Methane decreasing properties, nutrient digestibility, and energy value of brewer's or distiller's grains examined in vivo and/or in vitro

Abstract

An in vitro and an in vivo experiment were conducted to further evaluate methane losses and nutrient availability of brewer's grains (BG) and distiller's grains (DG) as components of ruminant diets. The objectives of the in vitro experiment were to determine the component(s) and concentration of BG or DG which cause methane production to decrease. Five in vitro trials included: increasing concentrations of BG or DG from 0 to 100% replacing alfalfa, increasing concentrations of com oil from 0 to 10% replacing com gluten feed (CGF), BG and DG with and without lipid, com gluten feed with 3% yeast or 14% beer, and 80% BG or 80% DG with 20% grass hay. Methane (percent of non-lipid GE) production was linearly decreased (P < 0.01) when BG was increased from incubating 20 to 100% of the substrate. Methane production was decreased (P < 0.01) for the DG trial only when the substrate contained 100% DG. Adding com oil to CGF linearly (P < 0.01) decreased methane production over concentrations ranging from 0 to 10%. Incubating BG or DG after removing the lipid from these by-products did not increase methane production. Incubating beer with CGF increased (P < 0.01) methane production 50%, whereas yeast had no effect. A mixture of 80% BG with grass hay responded similarly to the alfalfa mixture by decreasing methane (percent of non-lipid GE) production below that from forage alone, whereas no change in methane production was measured when incubating 80% DG with grass hay. The in vivo experiment evaluated methane decreasing effects, nutrient digestibility, and energy value of DG. Six steers were fed 0, 20, or 40% DG as part of a 60% concentrate diet in a 3 x 3 Latin square. Methane production was not significantly decreased by including DG as part of the diet. The only nutrients digested differently with DG addition were NDF and DE. Adding 20 and 40% DG to the diet increased (P < 0.05) NDF digestibility 17 and 30%, respectively when compared to the control at 46.7%. Digestible energy was 6.8% greater (P < 0.05) for the diet containing 40% DG, than the 0 and 20% DG diets and ME (Mcal/kg DM) content of the DG diets was 7% greater (P < 0.05) for each 20 percentage unit addition of DG to the diet. The higher ME content of the DG diets combined with numerically greater partial efficiency of ME use, suggests the NEm and NEg content of the DG diets were found to be at least 10% greater (P < 0.05) than the 1.95 and 1.56 Mcal/kg found for the control. Calculated by difference and extrapolated to NRC (1996) equivalents suggest the NEg content of the DG is approximately 1.83 Mcal/kg DM, about 20% above the current estimate.