Upland sheep production systems based on the utilisation of enclosed sown pastures are considered in relation to environmental constraints, recent trends in marketing requirements and a continuing need to improve economic efficiency. The need for quantitatively described decision making in relation to both the testing, development and application of new technology is discussed with particular reference to those factors influencing herbage growth, utilisation and management.
Relatively few upland farms are capable of producing marketable fat lambs before the decline in returns per kg lamb in June. Although higher returns for heavier fat or store lambs can be obtained in the autumn, the degree to which this maximizes the returns per ha will be dependent upon the stocking rate and ewe and lamb performance during the summer. It will also be dependent on the extent to which there is competition for pasture in the autumn and its effect on ewe live weight and condition during the pre-mating and post-mating period; weight and condition will affect reproductive performance which has a substantial effect on returns per ha.
The significance of sward height as a means of controlling the performance of sheep grazing sown pastures is reviewed in relation to ongoing and completed systems experiments and development projects. It is concluded that, for practical purposes, a sward height held between 3.5 and 5.5 cm will provide a sound basis for management of the lactating ewe and suckling lamb until weaning. The means of achieving sward height control in varying farming situations and the development of commercially viable management systems is considered.
In the development of systems towards improving production efficiency, a better description of responses to both level and pattern of N used is required. The need for a better understanding of responses of the ewe in terms of ovulation rate and embryo wastage to changing sward characteristics in the autumn and to the use of supplementary feeding is also required. New techniques, such as the endocrine manipulation of reproductive performance, need to be assessed in relation to existing practices and performance.