– Dr. Chris Teutsch, Extension Associate Professor and Forage Specialist, University of Kentucky
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I wrote this article several years ago for the forages session at the Kentucky Cattlemen’s Annual Meeting. It is a summary of management strategies for utilizing tall fescue in grazing systems. How we approach tall fescue management in grazing systems is NOT black and white, but rather nuanced by a number of practical considerations. In some cases, replacement of toxic stands with improved novel endophyte (non-toxic endophyte) varieties does not always make sense. The objective of this article is to help you work through those considerations to determine the best path forward for managing tall fescue in your operation.
Tall fescue (Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.) is the most important cool-season grass in the transition area between the temperate northern and subtropical southern United States. In most unimproved pastures, tall fescue is infected with a fungal endophyte that imparts tolerance to abiotic and biotic stresses. While this mutualistic relationship improves persistence in low input grazing systems, it also results in the production of alkaloids that cause tall fescue toxicosis. While there are a number of grotesque symptoms associated with this syndrome such as fescue foot, fat necrosis, and loss of ear tips and tail switches, symptoms that are not readily observed are the costliest. These include vasoconstriction resulting in high body temperature, lower forage intake, lower milk production, lower growth rates and weaning weights, compromised immune system, and lower conception/calving rates (Roberts and Andrae, 2004). This article will provide some practical approaches to mitigating the negative impact of tall fescue in grazing systems.
Assess endophyte levels. The first step in managing tall fescue toxicosis is to access the levels of endophyte in pastures. Since the endophyte cannot be seen with the naked eye, tiller samples must be collected and sent into a lab for screening. In Kentucky, the Division of Regulatory Services at the University of Kentucky provides this service. More information on collecting samples can be obtained by contacting your local extension office or consulting the following publication, Sampling for the Tall Fescue Endophyte in Pastures and Hay Stands, PPA-30.
Develop a management strategy. Once level of endophyte infection is known, an appropriate management strategy can be developed (Figure 1).
If the infection level is above 20 to 25%, then replacement of the stand is recommended. However, there are a number of factors that should be considered prior to replacement. For example, if the pasture is rented on a year to year lease, then investment in a novel endophyte tall fescue may not be wise. Other important considerations can be found in Figure 1.
Replacement of toxic stands. In cases where it is feasible to replace toxic stands with novel endophyte tall fescue, there are two approaches. The first is Spray-Wait-Spray. In this method tall fescue pastures are grazed or harvested for hay in the spring to keep viable seed from being produced. Pastures are then allowed to regrow (vegetative) and sprayed with a non-selective herbicide in mid-summer. Pastures are sprayed a second time with a non-selective herbicide just prior to planting in late summer. The second approach is Spray-Smother-Spray. In this method, pastures can be grazed in early spring and allowed to regrow. They are then sprayed with a non-selective herbicide in late spring and a summer annual smother crop is planted (sorghum-sudangrass or pearl millet). The smother crop can be grazed or hayed during the summer months. In late summer, pastures are sprayed a second time with a non-selective herbicide and the novel endophyte tall fescue is planted.
Managing existing tall fescue stands. In some cases, even with high infection rates, it may not make sense to replace tall fescue stands. These stands may be on land with short-term leases or high erosion potential (Figure 1). In these cases, managing existing stands may be the most practical approach. There are a number of management practices that can be implemented to mitigate the negative impacts of the toxic endophyte and together they can improve animal performance to a level almost equal to endophyte free or novel endophyte tall fescue (Figure 2).
Dilution with other forages. The negative impact of the endophyte can be mitigated by adding non-toxic forages to pastures (Figure 3). Red and white clover can be frost seeded into tall fescue pastures in late winter. For more information on frost seeding please AGR-271, Frost Seeding Clover: A Recipe for Success. Pastures can also be interseeded with other cool- and warm-season grasses. Crabgrass can be incorporated into thinning tall fescue pastures to provide non-toxic forage during the summer months. For more information on crabgrass please see AGR-232, Crabgrass.
Inclusion of forages with bioactive compounds. Research from the USDA Forage-Animal Production Unit located in Lexington, KY has found that some forage species, primarily red clover, contain compounds that can reverse the vascular constriction that is caused be the toxins found in tall fescue infected with toxic endophyte. From a practical standpoint, frost seeding red clover improves forage quality, converts nitrogen from the air into a plant available form, dilutes the toxins found in tall fescue, and reverses the effects of those compounds. The USDA is working on strategies to consistently supply red clover to animals grazing tall fescue pastures, including adding red clover leaves to mineral supplements. At this point in time, the best approach is frost seeding red clover into your pastures in February on an annual or biannual schedule.
