Varel V H, Nienaber J A, Freetly H C
USDA-ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 1999 May;77(5):1162-8. doi: 10.2527/1999.7751162x.
Feedlot cattle normally retain less than 20% of their dietary nitrogen intake. Sixty to 80% of the nitrogen excreted is normally lost through volatilization of ammonia, which is primarily generated from urea. This loss of ammonia nitrogen pollutes the environment and creates an unfavorable ratio of nitrogen to phosphorous (N:P) in the waste for crop growth. Two urease inhibitors, cyclohexylphosphoric triamide (CHPT) and N-(n-butyl) thiophosphoric triamide (NBPT) were evaluated for their ability to reduce the rate of urea hydrolysis in beef cattle feedlot pens. Initially, a total of six pens were used, two pens per treatment, with approximately 70 cattle per pen, and a single topical application of CHPT or NBPT at 20 mg/kg of manure. Essentially no urea was found in untreated pens. However, with CHPT treatment, 2 g of urea/kg of dry manure accumulated by d 4, and all gradually disappeared by d 11; NBPT conserved 3 and 3.5 g of urea/kg by d 4 and 9, respectively, and it had disappeared by d 14 (treatment [trt] x day, P = .003). A second study involved application of NBPT weekly for 6 wk. This caused urea to accumulate to a peak concentration of 17 g/kg of manure by d 30 (trt x day2, P = .001). Once the treatment was stopped the urea concentration began to decrease. When the NBPT was applied weekly, the concentration of ammonia in the waste was less for the treated pens (trt x day, P = .01), the total nitrogen was greater (trt x day, P = .04), pH tended to be lower (trt x day, P = .10), and the total volatile acids were not different (trt x day, P = .51) from untreated pens. We concluded that urease inhibitors could be used to control ammonia emissions from animal wastes, prevent environmental damage, and produce a more balanced (N:P) fertilizer from manure.
饲养场的牛通常仅保留其摄入日粮中不到20%的氮。排泄出的氮中，60%至80%通常通过氨的挥发而损失，氨主要由尿素产生。氨氮的这种损失污染了环境，并导致粪便中氮磷比（N:P）不利于作物生长。评估了两种脲酶抑制剂，环己基磷酸三酰胺（CHPT）和N-（正丁基）硫代磷酸三酰胺（NBPT）降低肉牛饲养场围栏中尿素水解速率的能力。最初，总共使用了六个围栏，每个处理两个围栏，每个围栏约70头牛，并以20 mg/kg粪便的剂量对CHPT或NBPT进行单次局部施用。在未处理的围栏中基本未发现尿素。然而，用CHPT处理后，到第4天每千克干粪便积累了2 g尿素，到第11天所有尿素逐渐消失；NBPT在第4天和第9天分别保留了每千克3 g和3.5 g尿素，到第14天尿素消失（处理[trt]×天数，P = 0.003）。第二项研究涉及每周施用NBPT，持续6周。这导致到第30天尿素积累到每千克粪便17 g的峰值浓度（trt×天数²，P = 0.001）。一旦停止处理，尿素浓度开始下降。当每周施用NBPT时，处理过的围栏中粪便中的氨浓度较低（trt×天数，P = 0.01），总氮含量较高（trt×天数，P = 0.04），pH值趋于较低（trt×天数，P = 0.10），总挥发性酸与未处理的围栏没有差异（trt×天数，P = 0.51）。我们得出结论，脲酶抑制剂可用于控制动物粪便中的氨排放，防止环境破坏，并从粪便中生产出更平衡的（N:P）肥料。
