AN ECONOMIC COMPARISON OF MANAGEMENT STRATEGIES ON REPRODUCTION AND REPLACEMENT IN SOW HERDS USING A DYNAMIC PROBABILISTIC MODEL

A dynamic probabilistic PC-model is used to compare six management strategies on reproduction and replacement in sow herds. The model uses the Markov chain approach to simulate herd dynamics, and derives from that technical and economic results of the herd. Under the circumstances studied, strategies based on the use of an economic culling index I and II, including age and productive history of individual sows, are the best. In the basic situation annual culling rate (CR) amounts to 47.4% and gross margin per sow per year (GM) Dfl. 1086. Economic differences between strategies depend mainly on realised differences in CR. Strategies that refer to guidelines given by extension service lead to an increase in CR (plus 5-6%) and a decrease in GM (minus Dfl. 15 ). The most strict strategy (no reinseminations) achieved the highest CR ( + 24.5%) and the lowest GM (minus Dfl. 62). A very liberal strategy, allowing in all cases 4 inseminations, resulted in almost the same results as strategies I and II. In case of low farrowing rates, low slaughter values or high prices of replacement gilts, differences between strategies I and II and more strict strategies increase. The model used is considered a useful tool in on-farm decision support, as an expansion of current management information systems. It allows for input modification, making it possible to study easily sensitivity for price and production circumstances.