Dear Aggie: Does lack of light affect cattle like it affects us?

Answer: These dark and gloomy winter days got you down? It’s common for humans to experience seasonal depression during the winter months, with a decrease in sun exposure and being cooped up indoors. Just like humans, livestock can experience similar feelings during the winter. In order to mitigate this, farmers can provide adequate artificial lighting to increase light exposure and productivity.

The livestock’s biological clock is regulated by light. A lack of light depresses metabolism and causes increased melatonin output; we see this effect in the shorter days of winter. According to extensive research, daily exposure of light improves the health and productivity of livestock. Regulating exposure to light influences the levels of melatonin, the hormone that affects functions such as sleep and contributes to animal well-being. There is a compilation of studies on how lighting, especially lighting during the winter months, effects dairy cattle.

In recent studies, it has been recommended that cows need 16 hours of daylight and eight hours of darkness each day to produce maximum amount of milk. On the basis of this advice, many dairy producers have added timers to barn lights to provide this regimen year-round, especially during the shorter days in the wintertime. Natural winter daylight, roughly 10 hours of light and 14 hours of darkness is drastically different than what is required to achieve maximum production of milk. In dairy herds with poorly lit barns and rely on natural light to light the majority of the barn, they could see a decrease in milk production with the change in seasonality lighting.

Long days can be created by exposing the cows to artificial or a combination of natural and artificial light. Researchers have found that increasing light from less than 12 hours a day to 16-18 hours a day, increases milk production by 7-10%. Long-day lighting also usually increases dry matter intake, up to 6%, to supply the extra nutrients needed for milk production. Farmers can see this change begin around two to four weeks after implementation. It is critical for the response that cows have an uninterrupted dark period. Cows under continuous light have production levels similar to cows that don’t have enough light. Dim red bulbs, 7.5 watt bulbs at 20-30 foot intervals, can be used during the dark period if cows must be moved or observed during that time.

In the growing heifer, long-day lighting has been found to increase gain, feed efficiency and mammary system development. One study with long-day lighting, 16 hours, increased heifer growth rate by 10%. It is interesting that this extra growth is not just a function of extra dry matter intake. In one of the first studies looking at differences in the growth rates between heifers with supplemented lighting of 16 hours and natural lighting, heifers in the supplemented lighting group averaged 1.9 pounds of daily gain compared to the 1.7 pounds for the heifers in a natural lighting scheme.

Lighting affects many different aspects of a dairy cow’s productive life, starting at an early age. Farmers have many different changes they could implement to increase milk production, including manipulating the amount of light available throughout the day. One practice that would yield significant results would be to start managing lighting at a young age. This overall leads to positive results seen within cattle, increasing well-being and herd efficiency.

If you would like to learn more, contact Gabby Wormuth, Cornell Cooperative Extension of Jefferson County’s dairy & livestock specialist.

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