When mentioning heat stress in pigs, many people think it occurs only in the summer.
However, heat stress in pigs occurs as soon as the ambient temperature of the pig exceeds the thermoneutral zone, the animal can no longer, or insufficiently, dissipate its own body heat. It does not have to be summer for this to happen!
THE THERMONEUTRAL ZONE
The thermoneutral zone is bounded both downward as well as upward by the so-called “lower and upper critical temperature.”
Both temperature limits depend on various factors such as:
- Environmental factors, (housing climate), relative humidity, air flow, radiant heat, type of floor, number of animals within a group, the presence or absence of cooling factors, (such as a moist or wet skin), and its surface area
- Age of animals, with associated weight and animal's own heat production
- The production stage, (for example: pregnant or lactating sows)
- Race or hybrid influences.
As you can see, all these factors have the same importance all year round!
HEAT STRESS
If the ambient temperature exceeds the critical temperature, then we speak of heat stress.
Pigs can hardly sweat, so they suffer from heat stress and try to get rid of the heat by changing their behavior.
- Panting with open mouth
- Trying to isolate themselves and moisten themselves with urine and/or manure in order to get rid of body heat through wet skin,
(Soiling themselves to cool off is totally atypical pig behavior, contrary to what many people believe, pigs are very clean animals!)
- Moving to a cooler place in the pen, (a slatted floor)
- Reduced feed intake in order to reduce energy intake. (Reduced energy intake means directly less heat production).
SOME EASY-TO-IMPLEMENT SUGGESTIONS THAT CAN HELP IMPROVE INDOOR CLIMATE FOR SOWS IN PARTICULAR:
SOLAR RADIATION AND WINDOWS
- Is there direct solar radiation through the windows of the farrowing pen? If so, check what type of glass is being used.
In my experience, the so-called HR++ glass does allow heat into the barn, but it does not transfer this heat back outside.
- If this is the case, simply paint the window glass with whitewash.
Disadvantage: the glazing blocks the light, but still gets warm!
- Install windbreak netting (1-1.5 mm), or other shading on the outside of the window glass.
When installing windbreak netting or other permanent shading, I recommend a 15 cm gap between the shading and the window glass.
VENTILATION & RELATIVE HUMIDITY
- Is the alarm system working as it is supposed to?
- Is the ventilation capacity sufficient?
As far as I am concerned, the capacity of a fan in the farrowing house should be 275 cubic meters per sow, this secures better heat dissipation.
- Keep the incoming air as cool as possible, a cooling system for incoming air is best. The air intake is preferably on the shady side of the barn, or even better on the north side.
- Are all fans in working order and are the air intakes also clean?
- Set the outside temperature-dependent adjustable bandwidth at 5 to 6 degrees, 3 degrees is as far as I am concerned the minimum.
The bandwidth is the temperature difference between the temperatures as they correspond to the minimum and maximum ventilation levels.
Should the bandwidth be set to a value that is too small, the fan will continuously turn on and off.
This is very bad especially for fattening pigs and piglets. It also creates a risk of draft.
During colder outside temperatures, (when less outside air is needed to cool the barn), the bandwidth can be increased to 9 degrees for piglets as well as for fattening pigs.
GETTING FRESH AIR AT THE SOW'S HEAD
- Lowers her wind chill
- Allows her to release more heat and water vapor via exhaled air
- It stimulates her appetite.
A correct relative humidity is between 40 - 60%.
If it rises, the wind chill automatically goes up, it feels more stuffy, especially hot weather in combination with high relative humidity is very harmful for pigs.
In such a situation, pigs cannot dissipate their heat through evaporation at the lungs.
As I stated earlier, pigs can hardly sweat.
THE FLOOR HEATING OF THE PIGLET NEST
Also look at the floor heating of the piglet nest, is it well insulated at the bottom?
If not, heat can still flow to the sow through the floor!
Source photos Marga Fogt, Magdalena Krebs