This crazy graph is a snapshot of only one month’s worth of weather variations in Wisconsin. Trying to advise a client on how to properly manage the ventilation in a cow barn in weather like this can be challenging. Some days are wet, some snowing, some foggy, others sunny and unseasonably warm.
Hence, it’s easy to become paralyzed when trying to make the right choice with your fans and curtains. With the thermal neutral zone of cows ranging from 41-77F, cold stress beginning at <18F, and heat stress beginning as early as >68F, we have considerable variances in and out of each of these zones throughout spring and early summer.
Additionally, spring brings with it higher humidity and precipitation ratios leading to more damp heavy air in our barns. This contributes to a greater need for ventilation despite the animal’s transition into a lower stress and ideal temperature zone.
This higher humidity means less airborne desiccation of bacteria and viruses; aka less passive “disinfection” and greater infectious loads. Couple this with the increased variability in feed quality which might be frozen rained soaked or beginning to have variable levels of yeast, mold and bacterial growth as temperatures rise, and we begin to enter the high-risk pneumonia zone or the time where our clinic sees increases in herd-wide respiratory outbreaks as well as increases in individual cow disease.
Due to concern about this high-risk time period people begin asking questions like: How should I manage curtains? When should the exhaust fans go on? How can I reduce the number of cows I’m treating?
Magic Bullet
Many people want a magic bullet for managing these variances during this high-risk period, unfortunately, there isn’t one. Research is clear on what we should implement on the lower end of the spectrum; progressively closing the barn as we approach 0f and avoiding icing and the issues it causes.
On the other end of the spectrum, the research is equally clear; you should be engaging all your available forms of cooling ventilation management at a greater than ~70-75 F and 50% humidity or a Thermal heat index of 68.
Management in between these stress zones is all about management intensity. At a minimum, your barn should exchange its full air capacity (Cubic Footage) four times per hour when temperatures are <40F. This minimum exchange should facilitate the desiccation of airborne infectious agents as well as reduce overall humidity in the barn.
As we stage up into the thermal neutral zone of 40-70F, the air exchanges should rise to ~16x per hour until we hit >70F at which point you want to hit 40-60x per hour.
Exchanging the requisite amount of air will require the progressive opening of curtains as the day warms up as well as the closure of curtains at the end of the day as temperatures drop overnight.
Ultimately, there is no silver bullet, just more intensive management that needs to happen as your barn swings between these three temperature zones. Tasks such as managing curtains are often better overseen by someone not engaged in spring or summer fieldwork or in other off-farm responsibilities that might take them away from the operation; allowing them to control and manage your barn’s air quality more actively.
The table below can be used to aid this chosen team member in properly preparing your ventilation system to spring into summer. Additionally, more help can be found by tapping into the Dairyland Initiatives certified consultants network https://thedairylandinitiative.vetmed.wisc.edu/professionals/industry-contacts/ to find an industry professional to aid in your ventilation plan.
Key checkoffs for producers before entering spring/summer:
- Has someone/an automated system been assigned to curtain management?
- Do all the curtains work? If automated, test motors and glides for function.
- Have my cooling fans been fully maintained?
- Have I cleaned and washed all the fans/blades? A 1/4” dust reduces performance by 40%.
- Have you done a “soft start” on your summer fan system to make sure everything is functioning?
- Has your summer cooling system had its wind speed audited in the last 2 years? This provides important insights into shortcomings and failings within the system.
- Are the water/sprinkler systems fully functional with the spray heads being replaced as needed?
