Thermal Control

 

Pigs lose heat by four natural methods

 

1 Conduction to the floor

2 Convection to the air

3 Radiation to other surfaces

4 Latent head (or moisture) mainly by respiration

 

This is illustrated in the drawing

 

This is useful as it allows us to calculate what extremes we can achieve by the four methods of heat loss.

 

For example (From Y. Choiniere and J. Munroe (1994):

A 7 kg weaner on a wire mesh floor produces around 29.5 watts of energy which it needs to lose. The animal kept within its thermal neutral zone without chilling in a standard nursery at 30C.

Estimates can be made for its heat losses:

Latent heat = 10% Conduction to the floor = 17% Radiation = 44% Convection = 28%

If we placed the weaner on a heated surface, so that the conduction to the floor was 0%, the pig still has to lose 29.5 watts. The Latent heat does not change, so we must allow the pig to loose more through radiation and convection to maintain it within the thermal neutral zone. Now the estimates for heat loss are:

 

Latent heat = 10% Conduction to the floor = 0% Radiation = 57% Convection = 32%

 

The room can now run at 23C and the air flow can be increased

This can provide a better environment