Raw data and R scripts

Ammonia (<b>NH</b>_{<strong>3</strong>}) pollution generated by animal manure represents a focal topic for the current livestock system, especially in the context of pig production. Standardized methods for measuring NH₃ concentration in animal slurry are needed to assess whether the different strategies applied at animal level (i.e. low-protein diets, additives) can reduce NH₃ pollution. Therefore, the aim of this study was to provide a standardized procedure and test the repeatability in measuring NH₃ concentration in pig slurry samples using an <i>in vitro</i> method based on a dynamic chamber system. Five slurry mixes of 348 g each were prepared starting from feces and urine samples of a single pig. Every mix was composed of 87 g of feces, 87 g of urine and 174 g of water. For each mix three replicates of 100 g were realized, obtaining fifteen slurry replicates coming from five different mixes. Then, the fifteen replicates were transferred in jars and placed in a water bath (21^oC) and a constant flow of synthetic air (2.8 L/min) was injected through them. At the same time, the samples were connected to a cavity ring-down spectrometer (<b>CRDS</b>, model G2103, Picarro Inc., Santa Clara, CA, USA) which, combined with a multichannel sampler (model A0311-s1, Picarro Inc., Santa Clara, CA, USA), was able to measure for seven days the NH₃ concentration (ppb) of the outgoing air flow from the slurry samples. Every sample was measured cyclically for 15 min, with a 10 min-interval between two different samples over the 168 h of measurements. For statistical analysis (R, v. 4.4.1), only the NH₃ concentration of the last minute out of the fifteen was considered, and data were interpolated on hourly basis, obtaining one NH₃ concentration value per hour. To test the repeatability of the method, coefficients of variation (<b>CVs</b>) of area under the curve for NH₃ concentration (<b>AUC NH3</b>_{<strong>3</strong>}, ppb x hour), NH₃ concentration peak value (<b>PV NH</b>_{<strong>3</strong>}, ppb) and time to reach the peak (<b>TTP</b>, hours) were calculated between pairs of replicates of the same mix and between pairs of mixes. For the mixes all the CVs calculated showed a variation lower than 10%. For the replicates only the CV related to the TTP registered a value higher than 10% for four pairs of replicates. In conclusion, the dynamic chamber system proposed in this paper represents a time-saving method with a good repeatability for measuring in vitro NH₃ concentration in pig slurry samples.