to dietary treatments for 7 days followed by 24-hour collections. Treatments (2×3 factorial) were subcutaneous injection of saline (-LPS) or saline containing LPS to supply 3μg (+LPS) per kg BW on day 7, and daily supplementation of no Leu (NO-LEU), intravenously-infused Leu (IV-LEU), or dietary ruminally-protected Leu (RP-LEU). The IV-LEU and RP-LEU supplied L-Leu at 15mg/kg BW daily. Lambs received jugular catheters 7 days before LPS. Rectal temperature and tumor necrosis factor-α were greater for +LPS than -LPS lambs receiving NO-LEU, and not different between +LPS and -LPS lambs receiving IV-LEU and RP-LEU (LPS×LEU; P≤0.10). Cortisol was greater for +LPS than -LPS lambs 2, 4, and 8 hours after LPS (LPS×hour; P < 0.01). Haptoglobin (24 hours after LPS) was greater for +LPS than -LPS lambs (P < 0.01). Lymphocytes were lower for +LPS than -LPS lambs receiving NO-LEU, and not different between +LPS and -LPS lambs receiving IV-LEU and RP-LEU (LPS×LEU; P = 0.03). Serum glucose was not different at 0, 1, 2, and 4 hours, but lower for +LPS than -LPS lambs 8 hours after LPS (LPS×hour; P = 0.06). Serum Leu, isoleucine, and valine were lower for +LPS than -LPS lambs 4, 8, and 12 hours after LPS (LPS×hour; P < 0.01). Serum Leu was greater for IV-LEU than NO-LEU and RP-LEU at 0 hours, not different among Leu treatments at 1, 2, 4, and 8 hours, and lower for IV-LEU and RP-LEU than NO-LEU 12 hours after LPS (LEU×hour; P < 0.01). These results indicate that Leu supplementation attenuates the inflammatory response to an endotoxin in sheep.