The objectives of the project were to: identify and quantify the major factors responsible for decreasing the nutritive value of different species and varieties of sorghum and millet crop residues. quantify the effects of environment on the nutritive value of cereal crop residues. carry out feeding trials involving growth and metabolism studies to evaluate improved selected varieties of sorghum and millet for feeding ruminants. assess the effects of traditional methods of storage and utilization on the phenolic content of sorghum stover during the last few weeks of grain maturation using contrasting varieties.

The complex mixtures of phenolic compounds found in extracts from sorghum samples were poorly separated by existing high pressure liquid chromatography (HPLC). Some considerable time at the beginning of the project was therefore committed to the development of more satisfactory analytical methods. The use of counter current chromatography (CCC) with existing HPLC procedures, post column derivisation and diode-array detection markedly increased the ability to separate and identify phenolic components. The amounts of phenolic compounds and their distribution through sorghum plant components (i.e. leaf blade, leaf sheath, stem) was examined in a number of experiments. Particular attention was paid to differences between sorghum varieties of both bird and non-bird resistant types. The effects of environment on the production and accumulation of phenolics was followed in some experiments involving a number of different varieties and four different growing sites. Other factors potentially influencing phenolic content of sorghum which were also examined were time of harvesting (or utilizing) the stovers, and the effect of period of storage between harvesting and feeding. Relationships between the phenolic contents of sorghum stover and its nutritional value were examined using in vitro assessment of nutritional quality, chemical analyses of other plant components and near infra red (NIR) spectral analysis.

The toxicity of phenolic extracts to rumen bacteria was examined together with their effects on rumen microbial fermentation characteristics. New methods were also developed for both aspects of the work. Experiments, all conducted in Ethiopia, examined differences in intakes and performances of oxen receiving stovers from different varieties of sorghum with comparisons between bird and non-bird resistant types. These production type experiments were extended to sheep and to goats and were enlarged to incorporate feeding strategy work. These included the amount of feed offered and the physical form of feed. The chemical composition and nutritional value (assessed by in vitro techniques) of a number of African and Indian varieties of millet were assessed. The content of phenolic compounds found in these samples was very low.