Swine Facilities Environment
| Requirements | Feed efficiency | Heat Increment and Fats | Moisture | Wind Velocity | Insulation | Thermal Stress |
Variation in EAT |
Upper Critical Temperature (UCT) ambient temperature which compromises growth rate due to excessive energy expenditures to dissipate heat
Lower Critical Temperature (LCT) ambient temperature which compromises growth due to excessive energy expenditures to conserve or create body heat
Heat Increment the energy converted to heat as metabolizable energy is converted to net energy (ME=NE+HI)
Effective Ambient Temperature (EAT) the aggregation of ambient temperature and how the animal perceives ambient temperature.
Ambient temperature perception is modified by:
- wind velocity
Managing the Basics
Requirements All classes of swine have specific thermal environment requirements. There are critical boundaries to these requirements.
Feed efficiency is lowered near the LCT because energy is being used to maintain core body temperature which would have been available for tissue accretion. Feed consumption is reduced near the UCT, and this increases feed efficiency. However, if UCT is exceeded, growth rates will be compromised because energy is expended to dissipate excessive heat and regulate body temperature. Managers intend to keep ambient temperatures near the UCT to minimize production costs as long as additional fuel costs do not exceed the savings in feed.
Heat Increment and Fats The UCT can be increased by feeding a feed with a lower heat increment. Fats have a lower heat increment than carbohydrates (CHO). Therefore, substituting some fat for CHO in summer months can effectively raise the UCT. Furthermore, fats have higher energy density, so inclusion of fat can preserve energy intake when feed consumption is reduced by high ambient temperatures.
Moisture (humidity or wet conditions) allows evaporative cooling, which can beneficial in summer months and misters are used to provide it. However, if wet conditions cause the EAT to be near the LCT, performance will be reduced and stress will increase disease susceptibility.
Wind Velocity influences conduction of heat from bodies. Drafts in winter months can cause the EAT to be below the LCT, but strategic use of drafts can make management easier. We know that drafts directed at the snouts of lactating sows very effectively reduces the EAT in a room where ambient temperatures need to be high to meet the requirements of baby pigs.
Insulation provided by bedding or comfort mats can raise the EAT. Similarly, direct exposure to surfaces with high heat conduction (like concrete or metal) can conduct heat away from the body.
Variation in EAT can be extremely stressful, especially to young pigs. The most modern nurseries can reduce variation in ambient temperature to 1/2 degree F per 24 hours. A reasonable goal is to keep variations in ambient temperature to 2F or less per 24 hours. An essential monitoring tool is a thermometer which minimum and maximum temperatures.
Copyright ©1997 by the University of Pennsylvania School of Veterinary Medicine
Faculty: Dr. Paul Pitcher
Student: Sandra Springer,'99