Yellow light improves milk quality, antioxidant capacity, immunity, and reproductive ability in dairy cows by elevating endogenous melatonin.

Abstract

BACKGROUND: Light is an important environmental factor influencing animal production. In livestock production, light management techniques are common. They can enhance production and reproductive performance. AIM: This study investigated the effects of light wavelength on dairy cows. It focused on production, immunity, antioxidant capacity, and reproduction. It emphasized yellow light. METHODOLOGY: In Experiment 1, 196 cows were divided into three groups and subjected to natural dark, red, and yellow light for 2 weeks. Results indicated yellow light was most effective. This prompted a second experiment. In Experiment 2, 80 postpartum cows received nocturnal yellow light until their next calving. Blood and milk samples were analyzed for immune, antioxidant, and reproductive markers. RESULTS: The findings demonstrated that yellow light significantly enhanced milk yield (32.39-37.58 kg) and composition, including milk fat percentage, milk protein percentage, lactose percentage, milk urea nitrogen, and somatic cell count. It improved immune status (TNF-α: 181.10-174.90 pg/ml, IL-6: 117.30-113.90 pg ml, IL-10: 31.18-32.86 pg/ml), antioxidant status (superoxide dismutase: 111.80-117.60 U/ml, total antioxidant capacity: 8.28-8.76 U/ml), and superior reproductive performance (the interval to first postpartum estrous cycle: 61.72 ± 1.27 to 56.91 ± 1.14 days, the pregnancy rate after first-insemination: 23.68 ± 4.42% to 38.15 ± 5.00%, the pregnancy days after first-insemination: 96.84 ± 4.88 to 82.95 ± 4.50 days). This was associated with enhanced melatonin levels in serum (36.30-59.48 pg/ml) and milk (20.49-29.22 pg/ml). CONCLUSION: Nocturnal yellow light exposure, by elevating endogenous melatonin, is a viable non-invasive strategy to improve overall productivity, health, and welfare in dairy farming.