Comparative evaluation of methods for ammonia (NH3) determination in rumen fermentation of legume and concentrate samples
Abstract
Ammonia (NH3) is the main product of ruminal protein degradation and serves as an indicator of nitrogen availability for microbial protein synthesis. Several analytical methods exist to quantify NH3 concentration, but their reliability varies with the analytical approach and experimental setup. This study aimed to compare four NH3 determination methods: Conway microdiffusion, Ion Selective Electrode (ISE), Indophenol, and Nessler, for evaluating in vitro fermentation of legumes and concentrate samples. Supernatants from legumes (n=7) and concentrate (n=7) after 4 h of in vitro rumen incubation, with four replicates each, were analyzed using these methods. Data were subjected to a 2x4 factorial randomized block design followed by Duncan's multiple range test. Correlation and regression analyses were conducted between the Conway method and other methods across legume, concentrate, and mixed samples. The ISE method produced the highest NH3 concentration (93.63 mM), while the Indophenol and Nessler methods yielded values closer to Conway. Significant correlations (P<0.05) were observed between Conway and other methods in mixed samples, with coefficients ranging from 0.5327 to 0.6663, indicating moderate relationships. In conclusion, the Indophenol and Nessler methods closely matched the Conway method, while the ISE method proved the most practical for rapid NH₃ determination in rumen fermentation studies.
