The digestion of food by the grazing sheep. IV. The effect of mastication on the release of soluble plant nitrogen

Abstract

The rate of release of soluble nitrogenous constituents from plant cells during the ingestion of green pasture plants has been studied. Boluses were collected either from sheep with oesophageal fistulae or from the rumen in sheep fitted with large rumen cannulae. Sheep grazing on pastures of different heights ingested food at widely varying rates. This was indicated by the rate of formation of boluses, which during 10-min collection periods ranged from 10.5 to 62.5 g/min. The rates at which bolus nitrogen reached the rumen ranged from 45 to 300 mg/min; of this, 20–45% (mean 26) was extractable with cold water. Approximately 50% of the extractable soluble nitrogen was protein nitrogen.