Comparison of the Kjeldahl method and a combustion method for total nitrogen determination in animal feed

The features of the Dumas combustion method (CM) and those of the Kjeldahl method (KM) were compared as they apply to total nitrogen determination in animal feed. Both methods achieved similar repeatability (S.D., 0.11–0.38 from Kjeldahl and 0.15–0.36 from combustion) and similar intra-laboratory reproducibility (S.D., 0.11–0.39 from Kjeldahl and 0.15–0.37 from combustion). R.S.D. is always below 2%. These results show that the CM is suitable for the analysis of protein content in animal feed (5–75% protein content). The CM is recommended owing to its shorter analysis time, its cost and its environmental suitability.