Technical note: Development of an indirect calorimetry system to determine heat production in individual lactating sows

Authors: Johnson, Jay; ZHANG, SAI - Michigan State University; MORELLO, GABRIELA - Purdue University; MASKAL, JACOB - Purdue University; TROTTIER, NATHALIE - Michigan State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2019
Publication Date: 2/7/2019
Citation: Johnson, J.S., Zhang, S., Morello, G.M., Maskal, J.M., Trottier, N.L. 2019. Technical note: Development of an indirect calorimetry system to determine heat production in individual lactating sows. Journal of Animal Science. 97(4):1609-1618. https://doi.org/10.1093/jas/skz049.
DOI: https://doi.org/10.1093/jas/skz049

Interpretive Summary: The ability to measure the heat production of livestock is a valuable tool for researchers to measure energy balance and understand the thermodynamics of animals to their environments. Unfortunately, many current systems require the use of multiple animals in a room to generate data for the group rather than the individual, precluding determination of animal to animal variability. In addition, methodological difficulties may be present that reduce the ability of researchers to determine total heat production in individual lactating sows independent of the litter. Methods to evaluate the environmental impact on total heat production in lactating sows are often limited to developing estimation models or measuring at the room or group level rather than in individual animals due to animal husbandry practices and indirect calorimeter design. The study objectives were to develop and test a cost-effective indirect calorimetry system capable of measuring total heat production in individual lactating sows and their litters, and to evaluate a technique to separate sow and litter data. It was determined that this system could accurately evaluate total heat production in sows and their litters both together and separately. Furthermore, as lactation progressed total heat production increased. These data have implications towards increasing the ability of researchers to measure the heat production of individual swine. This ability will allow for the design of facilities to help reduce thermal stress.

Technical Abstract: Indirect calorimetry is a valuable tool for researchers to measure energy balance. However, these systems may require the use of multiple animals to generate data for a group and the ability to determine total heat production (THP) in individual sows and litters can be logistically difficult. Therefore, the study objective was to develop an indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were designed to house 1 sow and litter in a crate throughout farrowing and a 21-d lactation period. Farrowing crates were placed within a high-density polyethylene (HDPE) pan filled with water and then a polyvinyl chloride (PVC) frame was constructed around the crate. The frame provided a structure to hold the inlet and outlet air pipes, feed and water inlets, and a polyethylene plastic sheet that was secured at the bottom of the frame and submerged under water to maintain an air tight seal. Chamber accuracies for O2 and CO2 were evaluated by ethanol combustion. One-week pre-farrowing, 6 pregnant multiparous sows (parity 2.9 ± 0.9; 218.3 ± 38.6 kg BW) were housed individually in each farrowing crate and maintained in thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation d 4, 8, 14, and 18, indirect calorimetry was performed on all sows and their litters, as well as 2 piglets from a sentinel litter to determine THP and the respiratory quotient (RQ). Sentinel piglet data were used to estimate THP and RQ for the sows independent of the litter. Sow + litter THP/kg BW0.75 increased (P = 0.01; 11.2%) on d 8 compared to d 4 and was greater (19.0%) on d 14 and 18 compared to d 4 and 8. Sow THP/kg BW0.75 was greater (P = 0.01) on d 8 (7.09 ± 0.32 kcal/kg BW0.75), d 14 (7.62 ± 0.32 kcal/kg BW0.75), and d 18 (7.09 ± 0.56 kcal/kg BW0.75), compared to d 4 (6.18 ± 0.29 kcal/kg BW0.75), and was greater on d 14 compared to d 8. No sow + litter RQ differences (P = 0.21; 1.02 ± 0.04) were detected by day of lactation, and sow RQ was greater (P = 0.01) on d 14 (0.98 ± 0.02) compared to d 4 (1.03 ± 0.03), d 8 (1.02 ± 0.02), and d 18 (1.04 ± 0.03). In summary, this system may allow researchers to accurately evaluate THP in individual lactating sows and their litters and separate the sow THP from the litter THP.