Use of the Artificial Rumen Technique to Estimate the Nutritive Value of Forages

A comparison has been made of the cellulose digestibility of 35 forages in vitro and in vivo. The in vitro system utilized ovine rumen microorganisms, all-glass fermentation vessels, and a 24-hour fermentation period, whereas the in vivo system utilized conventional 11-day digestion trials with two to four, usually four, sheep per trial. The forages tested were orchard grass, brome grass, Kentucky bluegrass, timothy, alfalfa and ladino clover. The correlation coefficient of +0.97 indicates a close, linear relationship between cellulose digestion in vitro and in vivo. Cellulose digestion in vitro was also significantly correlated (r=+0.92) with the digestible energy of these same forages. This correlation was considerably better than the correlation between determined digestible energy and calculated digestible energy by the Axelsson-Reid-Swift formula (r=+0.78).