SUBSTITUTION OF NEUTRAL DETERGENT FIBER FROM FORAGE WITH NEUTRAL DETERGENT FIBER FROM BY-PRODUCTS IN THE DIETS OF LACTATING COWS

Four lactating dairy cows that were ruminally and duodenally cannulate d were used iri an experiment with a 4 x 4 Latin square design to dete rmine the effects of the substitution of neutral detergent fiber (NDF) from forage with NDF, from wheat middlings, corn gluten feed, or a bl end of distillers dried grains and hominy. Dietary crude protein and N DF averaged 18 and 31%, respectively, for the diet with 71.2% of the N DF from forage (control diet) and for diets with 55% of the NDF from f orage (by-product diets). The substitution of NDF from these by-produc ts far forage NDF did not affect dry matter intake (20.1 kg/d) or dige stibility, of organic matter. Total tract digestibility of acid deterg ent fiber was lower for cows fed the diet containing a blend of distil lers dried grains End hominy than for cows fed the diet containing cor n gluten feed. Microbial crude protein synthesis, milk production (23. 9 kg/d), and milk fat percentage were similar for all cows, regardless of diet. Cows fed the diets containing wheat middlings or a blend of distillers dried grains and hominy had reduced ruminal pH compared wit h that of cows fed the diet containing corn gluten feed or the control diet. Diets containing 55% of total NDF from forage with 31% of total NDF from corn gluten feed, wheat middlings, or a blend of distillers dried grains and hominy can supply sufficient effective fiber to maint ain normal ruminal function.