Reducing Heat Stress Through Environmental Design Improves Milk Production, Pregnancy Rates
June 22, 2020
By Michael J. Wolf, consulting veterinarian, VES Environmental Solutions
The financial success of modern dairies is tied to the wellbeing of each animal throughout its
lifetime. Even before a calf is born, the specific environment in which it was conceived,
developed, raised, and nurtured can determine the overall health of the animal, as well as its
performance in the parlor.
Heat stress, particularly, can have a significant impact on milk production and fertility over the
lifetime of each animal. Even when a mild temperature humidity index (THI) is present where an
animal spends more than 35 percent of its time at a THI greater than 65, we begin to see strain.
Respiration rates exceed 60 breaths per minute (BPM) and rectal temperatures exceed 39 degrees
Celsius — and milk product loses equate to about 1.3 kilograms per cow each day. Similarly,
reproductive loses become detectable.
It also extends beyond the barn and into the parlor as well, where cows spend a significant
amount of time. Animals are susceptible to embryonic loss when the body temperature rises
above 39 degrees Celsius.
This is why it’s imperative that we create environments that are conducive to animal comfort,
milk production and reproduction. Creating such an environment can be distilled down to three
main factors: air exchange, effective cooling velocity, and ambient temperature drop. The presence
of appropriate fresh air ventilation, a cooling strategy with high pressure fogging and soaking
(depending on the climate) and lighting systems that can be programmed and adjusted to help
cows perform at their best throughout the pregnancy, development, calving, lactating, and dry
phases of a cow’s life.
Air quality is essential to the health and wellbeing of high-performing cows. Coincidentally,
research has shown that the highest-performing cows in regard to average milk yield actually
results in higher body heat expressed by those animals. For example, a cow that produces 54
kilograms of milk per day also produces 152,000 BTUs of body heat per day whereas a cow that
produces 18 kilograms of milk daily only outputs 79,000 BTUs of body heat. The specific areas
that are most important for controlling core body temperature is in the milking parlor and
holding pen, where the highest concentration of animals is experienced at any given time.
Adequately spaced fan systems pull fresh air from outside the facility and direct it onto the
animals, reducing core body temperature while also moving hot air, humidity, and gasses out of
the production area towards exhaust ports. The fan system along with high pressure fogging and
soaking will help you remove of BTU’s being produced especially from higher producing cows.
Additionally, the economics of targeting the parlor and holding pen is highly capital-effective as
the cost is amortized over all lactating cows, which can enter the parlor two or three times daily.
When designing an animal-centered ventilation system for your operation, the first goal should
be to return every cow to her basal core body temperature every 24 hours. Basal core body
temperature is the lowest measure of an animal’s typical temperature 39 degrees Celsius.
Another goal of an animal-centered ventilation system should be to minimize the level and
duration of core body temperature increases during peak times, especially during time spent in
the milking parlor and holding pen. Finally, mastitis risk is reduced by higher airflow removing
moisture from bedding. By having the right animal-centered environment design, the air not only
cools the animals and provides fresh air, it also dries the beds and help reduce insects.
When not in the parlor, a goal for a cow includes 50-60 percent of its day laying down making
milk. That time spent laying is critical for milk production and preventing disease as it increases
blood flow to the udder. Additionally, it makes it even more critical that the animals are
experiencing optimal ventilation to encourage increased laying time, as well as the appropriate
Shining the Right Light on Cow Environments
Throughout a cow’s different phases, precision lighting conditions help animals perform their
best based on their physiological needs. The modern, animal-centered approach to delivering
optimal lighting includes using efficient LED industrial light fixtures to produce light based on a
cow’s core retinal sensitivity for 16 hours per day.
Lighting spectrum around 6000K provides best response. Utilizing what is referred to as long-day
lighting also increases udder making cells and leads to healthy and leaner animals, reduces
the number of days on feed, and helps expedite the movement of a cow from the “cost” side of a
dairy’s balance sheet over to the “revenue” and production side.
Heifers also benefit from long-day lighting. Long-day lighting in growing heifers increases lean
growth, wither height, sooner puberty and milk production cells in the udder.
Exposing cows to longer periods of light has been found to increase milk production up to 8
percent with a corresponding Dry Matter Intake of about 4-6 percent. It is especially critical in
winter months, when the days get shorter and milk production drops, and at higher latitudes,
where production can be as much as 5 percent lower. When considering the installation and
operational costs, such as electricity and bulb replacements, most systems are able to pay for
themselves within a year.
During the dry periods, including late in pregnancy, operations should deploy shorter lighting
cycles to suppress Prolactin production but increase Prolactin Receptors, which can lead to more
rapid transition to milk production and mammary function. This approach is known as short day
lighting and is defined as 16-18 hours of lighting conditions of less than 22 Lux and 6-8 hours of
lighting of 215 Lux.
Holistically, the utilization of long-day lighting systems to deliver the right lighting conditions
for your herd not only maximizes milk production and overall animal wellbeing but increases
milk-making cells and improves reproduction.
To learn more about designing and implementing the right animal-centered ventilation and
lighting environments for your operation, connect with a trusted, scientifically-backed
professional who can work with you on the right solutions to maximize your cows’ wellbeing.