Canola Meal as a Protein Supplement in Dairy Rations

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Abstract
High-producing Holstein cows (30) in the 2nd wk of lactation were in a 4 mo. feeding trial to compare canola meal with soybean and cottonseed meals as single protein supplements in complete dairy rations. Diets were isonitrogenous and isocaloric and contained 11.7% canola, 10.4% cottonseed or 8.6% soybean meals. Actual and 4% fat-corrected milk production did not differ among diets. Cows fed canola meal tended to yield more milk than cows fed soybean or cottonseed meal. Milk component (protein, fat, total solids and solids-not-fat) percentages were not different. Solids-not-fat was the only component that was different, reflecting accumulated differences of milk production and percentage solids-not-fat. Diets did not affect milk flavor quality. Feed intake was similar for different diets. Rumen total volatile fatty acid content was higher for canola and soybean meal. Plasma urea N, total protein and albumin, as well as packed cell volume, red blood cell count, and Hb content did not appear to be affected by rations. Leukocytic scores were higher for cows fed soybean meal, but these were not affected by diet. Thyroid function analysis indicated on effect on canola glucosinolates on the thyroid gland.