Evaluation of canola meal derived from Brassica juncea and Brassica napus seed as an energy source for feedlot steers

This study evaluated the substitution of barley grain with two sources of canola meal (CM) derived from Brassica napus and B. juncea on performance of feedlot cattle. Crossbred steers [n = 300; initial body weight (BW) = 311 +/- 23 kg] were allotted to 25 pens with each pen randomly assigned to one of five treatments. The control backgrounding diet consisted of 39% barley silage, 30.4% barley grain, 22.8% brome hay and 7.8% supplement, while the control finishing diet consisted of 88.3% barley grain, 4.4% barley silage and 7.3% supplement (dry matter basis). The control diets contained no CM during backgrounding and finishing. Treatment diets included 15 and 30% B. napus or B. juncea meal during backgrounding and 10 and 20% during finishing, with canola meal replacing barley grain in both phases. In each phase the data were analyzed as a 2 x 2 factorial plus a control. Cattle fed CM substituted diets during backgrounding had greater (P<0.05) dry matter intake (DMI), average daily gain (ADG) and final BW relative to those fed the control diet. Gain to feed ratio (G:F) and calculated net energy for maintenance (NEm) and gain (NEg) were not affected (P > 0.05) by treatment. During finishing, DMI and ADG did not differ (P > 0.05) across treatments. Feed efficiency, NEm and NEg decreased (P<0.05) at the 20% CM level relative to 10%. Over the entire feeding period, G: F, NEm and NEg were reduced (P<0.05) with higher inclusion of CM in the diet. The percentage of cattle grading Canada AAA was reduced (P<0.05) by CM. These results indicate that regardless of type CM has a lower net energy value than barley grain and that it is not an equivalent energy substitute for cereal grains over the entire feeding period.