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Abstract
The pH of the contents at 10 positions along the gut of germ‐free and conventional chicks was measured in situ. Similar measurements were made on groups of conventional birds either fasted for 18 h or fully fed. The buffering capacity of caecal contents from germ‐free and conventional birds was also measured by titrating with hydrochloric acid.
The pH of the germ‐free gut contents were generally slightly higher than those of their conventional counterparts. These differences were greatest at the midintestine area and caeca. No differences were found between contents of either the proventriculus and gizzard of each group.
Starvation increased slightly the pH of intestine and lowered that of crop, proventriculus and rectum.
More acid had to be added to conventionalthan germ‐free caecal contents to attain pH 4 both when expressed in relation to the complete contents and per g of dry matter.
It was concluded that the microbial flora, by its secretion of acidic metabolites in general had greatest effect on pH in areas of the gut where it was most dense. This was assumed to be due to the secretion of acidic metabolites which caused a consequently greater secretion of neutralising buffering substances by the gut wall.
Notes
Present address: Medical Research Council Laboratory Animals Centre, Woodmansterne Road, Carshalton, Surrey, England.