McKinnon, J. J. and Walker, A. M. 2009. Comparison of canola and mustard presscake from biodiesel production as protein sources for growing cattle. Can. J. Anim. Sci. 89: 401-408. Two studies were conducted to examine in situ rumen degradation kinetics of biodiesel presscake from canola (CPC) (Brassica napa) and mustard (MPC) (Brassica hirta) relative to regular canola meal (CM) and to compare the performance of cattle fed these meals as protein supplements in backgrounding diets. In the in situ trial CPC and MPC had similar (P > 0.05) rates of DM, CP, fibre and crude fat disappearance relative to canola meal. However, CPC and MPC exhibited greater (P 0.05) in effective degradability of crude fat were observed. The feedlot trial involved 391 steers (323 +/- 24 kg) that were fed one of three experimental diets: a control diet consisting of barley silage (213 g kg(-1)) oat hulls (306 g kg(-1)), chopped straw (63 g kg(-1)), rolled barley (255 g kg(-1)) and CM (101 g kg(-1)), ora diet containing either CPC or MPC in place of CM as the protein supplement. Backgrounding performance was unaffected by treatment as no differences in DMI (P = 0.127), ADG (P = 0.679) or feed:gain (P = 0.792) were observed. Composition of gain estimated by ultrasound measurement of longissimus dorsi area and subcutaneous fat depth was unaffected by dietary treatment. It is concluded that biodiesel presscake from both canola and mustard seed provides a superior source of rumen degradable nutrients relative to CM and can be used as a protein supplement for growing cattle without any adverse affects on performance at levels up to 10% of the diet DM.
