Evaluation of several macroalgae species on methane emission and antioxidant activity based on in vitro rumen fermentation characteristics

Abstract

Marine macroalgae are the prospective and promising Indonesian natural resources containing bioactive compounds. This study aimed at evaluating various seaweed species with optimal biological activity to mitigate in vitro rumen methane emission and to confirm their antioxidant properties. In addition, relationships among several phenolic fractions and methane (CH4) production of seaweeds were elucidated by Pearson Correlation to screen seaweeds for their capacity to reduce CH4 formation. For in vitro batch cultures experiment, the diets were 500 mg of a substrate of seaweed. They were incubated with 50 ml of buffered rumen fluid (1:2 ratio of rumen fluid to buffer media) in a 100 ml serum vial at 39°C for 72 hours incubation time. A randomized block design was carried out with 14 dried seaweed treatments and 5 different cattle rumen fluid groups as a block. For total phenol, flavonoid, and antioxidant activity, a completely randomized design with 14 treatments and 3 replications was carried out. Data were analyzed by Analysis of Variance (ANOVA) and Duncan analysis. The results showed that the lowest methane production (ml/g DM incubated) significantly (P<0.05) was reduced by Halymenia sp. (0.24) and Caulerpa racemosa (0.41). Caulerpa racemosa showed high flavonoid content (1.5 mg Quercetin/g) and Ulva lactuca had the highest phenol content (0.55 mg Gallic Acid/g). Gracilaria coronopifolia had strong antioxidant activity DPPH radical scavenging activity (77.5% inhibition). It was concluded that Halymenia sp., Caulerpa racemosa and Gracilaria coronopifolia could be used as methane inhibitors and antioxidants for ruminants.