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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #411940
Research Project: The Roles of Forage and Phytochemicals at the Plant-Microbe-Animal Nexus for Sustainable Ruminant

Location: Forage-animal Production Research

Title: 5-hydroxytryphophan mitigates ergot alkaloid-induced suppression of serotonin and feed intake in cattle

Author
item VALENTE, ERITON E. - Western Paraná State University
item Klotz, James
item MARKMANN, RYANA - Western Paraná State University
item EDWARDS, JANICE - University Of Tennessee
item HARMON, DAVID - University Of Kentucky

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2024
Publication Date: 3/23/2024
Citation: Valente, E.L., Klotz, J.L., Markmann, R.C., Edwards, J.L., Harmon, D.L. 2024. 5-hydroxytryphophan mitigates ergot alkaloid-induced suppression of serotonin and feed intake in cattle. Journal of Animal Science. 102. Article skae083. https://doi.org/10.1093/jas/skae083.
DOI: https://doi.org/10.1093/jas/skae083

Interpretive Summary: Ergot alkaloids are toxins produced by a fungus that lives in tall fescue grass. They protect the plant from overconsumption by grazing livestock. Tall fescue is a very common forage in the eastern half of the United States. Livestock are frequently exposed to these toxins through grazing. This results in fescue toxicosis that costs livestock producers billions of dollars annually in lost profits due to animals that perform poorly. While there are many symptoms of fescue toxicosis, one of the primary problems is that animals eat less and consequently gain less weight. These toxins interact with cellular receptors for the neurotransmitter serotonin. This results in lower levels of serotonin in the animal. We have shown that providing animals with the compound 5-hydroxytryptophan (a chemical that can be made into serotonin by the animal) that the levels of serotonin increase. This experiment sought to determine if cattle with lower levels of serotonin caused by ergot alkaloids (fescue toxicosis) could be treated with 5-hydroxytryptophan. Cattle that received 5-hydroxytryptophan had elevated serotonin and increased feed intake compared to steers that did not receive 5-hydroxytryptophan. This is the first report of a treatment for fescue toxicosis increasing feed intake of affected livestock. Application of 5-hydroxytryptophan as a treatment for fescue toxicosis will be of interest not only to other researchers, but to producers that graze cattle where tall fescue is the major forage.

Technical Abstract: The impact of ergot toxicosis on livestock industries is expansive and treatments are needed in many countries. The objective of this study was to evaluate effects of chronic exposure to ergot alkaloids and 5-hydroxytryptophan (5-HTP) supplementation on feed intake, serotonin metabolism and blood metabolites in cattle. Eight Holstein steers (538 ± 18 kg) fitted with ruminal cannulas were used in a replicated 4 x 4 Latin Square design experiment with a 2 x 2 factorial treatment structure. The treatments were the combination of 0 (E-) or 15 µg ergovaline/ kg BW (E+) and 0 (5HTP-) or 0.5 mg of 5-hydroxy-L-tryptophan/ kg BW (5HTP+) administered daily for 6 d. Endophyte-free tall fescue and toxic endophyte-infected tall fescue seed were used as the control (E-) and to supply the ergot alkaloid ergovaline, respectively. Seeds were ground and placed into rumen immediately before feeding. The 5-HTP was dissolved in water and infused into the abomasum via the reticulo-omasal orifice. Blood was collected from a jugular vein catheter at 0, 1, 2, 4, 8 and 24 h after treatment administration. Ergovaline without 5-HTP (E+/5HTP-) decreased dry matter intake (DMI) in comparison to steers without ergovaline and 5-HTP (E-/5HTP-). However, 5-HTP infusion in association with ergovaline (E+/5HTP+) normalized the DMI. Although E+ did not affect the area under curve (AUC) of serum 5-HTP, 5-hydroxyindoleacetic acid, tryptophan and kynurenine, serum and plasma serotonin concentrations were decreased (P < 0.05). The infusion of 5-HTP increased (P < 0.05) the AUC of serum 5-HTP, serum and plasma serotonin and serum 5-hydroxyindoleacetic acid. In conclusion, ergovaline reduces DMI and circulating serotonin in cattle and the 5-HTP administration has potential to normalize both circulating serotonin and feed intake.