Clipping seedheads. Seedheads can contain five times more ergovaline (toxin in tall fescue) than leaf blades (Figure 4). Clipping seedheads in tall fescue pastures not only maintains forage quality, but also decrease ergovaline levels. Seedheads can also be controlled by plant growth regulators. Applied at the proper time, some herbicides can almost eliminate seedhead formation. More information of seehead suppression with Chaparral herbicide can be found at on the UK Forages Website.
Strategic avoidance. Avoiding tall fescue pastures during critical times of the year such as the summer months or late fall can reduce the negative impacts of the endophyte. For example, a summer annual or perennial forage could be incorporated into the grazing system, allowing cattle to avoid tall fescue during the summer months. Another example would be feeding hay during late fall to allow ergovaline levels in stockpiled tall fescue to decrease to a safe level (Figure 5).
Use local animal genetics. Herds that have been developed in the fescue belt have been indirectly selected for tolerance to tall fescue toxicosis. It is important to recognize that although some animals may have increased tolerance to tall fescue toxicosis it is not and will most likely never be complete tolerance. Genetic testing for tolerance to tall fescue toxicosis is in its infancy and one commercially available test is currently being marketed. A more practical approach may be closely observing animals and culling ones that exhibit signs of tall fescue toxicosis.
Supplement tall fescue pastures. Supplementation with energy and protein has been shown to partially alleviate tall fescue toxicosis (Figure 6), although the impact can be marginal, especially at lower supplementation levels. The impact of supplementation is likely two-fold. The first is decreased dietary toxins due to dilution and the second is increased levels of protein and energy
in the diet. As with other management strategies, there is a cost for both the supplement and feeding it.
Tall fescue toxicosis is one of the costliest livestock disorders in the southeastern United States. Its impacts often go undetected on many livestock operations. Developing a management strategy starts with testing pastures for the endophyte. Once this is accomplished, appropriate management strategies can be implemented. While management strategies can mitigate impacts, the only way to completely eliminate the harmful effects of endophyte on livestock is to replace infected stands with other forages or novel endophyte tall fescue.
Elizalde, J.C., J.D. Cremin, Jr., D.B. Faulkner, and N.R. Merchen. 1998. Performance and digestion by steers grazing tall fescue and supplemented with energy and protein. J. Anim. Sci. 76:1691–1701. doi:10.2527/1998.7661691x.
Kallenbach, R.L., G.J. Bishop-Hurley, M.D. Massie, G.E. Rottinghaus, and C.P. West. 2003. Herbage mass, nutritive value, and ergovaline concentration of stockpiled tall fescue. Crop Sci. 43:1001–1005. doi:10.2135/cropsci2003.1001.
Roberts,C. and J. Andrae, editors, 2018. Fescue Toxicosis and Management. ASA, CSSA, Madison, WI. doi:10.2135/2018.fescuetoxicosis.
Rottinghaus, G. E., Garner, G. B., Cornell, C. N., and Ellis, J. L. 1991. HPLC method for quantitating ergovaline in endophyte-infested tall fescue: seasonal variation of ergovaline levels in stems with leaf sheaths, leaf blades, and seed heads. J. Agric. Food Chem. 39:112-115.
Thompson, R. W., Fribourg, H. A., Waller, J. C., Sanders, W. L., Reynolds, J. H., Phillips, J. M., Schmidt, S. P., Crawford, R. J., JR., Allen, V. G., Faulkner, D. B., Hoveland, C. S., Fontenot, J. P., Carlisle, R. J., and Hunter, P. P. 1993. Combined analysis of tall fescue steer grazing studies in the eastern United States. J. Anim. Sci. 71:1940-1946.
FEATURED VIDEO
This month’s featured video is Practical Considerations for Utilizing Tall Fescue in Grazing Systems-Chris Teutsch, University of Kentucky. This presentation was given at the 2020 Forage Symposium at the Kentucky Cattlemen’s Association Annual Meeting, Tall Fescue: Past, Present, and Future, January 17, 2020, Owensboro, KY.
FEATURED PUBLICATION
This month’s featured publication is: Comparison of Commercially Available Novel-Endophyte Tall Fescue Forage Varieties by Kendra Phipps, Charlotte Talbott, Madeline Newsome, Deidre Harmon, and Matt Poore. NC Extension, Raleigh, KY.