Interaction of dietary antibiotic supplementation and stocking density on broiler chick performance and immune response.

The growth depression caused by reducing the space allowance in battery brooders from 0.047 to 0.019 m2 per chick was ameliorated by subtherapeutic inclusion rates of dietary antibiotics. However, the interaction of antibiotic supplementation and stocking density was not significant for the variables measured. Increasing stocking density improved the efficiency of food utilisation. The high density regimen resulted in decreased weights of the bursa and thymus relative to body weight but there was no concurrent reductions in antibody response, spleen weight or mortality.