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Title: The effects of a modified glucomannan on the performance of stocker cattle grazing endophyte infected tall fescue

Author
item Gunter, Stacey
item BECK, P - UNIV OF AR RES. CENTER
item KREIDER, D - UNIV. OF AR. FAYETTEVILLE
item GREGORINI, P - HAMILTON, NEW ZEALAND
item STEWART, C - UNIV OF AR RES. CENTER

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2009
Publication Date: 5/10/2009
Citation: Gunter, S.A., Beck, P.A., Kreider, D.L., Gregorini, P., Stewart, C.B. 2009. The effects of a modified glucomannan on the performance of stocker cattle grazing endophyte infected tall fescue. Professional Animal Scientist. 25:300-306.

Interpretive Summary: Producers have expressed interest in non-toxic endophytic fungus (Neotyphodium coenophialum) that infects tall fescue grasses (Festuca arundinacea). However, research has shown that the time required for a positive net return on investment and the magnitude of investment poses a considerable risk. Hence, technologies that reduce fescue toxicosis for cattle grazing tall fescue infected with toxic endophyte still have short term economic advantages. In an effort to exploit the use of tall fescue infected with the toxic endophyte, a product has been developed to bind the toxins. This product is the cell wall of a yeast grown in culture; aka, modified glucomannan that is a commercially available (FEB 200; Alltech, Inc.; Nicholasville, KY). In vitro trials have shown that this modified glucomannan can bind as much as 40% of the toxin (ergovaline). This experiment evaluated a modified glucomannan as an amendment to a liquid, self-fed supplement for cattle grazing tall fescue pasture infected with the toxic endophyte. To evaluate the efficacy of a modified glucomannan to mitigate fescue toxicosis, 45 Angus cross (BW = 619 ± 15.4 lb) steer calves were divided evenly among nine 5-acre pastures of endophyte-infected tall fescue in March of 2 years and allowed to graze for 133 days. The 3 treatments were: 1) non supplemented (CTL), 2) self fed liquid supplement (QLF, Inc., Dodgeville, WI) (SUP), or 2) SUP containing a modified glucomannan (FEB-200; MGL). Target intake for SUP and MGL was between 2.0 to 3.1 lb daily; MGL delivered 10 to 20 g of the modified glucomannan daily. Over the entire 133 day, MGL steers (1.12 lb/d) gained BW more quickly than SUP steers (0.90 lb/d), but the supplemented steers did not differ from CTL steers (1.10 lb/d). On day 133, BW (lb) of the supplemented cattle (767) did not differ from CTL steers (767); however, the BW of MGL steers was 6% greater than SUP steers. The CTL steers spent a greater percentage of time grazing (51%) than the SUP steers (41%), with MGL steers intermediate (46%). Steers fed SUP and MGL spent between 3 and 7% of their time at the lick wheel tanks; this difference from CTL was similar to the difference noted in grazing times. Overall, there were no observed benefits for SUP with steers grazing infected tall fescue during the spring to mid summer. Compared to SUP, it seems there was a positive response elicited by MGL.

Technical Abstract: To evaluate the efficacy of a modified glucomannan to mitigate fescue toxicosis, 45 Angus cross (BW = 281 ± 7.0 kg) steer calves were randomly assigned to nine 2-ha pastures of endemically-infected tall fescue in March of 2 yr and allowed to graze for 133 d. The 3 treatments were: non supplemented (CTL), self fed liquid supplement (QLF, Inc., Dodgeville, WI) (SUP), or SUP containing a modified glucomannan (FEB-200; Alltech, Inc., Nicholasville, KY) (MGL). Target intake for SUP and MGL was between 0.91 to 1.40 kg daily; MGL delivered 10 to 20 g of the modified glucomannan daily. Steers were weighed every 28 d and supplement intake was monitored weekly. Behavior was monitored from 0630 to 2030 one day every 2 wk. Behavioral measurements were: consuming supplement, grazing, consuming mineral, drinking, lying, and standing. Data were analyzed by period with Proc Mixed with treatment as the fixed effect and year and pasture as random effects. Least-square means were separated using contrasts: CTL vs. the average of SUP and MGL and SUP vs. MGL. Over the entire 133 d, MGL steers (0.54 kg/d) gained BW more quickly (P = 0.03) than SUP steers (0.41 kg/d), but the supplemented steers did not differ (P = 0.94) from CTL steers (0.50 kg/d). On d 133, BW (kg) of the supplemented cattle (348) did not differ (P = 0.96) from CTL steers (348); however, the BW of MGL steers was 6% greater (P = 0.03) than SUP steers. The CTL steers spent a greater (P < 0.05) percentage of time grazing (51%) than the SUP steers (41%), with MGL steers intermediate (46%). Steers fed SUP and MGL spent between 3 and 7% of their time at the lick wheel tanks; this difference from CTL (P < 0.01) was similar to the difference noted in grazing times. Overall, there were no observed benefits for SUP with steers grazing infected tall fescue during the spring to mid summer. Compared to SUP, it seems there was a positive response elicited by MGL.