Water is used by the herbivore as a medium for physical and chemical energy transfer, namely for evaporative cooling and intermediary metabolism. Therefore animal water turnover cannot be considered in isolation from energy metabolism. A detailed discussion of the physiology of water and energy use in the herbivore is given and a diagram of the interrelation between the two has been constructed. A simplified version of this 'soft' model has been used to simulate the energy budget and water turnover of the main livestock species in the African pastoral production system during the dry season. The analytical background to the model has been obtained from the literature, supported by field observations. However, data from Africa are scarce.
The information obtained on water and energy use by livestock in the traditional pastoral system has been applied to water and livestock development in the context of range, woodland and livestock management. There are numerous implications for research, notably for hypothesis and modelling, as well as component research for which priority topics and species are given. The research emphasis is placed on field work which is not as difficult as it used to be, because technical equipment is becoming increasingly compact and rugged and communications between the field and advanced laboratory facilities have improved.
An important contribution that the developer, and hence the scientist can make to the productivity of pastoral systems will be to increase the efficiency with which scarce water and energy resources are used.
