Craig Roberts

Research: Fescue Toxicosis

The major focus of the forage quality research program is Fescue Toxicosis, a livestock disorder that costs the Missouri beef industry $160 million each year and U.S. livestock producers $900 million each year; it is the most serious livestock disorder in Missouri. Fescue toxicosis occurs when cattle, sheep and horses graze tall fescue, the most common pasture grass in Missouri. Toxicosis reduces weight gains of steers by 50% and milk production from dairy cows by 30%. It also causes serious foaling difficulties in mares.

Fescue toxicosis is caused by common strains of Neotyphodium coenophialum, a microscopic fungus known as "the endophyte" because it grows inside ("endo") the tall fescue plant ("phyte"). The endophyte produces a class of compounds called ergot alkaloids. These compounds are similar to ergot toxins that plagued humans in Medieval Europe and that caused alleged bewitchment in colonial Salem, Massachusetts.

The goal of this research program is to quantify the effects of the environment and plant genetics on the toxin concentrations in tall fescue and to develop management strategies that reduce toxin consumption by domestic livestock. The program has produced techniques for rapid measurement of these toxins. Using these new techniques, the program has found that tall fescue toxins could be reduced five-fold by treating toxic hay with ammonia gas, a practice normally associated with nutrition rather than toxicology. The program has also found that toxins can be reduced to near-safe levels by using growth regulators to inhibit seedhead development, a reduction that likely occurs because toxins are highly concentrated in the reproductive structures of the maturing plant.

This program collaborates with the University of Arkansas in the use of Neotyphodium strains that were collected during a 1989 germplasm expedition in Morocco. These unique strains, dubbed by New Zealanders as "novel endophytes," produce little or no ergot alkaloids. The novel endophytes have been inserted into tall fescue plants to replace toxic strains of Neotyphodium, resulting in a plant that would prevent toxin consumption by the livestock. The beneficial effect of these strains has been verified by our group in a three-year, regional grazing trial, in which rate of weight gain doubled when steers grazed tall fescue infected with novel endophytes instead of the common endophytes. This is a significant accomplishment for the public, as it translated into a doubling of gross income on these small farms by merely planting a different seed source.

To make the continuing research more efficient, research from this program proved that acute toxicosis of steers on pasture could be predicted with a 17-day rat feeding trial, a screening procedure that costs less than 5% of the cost of a grazing trial. Current collaborations continue with the University of Arkansas and the Noble Foundation, in Ardmore, OK; this multi-state effort involves the development of endophyte-free plant germplasm that persists in field conditions.

Key Publications

  • Rogers, W.M., C.A. Roberts, J.G. Andrae, D.K. Davis, G.E. Rottinghaus, N.S. Hill, R.L. Kallenbach, and D.E. Spiers. 2011. Seasonal fluctuation of ergovaline and total ergot alkaloid concentrations in tall rescue regrowth. Crop Sci. 51:1-6.
  • Rogers, W.M., C.A. Roberts, R.L. Kallenbach, G.E. Rottinghaus, N.S. Hill, W.E. McClain, and D.G. Blevins. 2010. Poultry litter and its chemical equivalent can affect ergot alkaloid concentrations in tall fescue. Forage and Grazingl. Online. doi:10.1094/FG-2010-1203-01-RS.
  • Looper, M.L, R.W. Rorie, C.N. Person, T.D. Lester, D.M. Hallford, G.E. Aiken, C.A. Roberts, G.E. Rottinghaus, and C.F. Rosenkrans, Jr. 2009. Influence of toxic endophyte-infected fescue on sperm characteristics and endocrine factors of yearling Brahman-influenced bulls. J. Anim. Sci. 87:1184-1191.
  • Roberts, C.A., R.L. Kallenbach, N.S Hill, G.E. Rottinghaus, and T. J. Evans. 2009. Ergot alkaloid concentrations in tall fescue hay during production and storage. Crop Sci. 49:1496-1502.
  • Curtis, L.E., R.L. Kallenbach, and C.A. Roberts. 2008. Allocating forage to fall-calving cow-calf pairs strip-grazing stockpiled tall fescue. J. Anim. Sci. 86:780-789.
  • Roberts, C.A., C.P. West, and D.A. Spiers (eds.) 2005. Neotyphodium in Cool-Season Grasses. 392 p. Blackwell Publishing Professional, Ames, IA. Wiley listing.
  • Kallenbach, R. L., C.A. Roberts, T.R. Lock, T. R., D.H. Keisler, M.R. Ellersieck, and G.E. Rottinghaus. 2006. Performance of steers fed ammoniated straw from tall fescue seed fields. Online. Forage and Grazinglands doi:10.1094/FG-2006-0113-01-RS.
  • Roberts, C.A., H.R. Benedict, N.S Hill, R.L. Kallenbach, and G.E. Rottinghaus. 2005. Determination of ergot alkaloid content in tall fescue by near-infrared spectroscopy. Crop Sci. 45:778-783.
  • Roberts, C.A., and J.A. Andrae. 2004. Tall fescue toxicosis and management. Online. Crop Managm. doi. 10:1094/CM-2004-0427-01-MG.
  • Nihsen, M., E.L. Piper, C.P. West, R.J. Crawford, T.M. Denard, Z.B. Johnson, C.A. Roberts, D.A. Spiers, and C.F. Rosenkrans. 2004. Growth rate and physiology of steers grazing tall fescue inoculated with novel endophytes. J. Anim. Sci. 82:878-883.
  • Roberts, C.A., R.L. Kallenbach, and N.S. Hill. 2002. Harvest and storage methods affect ergot alkaloid concentration in tall fescue. Online. Crop Managm. doi. 10:1094/CM-2002-0917-01-BR.
  • Roberts, C.A., D.E. Spiers, A.L. Karr, H.R. Benedict, D.A. Sleper, P.A. Eichen, C.P. West, E.L. Piper, and G.E. Rottinghaus. 2002. Use of a rat model to evaluate tall fescue seed infected with introduced strains of Neotyphodium coenophialum. J. Agric. Food Chem. 50:5742-5745.
  • Roberts, C.A., R.E. Joost, and G.E. Rottinghaus. 1997. Quantification of ergovaline in tall fescue by near infrared reflectance spectroscopy. Crop Sci. 37:281-284.