Metabolizable protein as a basis for protein evaluation of silages
2002
Kaert, O. | Kaldmae, H. | Karis, V. (Estonian Agricultural Univ., Tartu (Estonia). Inst. of Animal Science)
In Estonia, an evaluation of feeds, including a more extensive protein evaluation was initiated in 2001. In the Laboratory of Chemistry of the Department of Animal Nutrition of the Inst. of Animal Science of the Estonian Agricultural University 1268 samples of silage prepared in Estonia were studied. A metabolizable protein content of silages and protein balance in the rumen were determined according to the Finnish calculation scheme of the Nordic system, to which we supplemented the correction figure for 1 per cent silage DM, concerning the effective degradability of protein. The metabolizable protein content of the investigated silages and the protein balance in the rumen were affected primarily by crude protein content of silage. Due to a considerably poor protein content of silages prepared in Estonia (12.6 per cent DM on an average), the metabolizable protein content was also low (73 g/kg DM), and protein balance in the rumen remained negative (-0.8 g/kg DM). As for protein utilization by ruminants, the protein evaluation of silages on the basis of digestible protein occurred to be inexact. The content of digestible protein was approximately twice as high as that of metabolizable protein in the silages rich in protein (lucerne, clover), which means that protein value was highly overestimated
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