Parotid saliva of sheep. 1. Effects of level of intake and type of roughage

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Abstract
In three experiments, quantitative collections of saliva were made from the right parotid duct of six Merino wethers. Experiment 1 assessed the repeatability of the collection techniques and found little difference in salivary parameters measured at intervals over a 6-week period. When chopped lucerne was given at three levels (experiment 2) the secretion rate of parotid saliva (g 19.5h-1) increased (P < 0.01) with increasing lucerne consumption as did the concentrations and amounts of total and urea nitrogen in saliva (P < 0.05 to P< 0.01). Only minor changes in the secretion of total and reducible sulfur occurred. Plasma urea nitrogen (P < 0.05) and blood sulfate sulfur (P < 0.01) concentrations increased with increasing lucerne consumption. Values are given to indicate the variability between sheep in volume and composition of parotid saliva secretions. In experiment 3 the sheep were offered four different roughage diets. The secretion rate of saliva (g 19.5h-1) increased (P < 0.01) when more fibrous roughages were given. The type of roughage also affected (P < 0.01) the concentrations and amounts of total and urea nitrogen in saliva, but there was little effect upon the secretion of total or reducible sulfur. Plasma urea nitrogen and blood sulfate sulfur concentrations were different (P < 0.01) on the various roughage diets. The results are compared with the findings of previous research, and estimates of the amounts of nitrogen and sulfur recycled to the rumen in saliva are made.