N2O, CO2 and NH3 emission from dung of bovine with different percentage of crude protein in diet

Abstract

The emission of nitrous oxide (N2O), carbon dioxide (CO2) and ammonia (NH3) in tropical dairy cattle (CLT) excreta, fed with different percentages of crude protein (CP), was quantified using static cameras. Sampling was performed at different times of day (7:00, 10:00, 13:00, 16:00, and 19:00 local time-LT-). The statistical model employed was a covariance analysis in a randomized complete block design with repeated measures. The variables were analyzed using the Glimmix procedure of the Statistical Analysis System (SAS) v. 9.2 with a covariance structure of compound symmetry. The best model that explains the flow of N2O-N and the emission of CO2 and NH3 is that which included the minimum ambient temperature and the pH as covariates, respectively. Treatment with 12 % of CP obtained the highest N2O-N flow and the lowest CO2 emission. Treatment with 14 % CP had the lowest N2O emission and treatments with 14 and 16 % CP reflected higher amounts of CO2 emissions. The hours of the day when there were greater emissions of NH3 were 10:00 and 13:00 LT, which in turn were the hours where less amount of CO2 and N2O was emitted. As the percentage of CP in the different treatments increases, there is also an increase in the weight gain of the animal, being the treatment with 16 % CP, commercial food, the diet that produced the highest increase in kilograms in animals.