Suppression of Melatonin Secretion in Île‐de‐France Rams by Different Light Intensities

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Abstract
The intensity of cool, white, fluorescent light required to suppress melatonin secretion in Ile-de-France rams were investigated. Animals were conditioned to 12L:12D, lights on 0600 hours, 104 .mu.W/cm2 (350 lux) at eye level and subjected to a 1-hour light pulse beginning 3 hours after lights off. Plasma melatonin measurements indicated that secretion was significantly suppressed by 0.30, 7.46, and 26.32 .mu.W/cm2 (1.02, 25.10, and 88.60 lux, respectively) but not by 0.043 .mu.W/cm2 (0.15 lux). A clear dose-response relationship was apparent between light intensity and degree of melatonin suppression.
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