Current Progressive Dairy digital edition

Barns & Equipment

Whether using a tiestall, freestall, dry lot or pasture, here are some tips for cow comfort and maintaining farm facilities and equipment.


Most dairy cows are now housed indoors for most, if not all, of their lives. Very few cows are moved to pasture or dirt lots during the dry period or when weather permits.

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Although it does not always seem like it, there is a lot of science that goes into milking cows these days.

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At recent dairy production workshops sponsored by the University of Minnesota and the Minnesota Milk Producers Association, Dr. Joe Harner, Kansas State University, offered Minnesota dairy producers a look at how high- producing cows spend their time.

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We have been hammering away at relieving heat stress on dairy cows for a long time, including how to design, build, modify and manage facilities. Heat stress occurs when the heat generated by the cow and heat received by her from the environment exceeds the amount of heat she can successfully release to her environment. SAAWW is a convenient tool for remembering the critical steps to cut heat stress.

• Shade for dairy cattle (any age) reduces the heat load on the animals from direct solar radiation.

• Air exchange is necessary when cows are inside a shelter to remove hot, stale, humid air and replace it with fresh outside air. A minimum 1000 cfm air exchange per cow is recommended.

• Air moving over cows at a high speed (220 to 440 feet per minute or 2.5 to 5 miles per hour) helps the cow increase the amount of heat she can lose from her body by convective cooling.

• Water is essential for a cow’s bodily functions. During heat stress conditions she needs extra water to enhance her cooling by evaporating it from her respiratory tract and the surface of her body. Plenty of clean fresh water to drink is the first step in any cow heat stress relief process.

• Water can also be applied to a cow’s skin and evaporation encouraged (sprinkling with a breeze) to remove more heat from her body. Passing air through a wet evaporative cooling pad or a fine water mist from a high- pressure misting nozzle will reduce the air temperature (and increase the humidity).

A mild day and a barn with inadequate air exchange (curtains closed or inadequate fans operating) can quickly increase the temperature humidity index (THI) and put a cow under heat stress conditions.

The upper temperature of a cow’s thermal comfort zone is usually expressed as about 77ºF. However, the impact of air humidity on the evaporation rate from the cow decreases cooling as humidity increases. This humidity can be a result of a hot, humid summer day or a hot, humid barn due to warm outside temperatures and inadequate air exchange. Cows can and do experience heat stress every month of the year due to poor or nonexistent ventilation systems.

A heat stress chart (Figure 1*) illustrates the relationship of air temperature and humidity and their impact on the cow’s stress level. A cow can begin to feel mild heat stress between 70 and 85ºF depending on the humidity in the air. At 80ºF and 80 percent relative humidity (RH) a cow in an under-ventilated, humid barn will feel a similar level of stress as a cow at 100ºF and 15 percent RH under a sunshade in the desert.

A dairy that does not respond to warm outside conditions with an appropriate increase in ventilation and drinking water could stress cows any month of the year. Does this happen at your dairy?

Use the chart in Figure 1* to learn the combined effect of temperature and relative humidity on heat stress. Humid, warm nights or barns with insufficient air exchange can be as harmful as higher temperatures when the relative humidity is low. PD

—Excerpts from Penn State Dairy Digest, April 2007

Robert E. Graves, Agricultural Biological Engineering Extension, Penn State University

Spring – time to plant corn, first cutting of hay and spread manure. But before you climb on the tractor seat, think about adjusting your barn ventilation in anticipation of warmer weather. That may be as simple as rolling up sidewall curtains or it may entail the removal of plastic tarps or plywood that protected structures from those brisk winter breezes. Regardless of what it takes, make sure to open up your barns before the hot weather.

The “comfort” zone for dairy cattle is 41 to 77ºF. Temperatures inside poorly ventilated barns could exceed that during the middle of the day even in early spring. Above 77ºF, cows are heat-stressed and dry matter intake suffers leading to a list of problems including reduced milk production, reduced reproductive efficiency and increased occurrence of metabolic disorders.

