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The Use of Silica as a Reference Substance in Digestion Trials with Ruminants

Oklahoma Agricultural Experiment Station²

Abstract

The percentage recovery of ingested silica was used to test the applicability of the silica-ratio procedure to digestion trials carried out under different experimental conditions with large animals on practical rations. The trials were conducted with steers in stanchions, in dry lot, and on pasture, and with sheep in metabolism crates of the usual type.

Dry matter and silica intake of the steers on pasture was calculated from the dry matter consumption: defecation ratios established for each steer during adjacent feeding periods. Feed intake during all other trials was determined in the usual manner.

The recovery of ingested silica was practically quantitative when the steers were in stanchions and the feces collected semimanually. When the steers were in dry lot and the feces collected in canvas sacks, the average excretion of fecal-silica exceeded the calculated intake by about 10 percent. When the steers were on pasture, fecal-silica excretion was 36 percent higher than the calculated intake, due presumably to dirt ingested by the animals in grazing. In the trials with sheep, fecal-silica averaged 107 percent of the calculated intake. Contamination apparently occurred when the feces were exposed to barn conditions during the day of collections.

In general the results indicate that under favorable conditions the silica-ratio procedure is adaptable to digestion studies with steers and sheep. Digestion coefficients so computed, where silica errors are 10 percent or less closely approximate those obtained in ordinary trials. Precautions, other than those usually observed in digestion trials, are necessary however, to keep silica contamination at a minimum. High results may be expected in trials conducted with animals on pasture.

¹ Present address, Department of Animal Husbandry, Cornell University.

² Departments of Agricultural Chemistry Research and Animal Husbandry, Stillwater, Oklahoma.