A Study on Nutritional Aspects of Forages |
A major constraint to the use of legumes as a livestockfeed is the presence of toxic and antinutritional constituents. Theseconstituents have different but adverse effects on animal performance includingloss of appetite and reductions in dry matter intake and protein digestibility.Tannins inhibit the utilization of nutrients through astringency, enzymeinhibition and reduced forage digestibility (Onwuka, 1983). Phytates chelate severalmineral elements, especially Ca, Mg, Fe, Zn and Mo, and interfere with theirabsorption and utilization (Ologhobo, 1980). Oxalates affect Ca and Mgmetabolism (Oke, 1969) and react with proteins to form complexes which have aninhibitory effect on peptic digestion (Oboh, 1986). The saponins act on thecardiovascular and nervous systems as well as on the digestive system. Largedoses of legume juices containing saponins cause distention of the rumen(Gestetner et al, 1986). Cyanogenic glycosides impart a bitter taste, reducepalatability and cause toxicity. Intact plants contain little, if any, freehydrogen cyanide but this may be formed rapidly under the influence ofß-glucosidase in cells injured by freezing, drying or maceration.