By Sjoerd Willem Duiker
Tall fescue is a cool-season grass with unique properties that explain its dominance in 40 million acres of U.S. pastures. ‘Kentucky 31’ is the most common variety of tall fescue. The predominant feature of ‘Kentucky 31’ 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. The reaction by animal nutritionists has been to recommend against ‘Kentucky 31’ tall fescue. This is unfortunate, because tall fescue is so common and because it can constitute an important component of a quality grazing plan. Let’s review a few ways ‘Kentucky 31’ tall fescue can successfully be used in a grazing plan.
- 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 88F 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 ‘Kentucky 31’ tall fescue can be used successfully in a grazing plan with the unique opportunity to use it for winter grazing.
Source : psu.edu