Date Full Report Received


Date Abstract Report Received



Primary Investigator:

Heat stress in growing pigs causes major economic and productivity losses for swine producers. While tunnel ventilation helps reduce heat stress by increasing airspeed inside barns to remove heat from the pigs, it becomes ineffective when the air temperature is equal to or greater than the skin temperature of the pigs. At this point, additional means for cooling are needed thus, for growing pigs, most facilities are equipped with low-pressure, large droplet sprinkler systems that are used for wetting the pigs. Once the pigs are wet, water evaporates from their skin and as water evaporates (changes from liquid to vapor) it removes heat directly from the pig. This cools the pigs and reduces the negative impacts of heat stress.

The major challenge with sprinkler systems is their operation. Currently, controllers operate with fixed “on” (sprinklers dispersing water) and “off” (evaporation time) intervals. This can lead to excess water usage and be ineffective at providing heat stress relief by: (i) applying more water to the animal when the previous water application has not evaporated and (ii) wasting unnecessary time once all the water has evaporated and the animal requires additional cooling. Further, there is no consideration for the environment inside the room and the impact it has on heat stress. Heat stress severity for growing pigs and estimated water evaporation rate must be characterized by the effective environment (air temperature, relative humidity, and airspeed) and pig body weight to make evidence-based and improved management decisions.

The goals of this project are to improve our understanding of the impact of cooling with sprinklers on growing pigs and create a new real-time control algorithm (Variable Interval Swine Sprinkler Control System; VISSCoS) that dynamically changes the ‘off’ interval (water evaporation time) based on dry-bulb temperature, relative humidity, airspeed, and pig body weight.

Initially, an analytical heat and mass transfer model for evaporating water on pigs was developed to estimate heat loss and the time for an assumed amount of water to be evaporated. This model was then validated using a simplified geometry (heat cylinder wrapped in chamois) in a custom environmental chamber. A control algorithm was then developed to determine the effective environment conditions to turn the sprinklers on (adapted from NPB#15-175) and estimate evaporation time. Two field performance evaluations were conducted. Exp. 1 was performed during summer 2018 in northeast Iowa, at a four room (~1,875 head per room) grow-finish facility with side-by-side rooms separated by a hallway. A mobile computer was interfaced with a custom multifunction data acquisition system to control the existing sprinkler system in two rooms while the other two room used the producers standard evaporating cooling pad operational protocol. Data were collected for 12 weeks (Jul 5 to Sep 30) to assess water usage, average daily gain of six pens per room, and thermal environment. Exp. 2 was performed in summer 2019 in northcentral Iowa at two wean-finish power-tunnel ventilated sites, each featuring four rooms (~1,200 hd per room). The sprinkler control algorithm was integrated into a commercial controller and used to operate the sprinklers in two randomly selected rooms per site which compared to the integrator’s standard hot weather protocol (1 minute “on,” 14 minutes “off”). Average daily gain was assessed for 6 pens per room by individually weighing pigs every 3 weeks for a 12-week duration.

The key findings of this project were:
• A completely new and unique approach to controlling sprinkler systems for cooling finishing pigs was created and tested such that producers can readily implement the direct outcomes of this project.
• The developed analytical model reasonably estimated the ‘off’ time interval for sprinkler systems, which is the duration needed for water applied to growing pigs to evaporate.
• The model was successfully integrated into a full-functional control logic for operating typical sprinkler systems in finishing facilities.
• Growing pigs raised in an environment conditioned with an evaporative pad were placed at heavier weights (p<0.05) and resulted in an overall lower ADG (0.95 kg d-1) compared to pigs raised with VISSCoS, which finished heavier (p<0.05) and an overall greater ADG (1.06 kg d-1; p<0.05).
• Growing pigs raised in a common high airspeed environment (tunnel) compared to pigs raised with high airspeed plus VISSCoS, showed no statistical difference in ADG at site A and site B.
This new information and technology will assist producers in the development of better management strategies for improving seasonal productivity limiting negative effects of heat stress. In addition, this new control algorithm has been successfully integrated in a commercially available controller for immediate use by producers.
For more information, please contact Dr. Brett Ramirez in the Department of Agricultural and Biosystems Engineering at Iowa State University. Email: bramirez@iastate.edu.