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There are many ways to test barn ventilation. A common one is watching how the cows act. You can also use a wind speed sensor to locate problem areas with the fans. Even fogging certain areas of the barn can do the job.
How do you know if the natural or mechanical system, negative pressure tunnels, cross-vents, or positive pressure hybrid system for ventilating mature cow barns is the most effective?
Below are a few easy strategies you can use to determine the correct option:
Testing the Barn Ventilation System
Observing Cow’s Physically
One strategy is looking at the dairy’s milk and repro records in comparison to the temperature change. According to our data, pneumonia cases tend to spike in the winter. On the other hand, mastitis cases peak in the summer. Also, lameness cases peak in the fall. Think laminitis.
1. Checking Bovine Reproductive Health
Summer heat stress is associated with a loss in fertility. It's also the reason for the higher somatic cell count. High cell count directly impacts cow’s milk production.
Such alterations indicate that the barn ventilation system is inadequate. It is unable to mitigate the environmental difficulties brought on by hot weather
2. Observing Cow’s Behavior
Please be sure to observe the cows by walking the barns. Do cows exhibit bunching behavior during the summer? They might gather in the barn's center to get out of the sun. Or if there is biting flies they will stand in a tight group.
3. Evaluating Cow’s Breathing Rates
Do cows have an increased respiratory rate, or are they panting?
Measure the breathing rates of at least 20 cows. You can do this while they are lying down or standing.
If you find that more than 25% of the group has an elevated breathing rate of more than 60 breaths per minute, it's a trigger alert.
Measure the breathing rates of at least 20 cows. You can do this while they are lying down or standing.
If you find that more than 25% of the group has an elevated breathing rate of more than 60 breaths per minute, it's a trigger alert.
It means that some cows are suffering from heat stress. In short, the air circulation and cooling systems are failing.
4. Other Measuring Factors
To examine the ventilation system in depth, you can calculate the following aspects:
- Fan capacity
- Air exchange per animal
- Air changes per hour
- Static pressures
- The amounts of toxic gases like ammonia using sophisticated machines
It's more complex than you might think. When identifying a fan's capacity rating, fan labels are often put in the most inaccessible and dangerous areas to read. However, this type of study usually requires pricey specialized equipment.
It is essential to audit the efficiency of ventilation systems. So, for the past couple of years, we have used more accessible, cost-effective equipment. We work with a particular emphasis on how they operate during the summer.
Not only this, but we used a portable propane bug killer stuffed with mineral oil. It works by fogging the barn to see airflow. Our experts also collaborated with Kestrel Instruments to use some of the equipment they built. It is excellent to detect temperature, humidity, and air speed.
Professional Methods for Evaluating Ventilation On-Farm
Check the inlet design, location, and staging of fans as you stroll the barn. An excellent way is to check the ceiling for cobwebs. You might also detect wetness running along the purlins. This way, you can spot signs of poor ventilation and condensation.
At the beginning of the ventilation evaluation, place the recorders for humidity and temperature in the cow pen of a naturally ventilated barn. You can also set the recorders in the intake and exhaust of a mechanically ventilated barn.
The loggers should take measures every five minutes for a visit, which usually lasts two days. Barns should have a maximum input and exhaust temperature difference of 3.6 degrees Fahrenheit.
Next, fog some portions of the barn. Doing so will show the following:
- Airflow between recirculation fans in naturally ventilated barns
- Airflow between around inlets and baffles in mechanically ventilated barns
Fogging will show how the air distribution takes place. It will also locate dead spots with insufficient airflow.
Finally, use a tripod-mounted vane anemometer with a data-logging feature. It will map air speeds in the pens' resting regions. The anemometer works by measuring speeds 1.5 feet above the bedded surface.
We trace air velocity using one-minute observations at various sites. It usually depends on the barn's layout and ventilation system. It may take up to two hours to finish this phase. That’s why it is the most extended area of the test.
After the tour, we may map the barn's air velocities. Our results will show where the barn needs ventilation upgrades. Some common examples are:
- Moving the Inlets
- Angling and spacing fans differently
- Moving baffles about
We hear barns are designed for 5–8 mph cross-sectional wind speeds. The problem with this plan is that it assumes consistent airflow across the barn's cross-sectional area. In actuality, this is not the case.
Instead, it goes over the cows to take the path of least resistance. Usually, the airspeeds in the alleyways and feed lanes are sufficient. But they are significantly lower in the area where the cows live.
Because of this, we conducted our ventilation evaluation in the confined space of a stall.
The minimum cooling air speed (MCAS) must be between 2.25 and 4.5 miles per hour. In simple words, it is 2 to 4 feet per minute. Measure 1.5 feet above the bedded surface. This is where the cow is located when laying down.
This audit provides an objective method for establishing whether or not a ventilation system is operating as it should. It can show you the locations with the most significant impact on dairy cows.
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