The objectives of this paper were to investigate the overall performance of Tswana and Simmental x Tswana genotypes as milk producers, obtain the tradeoffs between milk and meat production and formulate an optimum production strategy based on economic considerations. An array of performance measures was used for comparing the two genotypes under alternative production strategies, starting with conventional measures of performance, such as fertility and mortality, continuing with energetic efficiency and ending with economic efficiency. From this array of performance measures the rational livestock producer will choose firstly on the basis of economic criteria, and secondly, within the economically superior production alternatives, on the basis of his subjective conception of what constitutes an overall viable system.
The choice between the two genotypes as regards their potential for milk production without impairing herd viability is clearly in favour of ST. At the present cost of feed concentrates, a supplementation level of about 2.5 kg/head/d of ST lactating cows and a milk offtake rate of 60% yields the highest economic payoff. However, such a strategy is also associated with lower calf growth rates, a reduction in calf survival and a higher incidence of nutritional stress compared with the present system. The generally cautious livestock producer would probably view these abort-term indicators of herd performance as dangerously low and opt for a lower return at a lower risk. Thus, on the basis of both economic efficiency and subjective evaluation of herd viability and performance, a milking rate of 40% concurrent with a supplementation rate of 1.5 kg/head/d for lactating ST cows is suggested. For the breeding herd of 40 cows considered in this analysis, such a policy results in an annual offtake of about 48 t of milk and 7.5 t of carcass weight and requires about 10.3 t of feed concentrates per year.
Under the present pricing structure and the assumptions made in this analysis, adopting a mixed beef - dairy production strategy with ST cows results in a substantial increase of producer incomes. This conclusion proves robust to changes in the cost of concentrates, and still applies even when this triples or quadruples from its present level, and equally robust to variations in the prices received by livestock producers for milk and meat. Consequently, Botswana's prospects of meeting its domestic dairy needs appear good.
Despite the strong economic rationale for dairy production systems with crossbred cows, the promotion and implementation of a dairy development policy based on crossbreds must be carefully considered case by case. Consequently, the results obtained here should not be extrapolated to other environments without the regard for differences between the production systems. The extensive nature of Botswana's rangeland does not lend itself to dairy production unless the dairy enterprise is favoured by relatively good feed resources and has easy access to a reliable market for its products. This, coupled with the relatively small and isolated consumer centres, implies that dairy enterprises must be located near communal areas and must have security of land tenure, which is a precondition for making the necessary investments.
Finally, locally available feed resources are at present certainly inadequate to supply the high-quality feed needs of dairy operations on a large scale. These additional feed resources will have to be imported. The macro-economic implications of this latter option, both in terms of foreign exchange costs and security of supplies, need to be contrasted with those of continuing present dairy import trends. However, these macro-economic aspects are beyond the scope of this study.
