Lighting conditions are one of the most important environmental factors to get right in a dairy barn. Increasing the duration of light exposure for lactating cows increases milk production by up to 10%, but light levels also significantly impact reproduction. Therefore, when the ultimate goal is to get heifers into the milking herd and producing high-volume, high-quality milk as quickly as possible, the right lighting system is crucial.
Lighting Systems for Dairy Cows
Typically, two photoperiods (the duration of daily light exposure) are used commonly in the dairy industry, long-day lighting and short-day lighting.
- Long-day lighting – 16 hours of light, 8 hours of dark per day
- Short-day lighting – 8 hours of light, 16 hours of dark per day
Bulb options and Barn Lighting Installation
Installing a well-designed lighting system lowers energy costs and improves livestock performance. The right light can both save and earn a dairy farmer money, so taking the time to get it set up correctly is essential.
There are four main bulb types available for barn lighting; Incandescents, Halogens, Fluorescents, and LED lighting. Incandescents and halogens have a shorter lamp life (750–3000 hours) and are less energy-efficient, making them more expensive over the long term. For dairy barns in colder climates, however, an incandescent bulb performs well in temperatures up to -20ºF.
Fluorescents and LED bulbs have long been popular in commercial and residential buildings due to their energy efficiency and long life span of up to 20,000 hours. As changing a light bulb inside a barn isn’t as easy as one above the kitchen sink, increasing numbers of dairy farmers switch to LEDs to lower costs and maintain light levels for longer. For farms in colder temperatures, fluorescents require a starting temperature of 50ºF, so installing a cold starting ballast may be necessary.
When installing a lighting system to reap the benefits of a long-day photoperiod, 15 footcandles* of light above the stall area is needed. Use a light meter and measure three ft above the stall’s surface to ensure adequate light levels.
* footcandles are a unit of measurement for light
How does the duration of light impact dairy cow reproduction?
Many studies have shown that varying photoperiods to coincide with the different stages of a cow’s lifecycle leads to improved milk production, reproduction, heifer growth, and feed efficiency.
Long-day lighting has been linked to earlier breeding and calving in heifers compared to those kept under short-day lighting conditions. This is because heifers fed high-energy diets reach breeding size faster, and while feed intakes remain the same under both long and short-day lighting, heifers with increased light exposure spend less time eating. Long-day lighting systems make a heifer more feed efficient, increasing their daily gain by an average of 1.9lbs compared to 1.7lbs under natural lighting, speeding up the process of getting a cow back to breeding weight.
In prepubertal cows, long-day lighting also has a positive impact on mammary development and lowers the age of puberty by one month on average. A slight reduction that compounds over time to mean more pregnant heifers over shorter periods.
Increased light exposure has been linked to leaner growth in breeding cows, but this does not seem to affect their calf production or impact skeletal growth. However, what is clear is that 24 hour light conditions are hugely detrimental to reproduction and result in longer days between breeding and more days open.
Darkness does not impact a cow’s ability to feed, water, milk, etc., but it can prevent employees from continuing operations in the barn. A cow cannot perceive light under 5 footcandles, so installing low-intensity red lights provides enough light for humans while preserving the long-light photoperiod for the cows.
Among the dairy industry, it is generally believed that long-day lighting has a beneficial impact on dairy cow reproduction, leading to earlier breeding and greater milk production. For dry cows, however, a short-day photoperiod has been shown to increase milk production during the subsequent lactation, which is why it’s essential to adapt lighting conditions to a heifer’s stage.
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