LAUSR

BACKGROUND To overcome the negative effects of condensed tannins on crude protein (CP) and starch utilization, low- or zero-tannins faba bean varieties have been developed in Canada, however, their nutritional value has not been evaluated for incorporation in dairy ration. The objectives of this study were to investigate 1) chemical profile; 2) Cornell Net Carbohydrate and Protein System (CNCPS) protein and carbohydrate subfractions; 3) energy values; 4) ruminal, intestinal and total digestibility of CP; 5) metabolizable protein (MP) supply to dairy cows; and 6) protein inherent molecular spectral characteristics of high tannin containing brown-seeded (var. Fatima) and low tannin containing yellow-seeded (var. Snowbird) faba beans. RESULTS The results revealed that Fatima beans had higher (P < 0.001) contents (g kg-1 DM) of CP (324 vs. 295), and lower (P < 0.01) content (g kg-1 DM) of starch (411 vs. 444), as compared to Snowbird. Fatima had lower (P = 0.001) soluble subfraction (201 vs. 220) and higher (P < 0.05) slowly degradable fiber-bounded (24.9 vs. 14.7) and non-degradable (3.24 vs. 0) CNCPS CP subfractions as compared to Snowbird. Fatima had higher (P = 0.03) content of MP (117 vs. 111 g kg-1 DM) and metabolizable energy (ME; 3.12 vs. 3.10 Mcal kg-1 ) than the Snowbird. Molecular spectral intensities of the protein amide I and II (height and area) of Fatima were higher (P < 0.05) than Snowbird, reflecting their higher CP content. The ratio of protein spectral intensities, amide I: amide II height ratio and α-helix: β-sheet height ratio, differed (P < 0.05) between the two types of beans, highlighting differences in their inherent protein molecular structures. CONCLUSION The high condensed tannins containing (Fatima) faba beans had higher content of MP and ME. On average, both Faba beans had higher ME and MP contents than barley grains, highlighting their promising nutritional value for dairy rations. This article is protected by copyright. All rights reserved.