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Development and use of sow cooling pads during farrowing and lactation

Floor cooling is based on the conduction of heat from the sow to a sink while lying down.

Heat stress has negative effects on sow productivity and reproductive performance. It has multiple impacts on animal metabolism and physiology. These include: increased body core temperature, increased blood flow to the skin to dissipate radiant heat, increased respiration rates to remove the excess heat, and reduced feed intake as a strategy to reduce heat production. Consequently, sows under heat stress have reduced milk production and litter weight gain. Sows with excessive body protein loss during lactation have increased days from weaning to estrus and reduced conception rates.

During the last three decades, continuous selection for increased litter size and milk production has increased the heat production of sows and reduced their upper critical temperature. This selection has also resulted in decreased piglet birth weights and less body energy reserves at birth, requiring greater farrowing room temperatures and the use of heat pads or heat lamps to provide local heat for piglets.

The Animal Sciences and Agricultural Biological Engineering Departments at Purdue University and the USDA-ARS Livestock Behavior Research Unit have been working together for the last three years to develop a cooling pad able to efficiently remove excess of heat from lactating sows.

Floor cooling is based on the conduction of heat from the source (the animal) to a sink (chilled water running through the pipes), while the animal is lying down. Aluminum and copper are able to effectively transfer heat between the two temperatures. The cooling pad has been built with a heavy-duty aluminum plate in the surface, high-density polyethylene base and copper water pipes attached to the aluminum plate (Figure 1). From these initial tests, pad dimensions were enlarged, and the range of constant flow rates, time between flushes and desired upper set temperatures for different environmental conditions were refined.

Figure 1 – Current prototype of Purdue hog-cooling
Figure 1 – Current prototype of Purdue hog-cooling

The refined cooling pad designs have been used in sow lactation trials, shown in Figure 2. Sows with no cooling spent more time in a “dog like posture” to increase body heat dissipation to the environment, less time on the feeder and less time milking in comparison to the sows with an active cooling. After 80 min of cooling, sows with active cooling had lower respiration rates (45 versus 122 breaths/min), heart rates (100 versus 119 beats/min), vaginal temperature (39.2 versus 40.1ºC), rectal temperature (39.0 versus 40.0ºC) and skin temperature (38.6 versus 39.4 ºC) than sows with no active cooling, respectively. The heat removal rate was three to four times greater than previous cooling pad designs made of concrete and steel pipes, covering entire floor sections.

Figure 2 – Purdue prototype hog cooling pad being tested in farrowing house.
Figure 2 – Purdue prototype hog cooling pad being tested in farrowing house.

The effectiveness of the sow cooling pads for an entire lactation was evaluated under mild and moderate heat stress conditions. The moderate heat stress room was targeted to achieve 32ºC from 0800-1600 h and 27ºC for the rest of the 24-hour day. The mild heat stress room was targeted to achieve 27ºC and 22ºC for the same periods, respectively. Yorkshire-Landrace sows were blocked by parity and BW, and assigned to two farrowing rooms which differed only in environmental temperature. Each sow was provided an eight–row cooling pad. Sows received either a constant cool water flow of 0.00 L/min (CONTROL, n = 9), 0.25 L/min (LOW, n = 12), or 0.50 (HIGH, n = 10) L/min. Water inlet and outlet temperatures and flow rates were recorded to estimate heat removal. Respiration rates (RR), rectal temperatures (RT) and skin temperatures (ST) were recorded daily (0700 and 1500 h) from the second day in the farrowing room to weaning at a mean age of 19 days. The sow cooling pads reduced the measures of heat stress. The LOW flow rate was adequate for the mild heat stress room and the HIGH flow rate was needed for the moderate heat stress rooms. Figures 3 and 4 show the effect of the Purdue hog cooling pads on RR, while Figures 5 and 6 show the effect on RT.

Variable Pad Treatment Mild – 700 h Moderate – 700 h Mild – 1500 h Moderate – 1500 h
Respiration rate CONTROL 23 56 41 89
LOW 21 24 29 41
HIGH 18 20 24 27
Skin temp CONTROL 35.4 37.3 37.2 37.3
LOW 34.4 36.5 36.6 36.5
HIGH 33.7 36.2 36.5 36.2
Rectal temp CONTROL 38.8 39.0 39.2 39.6
LOW 38.8 38.8 39.1 39.0
HIGH 38.8 38.8 39.1 39.0

Figure 3 - Least-squares means for respiration rate for the mild heat stress room. Target temperatures for mild heat stress were 27 ºC from 0800-1600 h and 22 ºC for the rest of the day. RR was affected (P < 0.001) by the pad treatment (Trt), room temperature (Room), Time of day (Time), lactation day and the interactions of Trt x Room, Trt x Time, Room x Time.
Figure 3 - Least-squares means for respiration rate for the mild heat stress room. Target temperatures for mild heat stress were 27 ºC from 0800-1600 h and 22 ºC for the rest of the day. RR was affected (P < 0.001) by the pad treatment (Trt), room temperature (Room), Time of day (Time), lactation day and the interactions of Trt x Room, Trt x Time, Room x Time.

