title: The effect of size and density on mean retention time of particles in the gastrointestinal tract of sheep.
abstract: The selective retention of particles in the reticulo-rumen and in the gastrointestinal tract distal to the reticulo-rumen was studied in fistulated sheep maintained on a roughage diet. Polyethylene glycol and plastic particles of different lengths (1 and 10 mm) and densities (0.92, 1.03, 1.22 and 1.44 g/ml) were either fed or were introduced into the omasum. The mean retention time in the reticulo-rumen (MRTRR) of 1 mm long particles with a density of approximately 1.0 g/ml was about 67 h, that is eight times longer than the MRTRR of fluid; the heavier particles were retained only three times longer than fluid. Particles with a length of 10 mm were retained in the reticulo-rumen 19-28 h longer than 1 mm long particles of the same density. Particles with a length of 10 mm were reduced to smaller particles (0.5-4 mm) due to rumination. Multiple regression analysis indicated that particle density and particle size accounted for 59 and 28% of the total variation of MRTRR respectively. The mean retention time distal to the reticulo-rumen (MRTGut) of 1 and 10 mm long particles with a density near 1.0 g/ml was 18-19 h, similar to that of fluid (16 h). The heavier particles were retained about 3-8 h longer.
authors.affiliation: Department of Physiology, School of Veterinary Medicine, Hannover, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Kaske
authors.forename: W
authors.initials: W
authors.lastname: von Engelhardt
mesh_terms: D000818:Animals; D004032:Diet; D005260:Female; D005772:Gastrointestinal Transit; D008297:Male; D009851:Omasum / Q000502:physiology; D010316:Particle Size; D012159:Reticulum / Q000502:physiology; D012417:Rumen / Q000502:physiology; D012756:Sheep / Q000502:physiology*