Effects of pelleting diets containing cereal ergot alkaloids on nutrient digestibility, growth performance and carcass traits of lambs

Abstract

The effects of pelleting feed containing cereal ergot alkaloids was evaluated in performance and nutrient digestibility trials using growing lambs. Defined concentrations of ergot alkaloids [Control (C), no added alkaloids but background concentrations of ∼3 ppb; Low (L),∼169 ppb; High (H),∼433ppb] were achieved by substituting barley grain for ergot-contaminated screenings containing (fed basis) approximately 538g/kg barley grain, 300g/kg alfalfa and 160g/kg canola meal. Diets were fed either as a mash or as a completely pelleted feed. Total alkaloid concentrations did not differ between corresponding mash and pelleted diets, but ergotamine and ergosine were 2–3 times greater in mash feeds, while ergocornine, ergocristine and ergometrine were 2–3 times greater in pelleted diets. The total collection digestibility experiment used 12 ram lambs in a crossover design with 3 experimental periods. Alkaloid dose did not affect digestibility of DM, OM, or CP, but NDF and ADF digestibilities were linearly reduced (P<0.05) with increasing alkaloid dose. Alkaloid concentrations in feces depended upon the specific type of alkaloid measured. In preliminary results, ergocristine and ergotamine were the only alkaloids in higher concentrations (P<0.001) in feces from lambs fed H as compared to C diets. In the growth experiment, ram and ewe lambs (live weight 24.6±1.08kg) were randomly assigned to diets, weighed weekly and fed to a slaughter weight of ≥45kg. Dietary treatments did not affect carcass characteristics, although serum prolactin concentration was linearly reduced (P<0.001) by increasing alkaloid dosage and was lower (P=0.01) in lambs fed mash as compared to pelleted diets. Although pelleted diets had total alkaloid concentrations that were similar to mash diets, lambs fed pelleted diets had 60g/d greater (P<0.001) ADG than those fed mash diets. For H diets, lambs had lower ADG and feed conversion (P=0.03) than those fed C or L, Based on the results of this study, pelleting diets reduced negative impacts of ergot alkaloids possibly by changing alkaloid profiles.