In vitro short-term study of ammonium-nitrogen production from cattle urine: influence of ampicillin, hydroquinone and animal litter materials

The production of NH4+-N following in vitro incubation of cattle urine was monitored for 24 h in the presence of ampicillin sodium salt (0, 32, 64, 12 8 mg/l), hydroquinone (0, 16.7, 33.4, 66.8 mg/l), wheat straw (0, 3.3, 6.6, 13.2 g/l) or spruce sawdust (0, 3.3, 6.5, 13.2 g/l) with (20 IU) or withou t urease. Each concentration of ampicillin, hydroquinone, wheat straw or sp ruce sawdust was tested in triplicate. The equipment consisted of Woulff flasks containing 300 ml of a buffered so lution (0.02 M; pH 7.50) with 1 ml of cattle urine. The cattle urine was ch aracterized by measuring the main nitrogen contents, which were 6.52 mg tot al-N/ml, 5.96 mg urea-N/ml and 0.026 mg ammonium-N/ml. The initial pH of ur ine was 7.84. Ammonium and nitrate concentrations, and pH were monitored at zero-time and after 3, 6 and 24 h of incubation with the cattle urine. The addition of urease to the flasks containing urine induced a significant increase in the production of ammonium-N, from 1.83 to 6.32 mg NH4+-N/flas k after 24 h of incubation. In the presence of urease, an inhibitory effect was recorded in NH4+-N prod uction with ampicillin and spruce sawdust. In contrast, hydroquinone inhibi ted urease activity and wheat straw adsorbed the NH4+-N produced, both caus ing a dose-dependent relationship. In the absence of urease, ampicillin, hydroquinone, wheat straw or spruce s awdust caused a dose-related decrease in NH4+-N production. However, the hi ghest amounts of wheat straw (6.6 and 13.2 g/flask) exhibited a temporary i ncrease in NH4+-N production during the first 6 h. This is probably due to a generation of extra NH4+-N as compared to the control flasks without stra w. However, at 24 h, the situation paralleled the other materials. Although pH increased approximately from 7.50 to 7.65 during the hydrolysis of urea in the presence of urease, no gaseous ammonia was volatilized into a 0.1 M HCl flask. Moreover, no increase in nitrate concentration was foun d during the incubation. The present results suggest that ampicillin, hydroquinone and spruce sawdus t could be used in order to reduce NH4+-N production from cattle urine. The NH4+-N already produced could probably be absorbed on wheat straw.