Cow's eye

Most times, you'll be hard-pressed to find a dairyman who wouldn't take another 8 to 10 percent more milk per cow. Long-day lighting could help get them there.

"In general, milk yield rises 8 to 10 percent with long-day lighting, and cows eventually boost intakes to support the greater milk yield," noted Geoff Dahl, University of Florida, when discussing photoperiods at the Penn State Dairy Cattle Nutrition Workshop.

When light hits the eye, a cascade of hormonal events is triggered in the brain's pineal gland. This cascade begins with a signal to suppress the release of the hormone melatonin. As darkness falls, the inhibitory impact of light is dampened, and melatonin secretion rises.

Animals use the daily fluxes in the duration of elevated melatonin concentrations to set their internal clock, which influences the secretion of a number of hormones.

With long-day lighting, cows are exposed to 16 to 18 hours of light and 6 to 8 hours of darkness.

Research conducted by Dahl compared cows that were given 16 hours of light exposure to those provided with 12 hours of light. Cows exposed to 16 hours of light had greater circulating levels of IGF-1, a hormone that promotes tissue growth and development. This corresponded with a milk yield boost.

When compared to other lighting schemes, Dahl noted, "The Goldilocks of light is 16 to 18 hours."

The duration of darkness is just as important. "To see the benefits, you need to provide an uninterrupted 6- to 8-hour period of darkness," added Dahl.

Dark refers to the absence of artificial light, excluding dim red lights. "Herds milking 3x must also strive for 6 hours of darkness," noted Dahl. Milking and lighting schedules can be coordinated by barn, or dim red lights can be used to facilitate cow movement.

"Cows should not be left on a continual (24 hour) lighting scheme. They physiologically can't handle it," he concluded.

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(c) Hoard's Dairyman Intel 2015
November 30, 2015
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