September 5, 2017 at 3:32 p.m.

Positive pressure ventilation systems can help calves survive, thrive

Jenn Bentley<br /><!-- 1upcrlf -->ISU Extension
Jenn Bentley<br /><!-- 1upcrlf -->ISU Extension

By by Kelli Boylen- | Comments: 0 | Leave a comment

CALMAR, Iowa - Four of the keys to raising healthy calves are minimizing calf stress, providing fresh air while limiting drafts, providing a clean, dry and comfortable resting place and managing the effects of extreme weather.
Many dairy producers could tell you these four areas are important to raising calves, but what exactly does each one mean?
Jenn Bentley, Iowa State University Extension and Outreach Dairy Field Specialist, provided recommendations at the annual Iowa Dairy Days Program offered at six locations throughout Iowa in January.
It has been a practice on some farms to enclose a calf's pen to minimize the risk of draft and contact with other calves, but Bentley outlined the facts found during a 2006 study in Wisconsin.
Calf pens with more than two sides tend to restrict air movement too much, creating a "microenvironment" with higher airborne bacteria counts and increased respiratory disease.
Bentley says there should be solid panels dividing the calves, but the front and rear of the pen should be as open as possible to promote good air movement. A low rear panel of 18 to 20 inches can hold bedding, and a three to four foot walkway between the calf pens and the side wall curtain on the building can reduce drafts.
The Wisconsin study showed that reducing the number of panels in a calf pen from four to two resulted in a 20 percent reduction in respiratory disease.
If the air movement increases, maintenance of the body heat of the calves must be considered.
Bentley explained an easy way to check if the calves have enough bedding to stay warm is to see how they are "nesting." If a calf is resting on top of the bedding with legs exposed (nesting score of one), the calf does not have enough bedding. A calf that is nestled deeply in bedding with the legs not visible (nesting score of three) is most ideal.
A newborn calf's thermo- neutral zone (the temperature that the calf does not have to expend energy to maintain proper body temperature) is between 50 and 78 degrees, and for a one month old calf it is between 32 and 73.
If a calf is lying down with some leg exposed (nesting score of two), a calf blanket can help, but a blanket is not enough to make up for the heat the calf is losing if the nesting score is one.
A clean, dry resting surface (at least three inches between soiled bedding and the calf) is important to help insulate the calf against a cold floor and low air temperatures.
Calves spend more than 50 percent of their time in the day and almost 100 percent of their time at night lying down, so adequate space is important. Calves in individual pens should have at least 32 square feet per animal. Calves in group pens need at least 28 square feet per animal.
It is becoming more common to design calf barns like freestall barns - naturally ventilated with side curtains that can be opened and closed and an open ridge.
Bentley says there can be two potential problems with this building design: days with calm winds can leave the barn unventilated, and calves do not produce adequate heat with their bodies to create thermal buoyancy for air circulation though the open ridge.
She says a good calf management practice is to incorporate a positive pressure tube system into naturally ventilated and retrofitted calf facilities.
Bentley recommended working with an ag engineer to design the system properly. Things to consider include sizing fans so that the air in the barn is exchanged approximately four times an hour, selecting a tube diameter and air exit speed to maintain a uniform discharge of air along the entire length of the tube, and sizing the holes correctly so fresh air is delivered without creating a chilling draft. It is recommended that the fans never turn off and provide a continuous minimal level of air movement.
"There really is a minimal investment in doing this, considering the potential positive impact," she said, noting that installation of positive pressure tube systems along with best management practices can result in a 50 to 75 percent reduction in the treatment of calves for pneumonia.
The Dairyland Initiative in Wisconsin has designed a spreadsheet tool to help create properly designed positive pressure tube systems. Both Bentley and ISU Extension Ag Engineer Greg Brenneman have both been trained in this program and can provide assistance to producers interested in designing a system. Bentley can be reached at 563-382-2949 or [email protected] and Brenneman can be reached at 319-337-2145 or [email protected].
She notes that the calf environment and ventilation are just one piece in the puzzle to raising healthy calves. Excellent management in the areas of colostrum collection and delivery, management by employees, nutrition and health programs are all required steps when rearing calves.[[In-content Ad]]


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