Evaluation of rumen in vitro gas production and fermentation characteristics of four tropical seaweed species

Studies on the identification and characterization of numerous seaweed species from tropical oceans have not been widely reported. The objective of this study was to evaluate the rumen in vitro gas production and fermentation characteristics of four tropical seaweed species. The design of treatments was a randomized complete block design with four different seaweed species (brown seaweed: Laminaria sp. and Padina australis; red seaweed: Gracilaria sp. and Eucheuma cottonii) and four replications for each treatment. For the gas production, easily degraded fraction (a), potentially degraded fraction (b), rate of gas production of b fraction (c), and total fraction degraded (a+b) parameters of brown seaweed were higher and faster than those of red seaweed. The lowest methane production at 24 hours incubation was obtained for Gracilaria sp., which reduced methane production from blank (44.38%) and standard (Pangola substrate) samples (60.63%), followed by Padina australis at 28.98 and 49.73% respectively. Padina australis resulted in the highest propionate proportion (16.03%), lowest butyrate (11.92%) and A:P ratio (4.52) (P<0.05). There were no differences in NH3 (34.17-37.31 mg/100 mL) or microbe protein concentration (9.03-10.60 mg/100 mL) among the seaweed species. It was concluded that brown seaweed (Laminaria sp. and Padina australis) were more degradable than red seaweed (Gracilaria sp. and Eucheuma cottonii) in the rumen. Padina australis is the most potential as ruminant feed because it resulted in the highest propionate proportion, the lowest butyrate and A:P ratio, and low methane production and did not disturb the NH3 and microbe protein concentrations.