Written by Lee Johnston, Brigit Lozinski, Mike Reese, Eric Buchanan, Yuzhi Li and Adrienne Hilbrands, West Central Research and Outreach Center, Morris MN; Kevin Janni, Brian Hetchler and Erin Cortus, Department of Biosystems and Biological Engineering, St. Paul, MN; University of Minnesota
Food retailers and consumers worldwide are pressuring food producers (farmers) to reduce the use of fossil fuels and lower the carbon footprint of their production systems. Over the last couple years, researchers at the West Central Research and Outreach Center (WCROC) 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. 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.
As part of the Greening of Ag project, we are investigating the use of solar-generated electricity as a way to reduce heat stress of sows during summer and improve sow performance. During summer in Minnesota, lactating sows often experience heat stress which leads to reduced feed intake, increased sow weight loss and poorer postweaning breeding performance of sows. This suboptimal breeding performance makes it difficult for producers to hit their breeding targets which compromises the biological and economic efficiency of their farrowing 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 was designed to investigate a different and hopefully more effective approach to cooling sows.
For this project, we used two mirror-image, farrowing rooms equipped with 16 farrowing stalls each. Each farrowing stall in the COOL room was equipped with a cooled flooring insert under the sow (Cool Sow, Nooyen Manufacturing, Netherlands; Figure 1) and a single nipple drinker that delivered chilled drinking water to the sow. A water-source heat pump cooled water (60 to 65 °F) that was circulated in a closed loop under the floors that sows laid on. The heat pump also cooled water (55 to 60 °F) that was supplied to nipple drinkers for sows in a continuously circulating loop. Heat captured from the under-floor sow cooling loop was transferred to warm water (110 to 119 °F) that circulated through pads in the piglet creep area. The heat pump and all circulating pumps were powered by a 20 kW photovoltaic solar array (Figure 2).
The CONTROL room was nearly identical to the COOL room except there was no cooling of floor inserts or drinking water and supplemental heat for piglets was provided by one heat lamp (125 W) per farrowing stall (Group 1) or an electric heating pad (Hog Hearth, Innovative Heating Technologies; Group 2). Groups (n = 28 CONTROL sows and 28 COOL sows) were studied during summer months and room heaters were operated to keep rooms above 75 °F to ensure sows were heat stressed. Electric consumption for all systems (ventilation, piglet heating, lights, and cooling system) was measured and performance of sows and piglets were recorded over lactation. Our goal was to determine if the renewable electricity generated by the solar panels would be enough to operate the sow cooling system and if this cooling system would improve the performance of sows and piglets.
After two farrowing groups completed the study, we learned that the COOL room consistently used more electricity than the CONTROL room (Figures 3 and 4). For Group 1, the COOL room used 93.0 kWh/day while the CONTROL room used 35.3 kWh/day. Similarly in Group 2, the COOL and CONTROL rooms required 71.5 and 19.7 kWh/day, respectively. Production of electricity from the solar panels totaled 95.3 and 86.7 kWh/day during groups 1 and 2, respectively. Sows housed in the COOL room were more comfortable as indicated by a lower respiration rate (64.4 vs 96.8 breaths/min), higher voluntary feed intake (11.39 vs 9.25 lb/day) and reduced lactation body weight loss (35.1 vs. 54.2 lbs) compared with sows housed in the CONTROL room. But, this enhanced sow comfort in the COOL room had no effect on litter size at birth and weaning or weaning weight of pigs compared to the CONTROL room.
The cooling systems (cooled floor and cooled drinking water) and piglet heating systems studied effectively reduced heat stress of lactating sows but did not enhance sow or pig performance. Furthermore, these cooling systems required over 2.5 times more total electrical energy than a traditional lactation housing system without sow cooling. So, we satisfied our objective of cooling sows with renewably-produced electricity but we were not able to improve reproductive performance of sows and litters.
The focus on use of renewable energy in agricultural production systems will be on display at the Midwest Farm Energy Conference.
We appreciate the financial support for these projects provided by the State of Minnesota through the Minnesota Environment and Natural Resources Trust Fund and the Minnesota Agricultural Experiment Station.
|Figure 1. Cooled flooring (foreground) installed in a sow farrowing stall.
Photo credit: Esther Jordan
|Figure 2. Solar PV panels installed at WCROC for the sow cooling project.
Photo credit: Lee Johnston
|Figure 3. Total energy use by room (kWh) and total solar energy produced (kWh) per day for Group 1.|
|Figure 4. Total energy use by room (kWh) and total solar energy produced (kWh) per day for Group 2.|