The objectives of this project were: to select species of tropical forage legumes which by conventional methods of analysis appear to have similar nutritive value, but which support consistently different levels of animal performance, to use biochemical and microbiological methods to identify how tannin levels effect fibre digestion in the rumen, and to develop hypotheses which relate those differences to the observed effects on livestock performance.

Browse legumes are an important source of fodder for ruminants throughout the tropics. However, the presence of certain-nutritive factors may reduce intake and hinder the utilisation of these fodders for livestock.

Results showed that although the presence of tannins may decrease the loss of nitrogen from the rumen (this nitrogen is of no use to the animal as it is excreted in the urine) and increase nitrogen supply to the duodenum, in this experiment, nitrogen utilisation was not improved either because the increased nitrogen available in the rumen could not be utilised due to lack of energy, or because of poor digestion in the duodenum. The project also showed that feeding a legume with a high tannin content, (F. macrophylla), affected the digestibility of a low tannin forage, suggesting the need for a better understanding of the interactions between feeds to identify the principles on which to develop recommendations on optimal ration components (e.g. where a choice can be made as to which fodder tree species to grow).