Passage of Inert Particles Varying in Length and Specific Gravity through the Postruminal Digestive Tract of Steers

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Abstract
Postruminal passage of inert particles varying in specific gravity, length, and time of administration in relation to feeding, as well as interactions among thee factors, were studied in four ruminally cannulated steers. Animals were allowed access to a 40% grain mix, 60% long alfalfa hay diet for 6 h daily. Eleven combinations of particle specific gravity (0.9, 1.17, 1.41, or 1.77) and length (1, 5, or 10 mm) were used. Two hundred particles of each combination were placed in the abomasum at the beginning of the meal, the end of the meal, or 6 or 12 h after the end of the meal. Recovery of particles in feces within 24 or 48 h of administration and times of first appearance and maximal concentration were examined. Particle recovery 24 h after dosing as a percentage of 48-h recovery and time of maximal concentration in feces best described postruminal passage of inert particles. Passage was affected by specific gravity, but not length, of particles. Those having a specific gravity of 1.17 passed most quickly. Time at which particles were placed in the abomasum in relation to feeding affected the passage of particles varying in specific gravity. This interaction may be important in studies of ruminal passage that depend on marker appearance in feces.