Supplementation of Energy and Glucomannan to Alleviate Tall Fescue Toxicosis

An 84 d randomized block design using 96 beef calves (238.8 + 20.1 kg) in each of two years was used to assess the efficacy of energy supplementation and glucomannan (MTB) to alleviate tall fescue toxicosis. Groups of four calves were randomly assigned to 24 endophyte-infected tall fescue pastures (1.23 + 0.06 ha). Pastures of calves were randomly assigned to treatments: unsupplemented (CON), supplemented with soybean hulls (SH) at 0.33% BW (DM basis; LO), supplemented with SH at 0.66% BW (DM basis; HI), LO plus 20 g·hd^-1·d^-1 MTB-100® (LO-MTB), HI plus 20 g·hd^-1·d^-1 MTB-100® (HI-MTB). Calves were weighed and serum collected every 21 days. Fecal grab samples were taken from d 55 to d 59 and analyzed for dry matter chromium and ergot alkaloid concentrations. Tympanic temperatures were taken from one calf for 3 days each week from d 59 to d 84. Data were analyzed using the MIXED procedure in SAS with contrasts of effects of MTB, level of SH supplementation (LEVEL), MTB x LEVEL interaction, and CON vs. supplemented (SUPP). Treatments differed in ADG (P < 0.01) with LEVEL affecting weight gains (P < 0.01). Supplemented calves had increased weight gains compared to CON (P < 0.01). Supplementation increased gain per hectare (P < 0.01) and was influenced by LEVEL (P < 0.01). Control calves excreted higher concentrations of ergot alkaloids than SUPP (P < 0.01). Forage and total DMI increased as a result of supplementation (P < 0.01). Prolactin levels differed among the treatments on d 63 and 84 (P < 0.01) with increases attributed to LEVEL (P < 0.05). There were differences between CON and SUPP (P < 0.01) on d 63 and 84, where SUPP increased prolactin concentrations to twice that of CON. Tympanic temperatures were similar among treatments (P > 0.05); daily maximum temperatures and diurnal range differed among the treatments (P < 0.01). SUPP animals had lower maximum temperatures and decreased diurnal range compared to CON (P < 0.01). These findings indicate that SH supplementation can lessen the severity of fescue toxicosis; however, glucomannan fed at the current level only affected tympanic temperature.