This study was designed to evaluate the effects of feeding increasing dietary concentrations of ergot alkaloids from cereal grains (EA; 0, 0.75, 1.5, 3.0 mg/kg of dietary DM) to feedlot cattle over backgrounding (BG) and finishing (FS) phases on health, welfare, and growth performance. Two hundred and forty commercial steers (280 ± 32 kg BW) were stratified by weight and randomly allocated to 16 pens (15 steers/pen), 4 of which were equipped with the GrowSafe system (1 pen/treatment) to measure individual feed intake. Each pen was randomly assigned to a treatment (n = 4/treatment). Treatments included 1) control (CTRL), no added EA; 2) CTRL + 0.75 mg/kg EA (EA075); 3) CTRL + 1.5 mg/kg EA (EA150); and 4) CTRL + 3.0 mg/kg EA (EA300). Steers were fed barley-based BG diets containing 40% concentrate: 60% silage (DM basis) for 84 d. Steers were then transitioned over 28 d to an FS diet (90% concentrate: 10% silage DM basis) and fed for 119 d before slaughter. The diet fed to EA300 steers was replaced with the CTRL diet after 190 d on feed (DOF), due to EA-induced hyperthermia starting at 165 DOF. In the BG phase, average meal length (P = 0.01) and size (P = 0.02), daily feeding duration (P = 0.03), final body weight (BW; P = 0.03), and total BW gain (P = 0.02) linearly decreased with increasing EA levels, while gain to feed (G:F) responded quadratically (P = 0.04), with EA150 having the poorest value. Increasing concentrations of EA in the diet linearly increased rectal temperature (P < 0.01) throughout the trial. Over the full FS phase, a quadratic response was observed for ADG (P = 0.05), final BW (P = 0.05), total BW gain (P = 0.02), and carcass weight (P = 0.05) with steers fed EA150 having the lowest performance, as EA300 steers were transferred to CTRL diet after 190 DOF. Dressing percentage (P = 0.02) also responded quadratically, with the lowest values observed for EA300. Thus, EA reduced ADG during BG and FS phases, although more prominently in FS, likely due to increased ambient temperatures and high-energy diet in FS triggering hyperthermia. When EA300 steers were transferred to the CTRL diet, compensatory gain promoted higher hot carcass weight (HCW) when compared with steers fed EA150. In conclusion, feeding feedlot steers diets with > 0.75 mg/kg EA caused reductions in performance and welfare concerns, although this breakpoint may be affected by duration of feeding, environmental temperatures, and EA profiles in the feed.
Keywords: cattle; ergot; feedlot; performance.
Ergot alkaloids (EA) are produced by a parasitic fungus (Claviceps purpurea) during the cereal grain growth cycle. Feeding cereal grain containing EA to beef cattle can cause constriction of blood vessels, hyperthermia, gangrene of extremities (ears, hoof, and tail), reduced feed intake and growth, and even death. Feed cleaning and processing technologies have been developed to remove EA from the human food chain, thus diverting contaminated feed for livestock use. We performed a beef cattle feedlot experiment to evaluate the impact of increasing levels of EA (0, 0.75, 1.50, 3.00 mg/kg of diet DM) on performance, health, and welfare. Steers fed 3.0 mg/kg of EA were transferred to the control diet (without EA) in the last half of finishing due to toxicity (hyperthermia). As EA levels increased, growth rate throughout the backgrounding and finishing phases decreased, while rectal temperatures increased and altered feeding behaviors occurred. Steers removed from 3 mg/kg EA diet exhibited compensatory gain, but their respiratory rate remained elevated 50 d after EA were last consumed.
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