Abstract
IT has been shown by Barnett and Miller1 that the relationship between the soluble nitrogen content (Ns) and the total nitrogen content (Nd) of dried samples of grass silage can be represented by the formula : Ns/Nd= 0.854 – 0.100 pH ± 0.012. As the quality of silage is related to its pH, it seemed desirable to estimate the digestibility of the protein in dried silage by the pepsin method of Wedemeyer2. This method has fallen into disuse as it is stated to give results which are too high, but, so far as we are aware, no critical study of the method in connexion with silage exists. A study of the protein digestibility of the samples previously examined (about seventy in number) for their soluble nitrogen content revealed that a direct relationship existed between the soluble nitrogen content and the digestible protein content (Np)/(Nd). This relationship is given by the formula Np/Nd= 33.4 + 0.78 Ns/Nd ± 0.07. It is possible then, with regard to dried grass silage, to portray the nitrogen state, so to speak, as in Fig. 1, the results there being shown on a percentage basis. As the direct determination of Np/Ndinvolves a pepsin digestion which lasts forty-eight hours, whereas the corresponding operation of washing the dried silage to determine Ns/Ndtakes only forty minutes, the time saved by this method of approach is obvious.
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References
Barnett, A. J. G., and Miller, T. B., J. Agric. Sci., 40, 50 (1950).
Wedemeyer, K., Landw. VersSta., 51, 375 (1899).
Watson, S. J., “Science and Practice of Conservation: Grass and Forage Crops”, 508 (Pub. by Fertil. and Feed.-St. J., 1939).
Dijkstra, N. D., Versl. Landbouwk. Onderzoek., No. 55, 10 (1949).
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BARNETT, A., MILLER, T. Calculation of the Digestibility of the Protein in Silage. Nature 167, 997 (1951). https://doi.org/10.1038/167997a0
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DOI: https://doi.org/10.1038/167997a0
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