Figure 4 - Least-squares means for respiration rate (RR) for the moderate heat stress room.&nbsp; Target temperatures for moderate heat stress were 32 &ordm;C from 0800-1600 h and 27 &ordm;C for the rest of the day. RR was affected (P &lt; 0.001) by the pad treatment (Trt), room temperature (Room), Time of day (Time), lactation day and the interactions of Trt x Room, Trt x Time, Room x Time.
Figure 4 - Least-squares means for respiration rate (RR) for the moderate heat stress room.  Target temperatures for moderate heat stress were 32 ºC from 0800-1600 h and 27 ºC for the rest of the day. RR was affected (P < 0.001) by the pad treatment (Trt), room temperature (Room), Time of day (Time), lactation day and the interactions of Trt x Room, Trt x Time, Room x Time.

Figure 5 - Rectal temperatures for mild heat stress room. Target temperatures for mild heat stress were 27 &ordm;C from 0800-1600 h and 22 &ordm;C for the rest of the day. The sow RT were affected (P &lt; 0.038) by the time of day, day of lactation, pad treatment &times; room temperature, pad treatment &times; time of day, day of lactation &times; room temperature, and 3-way interaction of pad treatment &times; room temperature &times; time of day.
Figure 5 - Rectal temperatures for mild heat stress room. Target temperatures for mild heat stress were 27 ºC from 0800-1600 h and 22 ºC for the rest of the day. The sow RT were affected (P < 0.038) by the time of day, day of lactation, pad treatment × room temperature, pad treatment × time of day, day of lactation × room temperature, and 3-way interaction of pad treatment × room temperature × time of day.

Figure 6 - Rectal temperature for moderate heat stress room. Target temperatures for moderate heat stress were 32 &ordm;C from 0800-1600 h and 27 &ordm;C for the rest of the day. The sow RT were affected (P &lt; 0.038) by the time of day, day of lactation, pad treatment &times; room temperature, pad treatment &times; time of day, day of lactation &times; room temperature, and 3-way interaction of pad treatment &times; room temperature &times; time of day.
Figure 6 - Rectal temperature for moderate heat stress room. Target temperatures for moderate heat stress were 32 ºC from 0800-1600 h and 27 ºC for the rest of the day. The sow RT were affected (P < 0.038) by the time of day, day of lactation, pad treatment × room temperature, pad treatment × time of day, day of lactation × room temperature, and 3-way interaction of pad treatment × room temperature × time of day.

Acknowledgements

This research was funded by Purdue University as part of AgSEED Crossroads funding to support Indiana’s Agriculture and Rural Development and by USDA-ARS Project 5020-32000-013-00-D – Protecting the Welfare of Food Producing Animals. The authors also would like to thank Daniel Madson and Aaron Doke for their work in the building and refinement of the cooling pad devices.

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29-Jan-2018gary_belas2000gary_belas2000So meaning that ..a very helpful to the sow using the pads aluminum.. It's that right?
30-Jan-2018aschinckaschinckaluminum is the best metal for heat transfer. The goal is to effectivily and efficiently remove excess heat from the sow and transfer it into the water.
31-Jan-2018smelsersmelserHave you consider using aluminum tubing for water transfer to the pads opposed to the copper tubing that is more expensive.
05-Feb-2018aschinckaschinckyes aluminum pipes could be used. Would need to have same outisde diameter as copper tubes. It is balance of cost and ease of working with the alumunium versus copper.
21-Feb-2018constantinosconstantinosVery interesting concept! You are mentioning cool water circulation. At what temperature was the water? Do you have any data on water temperature change after the end of the cycle?
06-Mar-2018aschinckaschinckwe can use cooling water from about 13 to 20 C. With slow flow rate we gain 5 to 8 C in temp from going into and coming out of the pad. We can have constant flow or flush the pad based on its temp.
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