VARIABILITY IN THE RUMEN DEGRADABILITY AND POSTRUMINAL DIGESTION OF THE DRY-MATTER, NITROGEN AND AMINO-ACIDS OF CANOLA-MEAL

The rumen degradability and postruminal digestion of rumen escape dry matter (DM), nitrogen (N) and metabolically essential amino acids (EAA) for canola meal (CM) from five different processing plants (samples 1-5) and one sample of soybean meal (SBM) were compared. Rumen degradability was estimated by incubating sample-filled small nylon bags in situ in the rumen of steers for 0, 4, 8, 12, 16 and 30 h. Postruminal digestion was estimated using a sequence of ruminal in situ incubations for 0, 4, 8, 12 and 16 h, in vitro incubation in an acid-pepsin solution and a mobile nylon bag technique distal to the abomasum. The rumen escape of nutrients for CM1 was consistently lower compared to other CM samples, while CM4 resulted in the highest escape of nutrients at 30 h. An estimate of maximum degradability of EAA measured at 30 h differed among CM samples, with the rumen escape of EAA being CM4 > CM2 = CM5 greater-than-or-equal-to CM1 = CM3 > SBM. The DM, N and EAA content of mobile bag residues was relatively uniform among CM samples, particularly after 12 and 16 h of ruminal fermentation, but was higher for CM than for SBM, probably due to a low digestibility of CM hulls. The rumen degradability of CM from different processing plants differed and as a consequence the postruminal digestion of nutrients in CM differed.