Our objective was to evaluate how a particular zeolite-based flow agent affected ergot alkaloid digestion and physiological markers associated with fescue toxicosis. Twenty-four steers (226 ± 27.6 kg) were used to test effects of enhanced zeolite-based flow agent (KALLSIL, Kemin Industries, Des Moines, IA) on ergot-like alkaloid digestion. Treatments were control (E+) or enhanced zeolite inclusion (E+Z; 2 g/kg, DM basis). Steers were limit-fed diets (1.8% of BW, DM basis) containing 465 μg of ergovaline/kg of DM. Rectal temperature and respiration rate were recorded daily at 0700 and 1200 h from steers in a room kept at 18.5°C ± 0.33°C, 32.6% ± 2.19% relative humidity. Blood was collected on d 1, 7, 14, and 21 to measure prolactin. On d 21 prolactin stores were measured following infusion of thyrotropin- releasing hormone (TRH; 1 μg/kg BW). Feces and urine were collected every 8 h from d 17 to 20, with 2-h advancement daily for digestibility, N balance, and recovery of ergot-like alkaloids. Digestion and N balance were not affected by treatment. Zeolite did not affect fecal recovery of ergovaline. Serum prolactin declined over time. Serum prolactin was greater in steers fed E+Z. Following TRH infusion, prolactin was numerically greater for E+Z. Rectal temperatures and respiration rates were not affected by E+Z. Under the conditions of this experiment, addition of this particular zeolite-based feed additive had minimal impact on ergot alkaloid recovery and physiological markers associated with fescue toxicosis.

The objective was to evaluate the effect of days on feed (DOF) on performance and carcass characteristics of crossbred beef × dairy heifers. Beef × dairy heifers (n = 3,765; initial BW = 508 ± 8.55 kg) were blocked by arrival date and lot (n = 6 blocks at feedyard 1 and n = 7 blocks at feedyard 2) and randomly assigned to 1 of 4 DOF treatments of 323, 344, 362, or 385 when administered a Revalor-200 (200 mg of trenbolone acetate [TBA] and 20 mg of estradiol [E2]) on d 265. Dry matter intake was not affected by DOF, whereas final BW increased linearly from 593 to 655 kg. As DOF increased, ADG and gain: feed decreased quadratically. Hot carcass weight, LM area, calculated YG, and marbling score increased linearly as DOF increased. Across the 63-d serial slaughter period, hot carcass weight increased 0.67 kg/d. Dressing percentage and backfat thickness increased in a quadratic manner across DOF. Further, QG and YG distribution increased linearly as DOF increased. Liver abscess prevalence or severity did not increase with DOF. Implications and Applications Results of this study indicate that extending DOF by 63 d led to increased BW, hot carcass weight, LM area, marbling, YG, and QG but poorer ADG and feed conversion efficiency for beef × dairy crossbred heifers.