Improving respiratory health through tube ventilation systems
Over the past decade there has been an increase in housing pre-weaned dairy calves indoors. This has happened for many reasons. Human comfort of housing calves indoors during winter months is one major factor. Another factor is the increase of group feeding of dairy calves. Whatever the reason may be, when dairy calves are housed together in a barn, they are at an increased risk of respiratory disease when compared to being housed individually in hutches.
To help reduce respiratory disease in these facilities, producers often have to adjust management protocols to promote respiratory health. In addition, they often consider the installation of a positive pressure tube ventilation system.
The idea behind these tube ventilation systems is to reduce the air bacterial counts and provide more fresh air in the microenvironment of the calf. It is critical to understand that the microenvironment is the area where the calf breathes air within the pen. A calf does not breathe the same air that a human does when they walk into the barn. The way a tube ventilation system achieves a reduction in air bacterial counts is to aim for exchanging the air in the barn four times per hour.
The tube needs to be custom designed for each calf facility. Purchasing a “cookie cutter” tube system for your facility will yield poor results. The University of Wisconsin Dairyland Initiative has created a spreadsheet that generates a custom-made tube ventilation system. The Dairyland Initiative staff has trained veterinarians and industry professionals throughout the world on proper design of these systems. If you decide to purchase a tube ventilation system, you should consider getting it designed by someone experienced with the Dairyland Initiative spreadsheet and who has taken the training course. There are also “certified consultants” within the Dairyland Initiative network that have demonstrated advanced proficiency with the design of tube ventilation systems.
Tube ventilation system designs can be modified so that the tube can be placed in many different locations throughout the barn. Typically one tube will properly distribute air up to 40 feet of barn width. The design can be modified so that the tube can be placed under or within the trusses. In the case of a barn with a low ceiling or a bank barn, the tube can be placed along the wall or out of the way of machinery during barn cleanout. The hole size and location can be changed to accommodate basically any location within a barn.
A tube ventilation system is only one part of respiratory disease management. The system is designed to supplement natural ventilation, vaccination protocols, colostrum management, nutrition, and stocking density. Even a well functioning tube ventilation system can be overwhelmed by disease pressure if any of these management factors become inadequate.
Not all tube ventilation systems are created equal. If the performance of your tube ventilation system is suboptimal, there may be several reasons why. Assuming management factors are adequate, the most obvious reason why a tube ventilation system is ineffective is due to a poor design. Again, make sure someone who has been trained by the Dairyland Initiative designs your tube ventilation system. Another reason for poor tube performance is that the tube is not located where the design indicated it should be. A basic principle of tube ventilation system is that there is no draft on the calf. When air is at a velocity of 1 foot/second, it is imperceptible and does not create a draft. Most tubes are designed for the air to reach 1 foot/second at a height of 4 feet above the ground. This ensures that there is no draft placed on the calf. If the tube is placed higher or lower than what the design calls for, a calf may either get drafted or air is not distributed low enough to exchange air in the calf microenvironment. Either scenario leads to ineffective tube performance. Other common reasons for poor tube performance are tears in the tube, bends in the tube, debris (hay, dust, birds) within the tube, and fans that are beyond their useful life (typically 5 years).
There are some preconceived notions about tube ventilation systems that typically aren’t true. Some producers believe that tube ventilation systems will make calf barns cold during winter. Unpublished research has shown that tubes have minimal effect on the temperature inside a calf barn relative to ambient temperature. Another misconception is that managing curtains is no longer important.
Heat stress can have a negative impact on health and growth of calves. Typical tube ventilation systems are designed to exchange the air in a barn four times per hour. These tubes are not designed to cool calves, rather, only to improve air quality. Heat abatement can be achieved by the addition of other fans, or the installation of a summer tube ventilation system. Summer tubes are designed to purposefully and forcefully draft a calf to help cool the calf during hot weather. These tubes are much less common because they are much larger than the year-round tube ventilation systems.
It is important to continue to run the tube ventilation system all day, every day. Even when the barn seems to be receiving adequate natural ventilation on a given day, the tube ventilation system is further improving the microenvironment of the calf. Preventing respiratory disease will have significant positive economic benefits in regard to increased future milk production, reduced drug costs, less deaths, and increased weight gain.