Todd Richard W, Cole N Andy, Clark R Nolan
USDA-ARS Conservation and Production Research Laboratory, P.O. Drawer 10, Bushland, TX 79012, USA.
J Environ Qual. 2006 Feb 2;35(2):404-11. doi: 10.2134/jeq2005.0045. Print 2006 Mar-Apr.
Concentrated animal feeding operations are major sources of ammonia to the atmosphere. Control methods to reduce emissions include acidifying amendments, urease inhibitors, and absorbents. For beef cattle, decreasing crude protein (CP) in diets may be the most practical and cost-effective method to reduce ammonia emissions. Our objective was to quantify the effect of reducing CP in beef cattle diet on ammonia emissions. Two groups of steers were fed diets with either 11.5 or 13.0% CP and all urine and feces were collected. Manures from the two diet treatments were applied in a replicated laboratory chamber experiment, and ammonia emission was quantified using acid gas washing. In four seasonal field trials, manures from the two diet treatments were applied to two 10-m-diameter, circular, artificial feedyard surfaces, and ammonia emission was quantified using the integrated horizontal flux method. Manure from steers fed 11.5% CP diet had less urine, less urinary N, and a lesser fraction of total N in urine, compared with the 13.0% CP diet. Decreasing crude protein in beef cattle diets from 13 to 11.5% significantly decreased ammonia emission by 44% (p < 0.01) in the closed chamber laboratory experiment, and decreased mean daily ammonia flux by 30% (p = 0.10), 52% (p = 0.08), and 29% (p < 0.01) in summer, autumn, and spring field trials, respectively. No difference was observed in winter. On an annual basis, decreasing crude protein reduced daily ammonia flux by 28%. Reducing crude protein in beef cattle diets may provide the most practical and cost-effective way to reduce ammonia emissions from feedyards.
集中式动物饲养场是大气中氨的主要来源。减少排放的控制方法包括酸化改良剂、脲酶抑制剂和吸附剂。对于肉牛来说，降低日粮中的粗蛋白（CP）可能是减少氨排放最实用且最具成本效益的方法。我们的目标是量化降低肉牛日粮中CP对氨排放的影响。两组阉牛分别饲喂CP含量为11.5%或13.0%的日粮，并收集所有尿液和粪便。将两种日粮处理的粪便用于重复的实验室箱试验，通过酸性气体洗涤对氨排放进行量化。在四项季节性田间试验中，将两种日粮处理的粪便施用于两个直径10米的圆形人工饲养场表面，采用综合水平通量法对氨排放进行量化。与CP含量为13.0%的日粮相比，饲喂CP含量为11.5%日粮的阉牛粪便尿液更少、尿氮更少且尿液中总氮的比例更低。在封闭箱实验室试验中，将肉牛日粮中的粗蛋白从13%降至11.5%可使氨排放显著降低44%（p<0.01），在夏季、秋季和春季田间试验中，平均每日氨通量分别降低30%（p = 0.10）、52%（p = 0.08）和29%（p<0.01）。冬季未观察到差异。按年度计算，降低粗蛋白可使每日氨通量降低28%。降低肉牛日粮中的粗蛋白可能是减少饲养场氨排放最实用且最具成本效益的方法。
