The apparent digestibility of prairie hay of variable protein content, with some observations of fecal nitrogen excretion by steers in relation to their dry matter intake.

A COMPLETE knowledge of the factors that contribute to the nutritive value of native grass and hay is of both practical and scientific value. Seasonal and environmental factors contribute largely to variations in the nutrient content of the grass, and other less well-defined factors apparently influence the availability of these nutrients in digestion. Factors associated with the physical characteristics and palatability of grass need to be inves, tigated in relation to stage of maturty of the grass, its chemical composition, and nutrient digestibility. Finally, for practical purposes, it would be desirable to have an accurate estimate of the feeding value of native grass expressed in terms of the feed requirements of animals utilizing the grass. Recently, attempts were made to determine by indirect methods the sea, sonal variation in the apparent digestibility of native grass as grazed by steers on pasture (Hobbs, Gallup and Taylor, i945). Continuation of this work has been delayed by difficulties encountered in securing reliable estimates of the feed intake of animals while grazing. Seasonal variation in the digestible nutrients of native grass cured for hay (prairie hay) is now being investigated (Briggs et al., I946). In the progress of this and other work involving nitrogen balance experiments with steers, advantage has been taken of the opportunity to determine the digestibility of unsupplemented and supplemented native hay rations of varying composition. The digestive wastage of protein is considerable when cattle are fed fibrous rations, therefore particular attention was given to this loss in the digestion trials discussed in the present paper. Materials and Methods