How does this work?
Cows are sensitive animals and their day-and-night rhythm is of paramount importance. Particular light levels are necessary to impact the difference between the night-and-day rhythms on the cow’s body. A carefully planned lighting scenario will provide sufficient light to the cows in daytime and ensure a (dark) resting period as well. Outside, in daytime, as soon as a certain light level reaches the retina, the cow’s nerves will send a signal to the hypophysis in the brain to lower the secretion of the hormone melatonin. This hormone results in sleepiness, increases the percentage of body fats, and disturbs the animal’s productive capabilities. When the melatonin level decreases, another hormone, viz. IGF-I, increases in the animal’s blood. The function of the IGF-I hormone is to stimulate animal activity and, hence, its milk production. Therefore, more light means an increase of milk production. In barns there is usually not enough light, especially in winter time, to reach a natural light level. With correct lighting control, cows benefit most from a light intensity between 150 and 200 lux during a 16 hour period, combined with an 8 hour dark period. In the summer season, the natural light level may often be sufficient in itself, although lighting control may – even in summer time – provide benefits on cloudy, darker days.
