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Effect of Several Variables on in Vitro Rumen Fermentation¹

Department of Dairy and Animal Husbandry, Oregon Agricultural Experiment Station, Corvallis

ABSTRACT

In vitro rumen fermentations were carried out in which the effect of several variables on dry matter and cellulose digestion and/or volatile fatty acid production was determined. With the regimes imposed, it was shown that percentages of cellulose and dry matter digestibility were improved by a reduced concentration of substrate and an increase in rumen liquor. Mineral media concentration had little effect within the ranges employed. Different sources of rumen liquor at times had marked effects on substrate digestion, with significant differences observed between twin steers in two trials. Adjustment of pH was shown to have a significant influence on cellulose digestibility, with indications that the optimum pH may be dependent to some extent on the rumen liquor source. Decreasing particle size of an alfalfa substrate was observed to depress dry matter and cellulose digestibility, but had no effect on peavine hay.

Fritted glass disc crucibles were used to estimate dry matter digestion. The correlation between these data so determined, and cellulose digestibility on a limited number of comparisons, was .96 (P < 0.01).

¹ Technical Paper No. 1260.

² Department of Dairy and Animal Husbandry.

³ Experiment Station Statistician.