With the wide-spread adoption of electrical lighting, humans and animals became exposed to Artificial Light at Night (ALAN) of high intensities short wavelength illumination, similar to those of day time, resulting in suppression of Melatonin (hormone that mediate the darkness signal between the master clock to the tissues) production and consequently causing real health hazard to humans. In Jun 2012, American Medical Association declared that environmental factors that cause misalignment of internal physiology rhythms should be classified as “Chrono-disruptors” caused by “Light pollution”.
In the last several years we have conducted experiments that aimed to investigate the effect of ALAN on livestock welfare, performance and feed efficiency (FE). Suckling calves that were exposed to ALAN showed disruption in their heart rate (HR) rhythmicity and had significantly higher HR and heat production and lower melatonin concentration in the plasma compared to calves that were not exposed to ALAN. The results also showed that ALAN reduces FE and this trend was also maintained during the various stages of growth, hinting that there is a critical period for metabolic programming. Dairy cows and goats that were exposed to ALAN showed lower concentration of melatonin in plasma and milk and lower FE. They also had lower milk quality and their HR rhythmicity was disrupted compared to the animals that were exposed to natural illumination. These new results support the claim that ALAN should be defined as “light pollution” that has a negative effect on the welfare, health and production efficiency of livestock.