Gastro-intestinal pH and total lactic acid bacterial count
The stomach pH of the treated fish groups was lowered by the addition of KDF into the fish diet (Table 4). A dietary inclusion of (0.2% and 0.3% KDF) resulted in a significant (p < 0.05) reduction in the stomach pH compared with those of fish fed on the control diet. The pH levels decreased from 3.4 in the control group to 2.96 in the group fed on 0.3% KDF. However, no significant difference was found between the stomach pH of the control group and the group fed on 0.1% KDF. The upper gut pH showed a pH reduction by increasing the dose of the salt of the organic acid. A significant reduction of 0.45 in the pH level in the group treated with 0.3% KDF and of 0.23 in the group treated with 0.2% KDF compared with control group was observed. The results recorded a numerical reduction in the pH of other gut portions in all treated groups, but these were not significantly lower than those of the control group. There was a significant increase in the LAB count isolated from the gut of the treated groups fed on 0.3% KDF compared with those for the other treated groups. The LAB count varied from (23 ± 0.2 × 102 cfu/g) in the control group to (24 ± 0.3 × 103 cfu/g) in the groups fed on 0.3% KDF (Table 4). The isolated bacteria were gram positive cocci and bacilli, which were non-motile and oxidase- and catalase-negative.