Factors Influencing the Secretion of Nitrogen in Sheep Saliva

SUMMARY Quantitative measurements were made on the volume of saliva secreted hourly by the parotid glands of merino sheep over a period of 24 hours on three separate days. At the same time fluctuations in the concentration of urea and total nitrogen in the saliva were studied in relation to the production of ammonia in the rumen and changes in the level of blood urea that occurred throughout the day. Both the rumen ammonia and the blood urea levels followed a relatively simple cyclical pattern over each 24‐hour period. However, two distinct phases were apparent in the salivary nitrogen cycle. The first, a short phase, followed the stimulation changes associated with eating. The second phase was prolonged and more complex. It was influenced by changes in the level of blood urea, but additional factors also operated in the second phase. Changes in the second phase of the salivary nitrogen cycle have been discussed in relation to fluctuations in the concentration of rumen ammonia and blood urea.