Nutrient composition and degradation profiles of anthocyanidin-accumulating Lc-alfalfa populations

Abstract

Alfalfa (Medicago sativa L.) is one of the most used forages in the world but suffers the disadvantage of having poor protein utilization by the animal. The poor protein utilization is the result of excessive ruminal protein degradation, which might be reduced by the protein precipitating capacity of anthocyanidin (AC) and condensed tannins (CT). The objective of this study was to determine the effects of the Lc-transgene on survival, anthocyanidin, condensed tannin and chemical profiles in crossed populations of western Canadian-adapted Lc-alfalfa. These were compared with their non-transgenic (NT) parental varieties, Rangelander, Rambler, and Beaver. Lc-alfalfa forage accumulated enhanced amounts of anthocyanidin, with an average concentration of 197.4 µg g-1 DM, while condensed tannins were not detected. Both of these metabolites were absent in the NT parental varieties. Lc-alfalfa had a lower (24.8 vs. 27.3% DM; P < 0.02) crude protein (CP) and higher (58.3 vs. 55.5% DM; P < 0.01) carbohydrate (CHO) concentration, which resulted in their decreased (P < 0.01) N:CHO ratio (68.1 vs. 79.2 g kg-1) compared with NT alfalfa. Slowly degradable N:CHO ratio was decreased by 5.9 g kg-1 (P < 0.03) and total rumen-degradable N:CHO ratio was decreased by 12.9 g kg-1 (P < 0.03) in Lc-alfalfa compared with NT alfalfa. In conclusion, Lc-gene transformation resulted in the accumulation of anthocyanidin, decreased total protein content, increased total carbohydrate content and improved the balance between nitrogen and carbohydrates in the crossed transgenic populations of western Canadian-adapted alfalfa compared to their NT western Canadian parental alfalfa varieties. Key words: Alfalfa, anthocyanidin, Lc-transgene, protein and carbohydrate sub-fractions, nitrogen-to-carbohydrate degradation ratios