Effects of Phloroglucinol and the Forage:concentrate Ratio on Methanogenesis, In vitro Rumen Fermentation, and Microbial Population Density

This study was conducted to investigate the effects of phloroglucinol (PHLO) and the forage: concentrate ratio (F:C) on methane (CH4) production, rumen fermentation profiles, and the microbial population in vitro. Rumen fluid was collected from male Friesland sheep using a stomach tube before the morning feeding. The treatments comprised two different diets: a low F:C diet (20:80) and high F:C diet (80:20), and three PHLO doses (0, 6, and 10 mmol/L PHLO). The results showed that PHLO lowered CH4 production in both diets, whereas F:C did not have any effect on CH4 production. The CH4 decrease due to PHLO was accompanied by a simultaneous decrease in the relative quantity of methanogens and dry matter digestibility (DMD). This indicated that PHLO might decrease CH4 by directly inhibiting methanogen growth and by indirect effects through the retardation of digestibility. PHLO lowered total short-chain fatty acid (SCFA) production with the low F:C diet but increased total SCFA production with the high F:C diet. PHLO increased acetate production in high F:C diet but lowered acetate production of low F:C diet. This finding showed that PHLO might redirect rumen fermentation from CH4 production to acetate production. PHLO lowered the relative quantity of Ruminococcus albus, which might explain the retardation of digestibility by PHLO.