Animal Science Department


Date of this Version



In Proceedings of the American Society of Animal Science Midwest Section, March 19-21, 2012. Des Moines, IA. J. Anim. Sci. 90 (suppl 2): p 81


Two treatments (cattle diet) were used in anaerobic digestion of finishing cattle manure. Diet 1 contained 82.5% dry rolled corn (DRC) (CONT) and diet 2 contained 40% wet distillers grains plus solubles (DM basis) replacing DRC (WDGS). Cattle were housed in stanchions for 3 d with complete manure collection in a cement pit. Manure (feces and urine) was sampled and analyzed for minerals, DM and OM. Manure collected was weighed into individual allotments based on DM and frozen. Continuously stirred anaerobic digesters (n = 7, 1 L capacity) were inoculated and maintained for 5 mo before the trial to ensure steady-state. Temperature was maintained at 37°C and pH was maintained between 7.0 and 8.0 via addition of sodium hydroxide. Manure samples collected were thawed and hot water was added to bring total slurry volume to 50 mL. Each day, 50 mL of effluent was removed from each digester and replaced with 50 mL of fresh manure/water slurry (9% DM). Two collection periods were used with 35 d adaptation and 5 d collection, as a switchback. The DM and OM of effluent was measured and DMD and OMD were calculated. Concentration of methane was measured under constant flow of N2 gas. Organic matter in manure averaged 88.3% for CONT and 88.7% for WDGS. Manure DM was 18.3% for CONT and 17.8% for WDGS. CONT and WDGS manure did not differ in total N concentration, 3.95 and 3.79% of DM, respectively (P = 0.54). Sulfur, P2O5, Mg, Zn and Fe were greater in WDGS manure compared with CONT (P < 0.01). Minerals were concentrated approximately 2-fold in effluent compared with manure in both WDGS and CONT. Dry matter degradation was 42.7% for CONT and 44.9% for WDGS (P = 0.05). Organic matter degradation was 51.0% for CONT and 52.9% for WDGS (P = 0.10). Methane production was 0.551 L/d for CONT and 0.634 L/d for WDGS (P = 0.10), equal to 0.116 and 0.137 L/g VS fed (P = 0.05). Feeding distillers grains to cattle does not have large impacts on methane production or degradation of manure in anaerobic digesters compared with a corn based diet.