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An experiment was conducted to study the effects of water-soluble carbohydrate extracts from Cabbage tree ('Cordyline australis'), 'Acacia' ('Acacia pycnantha'), and 'Undaria' seaweed ('Undaria pinnatifida') (at 5 or 10 g/kg diet) on the performance and gut microbiota of broilers. The plant extracts had no negative effect on growth performance, except that a high level of 'Undaria' extract in the diet suppressed the growth of broiler chicks. Ileal digesta viscosity was increased (P < 0.05) and apparent ileal digestibility of fat was depressed (P < 0.05) in birds fed the higher level of Undaria extract compared with the negative control. The plant extracts increased (P < 0.05) the numbers of lactobacilli in the ileum and caeca. The high levels of 'Acacia' extract and 'Undaria' extract significantly (P < 0.05) reduced the population of coliform bacteria in the ileum compared with the negative control group. The population of 'Clostridium perfringens' in caeca, but not the ileum, was reduced (P < 0.05) by the plant extracts. An antibiotic positive control reduced the population of 'C. perfringens' in both the ileum and caeca compared with the negative control group. The plant extracts altered microbial fermentation patterns in the ileum and caeca. The higher level of 'Undaria' extract reduced villus height in the ileum while the antibiotic diet resulted in higher (P < 0.05) villus height and villus height : crypt depth ratio compared with the negative control group. The results of the study suggest that prebiotic plant extracts had no negative effect on performance of broilers except at a high level (10 g/kg diet) of 'Undaria' extract. The plant extracts beneficially modulated the composition of the microflora in the ileum and caeca by increasing the number of lactobacilli and reducing harmful bacteria, such as potential pathogenic coliforms and 'C. perfringens'. |
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