| الوصف: |
Fatty acid levels vary between day and night milking. Many dairy cows are kept under whole light at night (LAN) illumination using a white light-emitting diode (W-LED) suspected of disrupting circadian rhythms. We investigated the effect of W-LED LAN and same lux level red LED (R-LED) LAN, which is known not to disrupt circadian rhythms in other mammals, on milk yield and circadian composition, compared to a natural light-dark (LD)-cycle of 10-11 h light. Cows under the natural LD-cycle showed circadian variation in milk-fat composition, characterized by higher health-promoting monounsaturated fatty acid (MUFA) and lower saturated fatty acid (SFA) levels in 13:30-h (day milk, DM) than 03:30-h (night milk, NM). W-LED did not affect milk and milk-fat yields, yet abolished the circadian pattern of milk-fat composition towards a less healthy fatty acid profile by lowering MUFA levels of DM. Switching W-LED to R-LED reversed these circadian disruptions. Therefore, R-LED and W-LED have no commercial advantage over the tested LD-cycle, while W-LED is disadvantageous, showing a circadian disruption. Accordingly, if the illumination is indispensable, the R-LED regime is preferable over W-LED for cow’s wellbeing and for preserving the natural milk-fat profile; while differentiating DM from NM from a commercial-health-promoting perspective. |
