Ergovaline, an endophytic alkaloid. 1. Animal physiology and metabolism

Abstract

Abstract. Ergovaline is an ergot alkaloid found in some endophyte-infected ryegrasses and it has been implicated in the expression of ergotism-like symptoms of grazing livestock, as well as in the protection of the plant against invertebrate predation and abiotic stresses. These selection pressures have resulted in a conflict between the needs of the pasture for persistence and the needs of the animal for production. Ergovaline has not been well studied in terms of animal physiology until recently. There are several putative mechanisms that limit the bioavailability of ergovaline, ranging from microbial biotransformation to post-absorptive hepatic detoxification. Although there are mechanisms that protect the animal from ergovaline exposure, tissues are very sensitive to ergovaline, indicating that ergovaline is very potent and that small quantities have the potential to cause noticeable physiological effects. The range of physiological effects, including decreased circulating prolactin, vasoconstriction and increased susceptibility to heat stress are all linked to the interaction of ergovaline with biogenic amine receptors found throughout the body. This review will focus on understanding the variation of ergovaline concentration in terms of bioavailability, the myriad of hurdles a molecule of ergovaline must overcome to cause an effect, what the ergovaline-induced effects are in New Zealand livestock and how this relates to the potency of ergovaline.

Forms of selenium in vitamin-mineral mixes differentially affect serum prolactin concentration and hepatic glutamine synthetase activity of steers grazing endophyte-infected tall fescue

“…Consumption of ergot alkaloids by cattle is known to constrict the caudal artery (Aiken et al, 2007), right ruminal artery and vein (Foote et al, 2011), and mesenteric artery and vein (Jia et al, 2015). Ergot alkaloid-induced vasoconstriction is thought to be a contributor to several symptoms of fescue toxicosis (Klotz and Nicol, 2016). Therefore, the caudal artery luminal area was determined in this study as a parameter to assess potential Se-form treatment differences.…”

Effects of red clover isoflavones on tall fescue seed fermentation and microbial populations in vitro

“…Concerns of the alkaloids manifest with reduced blood flow to the periphery, reduced reproductive efficiency, and reductions in growth performance [ 2 – 4 ]. Of the alkaloids associated with endophyte-infected tall fescue, ergovaline is the most predominant of concern in the plant, as it imposes the greatest detrimental effects on livestock [ 5 , 6 ]. Reducing the consumption of endophyte-infected tall fescue has proven to be a challenge for livestock producers, as it occupies roughly 15 million hectares in the United States [ 7 ], with the majority in the east and southeast regions of the country.…”

Interaction of ergovaline with serotonin receptor 5-HT2A in bovine ruminal and mesenteric vasculature1

“…Structurally, ergot alkaloids are similar to biogenic amines, such as 5-HT, which allows them to act as agonists or antagonists (Berde, 1980) and bind to serotonergic receptor sites (Eckert et al, 1978). There are 14 different receptor subtypes of 5-HT (Hoyer et al, 1994;Klotz and Nicol, 2016) that could elicit different responses when exposed to various ergot alkaloids. Dyer (1993) showed that 5-HT 2 receptors are involved in vasoconstriction by ergovaline (ERV) and Schöning et al (2001) demonstrated that the vasoconstrictive effect of ERV is due to 5-HT 2A activation in rat and guinea pig arteries.…”