Evaluation of Local Tropical Plants by In vitro Rumen Fermentation and Their Effects on Fermentation End-Products

Seventeen local feed resources were collected and analyzed for chemical composition and were incubated in in vitro fermentation using gas technique. Based on the condensed tannins (CT) values, these feed resources could be divided into three groups: high (11.4-16.8%), medium (2.1-4.6%) and low (0.7-1.7%). Mangosteen peel had the highest and Pak Kayaeng had the lowest in terms of CT value. All samples were added with rumen fluid mixed with artificial saliva and incubated in in vitro gas fermentation for 48 h during which gas production and volatile fatty acids (VFAs) were measured. There were significant differences (P< 0.001) in gas production during 48 h incubation. Gas production was lower in the group having the highest level of CT, from 32.2 to 181.9 ml/gDM. There were significant differences (P< 0.05) in total VFAs (from 48 to 88 mmol/L1), individual VFA production and acetate to propionate ratio (from 1.6 to 4.6), however the values were respectively variable. Propionate production tended to be higher in the group with higher CT. The correlation coefficients (r) were relatively low between gas production after 48 h incubation with total VFAs (0.39), acetate (0.16) and butyrate (0.05) production. Furthermore, negative correlations were obtained between gas and propionate production (-0.20).