Enhancing the Sustainability of Tall Fescue Forage Systems for Beef Cattle Production with Non-Toxic Endophyte Technology

Enhancing the Sustainability of Tall Fescue Forage Systems for Beef Cattle Production with Non-Toxic Endophyte Technology

Summary

Grazing studies were conducted to determine animal growth performance, evaluate toxicosis, and compare grazing behavior in stocker cattle grazing non-ergot alkaloid-producing endophyte-infected (AR542 or AR502), endophyte-free (E-), or wild-type toxic endophyte-infected (E+) Jesup, Georgia-5, and Kentucky-31 tall fescue. Replicated 0.81-hectare tall fescue paddocks were established at the Central Georgia Branch Station at Eatonton and the Northwest Georgia Branch Station at Calhoun during October 1998 and were stocked with beef cattle from autumn 1999 through autumn 2001. Stocker cattle growth performance on AR542 and AR502 tall fescue pastures was similar to cattle growth on E- (P > 0.20) and exceeded (P < 0.05) cattle growth on E+ tall fescue. Indicators of toxicosis, depressed serum prolactin levels and elevated rectal temperatures, were observed only in cattle grazing E+ pastures. A final grazing season is planned for spring 2002 to complete the 3-year grazing study. In a second experiment at Eatonton to evaluate steer grazing behavior, steers were grazed on non-ergot alkaloid-producing “friendly” endophyte-infected (AR542), endophyte-free (E-), and wild-type toxic endophyte-infected (E+) Jesup tall fescue. Grazing behavior data were collected with computerized monitoring equipment over 5-day periods during March, April, May, and June in spring and during September, October, and November in autumn. Forage availability was higher (P < 0.05) in E+ pastures than E- pastures during spring grazing but was similar (P > 0.20) across pasture treatments during autumn grazing. Across April, May, and June, cattle grazing E+ pastures spent more (P < 0.01) time idling, more (P < 0.01) time standing, and used more (P < 0.01) water than cattle on AR542 and E- tall fescue. This was likely in response to heat stress associated with fescue toxicosis. Daily prehensions and biting rate were each higher (P < 0.01) on AR542 and E- tall fescue than E+ tall fescue in both grazing seasons. There were no differences among pasture treatments for bite size in either spring (P > 0.20) or autumn (P > 0.10). Steers grazing E+ pastures had depressed dry matter intake compared to steers grazing AR542 and E- pastures during spring (P < 0.10) and compared to steers grazing E- pastures during autumn (P < 0.05). Daily steer water usage was depressed (P < 0.10) in E+ pastures compared to AR542 and E- pastures during late autumn possibly related to reduced biting activity. Steer average daily gain was higher on AR542 and E- tall fescue than E+ tall fescue (spring, 0.60 and 0.71 vs 0.07 kg/day,P < 0.05; autumn, 0.57 and 0.55 vs 0.35 kg/day, P < 0.05). These results indicate that steers grazing AR542 and E- tall fescue exhibited grazing behavior that supported superior growth performance over steers grazing E+ tall fescue.

Objectives/Performance Targets

While grazing behavior differences have been observed in cattle on E- and E+ tall fescue, the impacts of AR542 tall fescue on cattle grazing behavior are unknown. Developing grazing systems to optimize utilization of tall fescue pastures necessitates an understanding of livestock grazing behavior in response to various endophyte situations. The objectives of the present study were to evaluate animal performance, toxicosis, and grazing behavior in stocker cattle on non-ergot alkaloid-producing endophyte-infected (AR542), E-, and E+ tall fescue pastures in Georgia.

Accomplishments/Milestones

Research comparing steer grazing behavior on non-ergot alkaloid-producing, endophyte-free, and wild-type endophyte-infected tall fescue pastures was concluded in December 2001. Stocker cattle growth performance trials will continue through spring 2002. Research results on cattle performance grazing non-ergot alkaloid-producing tall fescue pastures were presented at the American Society of Animal Science Annual Meeting in Indianapolis, Indiana in July 2001 and at the Southern Extension and Research Activity Information Exchange Group-8 Tall Fescue Toxicosis Workshop., Chapel Hill, Tennessee in November 2001.

Impacts and Contributions/Outcomes

Reduced animal growth and reproductive performance from tall fescue toxicosis costs the United States beef industry in excess of $600 million per year. The impacts of tall fescue toxicosis are widespread in the southeastern U.S., since it is an area of major tall fescue use. Until recently, use of non-toxic endophyte-free (E-) tall fescue as a replacement for toxic endophyte-infected (E+) tall fescue was one of the few options for alleviating tall fescue toxicosis. However, plant persistence advantages from endophyte presence are sacrificed, and E- forage stands do not tolerate poor grazing management. Non-ergot alkaloid-producing endophyte-infected or "friendly" tall fescue emerged as a forage option that capitalizes on endophyte-dependent plant persistence advantages without toxicity problems in grazing livestock. This technology eliminates the tradeoff between either excellent plant persistence or animal performance in tall fescue pastures. This research project is a component of the initial research effort in the U.S. to evaluate animal performance on non-ergot alkaloid-producing endophyte-infected tall fescue. Research findings from this study indicate that non-ergot alkaloid-producing endophyte-infected tall fescue pastures provide similar cattle growth performance as E- tall fescue pastures and superior growth performance over E+ tall fescue pastures. This is consistent with research results in grazing lambs. Renovation of E+ tall fescue pastures with non-ergot alkaloid-producing endophyte-infected (MaxQ, Pennington Seed, Inc., Madison, GA) tall fescue appears to be a viable option for alleviating tall fescue toxicosis.