Studies on the alimentary tract of merino sheep in South Africa. IX. The H-ion concentration in the forestomachs of fistula sheep under different experimental conditions

Abstract

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 to 7.7. 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.