Influence of Endophyte, Alfalfa, and Grazing Pressure on Steer Performance and Plant Persistence of Jesup Tall Fescue

Endophyte [Neotyphodium coenophiulum (Morgan-Jones & W. Gams) Glenn, Bacon, Price & Hanlin] toxicosis of cattle on tall fescue (Festuca arundinacea Schreb.) pasture can be offset by using an endophyte-free (E-) cultivar, adding a legume, or possibly by increasing grazing pressure. Release of a more persistent E-tall fescue, ‘Jesup’, and ‘Alfagraze’ grazing-tolerant alfalfa (Medicago sativa L.) may help in this regard. The objectives of this central Georgia study were to determine beef steer (Bos taurus × B. indicus) performance and plant persistence as affected by endophyte infected (E+) and E-Jesup tall fescue, alfalfa, and grazing pressure (GP) during spring and autumn on continuously stocked pastures. No grazing was done during summer. Average daily gain (ADG) from March to June for 3 yr on E+ tall fescue, E-tall fescue, E+ fescue with alfalfa, and alfalfa alone were 0.95, 2.50, 1.24, and 2.14 lb at low GP and 0.66, 2.04, 1.22, and 1.45 lb at high GP, respectively. High GP had a detrimental effect on ADG, and this effect was greater from October to December than in spring. Higher stocking rates were needed on E+ than on E-tall fescue to achieve similar GP. Both E+ and E-tall fescue survived well after a severe drought the first grazing season, indicating good drought tolerance of the Jesup cultivar. Alfalfa with E+ tall fescue improved ADG by 30% at low GP and 84% at high GP, even though the legume represented only 6% of the available forage. The high ADG obtained on Jesup E-tall fescue and excellent stand persistence indicate its potential for grazing by growing animals. Research QuestionAlthough endophyte-free (E-) tall fescue furnishes better animal performance than grass infected with the fingal endophyte, Neotyphodium coenophialum, present cultivars are not persistent with continuous high grazing pressure (GP) in stressful environments. A new productive E-tall fescue cultivar, Jesup, released by the University of Georgia, appears to have greater persistence. The present 3-yr study compared E- and endophyte-infected (E+) versions of Jesup tall fescue, E+ Jesup plus Alfagraze alfalfa, and Alfagraze alfalfa alone when grazed by beef steers at high and low GPs in central Georgia. Literature SummaryMany cattle producers have lost stands of E-tall fescue because of low tolerance to drought and GP. Since poor animal performance is often a problem when grazing E+ tall fescue, the addition of a legume to the pasture can offset this to a considerable degree. Ladino clover, the most commonly planted legume in tall fescue, does not persist well. Alfagraze alfalfa, selected for grazing tolerance, may offer more potential in diluting the toxic effects of E+ tall fescue pastures. Study DescriptionSixteen 2-acre pastures were used for the 3-yr experiment at the Central Georgia Branch Station, Eatonton. Pastures were E-Jesup tall fescue, E+ Jesup, E+ Jesup with Alfagraze alfalfa, and Alfagraze alone. Each of the four pasture treatments was grazed at high and low GPs with two replications. Beef steers were stocked continuously from March to June and again from October to December (except on pure alfalfa) with additional steers added as needed to maintain the desired GP. Applied QuestionsHow did the average daily gain (ADG) of steers compare on endophyte-infected and endophyte-free Jesup tall fescue? The ADG at low GP on E- was more than twice that on E+ tall fescue; and at high GP the ADG was tripled. Spring period ADG at high GP on E-Jesup averaged 2 lb/d over 3 yr. What was the effect of grazing pressure on ADG? High GP decreased ADG on all treatments but resulted in more gain per acre on E-tall fescue because of higher stocking rates. High GPs decreased ADG more on alfalfa than on E-tall fescue. How did alfalfa in endophyte-infected tall fescue affect ADG? Alfalfa stands were thin in the tall fescue so the legume constituted only 6% of the forage. Steer ADG was improved 84% at high GP and 30% at low GP. However, ADG on the mixture was substantially below that of E-tall fescue. How did stands of Jesup endophyte-free tall fescue persist under grazing? Even though, in the first grazing season, pastures were subjected to a severe summer drought with May to September rainfall only 32% of normal and daily maximum temperatures 5 to 10°F higher than normal, E-Jesup stand persistence was similar to infected tall fescue at both high and low GPs. RecommendationJesup E-tall fescue appears to be a superior persistent tall fescue cultivar with the potential for excellent animal performance. Its growing season is similar to that of Kentucky 31 and shorter than winter-productive cultivars such as AU Triumph. Alfalfa, planted with E+ tall fescue, can improve animal performance but the highly competitive nature of tall fescue will result in a short stand life in stressful environments.