COMPOSITION AND DIGESTIBILITY OF CANOLA PRESS CAKE AS A FEEDSTUFF FOR USE IN SWINE DIETS

Samples of canola press cake (PC) were collected from seven crushing plants in Western Canada over four successive weekly sampling periods to assess its nutrient and glucosinolate composition and variability. The digestibility of energy and crude protein (CP) (N x 6.25) of PC in growing pigs was also determined. Compared to canola meal (CM), PC contained more ether extract (EE) (21.21 vs. 3.92%), more gross energy (GE) (23.92 vs. 20.36 MJ kg-1) and less CP (34.10 vs. 41.85%), dry matter (DM) basis (P < 0.05). There were significant differences (P < 0.05) among crushing plants in the contents of EE, GE and CP in PC with the largest differences observed in EE; sampling period effects were small for all three components. Plant and period effects on amino acid concentrations in PC were similar to those effects on CP. Glucosinolate concentrations (oil-extracted DM basis) showed only slight reductions in PC from those in canola seed (CS). Both CS and PC concentrations were greater than in CM (P < 0.05) but myrosinase activity in PC was reduced to 0.65% of that in CS compared to 0.15% remaining in CM. Differences were found in total aliphatic glucosinolate concentrations among crushing plants (P < 0.05) (mean 23.75-mu-mol g-1) with only minor period effects. The digestibility of GE in PC was 75% and of CP 75%. On DM basis PC contained 17.94 MJ of digestible energy kg-1 and 25.6% digestible CP.