1. Depending on the carbohydrate content of the diet, the pH of
ruminal ingesta in Merino sheep, immediately after withdrawal through
rumen fistulae was found to vary between pH 5.5 and 6.8.
2. Whereas the feeding of lucerne hay yielded slightly acid ingesta
(pH 6.45 to 6.95), fresh green lucerne (flowering stage), as well as mature,
veld grass hay produced slightly alkaline conditions varying from pH 7.3
3. Normally the pH of rumen ingesta in sheep showed slight fluctuation
only during the digestion of a single meal, the tendency being towards
increased acidity within the first 4 to 6 hours after which it steadily reverts
to its previous level.
4. The "in vitro" fermentation of glucose by rumen ingesta resulted
in a rapid and definite acid production with pH ranging from 6.25 to 7.00.
5. The addition either of N. HCl or of N. NaOH to rumen material
showed that it was relatively well buffered between the pH 6 .8 to 7.8,
whereas beyond this range both on the alkaline and on the acid side the
efficiency of this buffering was distinctly reduced.
6. Dosing of 150 c.c. N. HCl directly into the rumen of sheep caused a
distinct though transitory depression of pH to 5.9, which however had no
obviously detrimental effects on ruminal function.
7. The colour and odour of rumen ingesta was found to be closely
correlated with its H-ion concentration and its ability to ferment glucose.
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