Department of Animal Nutrition and Management, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Department of Animal and Aquacultural Sciences, Faculty of Biosciences, Norwegian University of Life Sciences, Ås, Norway.
PLoS One. 2021 Jul 22;16(7):e0253776. doi: 10.1371/journal.pone.0253776. eCollection 2021.
Artificial light can be used as a management tool to increase milk yield in dairy production. However, little is known about how cows respond to the spectral composition of light. The aim of this study was to investigate how dairy cows respond to artificial achromatic and chromatic lights. A tie-stall barn equipped with light-emitting diode (LED) light fixtures was used to create the controlled experimental light environments. Two experiments were conducted, both using dairy cows of Swedish Red and light mixtures with red, blue or white light. In experiment I, the response to light of increasing intensity on pupil size was evaluated in five pregnant non-lactating cows. In experiment II 16h of achromatic and chromatic daylight in combination with dim, achromatic night light, was tested on pregnant lactating cows during five weeks to observe long term effects on milk production, activity and circadian rhythms. Particular focus was given to possible carry over effects of blue light during the day on activity at night since this has been demonstrated in humans. Increasing intensity of white and blue light affected pupil size (P<0.001), but there was no effect on pupil size with increased intensity of red light. Milk yield was maintained throughout experiment II, and plasma melatonin was higher during dim night light than in daylight for all treatments (P<0.001). In conclusion, our results show that LED fixtures emitting red light driving the ipRGCs indirectly via ML-cones, blue light stimulating both S-cones and ipRGCs directly and a mixture of wavelengths (white light) exert similar effects on milk yield and activity in tied-up dairy cows. This suggests that the spectral composition of LED lighting in a barn is secondary to duration and intensity.
人工光照可用作增加奶牛产奶量的管理工具。然而，奶牛对光的光谱组成的反应方式知之甚少。本研究旨在调查奶牛对人工非彩色和彩色光的反应。采用配备发光二极管（LED）照明装置的栓系牛舍来创造受控的实验光照环境。进行了两项实验，均使用瑞典红牛和具有红光、蓝光或白光的混合光的奶牛。在实验 I 中，评估了 5 头妊娠非泌乳奶牛对瞳孔大小随光照强度增加的反应。在实验 II 中，对妊娠泌乳奶牛进行了 16 小时的非彩色和彩色日光与昏暗的非彩色夜间照明相结合的测试，以观察对产奶量、活动和昼夜节律的长期影响。特别关注白天的蓝光可能对夜间活动的持续影响，因为这在人类中已经得到证明。增加白光和蓝光的强度会影响瞳孔大小（P<0.001），但增加红光强度对瞳孔大小没有影响。在整个实验 II 期间，产奶量保持不变，并且所有处理的褪黑素在昏暗的夜间光照下比在日光下更高（P<0.001）。总之，我们的结果表明，发出红光的 LED 灯具通过 ML-锥体间接驱动 ipRGCs，蓝光直接刺激 S-锥体和 ipRGCs，以及混合波长（白光）对栓系奶牛的产奶量和活动产生类似的影响。这表明牛舍中 LED 照明的光谱组成次于持续时间和强度。
