The potential of ruminants for the utilization of fibrous low-quality diets.

The continuously-increasing demand for food by a steadily-growing human population has created strong competition between man and animals for certain feedstuffs that can be used by both. Rations used for intensive beef and milk production are largely based on grain, which is the staple food for man in most of the developing countries with a general protein-energy deficiency (Lapedes, 1980). It has been estimated that in 1990 there will be a deficiency of grain for human consumption in the order of 100 million tonnes. At present, approximately 4090 of the world’s total grain production is used in the industralized countries, which contain 20Y0 of the world’s human population, and 60% of this grain is given to animals. Only 15% of total grain used in animal feeding goes into animal production in developing countries (Byerly, 1978; Dale, 1979). There seems to be another argument against intensive animal production now and in the future. The efficiency of conversion of dietary components to animal products is generally very low. The conversion of dietary crude protein to animal protein is 22-2570 in egg, milk and poultry production but as little as 4-5% in beef and mutton production. Energy conversion rates are equally poor (Janick et al. 1976). So the question has to be raised whether such low conversion efficiencies will really permit animal production in the future. On the other hand, only about I 17’ of the world’s land surface is arable land; of the remainder, 23.57’0 is permanent pasture, 32.4% forest and woodlands, and 34.370 other land (Crabbe & Lawson, 1981). Approximately, only half the dry matter harvested from arable land can be directly used for human consumption. The other half, together with material drawn from pastures and ‘other land’ (together more than 50% of land surface), can be utilized for feeding herbivorous animals. Such material includes fibre, by-products and waste from processing human food, protein of extremely-low value, and non-protein-nitrogen compounds. The enormous advantage lies in the fact that material unfit for human consumption can be converted into highquality animal protein although the conversion efficiency is generally low. Millions of tonnes of crude fibre are available for animal use but only a small part of it is actually consumed. Unfortunately cellulose is often incorporated into indigestible lignin structures thus reducing overall cellulose utilization (Van Soest, 1982). The digestibility of various lignified materials by ruminants can be increased by chemical treatment (Klopfenstein et al.