Tall fescue is a cool-season grass with unique properties that explain its dominance in 40 million acres of U.S. pastures. Most of these acres are dominated by unimproved tall fescue. The predominant feature of tall fescue is its persistence, even under abuse. It has a very tough root system, survives drought periods, is resistant to most insect pests, and comes back after overgrazing.
These characteristics can partly be attributed to an endophytic fungus that lives in symbiosis with the plant. Endophytic means 'inside the plant' because this fungus lives inside tall fescue plants. It will proliferate throughout the plant, although it is especially concentrated in the lower stem and in the seed. The endophyte produces alkaloid compounds that help protect the plant from pests, diseases, and drought. In return, the plant provides carbohydrates and nutrients to the fungus.
The problem is that the alkaloids also cause animal health problems at high concentrations due to vasoconstriction—blood vessels in animals contract causing poor blood circulation. This can cause things like hoof and foot problems, poor hair growth, and overheating in summer, which in turn can affect animal health, reproduction, and growth. If you plan on renovating a pasture you should choose an endophyte-free or endophyte-friendly varieties available from your seed supplier. However, if you have an unimproved tall fescue pasture you can still use it in a grazing plan if you follow these guidelines:
- Graze or mow spring growth, leaving at least 3–4 inches of stubble. The alkaloid concentration is highest in the seed heads, so you want to avoid this grass from creating seed. Tall fescue only produces heads on the first spring growth, so managing it this way will effectively suppress seed head production. The alkaloid concentration is higher in the lower plant part than in the tops of leaves, so do not graze below 3 inches stubble height.
- Rest tall fescue in summer. Tall fescue slows down its growth in the heat of summer while the alkaloid concentration increases. Above 88°F, animals become highly sensitive to the alkaloid (probably because of excessive heat stress). These rested pastures should be reserved for stockpiling—grazing in winter.
- Graze tall fescue in winter. Tall fescue has rigid leaves that keep quality better under snow than other grasses that tend to matt down more. Further, its robust root system withstands the effects of hoof impact better than that of most other forages. Finally, the alkaloid concentration in the standing forage decreases as much as 85% as winter progresses. By grazing tall fescue in the winter, you can really extend your grazing season, which means more natural and economical animal nutrition.
- Increase plant diversity. 'Dilution is the solution to pollution'. Therefore, including companion species with tall fescue reduces the toxic effect of the alkaloid. Other grass species can be mixed with tall fescue, while legumes are especially suited as companion species. Red clover is especially effective because it has 'vasodilating' or blood vessel-widening properties. Frost seeding red clover into tall fescue stands can be done in the coming months.
- Supplement with grain. While this is not an option if you are on an 'all forage' diet, supplementing 0.6% of body weight per day of corn grain will help reduce the effects of alkaloids, supply energy to the animals, and will not interfere with fiber digestion (the latter becomes a problem at higher corn supplementation rates). Corn gluten can be fed at higher rates without endangering fiber digestion.
With proper management, unimproved tall fescue stands can still be used successfully in a grazing plan with the unique opportunity to use it for winter grazing.
Acknowledgment
This work was supported by the USDA National Institute of Food and Agriculture and McIntire-Stennis Appropriations under Project #PEN04600 Accession No. 1009362, by The National Fish and Wildlife Foundation under a subcontract from Capital RC&D, and by USDA-Agricultural Marketing Service grant AM190100XXXXXG167. Its contents are solely the responsibility of the author and do not necessarily represent the official views of the USDA.
