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Intraruminal Addition of Mass or Removal of Rumen Contents on Voluntary Intake of the Bovine¹

Department of Animal Sciences, University of Kentucky, Lexington

ABSTRACT

Where inert polyethylene cubes comprised 4.0, 7.5, 13.5, and 22.6% of the total ration consumed, feed intake (not including polyethylene cubes) was reduced by 3.1, 4.4, 6.0, and 25.6%, whereas total intake (including polyethylene cubes) changed by 0.8, 3.5, 9.0, and –3.9%, respectively. The data show that 4.0 and 7.5% cubes in the diet had little effect on intake, which is taken as evidence that added mass or bulk in the diet was of minor importance in determining the voluntary feed intake of 500-kg cattle consuming daily quantities of dry matter in the amount of 12.9 kg or less. At the very high levels the animals discriminated against the cubes. Three trials were conducted to study the effect of additional inert mass placed in the rumen on voluntary intake. Mass (containerized polyethylene cubes or water) was added to the rumen at levels of 1.6, 4.9, and 8.2% of metabolic size. Voluntary intake of chopped alfalfa hay adjusted to that of a 500-kg animal was reduced by 0.5, 0.4, and 0.1 kg daily, respectively. These differences were not significant. In three additional trials, ingesta was removed from the rumen at levels of 1.6 and 4.9% of metabolic size prior to feeding and 8.2% metabolic size after feeding. A significant increase in adjusted dry matter intake of 0.4 kg per day occurred when 8.2% of metabolic size was removed three hours after feeding. These results are interpreted to mean that bulk added to the rumen in physiological amounts was not an important factor determining the dry matter consumed.

¹ Published with the approval of the Director of the Kentucky Agricultural Experiment Station as Journal Article no. 66-6-78.