Effect of increasing the dietary level of rapeseed meal on intake by growing beef steers1

Three experiments were conducted to determine the effects of rapeseed meal on intake by cattle. In the first experiment, the effect of increasing rapeseed meal level on intake, growth, and performance of growing beef steers was evaluated. In the second experiment, the effect of extrusion (glucosinolate reduction) on supplement intake by steers was evaluated. In the third experiment, the effect of increasing dietary rapeseed meal level on supplement intake was evaluated. In the first experiment, rapeseed meal replaced soybean meal at 0, 33, 67, or 100% of the supplemental protein. Dry matter intake, crude protein intake, and serum thyroxine levels were decreased linearly (P < .01) with increasing level of rapeseed meal in the supplement. Protein sources used in Exp. 2 were soybean meal, rapeseed meal, extruded rapeseed meal, and soybean meal containing rapeseed oil at the same level as the rapeseed meal. In Exp. 3, the protein sources were composed of different combinations of rapeseed meal and soybean meal (100% rapeseed meal; 67% rapeseed meal and 33% soybean meal; 33% rapeseed meal and 67% soybean meal; and 100% soybean meal). Supplement intake was measured at .5, 4, and 24 h after feeding in both experiments. Extrusion treatment, which reduced glucosinolate content in rapeseed meal 75%, did not improve (P > .10) supplement intake. Rapeseed meal resulted in lower supplement intakes at .5 and 4 h than the soybean meal and soybean meal+rapeseed oil supplements (P = .003).(ABSTRACT TRUNCATED AT 250 WORDS)