Abstract
1. A survey was conducted into down‐grading due to breast blisters at a large processing plant. 2. The relationships between incidence of down‐grading and age, body weight, sex, size of rearing site and its distance from the processing plant, and various weather conditions during the rearing period of each flock were examined using regression analysis. 3. Age and body weight and rearing site size were the only factors significantly correlated with amount of blistering.