by Dr. Gilbert Hollis
Pork producers have a tendency to assume if they're
comfortable inside a hog building the pigs are too. But
that's not necessarily true. Pigs have specific needs
and spend their time in a completely different part of
the building than their caretakers.
Swine buildings need to be managed from the pigs'
perspective. Here are some things to remember as you
strive to provide as stress-free an environment as
possible for hogs of all ages.
Pigs React to Stress
Like most animals, pigs have the ability to quickly
respond to environmental stress. Although they can't
always make dramatic changes in their microenvironment,
pigs can modify their surroundings through bodily
functions. Unfortunately, these responses to
environmental stress can be counter-productive to
performance. Growth and reproductive efficiency can be
directly affected. Hogs under stress waste nutrients.
Excessive stress can also impair a pig's
disease resistance. Even if death losses don't increase,
environmental stress can increase days to market and
lead to uneven groups of market hogs.
According to Dr. Stanley Curtis of The Pennsylvania
State University, a pig's initial reaction to stress is
involuntary. The adrenal glands increase the secretion
of glucocorticoids. High concentrations of these
hormones help animals survive short periods of stress.
However, glucocorticoids also mobilize amino acids from
muscle protein and interfere with some mechanisms of the
Evaluate The Pig's Microenvironment
The environment in which pigs are expected to live and
grow is really the composite of many environmental
factors. These factors interact with each other. This
makes it difficult to identify exactly which external
condition is causing pigs to perform poorly. Therefore
all environmental factors must be considered. Because
some can not be easily measured, trial and error is
sometimes the only way to find a solution.
It's important to obtain readings on environmental
factors throughout the building. If the pigs in a
particular pen always perform better or worse than their
counterparts in other parts of the building, thoroughly
investigate the microenvironment in those pens. You'll
probably learn something that can improve the
microenvironment for the entire building.
Swine managers must also keep changes brought on by the
time of day or the season in mind when evaluating the
environment inside a hog building. This is especially
important during the season when the weather is in
transition. The warm days and cool nights most parts of
the country are now experiencing can cause extreme
environment stress for hogs if buildings are not managed
properly. Check the temperature, air movement and signs
of dampness at different times of the day, especially in
the spring and fall.
Rapid environmental changes cause the greatest stress.
For example, if pigs are going to be moved from a
temperature-controlled building to an open front
finishing unit, it may be a good idea to pre-condition
the pigs by dropping the temperature a few degrees a day
for a week or so before moving them. Of course, this
kind of pre-conditioning requires an all-in/all-out
production schedule for the entire room.
How Air Quality Affects Pigs
Pigs raised in environmentally-controlled buildings have
no choice but to breath the air that's present in their
microenvironment. Pork producers and their employees can
wear protective equipment and spend considerable time
each day out of the building. Because a pig's
respiratory tract is in constant contact with the air,
pollutants can cause problems.
Most air pollutants found in hog buildings are created
by the hogs themselves. Of major concern are microbes,
dust and gases. Although some studies suggest pigs are
fairly tolerant of poor quality air, these pollutants
have been shown to directly alter metabolic reactions or
indirectly influence the health of pigs.
The concentration of bacteria in the air inside hog
buildings can be extremely high. During the summer when
air must be moved more rapidly to control temperature,
bacteria counts of around 500/cubic foot are common.
However, these counts can swell to 10,000/cubic foot in
cold weather. In modified open front buildings bacteria
counts can be as high as 5,000/cubic foot, even though
most fresh air only contains 10 bacteria/cubic foot.
A pig's respiratory system can normally clear bacteria
from the air and keep the lungs relatively sterile.
However, exposure to other environmental stresses can
depress this process and leaves pigs predisposed to
Dust in hog buildings is much more of a problem for
workers than the pigs. Even at high concentrations,
research shows dust has little direct influence on a
The two most important gases commonly found in hog
buildings that can influence the health of the pigs are
hydrogen sulfide and ammonia At acceptable levels, pigs
normally tolerate hydrogen sulfide well. But this gas
can be lethal to both pigs and humans above 1,000 ppm.
Levels that high normally don't occur unless a pit is
being agitated, but the presents of hydrogen sulfide may
be a warning that a potentially dangerous situation
Ammonia is present in virtually all hog buildings.
Concentrations can be as high as 100 ppm. When ammonia
reaches 50 ppm it can start to reduce a young pig's
ability to clear bacteria from the lungs. Ammonia levels
above 75 ppm have been shown to depress growth rate in
otherwise healthy young pigs. There are basically two
approaches to controlling air pollution inside hog
buildings: Prevention and dilution. Waste management
and sanitation are at the heart of any program designed
to prevent harmful air pollution. A good feed
distribution system is also a must when trying to
improve air quality inside a hog unit.
Eliminating air pollutants is best achieved through
ventilation. There is an air-exchange rate for all
buildings that will virtually eliminate all infectious
agents. Whether that rate is economically feasible is
another question. One approach that helps dilute air
pollutants without moving huge amounts of air through a
building is to have high ceilings so there is more air
to mix with pollutants.
Airborne bacteria and viruses generally die more quickly
when temperatures are high. Sunlight can also kill
microbes. Unfortunately, even in open front buildings,
many microbes are protected from the ultraviolet ray in