CASE STUDY: Use of dried distillers grains for calves grazing tall fescue

Two trials were conducted to define optimal levels of dried distillers grains with solubles (DDGS) for growing calves grazing either Kentucky 31 or Phyter tall fescue (TF; Lolium arundinaceum Schreb.). In Exp. 1, 48 Charolais crossbred heifers (average initial BW = 258 ± 18 kg) were randomly assigned to one of four 0.8-ha pastures of Kentucky 31 TF (9.1% CP, 60.6% NDF, 35.4% DM) with low or very low ergovaline concentrations (88 vs. 11 μg/kg, respectively) with average forage availability of 5,340 kg of DM/ha. The DDGS was supplemented at 0, 0.45, 0.91, or 1.36 kg of DDGS/d per animal. The control consisted of 0.11 kg/d of soy hulls. Supplementation of DDGS at 0.91 and 1.31 kg tended to increase ADG greater (P < 0.08) than the soy hulls control. Also, DMI of the forage as a percentage of BW tended to be greater (P < 0.10) for very low ergovaline versus low ergovaline TF. In Exp. 2, a 90-d study was conducted using 30 Angus × Simmental crossbred calves (15 steers and 15 heifers; average initial BW = 240.5 ± 1.2 kg) to evaluate level of DDGS for calves grazing endophyte-free Phyter TF with average forage availability of 2,230 kg of DM/ha. The 4 treatments were 0 (control), 0.68, 1.32, and 1.91 kg of DDGS/d per animal. Overall, ADG responded in a linear (P < 0.0001) and quadratic (P < 0.06) fashion with increasing level of DDGS. Level of supplemental DDGS resulted in a linear increase (P < 0.003) in change in back-fat during the grazing study. In conclusion, ADG of calves grazing Phyter TF responded in a linear and quadratic fashion with increasing level of DDGS up to 1.91 kg/d; the lack of increase in ADG in calves grazing Kentucky 31 TF above 0.91 kg of DDGS/d may be attributed to lower daily gains not requiring additional supplemental escape protein.