Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2005
Publication Date: 6/1/2005
Citation: Grings, E.E., Blummel, M. 2005. Application of rates of fermentation to prediction of forage intake. Journal of Animal Science Supplement 83(Suppl. 1):238. Interpretive Summary:
Technical Abstract: In vitro techniques used in ruminant nutrition can be classified into those that estimate digestibility/degradability gravimetrically by quantifying insoluble incubation residues and into those that measure appearance of products of fermentation, such as gases. While in vitro gas techniques have received much attention over the last two decades due to the ease with which fermentation kinetics can be measured, there is little evidence of their superiority over gravimetric techniques in the prediction of feed intake. Furthermore, a conceptual problem with in vitro gas measurements arises when rejecting proportional constancy between main products of microbial degradation: short chain fatty acids (SCFA), microbial biomass, and gases. While there is a close stoichiometrical relationship between SCFA and gas production, a potential competitive relationship for substrate utilization between these two products and microbial biomass can be demonstrated. This problem can be overcome by measuring in vitro true substrate degradability concomitantly with gas production. Intake predictions for a wide range of temperate and tropical roughages based on in vitro 1) gas production rates, 2) true degradability, and 3) combinations of both, show that the latter approach can result in more accurate prediction of intake than measurement of either alone.