| Autor: |
Simon Mole, Larry G. Butler, Carlos J. Morell, John C. Rogler |
| Rok vydání: |
1990 |
| Předmět: |
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| Zdroj: |
Biochemical Systematics and Ecology. 18:183-197 |
| ISSN: |
0305-1978 |
| DOI: |
10.1016/0305-1978(90)90056-l |
| Popis: |
The consumption and utilization of food by rats fed diets both high and low in condensed tannin was analysed on a dry weight basis and on a Kjeldahl nitrogen basis. Growth analyses followed the protocol devised for insects by Waldbauer. The hypothesis that tannin-induced proline-rich salivary proteins (PRPs) diminish the antinutritional effects of dietary polyphenolics in mammals was investigated by supplementing diets with 0.05% propranolol to suppress PRP production. Rats fed diets high in tannin gained less weight than those fed low tannin diets. This effect was too pronounced to be explained by differences in feed consumption and could only be attributed to depressed efficiency in converting injested food to body matter. The reduction in approximate digestibility (AD) with high tannin sorghum diets was low relative to the severe reduction in the conversion of digested food into body matter (ECD) for high tannin diets. The main growth reducing effect of tannin thus appears to have been on the post-absorptive utilization of nutrients rather than on the digestibility of the diet. On a nitrogen basis, AD(N) is reduced in the presence of tannins so tannins did act preferentially on the digestion and absorption of nitrogen. Nevertheless, on a nitrogen basis ECD(N) was even more substantially depressed by tannins and so it could not be concluded that tannins act only or even mainly as digestibility-reducing agents. Propranolol only produced adverse effects in combination with tannin but these were much more severe than those with tannin alone. Further evidence suggested that the cause was the suppression of PRP production. PRPs are known to bind to tannins in competition with other proteins and their absence denies the animal the means to neutralize dietary tannin. This study also examines the effect of sodium chloride (0.5%) in the diet following a previous report that salt alleviates the effect of dietary tannins in mice. In our experiments this had negligible effects. We conclude by comparing our data for a mammal to previous studies on insects using these same parameters to assess consumption and utilization of foods. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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