Isoflavone Containing Legumes Mitigate Ergot Alkaloid-Induced Vasoconstriction in Goats (Capra hircus)

SIMPLE SUMMARY: When endophyte-infected tall fescue is consumed by grazing livestock it can cause persistent vasoconstriction resulting in fescue toxicosis. Legumes are commonly utilized in livestock production to improve diet quality. Legumes also contain vasodilatory 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 goats. Rumen fistulated Wether goats were assigned to each legume treatment at equal levels of supplementation by weight. Goats were subjected to a fescue toxicosis challenge with toxic tall fescue seed, and the carotid artery area was monitored using Doppler ultrasonography. All isoflavone treatments were able to partially mitigate vasoconstriction. Red clover, with the greatest concentration of isoflavones, was the most effective. These results demonstrate that red clover, white clover, and soybean meal supplementation can be used to reverse the vasoconstriction associated with fescue toxicosis in goats despite 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. ABSTRACT: Ergot alkaloids produced by a fungal endophyte that infects tall fescue (Lolium arundinaceum; (E+ TF) can induce constriction of the vasculature in ruminants, resulting in “fescue toxicosis”. Legumes contain isoflavones that have been demonstrated to prevent and reverse E+ TF vasoconstriction. Several legumes are conventionally utilized in ruminant production, but can vary in both isoflavone concentration and composition. A feeding study was conducted to determine if isoflavone supplementation via red clover (Trifolium pratense), white clover (Trifolium repens), or soybean (Glycine max) meal can alleviate vasoconstriction when wether goats were challenged with E+ TF seed. The basal diet was chopped grass hay ad libitum. Carotid luminal areas were obtained pre- and post-ruminal infusions of E+ TF seed (15 µg kg BW(−1) ergovaline + ergovalanine ± red clover, white clover, or soybean meal at 2.61 mg kg BW(−1)). When goats were challenged with E+ TF seed, the mean carotid luminal areas decreased by 56.1% (p < 0.01). All treatments were able to partially mitigate vasoconstriction, with red clover being the most effective (+39.8%), and white clover and soybean meal eliciting an intermediate response (+30%, p < 0.01). Results indicate that legumes can relax vasoconstriction in goats consuming ergot alkaloids, despite differences in isoflavone profile and concentrations.