1707
Feed value for ruminants of newly developed black and yellow type of canola seeds
Canola is one of the most valuable agricultural crops in world trade and a major oilseed crop in western Canada. The objective was to evaluate the nutritive value of canola seed, for ruminants, in terms of: 1) nutritional profiles, 2) degradation kinetics, 4) in vitro intestinal protein digestibility, and 4) energy values. Yellow (CS_Y) and black (CS_B) canola seeds (n=4) were collected from two harvest years (2010, 2011). Three dry Holstein cows with rumen cannula were used in an in situ trial; then a three-step in vitro procedure was conducted to determine protein intestinal digestibility. According to this procedure the dried ground rumen residues, (contain 15 mg of N) after 12h of ruminal incubation, were exposed to HCl solution containing pepsin. The pH was neutralised with NaOH and phosphate buffer (pH 7.8) containing pancreatin, which were added to the solution and incubated. After 24h incubation, trichloroacetic acid (TCA) was added to precipitate undigested proteins. The samples were centrifuged and the supernatant was analyzed for N. Protein digestibility was calculated as TCA-soluble N divided by the amount of N in the 12h residue sample. The non-protein N (NPN) was analyzed by precipitating of true protein with tungstic acid and calculated as the difference between total N and the N of the residue after filtration. Soluble CP (SCP) was determined by incubating the sample with bicarbonate-phosphate buffer and filtering. The study revealed that the CS_Y was lower in NDF (122.1 vs. 154.5 g kg-1 DM, P<0.05), ADF (60.7 vs. 98.6 g kg-1 DM, P<0.05), NPN (g kg-1 SCP), ADICP (g kg-1 DM), soluble protein fraction (28.59 vs. 34.11, P<0.05) and higher (67.28 vs. 59.02, P<0.05) in degradable protein fraction and in vitro intestinal digestibility (56.6 vs. 44.6 g kg-1 CP in ruminally incubated residues, P<0.05) than the CS_B. CS_Y contain lower amount of total phenolics compared to CS_B (626.0 vs. 718.0 mg/100g). No significant differences were obtained between the two canola varieties, for the total fatty acids (902.0 vs. 910.7 mg FA/g, SEM 5.17, P>0.05), the CP (g kg-1 DM) and the SCP (7.0 vs. 8.5, P>0.05). Total digestible nutrients, metabolizable and digestible energy was higher (P<0.05) for the CS_Y than for the CS_B. Overall, the results demonstrated that the yellow-seeded canola has the potential to be a greater source for energy and protein supply for ruminants compared to the black canola seed.
Keywords: canola, protein supply, ruminal and intestinal digestion