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• Exposure to white LEDs with high blue light intensity increased plasma melatonin and cortisol concentrations during the dark period compared with induction lighting with low blue light intensity.
• White LED exposure tended to elevate plasma NEFA concentrations, suggesting that differences in light wavelength may influence lipid metabolism.
• No differences in milk production performance were observed between cows exposed to white LEDs and those exposed to induction lighting.

White LEDs (WLEDs) emit strong blue light, while induction lighting (IL) has lower blue intensity. This study investigated the effects of WLED and IL on milk production and blood parameters of lactating cows under a long-day photoperiod (16 h light, 8 h dark). Milk yield and composition did not differ between treatments. However, plasma melatonin and cortisol during the dark period were higher in WLED-exposed cows. Elevated cortisol suggests WLED may stress cows. Plasma NEFA tended to be higher in the WLED group, possibly linked to increased melatonin and cortisol. Further studies are needed to clarify how light wavelength differences during the transition period affect milk production and reproduction.

• Journal: Domestic Animal Endocrinology
• Title: Comparison of milk production and endocrine profiles of dairy cows exposed to either white light-emitting diode or induction lighting
• Authors: Y. Inabu, Y. Takakura, Y. Shinohara, M. Sunadome, R. Watanabe, S. Kushibiki, T. Sugino
• DOI: 10.1016/j.domaniend.2025.106958