An experiment was conducted to evaluate the effects of adding fiber sources to reduced crude protein, amino acid-supplemented diets on nitrogen excretion and methane, carbon dioxide and ammonia emissions from the manure. To produce the manure, twenty four barrows were allotted randomly to two dietary treatments. Dietary treatments were: 1) fortified corn-soybean meal control (Control), and 2) as Diet 1 with crude protein lowered by four percentage units and supplemented with lysine, threonine, methionine, and tryptophan plus 10% soybean hull addition (LPAA + fiber). Due to the decreased nitrogen concentration of the LPAA + fiber diet, total nitrogen intake was reduced. Fecal dry matter excretion tended to be greater for pigs fed LPAA + fiber diet, most likely due to the higher fiber content of the diet. Fecal nitrogen excretion (g/d) for pigs fed LPAA + fiber diet was increased slightly. Urinary nitrogen excretion was reduced dramatically by feeding the LPAA + fiber diet. As a result, total nitrogen excretion was reduced by approximately 35% for pigs consuming the LPAA + fiber diet. Furthermore, the proportion of nitrogen excreted in the feces was greater for pigs fed the LPAA + fiber diet.
Following completion of the excretion work, manure (feces and urine) were collected and loaded into a pilot-scale facility capable of recreating the physical and operational environment of lagoons was set-up to model the physical characteristics of the OSU Swine Research Center lagoon. Methane, carbon dioxide, and ammonia emitting from the pilot-scale facility were determined every 30 minutes for methane and carbon dioxide or every minute for ammonia. Manure was fed into the pilot-facility on an equivalent nitrogen basis. Ammonia emissions were reduced by 10% for manure produced by pigs fed the LPAA + fiber diet when loading rate was based on nitrogen. However, if loading rate was based on carbon or solids basis, ammonia
emissions would have been reduced by approximately 50%. Carbon dioxide emissions were not affected by diet, but methane and total carbon emissions were increased for manure produced from pigs fed LPAA + fiber. These results suggest that diet can markedly affect nitrogen excretion and ammonia emissions. However, at the same time, diet composition may increase the generation of other potentially important gases such as methane.