The potential nutritive value of Sargassum fulvellum as a feed ingredient for ruminants

Abstract The aim of present study was to evaluate the nutritional value of Sargassum fulvellum (S. fulvellum; gulfweed, mojaban, hondawara) as a feed ingredient and investigate whether its functional metabolites could be helpful for increasing rumen fermentation characteristics. Rumen contents were collected from two rumen-cannulated Hanwoo cows (BW = 450 ± 30 kg). The in vitro trial was performed after 3, 6, 9, 12, 24, 48, and 72 h with S. fulvellum inclusion at concentrations of 1, 3, 5 and 10% of total ration. Total gas emission indicated that each S. fulvellum dose was significantly higher at 3, 6 and 9 h of incubation compared with the 0% inclusion sample but did not affect methane and carbon dioxide emission. Supplementation with 10% S. fulvellum significantly increased total volatile fatty acid (VFA) concentrations over those without supplementation. The in situ trial was performed 6, 12, 24, 48 and 72 h, with 5 g S. fulvellum, to estimate the dry matter disappearance (DMD) from the bag in the rumen. The DMD of S. fulvellum was significantly higher than that of timothy hay at 6, 12 and 24 periods. Proton nuclear magnetic resonance (1H NMR) was used to identify and quantify functional metabolites in S. fulvellum. The most abundant metabolites were guanidoacetate, ethylene glycol and alanine. Although the level of arsenic (As) in S. fulvellum was high, it was still within the acceptable limit for ruminants, and was not likely to cause any health defects, especially as S. fulvellum also contained many beneficial minerals. Overall, the inclusion of S. fulvellum as an alternative feed ingredient in ruminant diet has many potential nutritional benefits. Nevertheless, further in vitro studies using S. fulvellum and different basal diets combinations and, ultimately, in vivo studies are necessary to determine its value.