In vitro and in situ evaluation of Undaria pinnatifida as a feed ingredient for ruminants

The aim of this study was to evaluate the potential effects of feeding the brown alga Undaria pinnatifida (sea mustard, miyeok, wakame) on in vitro rumen fermentation parameters and in situ dry matter disappearance (DMD) and to identify functional metabolites using proton nuclear magnetic resonance (1H-NMR). Rumen fluid donors were two rumen-cannulated Hanwoo cows with free access to water and a mineral-vitamin block. The in vitro trial was performed after 3, 6, 9, 12, 24, 48, and 72 h with U. pinnatifida added at concentrations of 1, 3, 5, and 10% of total ration. The U. pinnatifida DM digestibility was higher than that with the 0% added samples at several incubation times. Microbial growth rate was significantly higher (quadratic effect, P = 0.0003) after 6 h of incubation with 3, 5, and 10% added fermentation than 0% added samples. Supplementation with 10% of U. pinnatifida significantly increased total VFA concentrations compared to those with the 0% added samples. The in situ trial was performed for up to 6, 12, 24, 48, and 72 h with 5 g U. pinnatifida to estimate DMD from the bag in the rumen. The DMD of U. pinnatifida was significantly higher (P < 0.0001) than that of timothy hay at all fermentation periods. 1H-NMR was used to identify the functional metabolites in U. pinnatifida, including amino acids, carbohydrates, lipids, vitamins, and organic acids. These results indicated that U. pinnatifida has considerable potential to enhance feed conversion efficiency and contains component with nutritional benefits. Long-term feeding trials are required to determine the effect of U. pinnatifida as a feed ingredient for ruminants.