Nitrogen degradability and intestinal digestibility of rumen undegraded protein in rapeseed, rapeseed meal and extracted rapeseed meal

In this study, nutritive values of rapeseed (R), rapeseed meal-expeller A (RM-A), rapeseed meal-expeller B (RM-B) and extracted rapeseed meal (ERM) were compared. The trials were performed using the in sacco method with three steers of the Czech Fleckvieh breed, which were fitted with a permanent ruminal carmula. Nylon bags with samples were incubated in the rumen for 2, 4, 8, 16, 24 and 48 hours. The effective degradability (ED) of crude protein (CP) was calculated at 0.08, 0.06 and 0.04 1/h of rumen particulate outflow rates (k), and the obtained ED values were 65.4, 70.8 and 77.4% for R, 86.7, 88.1 and 89.7% for RM-A, 82.2, 84.4 and 87.0% for RM-B and 56.3, 62.1 and 69.6% for ERM, respectively. The ED values significantly differed between feeds (P < 0.05) for all rumen particulate outflow rates. Disappearances of amino acids (AA) after 16 hours of incubation in the rumen of R, RM-A, RM-B and ERM were determined. In all cases, the concentrations of AA in the feeds determined after incubation in rumen were lower than in the original feeds. A mobile bag technique was used to determine intestinal digestibility. In the experiment, three dry cows fitted with permanent large ruminal cannula and the T-piece cannula in the proximal duodenum were used. The intestinal digestibilities of rumen undegraded CP (DSI) wereestimated 30.0% in R, 15.4% in RM-A, 27.6% in RM-B and 65.3% in ERM. The DSI values significantly differ between the feeds (P < 0.05), except for the difference between R and RM-B.