Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2008
Publication Date: 10/1/2008
Citation: Aiken, G.E., Mcclanahan, L., Schrick, F.N. 2008. Steer responses to feeding soybean hulls on toxic tall fescue pasture. Professional Animal Scientist. 24:399-403. Interpretive Summary: Tall fescue is a cool-season perennial grass that is grown on approximately 15 million ha east of the Great Plains between the temperate Northeast and subtropical Southeast, a region commonly referred to as the “fescue belt”. An endophyte (Neotyphodium coencaphialum) infects tall fescue plants and produces ergot alkaloid toxins that induce fescue toxicosis. Symptoms of the malady include retention of rough hair coat, elevated body temperature, labored respiration, and poor bodyweight gain. Consequently, cattle grazed on toxic tall fescue are vulnerable to severe heat stress. Poor bodyweight gain and market value of cattle exhibiting symptoms of toxicosis have limited the wide spread use of tall fescue for commercial stocker production. Feeding low cost feeds, such as soybean hulls, could dilute dietary ergot alkaloid concentrations and enhance bodyweight gains. A grazing experiment with yearling steers was conducted with toxic fescue to evaluate the effects of feeding soybean hulls on average daily gain and determine if there was effective dilution of ergot alkaloids to alleviate or reduce the severity of fescue toxicosis. Although there was a 175% increase in average daily gain with feeding soybean hulls, rectal temperatures and the percentages of steers with rough hair coats were similar between with and without soybean hull feeding treatments. Feeding pelleted SBH can increase steer weight gain, but will not alleviate or reduce severity of toxicosis. Therefore, feeding soybean hulls to calves grazing toxic tall fescue can effectively increase average daily gain, but vulnerability of the cattle to heat stress is not diminished.
Technical Abstract: A grazing experiment was conducted in 2004 and 2005 to evaluate effects of feeding pelleted soybean hulls (SBH) on weight gain, hair coat rating, rectal temperature, and serum prolactin of steers grazed on toxic tall fescue [Schedonorus arundinaceus (Schreb.)]. Forty steers [initial BW in 2004 = 257 ± 22 (SD) kg, initial BW in 2005 = 348 ± 27 kg] were assigned to five, 3-ha pastures of toxic tall fescue that were randomly assigned either with (n = 2) or without (n = 3) pelleted SBH (2.3 kg/steer/d, as fed) feeding. Grazing was initiated in early June and was terminated at 112 days of grazing in 2004 and at 102 days of grazing in 2005. Feeding pelleted SBH increased (P < 0.05) average daily gain (ADG). Although the response to SBH was not different (P > 0.10) between the two yr, ADG was less in 2005 when there was drier weather. Cost of additional ADG from feeding pelleted SBH was below (P < 0.05) a breakeven of $170/ton pelleted SBH for a cattle price of $2.43/kg BW, and was below a breakeven of $120/ton pelleted SBH for a cattle price of $1.76/kg BW. Percentages of steers with rough hair coat averaged 93% and were not different (P > 0.10) between treatments at the conclusion of grazing in both years. Rectal temperatures were not different (P > 0.10) between years and treatments. Prolactin concentrations were not different (P > 0.10) between treatments in 2005, but tended to be lower in SBH steers in 2005. Results indicated that feeding pelleted SBH can cost effectively increase steer weight gain, but will not alleviate or reduce severity of toxicosis.