Broiler production under varying population densities: a field study

The influence of two different stocking densities (approximately 25 and 30 kg live weight per square meter floor area) on production performance, health and housing environment was studied on 9 Swedish broiler farms during the summer and winter season, 1992/93. Bird performance data were collected by the famers and by the processing plants. Data on environmental and bird conditions were collected when the birds were 3 weeks of age and the day before slaughter, always by the same person (the National Standards Officer) together with a veterinary officer employed by the local processing plant. With a few exccptions there were significant differences hetween the summer and winter season and between farms considering all studied variables. There were also several significant seasonxfarm interaction effects. Stocking density significantly influenced growth rate, and birds in low density groups were, on average, 27 g (1.8%) heavier than in high density groups. Close to slaughter there were relatively large local variations in individual houses considering the concentrations of air humidity, ammonia and carbon dioxide, especially during the winter season. The maximum ammonia concentrations noticed the day before slaughter were, on average, 16 ppm during the summer and 25 ppm during the winter. Increasing stocking density increased air humidity and decreased litter dry matter content. Lesion scoring of intestinal walls and litter examination indicated low infection presure of coccidiosis. It is proposed that maximum permitted stocking densities in broiler houses should be related to the quality ofthe management of individual farms. As a consequence of these results the maximum stocking density permittcd for broilers in Sweden has been increased since 1994 from 25 to 33 kg live weight per m 2 floor area for farmers fulfilling certain levels of management.