article describes the effects of barn design and construction
on the health and well-being of animals and your ability to
keep them healthy.
Three rules should be remembered concerning ventilation
of barns: 1) Cows breathe out moisture (they also produce
heat); 2) Air exchange removes moisture (it also removes
heat); 3) Air moves through holes.
To maintain a healthful environment in any animal en
closure there must be a continuous supply of fresh air. A
1,400 pound cow will breathe out approximately 4.5 gallons
of water per day regardless of outside temperature. There
fore it is necessary to exchange air even during cold
weather. The same cow will continuously produce about 670
watts of heat. This heat will have to be removed from
around the cow on all but the coldest days. The warmer the
outside air the more fan capacity required.
When you examine a barn you should be able to identify
how the fresh air gets into the barn (inlets), how the fresh air
gets to all the cows (distribution), the force that causes the
air to move (fans, wind, buoyancy), and finally how the foul
air gets out of the barn (outlets). A poorly ventilated barn
will have one of more of these items missing.
Signs of poor ventilation include: condensation on walls,
ceilings and fog in the air; hot stuffy locations in the barn;
and dust, gases and odors. In general, in the winter time if
the bam “smells like a barn,” it’s under-ventilated.
Mechanical Ventilation
Mechanically ventilated barns utilize fans to cause air to
move. Exhaust fan systems are most common. Ventilation
rates required vary with outside temperature, therefore,
more than one fan or fan speed is necessary. A small fan
should run all the time to control moisture. Other fans will
need to come on as temperatures rise.
The most common method of bringing air into a barn and
providing for distribution in an exhaust fan system is a con
tinuous slot inlet. Inlets should run along both long sides of
the barn except near the fans. Barns wider than 38 feet may
require center inlets. Thermostats for controlling fans
should be mounted where they will sense the general barn
temperature, away from the ceiling and other obstructions
(normally over the center aisle). A thermometer should be
located with the thermostats. For animals where a wide
swing in temperature can cause problems, use a maximum
/minimum thermometer.
The most common problems in mechanically ventilated
barns are inadequate or inappropriate inlets (holes) and im
proper fans. If the fans shut off regularly during cold
weather, a smaller continuously running fan is probably
necessary. If the bam becomes stuffy on mild days, a larger
fan or more inlets are usually necessary. Extra openings
such as gutter cleaner chutes, broken windows or loose fit
ting doors can result in short circuiting of air and poor dis
tribution. Various extension publications are available to
aid in troubleshooting ventilation systems (Brugger, 1983).
Natural Ventilation
Naturally ventilated barns utilize openings, external
winds, and thermal buoyancy to provide for air exchange.
At least three types of openings are required (Graves, 1984).
A continuous opening at the ridge or top of the barn allows
warm moist air to exit year round. Continuous sidewall
VENTILATION
openings (usually at the eaves) provide small amounts of air
during cold weather. For summer conditions large sidewall
openings are needed. Ideally, during hot weather all
sidewalls would be gone and the barn would act like a
sunshade. This exposes the animals to any outside breeze.
Many naturally ventilated barns still do not have open
ridges. This results in trapping moisture during cold
weather and heat during hot weather. Older free stall barns
often have insufficient sidewall openings for summer cow
comfort. For various reasons farmers are reluctant to make
adequate openings in existing and often new barns.
HOT WEATHER COMFORT
High ambient temperature and humidity can have pro
found effects on milk yield, reproductive performance,
growth and health.
The basic approach to hot weather cow management in
cludes:
•keep cows out of the hot midday sun
•maximize air movement around the cows (2-5 mph at
the cow is recommended)
•provide adequate air exchange to remove foul air from
barns
•provide plenty of fresh cool drinking water (extra tubs
may be needed during the summer).
Areas of particular concern during hot weather include
holding areas where cows are crowded close together and
feeding areas. Farmers are encouraged to take steps to pro
vide fresh palatable feed and fresh water in a comfortable
environment. If the barn or shade tree is more attractive
than the feed bunk or water trough it is likely that feed con
sumption will decline. Management changes that may be
considered include: feeding time and frequency, manure
scraping times, use of outside paddocks at night or early
morning, and bringing cows into well ventilated barns
during the heat of the day.
Sprinkling Cows
Farmers using water sprinklers at feed bunks to improve
cow comfort in hot weather and thus maintain feed intake
report good results. This practice must be approached with
care to be sure it does not result in wet sloppy udders.
Sprinkling should be considered after all reasonable meth
ods of opening barns and improving air exchange have been
exhausted. Sprinkling cows in an enclosed barn or holding
area, with inadequate air exchange, will result in a steam
bath.
For additional comfort, large fans can be arranged to
blow directly on cows to enhance drying. It is the evapora
tion of water directly from the cow’s hide that provides the
most heat removal or cow cooling. Recent reports from Flor
ida (Means, S.L. et al, 1992) indicate that large quantities or
long time periods of water are not necessary. An automated
system that alternated 1.5 minutes of sprinkling and 13.5
minutes of fans was operated whenever temperatures were
above 78° F. Flow rates were varied from 0.6 gpm per cow to
1.3 gpm per cow. There was no increase in cow comfort or
productivity with higher flow rates.
An easy way to apply water is to drill and tap a 3/4 inch
PVC or galvanized pipe every 4-8 feet to accept a spray
nozzle or small lawn sprinkler. Place the pipe and nozzles to
direct water onto the center of the cow’s backs. The water
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