Effect of force: Extent and severity of tissue damage was related to the force applied. Sequence of visible or chemical changes was consistent regardless of force applied.
Location: More tissue damage was encountered in bruises inflicted close to bones.
Effect of age: Chickens aged 4-6 weeks healed significantly faster (3.6 days) compared to broilers (age 8-10 weeks; healing time 4.4 days) and old birds (age 28-30 weeks; healing time 5.2 days).
Multiple bruises: In chickens with 1, 2 or 3 bruises, the most recent bruise healed in 4.4, 3.8 and 3.2 days, respectively.
Temperature: Sudden decreases in environmental temperature (45°F), decreased susceptibility to bruising and decreased healing rate compared to birds subject to higher temperature (86°F) which bruised easily but healed at a faster rate.