Submitted to: Kentucky Forage and Grassland Council
Publication Type: Proceedings
Publication Acceptance Date: October 14, 2008
Publication Date: October 23, 2008
Citation: Aiken, G.E. 2008. Practical Grazing Management and Feed Strategies to Alleviate Fescue Toxicosis. Kentucky Forage and Grassland Council. Pgs 17-21. Interpretive Summary: Tall fescue grown in Kentucky is productive and persistent and that is why the state has 5 million acres of the grass. A fungal endophyte infects most tall fescue plants that impart tolerance to environmental stresses, but this agronomic advantage is offset by reduced calving percentages and calf weight gains caused by consumption of ergot alkaloids produced by the endophyte. Ergot alkaloids affect the physiology of cattle to cause elevation in body temperature, reduced sweating, retention of winter hair coats and uncontrollable growth of summer hair coats. Cattle inflicted with this toxicosis suffer from heat stress with high air temperature and humidity to reduce grazing time and dry matter intake. There presently are three management options for improving cattle performance on toxic fescue. First, cattle can be moved from toxic fescue to warm-season perennial grass pastures in the late spring or early summer to avoid vulnerability to heat stress during the summer. Secondly, replacing some of the toxic fescue in cattle diets with concentrate/by-product feeds, or by interseeding clovers have both consistently shown to dilute the ergot alkaloids and enhance performance and physiology. Thirdly, novel endophyte strains have been discovered and developed that do not produce the toxic ergot alkaloids. These novel endophyte fescues offer a non-toxic alternative to toxic fescue. Use of these options could substantially reduce the billion dollar annual cost of toxic tall fescue to the cattle industry.
Technical Abstract: Fescue has tolerances to drought, low fertility, and over-grazing that are attributed to a fungal endophyte which infects most tall fescue plants. Unfortunately, these advantages of tall fescue that livestock producers appreciate are offset by reduced calving percentages and calf weight gains caused by consumption of ergot alkaloids produced by the endophyte. Ergot alkaloids affect the physiology of cattle to cause elevation in body temperature, reduce sweating, retention of winter hair coats and uncontrollable growth of summer hair coats. There are three management options for improving cattle performance on tall fescue. First, cattle can be moved from endophyte-infected fescue to warm-season perennial grass pastures (for example, eastern gamagrass or bermudagrass) in the late spring or early summer when maximum daily air temperatures increase (> 80°F). Secondly, ergot alkaloids can be diluted in the diet by feeding concentrates/by-product feeds, or by interseeding fescue pastures with legumes, such as ladino white clover or red clover. A third option is to replace ‘Kentucky 31’ tall fescue infected with the wild type endophyte with tall fescue that is infected with novel endophytes, which do not produce the toxic ergot alkaloids. Results from various grazing experiments have inducted success with each management option in improving cattle performance and well being on endophyte-infected tall fescue.