Isoflavone containing legumes mitigate ergot alkaloid-induced vasoconstriction in goats (Capra hircus)

Authors: Harlow, Brittany; Flythe, Michael; GOODMAN, JACK - University Of Kentucky; JI, HUIHUA - University Of Kentucky; AIKEN, GLEN - University Of Florida

Submitted to: Animals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2022
Publication Date: 3/17/2022
Citation: Harlow, B.E., Flythe, M.D., Goodman, J.P., Ji, H., Aiken, G.E. 2022. Isoflavone containing legumes mitigate ergot alkaloid-induced vasoconstriction in goats (Capra hircus). Animals. 12(6). Article 750. https://doi.org/10.3390/ani12060750.
DOI: https://doi.org/10.3390/ani12060750

Interpretive Summary: Tall fescue is the most prevalent cool-season perennial grass in the United States. Most tall fescue is infected by a fungal endophyte that can produce toxic alkaloids. When these toxins are consumed by grazing livestock, they cause persistent vasoconstriction resulting in fescue toxicosis. A variety of legumes are conventionally utilized in livestock production systems including red clover, white clover, and soybean to improve diet diversity and quality. In addition to their utility as protein supplements, legumes contain vasodilatory phytochemicals called isoflavones that have been shown to alleviate fescue toxicosis in goats and grazing cattle. Different legumes contain varying levels and types of isoflavones. A pen study was conducted to determine if isoflavone supplementation via red clover, white clover, or soybean meal can mitigate vasoconstriction associated with fescue toxicosis in wether goats. Rumen fistulated wether goats were assigned to either a red clover, white clover, or soybean meal treatment at equal levels of supplementation. Goats were subjected to a fescue toxicosis challenge with toxic tall fescue seed and carotid artery area was monitored using color Doppler ultrasonography. All isoflavone treatments were able to partially mitigate vasoconstriction associated with fescue toxicosis, with red clover being the most effective. The results of this study demonstrate that red clover, white clover, and soybean meal supplementation can be used to mitigate the vasoconstriction associated with fescue toxicosis in goats despite vast differences in isoflavone concentration and composition. The impact of this research is a legume-derived phytochemical that can be applied in ruminants consuming toxic tall fescue to reverse fescue toxicosis and improve animal health and productivity.

Technical Abstract: Ergot alkaloids produced by a fungal endophyte (Epichloë coenophiala;) that infects tall fescue (Lolium arundinaceum) can induce persistent constriction of the peripheral vasculature in ruminant animals, resulting in “fescue toxicosis.” Legumes contain isoflavones that have been demonstrated to both prevent and reverse alkaloid-induced vasoconstriction. A variety of legumes are conventionally utilized in ruminant production systems including red clover (Trifolium pratense), white clover (T. repens) and soybean (Glycine max). However, these legumes vary in both isoflavone concentration and composition. A pen study was conducted to determine if isoflavone supplementation via red clover, white clover, or soybean meal can mediate relaxation of the carotid artery during ergot-alkaloid-induced vasoconstriction in wether goats. Goats were fed chopped grass hay ad libitum as the basal diet. Measures of carotid luminal areas were obtained pre- (baseline) and post-ruminal infusions of endophyte-infected tall fescue seed (15 µg kg BW-1 ergovaline + ergovalanine) ± red clover, white clover, or soybean meal (2.61 mg kg BW-1). When goats were challenged with endophyte-infected tall fescue seed mean carotid luminal areas decreased 56.1%. All isoflavone treatments were able to partially mitigate ergot-alkaloid-induced vasoconstriction, with red clover being the most effective (+39.8%), and white clover and soybean meal eliciting an intermediate response (+30%, P < 0.0001). Results from the current study indicate that legume supplementation can relax vasoconstriction in goats consuming ergot alkaloids, despite differences in isoflavone profile and concentrations. Future research is needed to determine how isoflavone composition influences vasoactive potential and to identify threshold concentrations of isoflavones in the diet to yield maximum benefits.