In situ rumen digestion and escape of dry matter, nitrogen and amino acids in canola meal

Three rumen-cannulated steers were used in three separate trials wherein canola meal (CM) was incubated in situ for 0.1, 4, 8, 12, 16 and 36 h in Dacron bags. Disappearance parameters were estimated for dry matter (DM), nitrogen (N) and individual amino acids (AAs). Effective degradabilities (EDs) were estimated at rumen particulate outflow rates of 0.08, 0.05 and 0.02 h−1. An ED for DM that was lower than that of most AAs indicated there was a limit to its degradability. In contrast, the ED of N was higher than that of 11 of 17 AAs; the disappearance parameters for N were a poor indicator of those estimated for individual AAs. The concentrations of AAs in escape CM estimated at the specified rumen outflow times, compared with non-incubated CM, were higher for all AAs except cystine, proline and glutamate, whose concentrations were lower, and histidine and arginine, whose concentrations did not differ. Compared with non-incubated CM, in escape CM there was a 33% reduction in concentration of glutamate, a 28% enrichment of tyrosine, a lower enrichment, ranging from + 14 to + 23%, for valine, isoleucine, threonine, phenylalanine, serine, aspartate and alanine, and little change in concentration for other AAs. Although the concentrations of AAs in rumen escape CM differed from that in non-incubated CM, those concentrations in escape CM were relatively uniform among outflow rates of 0.08, 0.05 and 0.02 h−1. Key words: Canola meal, in situ digestion, rumen degradability, rumen escape, protein, amino acids