Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/25/2005
Publication Date: 7/6/2006
Citation: Panetta, D.M., Powers, W.J., Xin, H., Kerr, B.J., Stalder, K.J. 2006. Nitrogen excretion and ammonia emissions from pigs fed reduced crude protein diets or yucca extract. Journal of Environmental Quality. 35:1297-1308. Interpretive Summary: Manure ammonium, produced when urinary urea is hydrolyzed by fecal microbial ureases, is subsequently converted to ammonia and volatilized during storage. The compounded impacts of decreased nitrogen value of manure, risks of ammonia emissions on animal health, and the effects of ammonia emission on environmental quality have fueled interest in quantifying and reducing the volatilization of ammonia from animal manures. Reduction of dietary crude protein content accompanied by supplementation of limiting amino acids decreases the intake of excess amino acids while meeting nutrient needs. Using mass balance methods or by directly measuring emissions from swine manure stored in vitro, dietary strategies have been shown to reduce ammonia emissions by 28 to 79%. Summarizing nitrogen balance studies suggests that nitrogen excretion from swine decreases an average of 8.4% for every one-percentage unit decrease in dietary protein, with much of the reduction in the form of urinary urea-nitrogen. Dietary addition of an extract from yucca schidigera is also believed to reduce emissions through the binding or conversion of ammonia to less volatile forms. However, significant effects of yucca on urinary ammonium concentrations have not been established. These experiments were conducted to directly quantify the effects of dietary strategies on ammonia emissions, and on ammonium and total nitrogen excretion from growing-finishing pigs. Data from these experiments reported that total fecal nitrogen decreased with the reduction in dietary protein, but urinary ammonium concentrations were increased in pigs fed the lowest crude protein diet compared to pigs fed the standard or medium crude protein diets. Ammonia emission rates were reduced when pigs were fed the lower crude protein diets. The dietary addition of yucca schidigera extract had no effect on total fecal nitrogen, urinary ammonium concentration, or on ammonia emission. Research results described in this report provides nutritionists at universities, feed companies, allied industries, and swine production facilities data showing that feeding reduced crude protein diets can dramatically reduce ammonia emission rates while yucca extract addition will likely have little to no impact on ammonia emission.
Technical Abstract: Two trials were conducted with growing-finishing pigs (initial BW 47 ± 2 and 41 ± 3 kg for trials 1 and 2, respectively) to evaluate the effects of reduced crude protein (CP), amino acid-supplemented and yucca extract-supplemented diets on ammonia emissions. In trial 1, nine pigs, allocated to three environmentally controlled chambers were provided ad libitum access to a corn-soybean meal control diet (C, 17.4% CP), a lysine-supplemented, reduced CP diet (L, 17.0% CP), or a 14.5% CP diet supplemented with lysine, methionine, threonine, and tryptophan (LMTT), assigned weekly for 4 wk. In trial 2, nine pigs were fed diet L as the basal diet, but supplemented with 0, 62.5, or 125 mg of yucca extract per kg diet. Each feeding period consisted of a 4-d dietary adjustment followed by 72 h of continuous ammonia measurement from chamber exhaust. Pigs and excess feed were weighed, urine and fecal samples collected, and manure pits cleaned after each period. In trial 1, feeding the LMTT diet reduced (P < 0.10) average daily gain (ADG) and feed efficiency (G:F) compared to diet L. Total Kjeldahl nitrogen concentration in the feces decreased with a reduction in dietary CP, but urinary ammonium concentration increased when pigs were fed diet LMTT (0.20%, wet basis) compared to when they were fed diet C (0.11%) or L (0.10%). Ammonia emission rates were reduced when pigs were fed lower CP diets (2.46, 2.16, and 1.05 mg/min) for diets C, L, and LMTT, respectively). In trial 2, yucca had no effect on ADFI, ADG, or G:F, and total nitrogen and ammonium concentrations of the manure and ammonia emission rates did not differ with dietary yucca content. Reducing dietary CP and supplementing with amino acids can be very effective in reducing ammonia emissions from swine facilities, while feeding yucca extract resulted in no consistent effects on growing-finishing pigs or chamber ammonia emissions.