EFFECTS OF CANOLA-MEAL TREATED WITH ACETIC-ACID ON RUMEN DEGRADATION AND INTESTINAL DIGESTIBILITY IN LACTATING DAIRY-COWS

Five midlactation lactating Holstein cows (628 +/- 42 kg) fitted with large rumen cannulas and T-type cannulas in the proximal duodenum were used in a 4 x 4 Latin square experiment to determine the effects of acetic acid treatment of canola meal on rumen degradation of its protein, rumen fermentation, and postruminal digestion. Canola meal was mixed with 3% (vol/wt) acetic acid in a mixer, followed by drying at 105-degrees-C. Acetic acid treatment of canola meal reduced is in situ rumen DM and CP degradability by up to 17.0 or 28.6 percentage units, respectively, dependent upon the assumed rumen turnover rate. Cows were fed TMR twice daily containing 60% concentrate, 8% alfalfa silage, and 32% whole crop oat silage on a DM basis. Treated canola meal replaced untreated canola meal in the concentrate at 0, 33, 67, and 100%. Each experimental period was 21 d. Average concentration of rumen acetate and isobutyrate increased linearly, but rumen pH, NH3 N, lactic acid, and VFA concentrations, other than acetate and isobutyrate, were not affected by inclusion of treated canola meal. Treatment of canola meal with acetic acid was effective in increasing escape from the rumen of postruminally digestible canola meal protein.