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

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.

Keywords: ergot alkaloids; goats; isoflavones; tall fescue; vasoconstriction.

Figure 1

Ultrasonic measures of proportionate differences from baseline measures for luminal area of the carotid artery in rumen-fistulated wether goats that were infused with toxic E+ TF seed ± red clover, white clover, or soybean meal. Baseline measures were taken with goats receiving ad libitum chopped orchardgrass (Dactylis glomerata)—timothy (Phleum pratense) hay with no rumen infusion treatments. Images for determining baseline measures were collected on the last 2-d of the adaptation period. Means lacking a common letter (a,b,c) are different. Treatment: p < 0.0001; period: p = 0.2415; block: p = 0.3030; period × treatment: p = 0.8491; Pooled SEM: Treatment = 0.0313; period = 0.0354; block = 0.0532; period × treatment = 0.0639.