The results of twelve production cycles of broiler chickens, fattened in a private farm in the years 2001–2003, were analysed in the research. The broiler fattening was carried out in the intensive system including straw bedding, and the chickens were weighed every seven days throughout the whole fattening period. The adjustment of the model and estimation of the function parameters: feed costs as well as average and marginal product, were attempted. The intersection points of the average and marginal product functions made it possible to approximately calculate the moment in which further broiler fattening became non-profitable because of the feed costs.

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