EFFECT OF VARYING FORAGE-TO-CONCENTRATE RATIO OF ISONITROGENOUS RATIONS ON FEED INTAKE BY RUMINANTS

Three completely pelleted isonitrogenous rations consisting of alfalfa hay:concentrate ratios, 100:0, 67:33, and 33:67 were fed to six nonpregnant Holstein heifers in a 3 × 3 Latin-square digestion trial to determine the effect of increasing energy concentration on voluntary intake. Apparent digestibilities indicated an increase in dry matter, crude protein, and gross energy digestibility coefficients as the per cent concentrate increased in the diet. Daily dry matter intake decreased as the per cent concentrate increased in the ration, and daily energy intake was similar for all rations. Density measurements of the various rations increased as the amount of concentrate increased in the ration. Acetic acid decreased and propionic and butyric acids increased in the rumen as the concentrate increased in the rations. Results of this experiment suggest that ruminants, while being fed isonitrogenous rations varying in energy concentration will adjust voluntary feed intake in relation to physiological energy demands if fill or rumen load does not limit their consumption. © 1969, American Dairy Science Association. All rights reserved.