Microbial Biomass Production (mg/g)

Microbial biomass production (MBP) is measured directly by analyzing the substrate that remains after 48 hour incubation with a NDF analysis (w/o amylase or sodium sulfite). The difference between the weight of the substrate before and after NDF analysis is the microbial biomass. Early versions of FermentricsTM quantified VFA’s and gas production, and then used a stoichiometric equation (Blummel et al., 1997) to predict the microbial biomass produced during the fermentation.

Higher MBP is somewhat the “gold standard parameter” associated with higher milk production. If the dry matter intake (DMI) of the diet is known, it is possible to convert MBP to estimated grams of rumenmicrobial protein produced by using this equation: MBP x 0.41 x 1.3 x Kg of DMI. The 0.41 is the assumed amount of microbial protein contained in the biomass being measured, 1.3 is an adjustment factor accounting for about 30% of the rumen bacteria existing in the liquid phase thus not measured in the biomass value. Using an actual TMR example with 160 mg/g MBP and an average cow DMI of 23.5 kg, equates to 2004 grams of microbial protein produced (Ipharraguerre and Clark, 2005). Total dietary microbial protein in grams divided by 70 equals the liters of milk potential from a protein perspective. The total contribution of microbial protein plus any RUP provided in the diet is what will contribute to the total protein supply utilized for milk production.