The effects of heat stress can haunt you for the rest of the year – recall that 1 pound of peak milk translates into 225 to 240 pounds per lactation. For example, 4.5 pounds decrease in peak milk can lower the lactation yield by 1,000 pounds. So make sure you have the capability to cool early lactation cows. Ration adjustments may be needed to compensate for reduced dry matter intake.

A great place to start addressing heat stress is the holding pen and the feed bunk. These two areas of higher cow traffic are prone to heat stress. Look for ways to provide fans and possibly sprinklers on cows at these locations. Below is a list of items to consider as the temperature rises:

• Open up barns (remove sides, roll up curtains) to maximize natural ventilation.

• Clean dust and residue off of fan cages as it can cause drag, which compromises the air-moving ability of the fan. (You would be amazed at how much better a clean fan can function relative to a dirty fan.)

• Ask yourself if any structures around cow housing can be removed or modified to allow for better air flow. Do you really need that ivy-covered corn crib you haven’t used in 10 years?

• Consider installation of a cow sprinkler system. (Your local dairy extension agent should be able to assist you in the design of these systems.)

• Is your feed bunk and holding pen adequately shaded? Is this true at different times of the day as the position of the sun changes? PD

—From Virginia Tech Dairy Pipeline, May 2007

M. Chase Scott, Extension Agent, Virginia Tech

As animal housing continues to move toward larger buildings, the research team at the Bioenvironmental and Structural Systems (BESS) Lab at the University of Illinois is working hard to keep up with industry trends. What this means is that the BESS Lab, which is known worldwide for testing livestock ventilation fans, is checking out larger and larger fans.

“For most new construction, the standard ‘large’ fan is no longer 48 inches, but rather 50 to 54 inches,” said Steven Ford, a research engineer in the U of I Department of Agricultural and Biological Engineering and manager of the BESS Lab. “Airflow rates have increased proportionally, so fan airflow capacities are reaching the limit of our current test chamber.”

Therefore, Ford has taken the lead on garnering industry support to build a larger test chamber.

“We have funds committed from ag ventilation companies in Canada, Michigan, Indiana, Illinois and Alabama,” said Ford, “as well as in-kind equipment donations from companies in Illinois and Wisconsin.”

The BESS Lab first opened in 1990 to provide unbiased engineering data to aid in the design, development and selection of efficient livestock ventilation fans. The lab tests ventilation fans sent to them by equipment manufacturers, or the manufacturers can rent the lab for a day, which Ford said is the most economical option.

“Companies bring their fans to the lab, along with one or two people to assist with the set-up,” he said. “This helps keep costs low and industry participation high, which ultimately is good for the livestock producer.”

Ford estimated that the lab has done more than 3,000 tests over the last 16 years.

“We work with manufacturing companies around the country,” Ford said. “We’ve tested fans from Europe and even Australia. We’re fairly well- known throughout the ag ventilation industry.”

Manufacturers have the option of listing their test data in “Agricultural Ventilation Fans: Performance and Efficiencies,” a biennial publication that provides performance test results of over 800 commercially available fans. This information can be accessed at the BESS website at, or a hardcopy of the book can be purchased through the Midwest Plan Service at or the National Food and Energy Council at as well.

Ford pointed to the impact testing has had on ventilation fan performance over the years.

“From 1991 to 2003, the average airflow performance of commercial livestock ventilation fans increased over 15 percent, and average electrical efficiency increased more than 20 percent,” he noted. “Those numbers tell me that manufacturers will improve their product performance when there is an active performance test lab.”

Ultimately, said Ford, the goal is to help producers make more informed choices in ag ventilation systems. “The right fan will reduce odors, minimize the health risk of inhaling dust-laden air and optimize profits,” he concluded. “Efficient ventilation systems are essential to producers.” PD

—Excerpts from University of Illinois College of Agricultural, Consumer and Environmental Sciences (ACES) News website

Leanne Lucas, College of Agricultural Consumer and Environmental Sciences, University of Illinois