Effects of malate under normal and subacute ruminal acidosis conditions on in vitro rumen fermentation of a high-concentrate diet for beef cattle

The objective of this study was to investigate the effects of malate salts under normal and subacute ruminal acidosis (SARA) conditions on rumen fermentation of a high-concentrate diet for beef cattle using a rumen simulation technique (Rusitec). In vitro incubation was performed over 14 days using a high concentrate basal diet of 80% concentrate and 20% barley straw supplemented with 500mg/L malate salts. Induction of SARA conditions severely suppressed ruminal fermentation. Production of total volatile fatty acid (VFA), acetate and methane, NH3-N concentration, total protozoa and digestibility of dry matter (DMD) decreased in SARA compared to normal rumen conditions (P<0.05), while propionate and butyrate productions were not affected by SARA. Malate, however, had no significant effects on in vitro ruminal fermentation parameters under both normal and SARA conditions except an increase tendency (P=0.079) in propionate production. In conclusion, the supplementation of malate salts did not improve ruminal fermentation of a high-concentrate diet for beef cattle under normal and SARA conditions and was ineffective in preventing SARA in a simulated rumen.