Solar Cooling of Sows

L. Johnston, M. Reese, E. Buchanan, K. Janni, and K. Sharpe

May 2017

Over the last couple years, WCROC researchers have been involved in a project entitled “Greening of Agriculture”.  This project focuses on methods to reduce the use of fossil fuels in production agriculture.  Many markets and food supply chains are encouraging food producers (farmers) to reduce their use of fossil fuels as a way to reduce the carbon footprint of current food production systems.  Currently, as part of this project, we have research studies underway in the areas of agronomy, dairy production, and swine production.  The overarching objective of these studies is to help farmers respond to market demands in a way that will reduce environmental impacts and maintain the economic viability of their production systems. 

Solar PV panels

Solar PV panels mounted on the roof of a WCROC swine barn.

As a next step in the Greening of Ag project, we are investigating the use of solar-generated electricity as a way to improve sow performance during summer.  During summer in Minnesota, sows that are nursing their piglets often experience heat stress.  High environmental temperatures in rooms that house sows and their litters cause sows to reduce feed intake which causes increased weight loss from sows and poorer breeding performance of sows after pigs are weaned.  Poorer breeding performance requires pig farmers to maintain extra sows during summer breeding to ensure they get enough sows pregnant to keep their barns full of pigs.  But, maintaining extra sows to offset poor reproductive performance compromises the biological and economic efficiency of a swine breeding operation.  There are several approaches to help sows cope with heat stress such as reformulation of diets fed to sows during summer, installing drip cooling and/or cool cells in the barn, and changing management approaches to encourage higher feed intake by sows.  These mitigation strategies are helpful but not entirely effective and many have specific drawbacks.  So, the current project is designed to investigate a more effective cooling system. 

Cooled flooring installed in a sow farrowing stall

Cooled flooring installed in a sow farrowing stall.

In the cooling system designed for this project, we will use a 20 kW solar photovoltaic array to power a chiller.  The chiller will circulate cool water (70°F) under the metal floor that sows lie on providing a cooling effect in the same way a residential under-floor heating system can heat a home.  The cooled water will cool the floor and thus cool the sow as she lies on the floor.  During hot periods of the day, sows typically spend much of their time lying.  In addition to the cooled flooring, we will supply cooled water (55 °F) to the drinker that supplies drinking water to the sows.  Our preliminary data collected on commercial swine farms suggests that drinking water for sows can range from 55 to 78 °F throughout the year.  So, we expect that a consistent supply of cool drinking water will help cool sows.  Our approach is to cool sows from the outside with the cooled flooring and from the inside with cooled water.  A cool sow will be more comfortable, will eat more feed, and be more productive than a heat-stressed sow. 

We expect to conduct this experiment during the summer of 2017 and possibly in the summer of 2018.  In addition to effects on sow comfort and performance, we will evaluate sow and piglet behavior, monitor effectiveness and robustness of the cooling system, track quality of the environment within the barn, and calculate the economic feasibility of using such a system.  Stay tuned for results as they become available. 

This project is funded by the State of Minnesota through the Minnesota Environment and Natural Resources Trust Fund and the Minnesota Agricultural Experiment Station. 

More Info

Greening of Ag: Swine Production

Greening of Ag: Crop Production

Greening of Ag: Dairy Production