Rumen microorganisms, methane production, and microbial protein synthesis affected by mangosteen peel powder supplement in lactating dairy cows.

Four crossbred dairy cows (50 % Holstein-Friesian × 50 % Thai native), 404 ± 50.0 kg of body weight (4 years old) and 90 ± 5 day in milk with daily milk production of 9 ± 2.0 kg/day, were randomly assigned according to a 4 × 4 Latin square design to study the effect of mangosteen (Garcinia mangostana) peel powder (MSP) supplementation on rumen microorganisms, methane production, and microbial protein synthesis fed concentrate containing yeast fermented cassava chip protein (YEFECAP). The treatments were different levels of MSP supplementation at 0, 100, 200, and 300 g/head/day. Rice straw was used as a roughage source fed ad libitum, and concentrate containing YEFECAP at 200 g/kg concentrate was offered corresponding to concentrate-to-milk-yield ratio at 1:2. A quantitative real-time PCR approach was used to determine the population densities of ruminal microorganisms. The results revealed that supplementation of MSP did not affect on Fibrobactor succinogenes, Ruminococcus flavefaciens, and Ruminococcus albus (P > 0.05). However, total bacteria was linearly increased (P < 0.01) while methanogens and protozoal population were linearly decreased (P < 0.01) with increasing level of MSP supplementation. Increasing level of MSP supplement could decrease rumen methane production from 27.5 to 23.7 mmol/100 ml(3). Furthermore, cows that received MSP at 300 g/head/day had the highest microbial crude protein and efficiency of rumen microbial N synthesis (416.8 g/day and 16.2 g/kg organic matter truly digested in the rumen (OMDR), respectively). In conclusion, supplementation of MSP at 300 g/head/day with YEFECAP as a protein source in the concentrate mixture revealed an enhancement of rumen fermentation and methane reduction in lactating dairy cows.