Lighting programs in commercial turkey production manipulate growth and reproduction with welfare consequences that are less visible than physical health problems but equally significant.
Turkeys kept under continuous or near-continuous light cannot follow their natural circadian rhythms of activity and rest. Sleep deprivation causes elevated cortisol, increased fearfulness, and abnormal behavior. The disruption of normal light-dark cycles is a form of chronic stress that is invisible in production metrics but measurable in behavioral and physiological welfare indicators. Providing adequate dark periods is a simple, low-cost welfare improvement whose adoption has been slow due to inertia rather than genuine production constraints.