Evaluation of crowding of caged laying hens (Gallus domesticus) using fuzzy set decision analysis

Crowding of caged laying hens was evaluated using fuzzy set decision analysis. Membership values and their complements were calculated for fuzzy sets of biological responses of laying hens for different levels of population density. Biological responses were egg production, mortality, and serum corticosterone levels of hens associated with population densities of 2, 3, 4, 5 and 6 hens per cage (1549 cm²). The data were set up as a fuzzy decision analysis problem. The optimal decision was based on the maximum of the minimum (maximin) membership values in the decision set. Based on the goals and constraints of the problem, the number of birds per cage at the break-even point (maximin) between a crowded and uncrowded condition was 3 hens per 1549-cm² cage. Fuzzy decision analysis of behavior, physiology, and productivity responses would be useful in evaluating the welfare of animals in existing and proposed environmental systems.