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Effects of Tall Fescue Inoculated with Novel Endophytes on Steer Growth and Development M. E. Nihsen, 1 E. L. Piper, 1 C. P. West, 2 T. Denard, 1 J. Hayward, 2 R. C. Crawford, 3 and C. F. Rosenkrans, Jr. 1 Story in Brief Fescue toxicosis is thought to be caused by ergot alkaloids produced by the endophyte Neotyphodium coenophialum. A study was designed to determine if cattle grazing tall fescue infected with novel endophytes show signs of fescue toxicosis. Steers were allotted to paddock treatments of novel endophyte (HiMag 4 and HiMag 9), endophyteinfected (E+), and endophyte-free (E-) tall fescue. Average daily gain (ADG), respiration rate, rectal temperature, and hair scores were determined during the grazing period. Blood was collected via jugular veni-puncture and used for prolactin analysis. Steers grazing novel endophyte varieties had similar weight gains as steers grazing the E- variety, and greater gains (P < 0.05) than steers on E+ paddocks. Steers grazing E+ paddocks had higher (P < 0.05) respiration rates, rectal temperatures, and hair scores, compared with steers grazing novel endophyte and E- paddocks. Prolactin concentrations were suppressed (P < 0.05) in steers grazing E+ paddocks compared to steers grazing novel endophyte and E- paddocks. These results indicate that tall fescue varieties infected with novel-endophytes, which are void of the ergot alkaloids, may alleviate the fescue toxicosis problem by enhancing animal production, while protecting the plant from environmental stressors. Introduction Tall fescue (Festuca arundinaca schreb) is a very popular forage for beef producers throughout portions of the United States because of its persistence and quality. However, a large portion of the fescue plants are infected with an endophytic fungus (Neotyphodium coenophialum) that results in stress tolerance for the plant, but toxic effects on cattle. In fact, losses in cattle production due to fescue toxicosis have been estimated at $600 million annually (Hoveland 1993). The grazing trial presented in this report is part of a long-term research project aimed at developing tall fescue varieties that have stress tolerance and are not toxic to animals. Our objective was to determine if cattle grazing tall fescue varieties containing an endophyte that does not produce ergot alkaloids show signs of fescue toxicosis. Experimental Procedures A two-year grazing study was conducted at the Arkansas Agricultural Experiment Station, Fayetteville and the Southwest Missouri Research Center, Mount Vernon. Procedures and results are presented by location due to differences in management and design. Development of varieties: The experimental grasses (‘HiMag 4’ and ‘HiMag 9’) were developed by collecting fescue plants from around the world. Those plants and their associated endophytes were screened based on their production of ergot alkaloids. The endophytes which did not produce ergot alkaloids were considered novel endophytes, and were transferred into the endophyte-free tall fescue variety ‘HiMag’, which was developed at the University of Missouri. Fayetteville paddocks: Initially, eight 4-acre paddocks were randomly selected for seeding to one of four tall fescue varieties. The four varieties were endophyte-infected Kentucky-31 (K-31; E+), endophyte-free HiMag (E-), HiMag 4, and HiMag 9. Therefore, each variety had two replicate paddocks except one of the E+ paddocks was overtaken by annual ryegrass and was removed from the study. For the second year, another replicate paddock (4 acres each) of each variety was added. Again, the same E+ paddock was overtaken by annual ryegrass and was removed from the study. Each paddock had a mesh covered shade and was randomly assigned four crossbred steers. Forage was maintained in a vegetative state by mowing and(or) grazing by additional animals. Mount Vernon paddocks: Nine 2-acre paddocks were randomly assigned to seeding with one of three tall fescue varieties. The varieties used were E+, E-, and HiMag 4. Each 1 Department of Animal Science, Fayetteville. 2 Department of Crop, Soil, and Environmental Sciences, Fayetteville. 3 Southwest Research Station, Mt. Vernon, MO. 130
AAES Research Series 488 of the nine paddocks (no shade) had three crossbred steers randomly assigned. Forage availability was maintained in the vegetative state by grazing additional animals. At both locations, steers had ad libitum access to mineral supplement and water during the grazing season which was approximately 150 days, initiated in June and concluded in October. Steers were weighed and blood collected at 28 day intervals throughout the grazing season. Blood was used to prepare serum which was analyzed for prolactin concentrations. In addition, steer body temperature and respiration rates were determined on days when daytime temperatures exceeded 90°F. At Mount Vernon, steer hair coat was scored based on the following system: 1 = slick, short-haired animal (less than 1/2” in length); 2 = has some medium length hair (1/2” to 1”); 3 = medium length hair coat covers most of the body; 4 = medium hair plus some rough, long, dead hair; 5 = hair coat consists primarily of rough, long, and dead hair. Within each location data from both years were combined and least squares means ± standard error are presented. Analysis was conducted using a general linear model (SAS Institute, Inc. Cary, NC). In the model, forage variety and year were treated as class variables. Implications Both novel endophtye varieties (HiMag 4 and HiMag 9) of tall fescue survived the hot and dry summers during this grazing trial. In addition, those varieties produced animal gains and physiological responses similar to the endophytefree control steers. These forages could be very useful for profitable production of livestock. Literature Cited Bouton, J., et al. 2000. Alleviating tall fescue toxicosis problems with non-toxic endophytes. Proc. Tall Fescue Toxicosis Workshop. October 16-17. Chapell Hill, TN p 9-15. Hoveland, C.S. 1993. Ecosystems. Environ. 44:3. Results and Discussion Fayetteville results: Values shown in Table 1 represent the mean for the combined year effect for each item. Steers grazing E+ had a lower (P < 0.05) ADG (0.93 lb/d) than steers grazing HiMag 4, HiMag 9, and E- (1.43, 1.36, and 1.61 lb/d, respectively). Mean respiration rates were higher (P < 0.05) in cattle grazing E+ (91.3 breaths/min) compared to those steers grazing HiMag 4, HiMag 9, and E- (59.8, 62.3, and 63.3, respectively). Mean rectal temperatures for steers grazing E+ pastures (105.3°F) were higher (P < 0.05) than in cattle grazing HiMag 4, HiMag 9, and E- pastures (103.6, 103.8, and 103.5°F, respectively). Mean prolactin concentrations were higher (P < 0.05) in cattle grazing E+ pastures (42.48 ng/ml), compared to the cattle grazing E-, HiMag 4, and HiMag 9 (152.46, 146.82, and 165.32 ng/ml, respectively). Mount Vernon results: Table 2 presents the combined year means for each item. Average daily gain (ADG) was decreased (P < 0.05) in steers grazing E+ (0.55 lb/d), compared to that of steers grazing E- (1.21 lb/d) and HiMag 4 (1.21 lb/d). Mean hair score for cattle grazing E+ (3.96) was higher (P < 0.05) than those grazing HiMag 4 (2.46) and E- (2.13) pastures. Cattle grazing E+ pastures had higher (P < 0.05) respiration rates (122.8 breaths/minute), compared to those grazing E- and HiMag 4, which were 93.2 and 103.6, respectively. Mean rectal temperature for steers grazing E+ was 106.3°F. This was higher (P < 0.05) than for steers grazing E- (104.3°F) and HiMag 4 (104.9°F), which were different from each other (P < 0.05). Mean prolactin concentrations were lower (P < 0.05) in cattle grazing E+ pastures (16.46 ng/ml), compared to cattle grazing E- and HiMag 4 (108.27 and 154.63 ng/ml, respectively). The results of this study confirm other studies (Bouton et al., 2000) that indicate that tall fescue can be inoculated with non-toxic endophytic fungus. 131
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