PROJECT RESULTS

Performance Evaluation of Heat Mats in Swine Farrowing Facilities

Table of Contents:

• Background and Objectives
• Procedure and Project Activities
• Results and Discussion
• Conclusions

ARDI Project:

Total Approved:

Date Approved:

Project Status:

#98-149

$32,120

November 16, 1998

Completed January, 2000

Background and Objectives:

Newborn piglets require relatively high environmental temperature to prevent excessive body heat loss. However, relatively low room temperature is desirable for the comfort of sows. It is thus a common practice to provide localized heat to the piglets while maintaining a lower room temperature for the sows in swine farrowing barns. Heat mats (pads), which are made of solid or flexible boards with embedded heating elements, have been considered by the swine industry as a choice of localized heating system.

1. Evaluate the thermal performance of commercial heat mats.

2. Investigate the resting behavior of piglets on heat mats.

3. Elucidate the principles of heat transfer in mat heating to assist mat designers and operators to better understand the heat mat operation.

Procedure and Project Activities:

Laboratory and in-barn tests were conducted on four mats to determine the thermal characteristics of commercial heat mats. Among the four mats tested in the laboratory, Mat C (made in Manitoba) showed the most uniform surface temperature distribution and was, therefore, selected for in-barn tests. Mat C is a double mat and measured 6.10 x 1.22 m (2 x 4 ft). It was electrically heated with embedded heating elements and had embedded temperature sensors. These temperature sensors provided feedback signals to the controllers for mat temperature regulation. The wattage ratings of the heating elements was 120 W. The rated power capacity per crate (single mat) was 60 W. The tests were conducted in an environmentally controlled farrowing room maintained at 21° C (70° F). Two widened crates (2.4 x 2.13 m or 8 x 7 ft.) were used in the tests. A sow was brought into each crate about two days before the expected farrowing date for each trial and piglets were weaned in two to three weeks. Mat surface temperature was measured using an IR imager (Inframetrics PM250) and type T (copper-constantan) thermocouples. A video camera (Panasonic, WV-CP410) was mounted directly above the heat mat in each crate to monitor the mat usage by piglets, and the video images were recorded using a time-lapse VCR (Panasonic, AG-6730). The video images were also digitized to determine the mat surface areas that were occupied by piglets when resting on the mat.

Results and Discussion:

Table 1.  Daily average mat usage (DAMU) and lying area.

Conclusions:

Electrical heat mats may contain hot spots (> 43° C or 109° F) if not designed or operated properly. Multiple temperature sensors should be embedded within the pig resting area of the mat to facilitate the controllability of the mat temperature. Without temperature feedback control (embedded sensors), mats can become excessively hot (> 43° C) for piglets lying on the mat for an extended time period. Based on model simulations, a design power-density capacity of 188 W/m², or 68 W for a single mat (1 x 4 ft), is recommended for maintaining the thermalneutrality (TN) of newborns (1.5 kg), and the power density can be reduced to 100 W/m², or 36 W per single mat when piglets have reached an early weaning weight of 4.0 kg. The power requirement for maintaining TN of piglets increases markedly as the environmental temperature decreases, the air velocity increases, or feed (milk) intake decreases. Mat usage by piglets varies with the pig age. The usage was low (19%) for 1-day old piglets and the peak usage (61%) occurred three days after farrowing. The piglets preferred the mat placed near the rear end of the sow. A mat surface area of 0.044 m²/pig (0.47 ft²/pig) should be provided to newborn piglets.

Project partners involved in this proposal include Alternative Heating Systems Inc. from Manitoba and the Iowa Energy Center in Ames, Iowa.

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