Inert plastics as indicators of physiological processes in the gastrointestinal tract of ruminants.

Various types of plastics with different physical properties have been useful in measuring rumination and passage events in the gastrointestinal tract (GIT) of ruminants. Plastic ribbons and monofilaments are available in different diameters, specific gravities and hardness and they can be cut to various lengths. Specific studies that are amenable to these materials include physical appetite control, regurgitation for rumination, passage from the rumen with or without rumination and passage through the entire GIT. Passage of particles through specific portions of the GIT can be measured in animals with various fistula preparations. The rumination of plastic ribbon in the rumen is similar to that of long forage. If the particle length is 7 cm or less, the particle can be regurgitated and produces normal rumination patterns. Movement of particles from one part of the rumen to another can be measured. Multiple sites can be studied in the same experiment by using particles of different colors. Isolating particles from ingesta or fecal residues usually starts with sieving to remove the small particles. Various subsequent separation schemes include flotation or sedimentation, air streams or acid digestion; when other methods fail, particles can be manually separated and counted. Plastic markers have several potential uses in ruminant research but they also have limitations. Because they are inert, they cannot undergo the hydration, density and size changes that occur with normal feed particles.