abstract
The objective of this experiment was to evaluate the effect of mangosteen peel powder (MSP)
on rumen fermentation, nutrient digestibility and microbial population in swamp buffaloes
(Bubalus bubalis) fed on a rice straw based diet. MSP is a fruit peel that contains plant secondary
compounds (condensed tannins and saponins). Eight, rumen-fistulated 4-year old, male swamp
buffaloes with 35074 kg live weight were randomly assigned to receive two dietary
treatments (T1¼non-supplementation of MSP and T2¼supplementation of MSP at 100 g/
(head day)) according to a t-test design. All animals were fed concentrate mixtures at 0.5% of
body weight and rice straw was fed ad libitum for 37 days with the first 30 days for feed
adaptation and voluntary feed intake measurement, while the last 7 days were for samples
collection. The results revealed that there was no difference between treatments on dry matter
intake and nutrient digestibility by MSP supplementation (P40.05). Furthermore, MSP
supplementation did not influence ruminal pH, temperature, ammonia nitrogen and blood
urea nitrogen. Interestingly, propionic acid (C3) production was significantly increased by MSP
supplementation (Po0.05) while total volatile fatty acids, acetic acid (C2) and butyric acid were
similar between treatments. Moreover, C2:C3 ratio was reduced by MSP supplementation.
In addition, estimated rumen methane was significantly reduced by MSP supplementation
(Po0.05). Application of quantitative PCR to quantify cellulolytic bacteria (16S rRNA) targets
revealed that MSP supplementation did not change population of Fibrobacter succinogenes and
Ruminococcus albus (P40.05) while total bacteria population were significantly increased by
MSP supplementation. The Ruminococcus flavefaciens and methanogens population were
significantly decreased as MSP were supplemented (Po0.05). Nitrogen intake, excretion (fecal
and urine) and balance (absorption and retention) were similar between treatments whilst
microbial nitrogen supply and efficiency of microbial protein synthesis were increased by MSP
supplementation. In conclusion, supplementation of MSP as a source of plant secondary
compounds exhibited no negative effect on feed intake, nutrient digestibility, ruminal
fermentation characteristics, nutrient utilization and microbial protein synthesis. But rather,