[Ruminal nitrogen metabolism in calves and sheep. 3. Effect of hay-concentrate ratio in calves].

During the milk feeding period (ca. 55th day of life) and 2 weeks after the milk feeding period (ca. 80th day of life) the influence of a hay quota in the ration (on DM basis) of 6, 10, 14 and 18% in the milk feeding period and of 16, 23, 31 and 37% in the period after milk feeding was tested as to ruminal N metabolization with calves supplied with duodenal re-entrant cannulae. The increase of the hay quota in the ration for ruminating calves reduced as a tendency duodenal NAN passage, its bacterial N-quota, post-ruminal NAN digestibility and, due to a worse utilization of available N for bacterial N-synthesis, bacterial N-synthesis rate. The apparent fermentation of organic matter was, as a tendency, increased with the growing hay quota in the ration.