Factors Affecting the Variability of An in Vitro Rumen Fermentation Technique for Estimating Forage Quality

Abstract

Alfalfa, bahiagrass, bermudagrass, and ryegrass hays, and corn silage were fed to three fistulated donor animals and also used as substrates in several in vitro diges- tion trials. Source and activity of inoculum, as in- fluenced by animals and diets, on the sub- strafe digestible dry matters were deter- mined when digested with and without urea and glucose. Each substrate was digested in duplicate during three succes- sive periods with inoculum from each donor animal consuming each diet. There was a highly significant (P < .01) difference in the in vitro digestible dry matters of the substrates when digested with inocula from different diets and donor animals without urea and glucose. With the addition of these nutrients, no signif- icant differences were found in the in vitro digestible dry matters among donor ani- mals. Addition of urea and glucose signif- icantly reduced the standard deviations of digestible dry matter among diets within each substrate and among substrates within each diet. There was a between-trial standard devia- tion of 2.81 without the nutrient additive. This deviation was reduced to 1.74 by the addition of urea and glucose to the fermentation media. The standard devia- tion of duplicates within trials was 0.40.