Residual effects of abomasal 5-hydroxytryptophan administration on serotonin metabolism in cattle

Authors: VALENTE, ERITON - WESTERN PARANÁ STATE UNIVERSITY; DEMASCENO, M. - WESTERN PARANÁ STATE UNIVERSITY; Klotz, James; HARMON, DAVID - UNIVERSITY OF KENTUCKY

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2021
Publication Date: 3/23/2021
Citation: Valente, E.E., Demasceno, M.L., Klotz, J.L., Harmon, D.L. 2021. Residual effects of abomasal 5-hydroxytryptophan administration on serotonin metabolism in cattle. Domestic Animal Endocrinology. 76. Article 106627. https://doi.org/10.1016/j.domaniend.2021.106627.
DOI: https://doi.org/10.1016/j.domaniend.2021.106627

Interpretive Summary: There is interest in understanding serotonin metabolism and how to manipulate serotonin concentrations in cattle as a possible means of modulating feed intake and energy metabolism. This study evaluated post-ruminal infusion of different levels of 5-hydroxytryptophan (5-HTP; a serotonin precursor) and evaluated how long circulating serotonin levels were altered by the infusion. It was observed that post-rumninal infusions of 5-HTP up to 1 mg/kg body weight increased circulating serotonin for up to 2 days without causing negative effects. This work is presently of interest primarily to other researchers focused on cattle. However, it may eventually be of interest to producers as a low cost neutraceutical used to manipulate serotonin concentrations in cattle to modulate the many effects of serotonin.

Technical Abstract: Studies of serotonin in husbandry animals has received growing interest. However, there is limited information about serotonin manipulation using 5-HTP administered post-ruminally and its residual effects in cattle. The objective of this study was to evaluate effect of different doses of abomasally infused 5-HTP on short and long-term circulating serotonin in cattle. Four Holstein steers (487 ± 7.6 kg) fitted with ruminal cannulas were used in a 4 x 4 Latin Square design experiment. The treatments were intra-abomasal infusion of 5-HTP at 0, 0.25, 0.5 and 1 mg/kg BW. Blood was collected from the jugular vein of each steer at -60, -30, 0, 30, 60, 120, 240 and 480 min from 5-HTP infusion for basal and short term evaluation and, at 1, 2, 4 and 7 d after 5-HTP infusion for long term evaluation. Dry matter intake was not affected (P > 0.05) by intra-abomasal infusions. The half-life of 5-HTP was dose-independent (128 min). The serum 5-HTP, serotonin, and 5-hydroxyindoleacetic acid area under curve increased (P < 0.05) linearly with increased dose of 5-HTP. Serum 5-HTP reached peak concentration in about 30 min after intra-abomasal infusion while serum and plasma serotonin peaked after 240 min from infusion. Serotonin was greater than control for all 5-HTP doses 1 d and 2 d after infusion in serum and plasma, respectively. Intra-abomasal infusion of 5-HTP at doses up to 1 mg/ kg BW increased circulating serotonin for up 2 days with no adverse effects.