CategoryAnimal Science - Animal Science
Date Full Report Received12/31/2017
Date Abstract Report Received12/31/2017
InvestigationInstitution: University of Minnesota
Primary Investigator: Dr. Erin Cortus
Co-Investigators: Joseph Darrington, Robert Thaler
Funded ByNational Pork Board
As pig genetics and feeding programs advance, the heat production and environmental needs of pigs also change. Grow-finish pigs are especially susceptible to hot weather conditions that our existing ventilation systems cannot completely mitigate. There are various ways to further cool pigs using evaporation, convection and conduction, but each heat transfer method also requires additional resource inputs in the form of water or energy, which have associated costs.
The long-term goal of this research is to understand the effects of floor temperature control on conductive heat transfer through the skin of the pig, swine performance, and management implications of utilizing this technology. An initial knowledge gap we set out to answer is ”With modern genetics and leaner pigs, how has the tissue resistance of the animals changed?” Specifically, the objectives were to: (1) Evaluate the postural (resting, standing) effects on heat flux and tissue thermal resistance; (2) Refine existing animal growth models to accommodate conductive heat transfer and activity, for modern pigs; and (3) Develop a monitoring methodology to measure the postural effects of floor tempering in group-housed animals.
Heat flux (flow of heat energy per unit area and time) measurements were collected from twelve individually-housed active barrows in the average (±standard deviation) weight ranges of 95.6±15.5 kg (210±34 lb) and 111±13.9 kg (245±31 lb), and referred to as Trials 1 and 2, respectively. Heat flux measurements were collected every minute from the right and left sides and rumps of the pigs over a six hour period. An overhead video camera system recorded pig behavior and positioning within a pen throughout the trials.
The average measured heat flux from the side of a 50 kg pig was 131 W/m2, and the heat flux decreased 2.64 (SE 0.83) W/m2 for every 10 kg (22 lb) increase in pig mass, up to 120 kg (265 lb). Fat and thicker skin and muscle tissue provides more resistance to heat flow, thus decreasing the rate of heat flow for a given area. The heat flux measurements were collected from a shaved area, so the variable impact of the pig’s coat was not considered.
Tissue resistance is related to both pig mass/size and ambient temperature conditions. In the limited ambient temperature window of 20ºC to 25ºC, the tissue resistance (coat not included) for the barrows in these trials was less than tissue resistance values prescribed in the early 1990s. Tissue resistance values estimated for these project pigs suggest a minimum and maximum tissue resistance of 0.0015 and 0.014 ºC m2/W for ambient temperatures of 39ºC and 0ºC, respectively.
Behavior monitoring provides insight into how environment influences positioning and activity, which in turn affects feed conversion. Video cameras and game cameras were used in this project, though not simultaneously. Our experience showed that the camera positioning and picture frequency were more influential than the technology used. Daily patterns of feeder occupancy and number of pigs lying on the solid floor are suitable variables to measure with time lapse or motion detection technology available in relatively inexpensive game cameras.
Heat production and flux or transfer to the environment are affected by many factors including nutritional plane, growth rate, internal temperature, environmental temperature, evaporation from the skin and respiratory tract, airflow rate, surface temperatures, and body position. This study captured heat flux data from active grow-finish pigs. In the course of detecting heat flux patterns and conditions based on the lying or standing position, the influence of other environmental factors like manure on the skin surface or air gaps were also evident. As animal and environmental models progress, including conduction along with convection and evaporation (planned and unplanned) will add more complexity, but will ultimately help us better evaluate an animal’s response to varying environments and management strategies to promote efficient production and animal welfare in all conditions.
• The average measured heat flux from the side of a 50 kg (110 lb) pig was 131 W/m2, and the heat flux decreased linearly to 113 W/m2 for a 120 kg (265 lb) pig.
• Tissue resistance estimates were 0.023 to 0.034 ºC m2/W for 40 to 130 kg (88 to 287 lb) pigs, respectively, in the ambient temperature conditions of 22.5ºC (72.5ºF).
• Daily patterns of feeder occupancy and number of pigs lying on the solid floor are suitable variables to measure with time lapse or motion detection technology available in relatively inexpensive game cameras.
For more information, please contact Erin Cortus, University of Minnesota (612-625-8288; email@example.com) or Joseph Darrington, South Dakota State University (605-688-5672; firstname.lastname@example.org).