LAUSR

Abstract Effects of cashew nut shell liquid (CNSL) feeding on rumen fermentation and microbial profiles were investigated using Thai native cattle (n = 4) and swamp buffaloes (n = 4). Rumen fistulated animals were assigned to an experiment in one factor design: they were fed a concentrate (1 kg) and rice straw (90% of ad libitum intake) diet supplemented with control pellets followed by CNSL-containing pellets for 4 wk each (control and CNSL periods, respectively). Rumen content was sampled at the end of the control period (d 27 and 28) and at 2 wk (d 13 and 14) and 4 wk (d 27 and 28) of the CNSL period to monitor rumen characteristics. Feed intake, ruminal DM disappearance, ruminal pH and ammonia concentration were not obviously affected by CNSL feeding. Methane production potential, monitored by a batch culture system supplemented with the same diet formula, was decreased by 53% and 73%, after 4-wk CNSL feeding to Thai native cattle and swamp buffaloes, respectively. Although volatile fatty acid level in the rumen was not changed by CNSL feeding, propionate proportion was greatly elevated by 23% and 31% in native cattle and buffaloes, respectively, after 4-wk CNSL feeding. Enhanced propionate was observed even in the 2-wk samples. Results of quantitative PCR analysis showed that although numbers of methanogenic archaea in the rumen did not change, protozoa were decreased and some bacterial groups including genus Prevotella were increased by CNSL feeding in both native cattle and buffaloes. This is in agreement with the results of Miseq analysis of 16S rRNA genes of rumen microbes, which showed increases of Prevotella with CNSL feeding. Increase of Succiniclasticum and decrease of unclassified Bacteroidales by CNSL were also observed for both native cattle and buffaloes. Changes in archaeal community were also similar between these two genera of ruminants. These ruminal responses indicate that CNSL feeding is useful for modulating rumen fermentation in Thai local ruminants, major contributors to methane emission in this area. This is the first report describing the effect of CNSL feeding on rumen fermentation in relation to detailed analysis of rumen microbial community.