Effect of Diet Supplemented with Rumen-protected 5-Hydroxytryptophan on the Concentration of 5-Hydroxytryptophan and Melatonin in the Plasma of Sheep
Effect of Diet Supplemented with Rumen-protected 5-Hydroxytryptophan on the Concentration of 5-Hydroxytryptophan and Melatonin in the Plasma of Sheep
Fang Zhao, Gen Wang, Xiaobin Li, Guodong Zhao, Hui Chen, Chen Ma and Kailun Yang*
ABSTRACT
This study was conducted to investigate the effect of diet supplemented with rumen-protected 5-hydroxytryptophan (RPT 5-HTP) on the concentration of 5-hydroxytryptophan (5-HTP) and melatonin (MLT) in the plasma of sheep. Eighteen sheep were assigned randomly to three diet groups (n = 6). The treatment groups included control (CT, corn-soybean meal basal diet), CT + 111 (CT + 111 mg/kg BW RPT 5-HTP), and CT + 222 (CT + 222 mg/kg BW RPT 5-HTP) groups. The experiment lasted for 16 d. On the 16th day of the experiment, blood samples from the sheep were collected at 0 h before feeding and at 1.5, 3, 4.5, 6, 8, 10, and 12 h after feeding in the morning. The plasma concentration of 5-HTP, tryptophan (Trp), 5-hydroxytryptamine (5-HT), and MLT was determined. The plasma concentration of 5-HTP at 6, 8, and 10 h after feeding in the morning increased (P < 0.05) in response to RPT 5-HTP supplementation when compared with that at 0 h before feeding. The plasma concentration of Trp remained unchanged with RPT 5-HTP supplementation. However, the plasma concentration of 5-HT increased significantly in the sheep of CT + 222 group at 3, 4.5, 6, 8, and 12 h post feeding in the morning when compared with that at 0 h before feeding. The effect of RPT 5-HTP supplementation on the plasma MLT concentration was observed. The concentration of MLT increased (P < 0.05) from 1.5 to 6 h after feeding. In conclusion, RPT 5-HTP supplementation increased the plasma 5-HTP, 5-HT, and MLT concentrations in the sheep. However, the plasma Trp concentration in the sheep remained unchanged after RPT 5-HTP supplementation.
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