Managements for mitigating fescue toxicosis

Authors: Flythe, Michael

Submitted to: American Forage and Grassland Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/16/2018
Publication Date: 3/16/2018
Citation: Flythe, M.D. 2018. Managements for mitigating fescue toxicosis. American Forage and Grassland Conference Proceedings. http://www.afgc.org/proceedings/2018/.

Interpretive Summary:

Technical Abstract: Fescue toxicosis is an ongoing problem for cattlemen and other livestock producers in regions where tall fescue is prevalent. Logically, there are two ways to alleviate or mitigate the toxicosis; either make the forage less toxic or make the animals less sensitive. Think of it in terms of four basic approaches: establish a new forage, change the physiology of the forage you have, establish new genetics in your herd or change the physiology of the animals you have. 1) Replace the tall fescue with non-toxic forage. The pastures can be reestablished with another grass or with a non-toxic endophyte tall fescue. Another lecture in this section will cover novel-endophyte fescues in detail. 2) Change the physiology of the toxic fescue. Chemical seed head suppression will maintain fescue in the vegetative state. Because the toxic alkaloid concentrations are the greatest in the seed heads, the animals will consume less toxic forage. 3) Replace sensitive animals with more tolerant animals. Since the 1990’s, studies have shown that Brahman-influenced cattle are less susceptible to fescue toxicosis. Current research indicates that genotypes within British and Continental breeds can be more tolerant through differences in liver enzymes and blood vessel receptors. Another lecture in this section will discuss new data about how some cattle have rumen bacteria that metabolize ergot alkaloids differently. 4) Change the physiology of susceptible animals. Ergot alkaloid binders that purportedly prevent absorption are commercially available. However, there is still little data to show their efficacy. Isoflavones found in legumes are vaso-relaxants and counteract vaso-constriction by ergot alkaloids. Red clover has more isoflavones than other common forage legumes, but experiments also show that white clover, soybean meal and soy hulls can also improve blood flow in fescue toxicosis. Not all strategies will be viable for all farms, but one, or a combination, is feasible in many circumstances. For example, seed head suppression in years prior to establishment of a novel endophyte fescue would mitigate toxicosis in the short term and decrease immergence of the old variety from the seed bank. Clovers could be used to improve the performance of susceptible animals while tolerant genotypes are introduced. Ongoing research by public and private scientific teams addresses each of these four strategies for mitigation or alleviation of fescue toxicosis.