Nutritional implications of work in draught animals.

Draught animals have not been used to any great extent in agriculture in the developed countries since the introduction of tractor power in the 1930s and the rapid expansion of agricultural mechanization over the succeeding decades. In the Third World, however, draught-animal power continues to make an important contribution to rural and urban economies. In fields that tractors cannot reach, such as terraced hillsides, and on farms where the size and scale of enterprise, as well as finance, rule out tractors, animal power is the farmer’s only means of cultivating the land, other than by hand. It is difficult to see farmers replacing animal power by mechanical power in these situations. Indeed, some areas of the world have experienced an expansion in the use of animal power over the last two decades. In parts of sub-Saharan Africa for instance, where human power has tended to predominate in agriculture, disease control and prevention measures have now extended the areas in which animals can be kept and they are replacing human power for many of the tasks involved in land cultivation. Until relatively recently feeding working animals was an empirical business. Only during the last 15 years have scientists begun to obtain systematic information on the nutritional implications of work on draught animals. One of the main research topics has been to measure energy expenditure of draught animals so that their requirements can be quantified to the same extent as those of other classes of livestock. Other investigations have centred on the supply of nutrients to meet these requirements. Ruminants have received the most attention as they are numerically the most important draught animals (Ramaswamy, 1985). Cattle are used on many small farms in Africa, Asia and parts of Latin America. Water buffaloes are important in the more humid areas. Interest in the nutrition of working horses and donkeys, as opposed to the needs of horses in sport, has increased (Fielding & Pearson, 1991). Camels, elephants, mules, yaks, llamas, and some sheep and goats are also used as draught animals in a variety of different operations, from transport and cultivation to harvest operations and water lifting. The nutritional implications of work in these animals is less completely understood than those for cattle and buffaloes. In recent years there has been an increasing move towards the use of cows for work on many smallholder farms (Matthewman, 1987). In areas of constant feed shortage, for example in parts of Bangladesh, females are replacing male work animals, thus removing the need to maintain draught oxen on the farm. In other areas where draught animals are