Measures of space in pairs of hens in battery cages

An experiment was designed to test whether distances between 2 hens depend on the amount of available space in a cage. Interindividual distances were recorded as well as contact behaviour since it represents the most extreme reduction of interindividual distance. Pairs of hens from 2 strains (Rhode Island Red x White Plymouth and White Leghorn) were observed in cages of a battery-like system. The experimental schedule was: 1 week at initial densities; 10 weeks at changing densities; 1 week at final densities which were identical to the initial ones. The initial conditions were Small (900 cm(2)/bird), Medium (1400 cm(2)/bird) and Large (1900 cm(2) /bird). Each of these conditions was gradually changed to two intermediate conditions by means of successive weekly density increases or decreases (100 cm(2)/ bird) for 5 weeks: thereafter, the final densities were restored by successive weekly decreases or increases. The intermediate conditions were: Very Small (400 cm(2)/bird) or Medium (1400 cm(2)/bird) for small cages; Small (900 cm(2)/bird) or Large (1900 cm(2)/bird) for medium cages and Medium (1400 cm(2)/bird) or Very Large (2400 cm(2)/bird) for large cages. It was found that the larger the cages, the larger were the interindividual distances. Thus, it is the objective space which determines the occupation of a cage; hens do not use all the available space in their cage at any density. Contact behaviour was more frequent in the smaller the cages. The results are discussed in the context of welfare with regard to the minimum space required by laying hens in battery cages. Recommendations are made on the basis of the average distances which were recorded in all the experimental conditions.