How to Use Sunlight Exposure to Improve Milk Production in Dairy Cattle

The photoperiod effect of sunlight influences physiological processes in cattle that can increase milk yield and milk components.

Carson O.
9 Min Read

Milk production is a key economic factor in dairy farming operations. Finding ways to maximize milk output efficiently and cost-effectively is crucial for dairy farmers to maintain profitability. One often overlooked factor that can significantly influence milk yield is sunlight exposure for dairy cows.

Providing dairy cows access to direct natural sunlight and daylight cycles has been shown in multiple studies to positively impact milk production. The photoperiod effect of sunlight influences physiological processes in cattle that can increase milk yield and milk components. Understanding the science behind this phenomenon and implementing practical sunlight exposure practices can help unlock the benefits of this natural solution for improved productivity in a dairy herd.

How Sunlight Influences Milk Production

There are several mechanisms by which sunlight exposure influences milk synthesis and overall production in dairy cows:

Vitamin D Synthesis

Just like in humans, when cows are exposed to UV rays in sunlight, their skin produces vitamin D. This vitamin D is then activated in the liver and kidneys to create the active hormonal form known as calcitriol. This hormone plays a key role in calcium homeostasis and metabolism which is essential for key bodily and mammary gland functions.

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Circadian Rhythm Optimization

Sunlight exposure helps synchronize circadian rhythms in dairy cows. The day-night cycles regulate physiological processes like metabolism and hormone secretion to peak at strategically important times. When circadian rhythms are aligned optimally with natural daylight patterns, it can improve metabolic efficiency and grazing patterns in ways that promote better milk production.

Increased Melatonin Regulation

The hormone melatonin is produced in the pineal gland of dairy cows. Sunlight suppresses melatonin, while darkness stimulates it. This daily fluctuation influences reproductive hormones like estrogen, gonadotropin secretion, and prolactin which affect milk yields. Managing melatonin levels with sunlight exposure helps regulate these interrelated hormonal systems.

Improved Immune Function

Vitamin D synthesized when cows are exposed to UVB rays from the sun also plays an important role in modulating immune function. Optimal vitamin D levels can help dairy cows fight infection and illness, which supports their energy levels and productivity.

Implementing Sunlight Exposure Best Practices

Now that we understand the various physiological factors at play, here are some best practice recommendations for using sunlight to maximize milk production in dairy cattle farming:

Provide Access to Pasture Grazing

Allowing dairy cows to graze on open sunny pastures for at least part of the day enables natural sunlight exposure. If affordable land resources allow, practising rotational grazing on pasture is ideal.

Design Barns with Sunlight Access

If cows will be housed in barns, position the structures to face east to west to allow sunlight to enter. Open windows fitted with UV passing glass are also an option.

Limit Nighttime Lighting

Light at night from indoor lighting disrupts melatonin cycles and circadian rhythms. Use dim, red lights or keep nighttime barn lighting at a minimum.

Track Daylength and Adjust Accordingly

The hours of daylight shift over the seasons, and cows adjust their metabolisms accordingly. Track day length changes and make adjustments like supplemental lighting to align with sunlight patterns.

Provide Outdoor Access in Winter

Even during colder months, provide some acclimated outdoor access if possible to prevent vitamin D deficiency. A paddock or yard with a sunny exposure can be sufficient even if the full pasture is not usable.

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Monitor and Supplement Vitamin D

Check vitamin D levels, especially during winter months, and supplement accordingly under veterinary guidance to maintain optimal status.

Transitioning Management to Optimize Sunlight

Now that we have reviewed the scientific evidence behind the importance of sunlight for dairy cattle productivity, we need to discuss how to transition operational practices to optimize exposure. Adapting dairy farm management requires consideration of the labour, land resources, layout, schedules and cost implications of changes.

Here are some recommendations on transitioning to leverage the benefits of sunlight:

Gradually Increase Pasture Access

If cows are currently housed indoors, incrementally begin to provide them acclimated time outdoors in the pasture. Start with just a few hours per day and increase duration over a 2-3 week period.

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Assess Barn Conditions

Evaluate barns and structures to identify where modifications like adjusting window angles or adding glass panels could allow more natural light. Consult with qualified contractors for structural changes.

Account for Increased Land Usage

If transitioning to more extensive grazing, evaluate if additional land rental or acquisition is required and factor costs accordingly. Also budget for any new fencing or water system investments.

Adjust Milking and Feeding Schedules

Work schedules with staff may need to be shifted to allow for cattle sunlight exposure periods. For example, milking or supplement feeding may need to be delayed or split into multiple sessions.

Plan Seasonal Variations

Remember that daylight hours shift significantly over the year. Adjust schedules seasonally and be prepared to supplement lighting in winter as needed.

Review Nutrition Plans

Working with nutritionists to review feed rations is prudent when making major management changes to ensure balanced diets still meet Requirements.

Key Considerations for Sunlight Optimization

Here are some additional factors to keep in mind when implementing sunlight exposure practices:

  • Start gradual changes before production peak seasons to allow an adjustment period
  • Avoid heat stress by providing shade options in summertime
  • Consider sunlight needs when assigning pasture rotations
  • Monitor milk components like protein and fat percentages for any diet adjustments
  • Have backup lighting available in case of electricity outage or extreme weather
  • Review cow body condition; increased walking may require ration adjustments

Looking at the Herd as a Whole

Getting the full benefits of sunlight exposure requires looking at the dairy herd holistically. Some key points:

  • Sun requirements vary by breed and coat colour; manage groups accordingly
  • Heifers and dry cows have different needs than lactating herds
  • Sick cows in isolation may need UV lighting for recovery
  • Cows at the end of the lactation cycle will need more overall energy
  • Genetics, size, and age all factor into sunlight needs

There is no universal perfect sunlight exposure prescription; it requires flexibility and adapting to each unique herd. However, the results of improved milk yield and component levels make sunlight optimization efforts very worthwhile.


Adding sunlight exposure practices requires change but can transform dairy farm productivity and profitability.

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By understanding the scientific relationship between sunlight and milk synthesis pathways in cattle, setting up the housing and land resources to optimize exposure, and managing the herd holistically, dairy producers can leverage this free natural solution.

Adjusting dairy cow sunshine access takes planning and preparation, but the return on Investment can make it well worthwhile. With the right approach and commitment to gradual change, the benefits of sunlight best practices on milk outputs will become clear.

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I am a multi-faceted professional with a strong foundation in Business and Finance, honed since 2020. Additionally, I possess a deep passion for automobiles, serving as an avid car enthusiast. In parallel to my diverse interests, I am also a dedicated student pursuing a career in the medical field.
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