Total feed intake, intake of rice straw, digestibility of dry matter, organic matter, and crude protein were not affected by feed supplementation (PN0.05); however, fiber digestibility (NDF, ADF) was changed following supplementation (Pb0.05). Mangosteen peel supplementation resulted in lower NDF and ADF digestibility when compared with the COM treatment (Pb0.05), though not different from the control group (PN0.05).