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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #375988

Research Project: Optimizing the Biology of the Animal-Plant Interface for Improved Sustainability of Forage-Based Animal Enterprises

Location: Forage-animal Production Research

Title: 5-Hydroxytryptophan strongly stimulates serotoninsynthesis in Holstein steers

item VALENTE, ERITON - University Of Kentucky
item Klotz, James
item HARMON, DAVID - University Of Kentucky

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: 9/12/2020
Citation: Valente, E.E., Klotz, J.L., Harmon, D.L. 2020. 5-Hydroxytryptophan strongly stimulates serotoninsynthesis in Holstein steers. Domestic Animal Endocrinology. 74. Article 106560.

Interpretive Summary: There is interest in understanding serotonin metabolism and how to manipulate serotonin concentrations in cattle as a possible means of mitigating the toxic effects of ergot alkaloids. This study evaluated post-ruminal infusion of 5-hydroxytryptophan, a serotonin precursor as a means to directly altering circulating serotonin levels. This was indeed the case. Infusion of 5-hydroxytryptophan effectively increased blood serotonin concentrations in cattle. However, cattle seemed particularly sensitive to higher dosages successfully applied to non-ruminants, as feed intake decreased and plasma fatty acid concentrations increased. Researchers investigating strategies to mitigate the negative effects of ergot alkaloids will benefit from this research presented in this manuscript.

Technical Abstract: Although serotonin has been extensively studied in many species, there is a lack of information in ruminants and no research has evaluated if its precursor, 5-hydroxytryptophan (5-HTP), administered into the abomasum may be used as a means to manipulate serotonin metabolism. Thus, the objective of this study was to evaluate if intra-abomasal infusion of 5-HTP increases circulating serotonin in the bovine. Eight Holstein steers (471 ± 8.9 kg) were used in a replicated 4 x 4 Latin Square design experiment. The treatments were intra-abomasal infusion of 5-HTP at 0.5, 1, 2.5 and 5 mg/kg BW. Blood was collected at 0, 2, 4, 6, 8 and 24 h after infusion. The circulating concentration of 5-HTP had increased quadratically (P = 0.005) with a peak at 2 h after administration. When 5-HTP was dosed at 2.5 mg/kg or higher, intake decreased and there was an altered manure consistency. The 5-HTP administration increased (P < 0.05) serum serotonin in comparison with baseline with no difference (P > 0.05) between the doses of 5-HTP. The serum 5-hydroxy-indole acetic acid concentrations followed the same pattern as 5-HTP. Plasma glucose content was not affected (P > 0.05) by 5-HTP dosing. However, NEFA concentration in the plasma was lower (P > 0.05) than baseline for the infusion levels of 0.5 and 1 mg/kg. Intra-abomasal infusion of 5-HTP efficiently increases serum serotonin cattle. However, it seems that cattle are more sensitive to 5-HTP administration than non-ruminants.