Effects of Feed Protein Level and Feed Additives on Greenhouse Gas and Odour Emissions from Stored Swine Manure

The effect of dietary manipulation on odour and GHG emissions from stored swine manure was evaluated at the production scale. Two feed protein (17 and 14% CP) and four nonstarch polysaccharide (NSP) treatments (control, added beet pulp, added cornstarch, added xylanase) yielded eight diets. Each diet was fed to a separate group of pigs for six weeks, and a 150-L cumulative manure sample was collected from each group in a 200-L vessel and analyzed for nutrient content. The vessel headspace was ventilated at 2 L/min and the manure was stirred continuously at 5 rpm to promote the even release of gases. Inlet and exhaust air from each vessel headspace were analyzed weekly for CO2, CH4 and N2O for eight weeks, and odour concentration was evaluated once every two weeks using dynamic olfactometry. The trial was replicated three times. The dietary treatments had no effect (p<0.05) on the performance of the pigs. Manure sulfur concentration and pH decreased (p<0.05) with dietary protein. NSP treatments had numerous effects on manure chemistry. The mean odour concentration of the headspace ventilation air increased from 158 to 2276 OU/m3 (inlet to outlet). Lower dietary protein was associated with 8.4% less odour than high protein (not significant at p<0.05). Mean headspace concentrations of CH4 and CO2 increased by 331 and 3985 ppm (42 and 1400 g•d-1•m-3 manure), respectively (inlet to outlet). There was no significant N2O emission. The effects of the dietary treatments on CH4 and CO2 emissions from the manure were inconclusive.