Effects of Differential Solid-Liquid Removal Rates on Fermentation Parameters in Continuous Cultures of Rumen Contents

Abstract

Fermentation responses to diet composition, feed particle size, inoculum source and length of fermentation were determined in rumen fluid cultured in a system with differential solid and liquid removal rates. The parameters measured included dry matter and acid detergent fiber digestibility, volatile fatty acid production and protozoa numbers. Decreased feed particle size did not affect dry matter or acid detergent fiber digestibility, but did reduce protozoa numbers and result in decreased total volatile fatty acid production and a reduced proportion of propionic acid. The diet composition change consisted of substituting a semi-purified diet for a natural diet. Increased dry matter and acid detergent fiber digestion resulted from feeding the semi-purified diet, along with marked decreases in protozoa numbers and changes in the molar proportions of acetate and propionate. The length of incubation, within the limits studied, did not affect the parameters measured. It appeared from these results that the inocula source can, if not carefully controlled, affect the results of the fermentations.