Recently it was reported: "the fat content of the milk produced may be varied more than sixty per cent, at will, for the entire lactation by changing the physical characteristics of the roughage which the cow receives. This can be done at will and without changing the quantity of milk produced."2 Two trials at this Station, in which the roughage was ground, should throw additional light on this subject. In the first double-reversal trial, a grain mixture consisting of three parts ground corn, three parts ground oats and one part linseed oil meal was fed, together with corn silage and a good grade of alfalfa hay. During alternate periods the alfalfa was cut into lengths of one-fourth inch and fed mixed with the grain. Actually much of the alfalfa was reduced to a powder or was in the nature of a finely ground meal. Four animals in each group completed the trial. The results of this trial are shown in Figure 1.