Author
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Klotz, James |
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NICOL, ALASTAIR - LINCOLN UNIVERSITY - NEW ZEALAND |
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Submitted to: Animal Production Science
Publication Type: Review Article Publication Acceptance Date: 6/28/2016 Publication Date: 8/19/2016 Citation: Klotz, J.L., Nicol, A.M. 2016. Ergovaline, an endophytic alkaloid. 1. Animal physiology and metabolism. Animal Production Science. 56:1761-1774. http://dx.doi.org/10.1071/AN14962. DOI: https://doi.org/10.1071/AN14962 Interpretive Summary: In the scientific literature experimental conditions are created that deliberately enhance the toxic potential of ergovaline so that the resulting malady can be studied. There is a broad spectrum of effects that can be experimentally related to ergovaline. However, there is a definite boundary between the physiologic and production level effects described in the scientific literature that are related to ergovaline. The scenarios that result in production losses can be severe, but can (and often are) be managed around to minimise the occurrence. The physiologic effects of ergovaline are less likely to be observed in production settings (therefore less likely for the producer to be aware of) than in an experimental setting, but should nevertheless not be ignored as animal productivity may be at stake. In addition to highlighting the range of ergovaline-related effects, this review demonstrates the ability of the ruminant to tolerate (breakdown and excrete) a certain amount of ergovaline. The issue key to New Zealand producers is keeping the level of ergovaline at levels that are low enough not to exceed the ability of livestock to metabolise it, but also have levels that are sufficient to impart some of the positive benefits provided by ergovaline that improve pasture persistence. The role that ergovaline plays in animal toxicoses is becoming increasingly well defined. However, the role that ergovaline can play in drought resistance and insect feeding deterrence and the relationship to anti-herbivory must also continue to be delineated as this will dictate the importance of maintaining ergovaline at the plant-animal interface. Technical Abstract: Ergovaline is an ergot alkaloid found in some endophyte-infected ryegrasses and 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 a number of 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. |
