Ophthalmopathy in a broiler breeder flock reared in dark-out housing

Eight 22-week-old broiler breeder replacements were presented from a flock experiencing a mild mortality problem. Approximately 2-3% of the birds were not getting onto the slats to eat or drink. The birds had been reared in dark-out houses under an experimental lighting schedule. Upon examination, several birds appeared blind or partially blind; others exhibited a photophobic response. Two birds lacked a unilateral menace reflex. No other gross abnormalities or lesions were noted. Histopathologic sections of the eyes revealed retinal degeneration and detachment with early degenerative lesions in one lens. The breeder flock came into production normally but peaked below average. Light intensity in the pullet house was measured at 0.3 footcandles (3.2 lux). Although the lighting program under which the pullets were grown is suspect, the etiology of the disorder remains unclear.