Technical note: development of an indirect calorimetry system to determine heat production in individual lactating sows1

Abstract

The ability to determine total heat production (THP) in individual sows and litters can be logistically difficult and often requires the use of multiple animals to generate data on a per room basis. Furthermore, these systems may be costly to construct, precluding their use by many researchers. Therefore, the objective was to develop a low-cost indirect calorimetry system to determine THP in individual lactating sows and litters. Six indirect calorimeters were constructed 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 pan filled with water and then a polyvinyl chloride frame was constructed around the crate. The frame provided a structure to hold the inlet and outlet air pipes, feed and water inlets, air circulation fans, 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 O 2 and CO 2 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 the calorimeters were maintained at thermoneutral conditions (20.9 ± 2.6°C and 43.7 ± 18.6% relative humidity) throughout lactation. On lactation day 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 (kcal/h) increased (P = 0.01; 16.6%) on day 8 compared to day 4 and was greater (27.3%) on day 14 and day 18 compared to day 4 and day 8. Sow THP was greater (P = 0.01) on day 8 (401.19 ± 17.15 kcal/h) and day 14 (430.79 ± 12.42 kcal/h) compared to day 4 (346.16 ± 16.62 kcal/h), and was greater on day 14 compared to day 8, and on day 18 (386.16 ± 20.02 kcal/h) compared to day 14. No sow + litter RQ differences (P = 0.21; 1.02 ± 0.04) were detected by day of lactation. However, sow RQ was reduced (P = 0.01) on day 14 (0.98 ± 0.02) compared to day 4 (1.03 ± 0.03), day 8 (1.02 ± 0.02), and day 18 (1.04 ± 0.03). In summary, this cost-effective system (total cost: $1,892 USD) can allow researchers to accurately evaluate THP in individual lactating sows and their litters.

Effect of dietary near ideal amino acid profile on heat production of lactating sows exposed to thermal neutral and heat stress conditions

“…Thirty-two multiparous (parity 3.25 ± 0.54) lactating Yorkshire × Landrace sows were used, with 8 sows randomly assigned to 1 of 2 dietary treatments per block. In each block, sows were individually housed in farrowing stalls, with 6 located in chambers [12], and 2 for backup substitutes outside of chambers. Sows were exposed to a TN environment (21.0 ± 1.5°C and 41.8% ± 6.5% relative humidity) in blocks 2 and 4, or cycling HS environment (24.0 ± 1.7°C and 32.0 ± 1.3°C during nighttime and daytime, respectively, and 47.3% ± 5.4% relative humidity) in blocks 1 and 3, described in further details below.…”

“…These 2 sows were weaned on days 15 and 16, respectively. Calorimetry was conducted in accordance with methods described in detail by Johnson et al [12]. Briefly, within each indirect calorimetry testing day, THP was determined from 19:00-07:00 (overnight), 07:00 (pre-feeding), 08:00, 09:00, 10:00, 11:00, 13:00 (pre-feeding), 15:00 and 19:00 (pre-feeding).…”

“…Briefly, within each indirect calorimetry testing day, THP was determined from 19:00-07:00 (overnight), 07:00 (pre-feeding), 08:00, 09:00, 10:00, 11:00, 13:00 (pre-feeding), 15:00 and 19:00 (pre-feeding). Indirect calorimetry was also conducted on sentinel piglets to measure their THP on days 4, 8, 14 and 18, and detailed in Johnson et al [12]. The sentinel litter data were then used as a correction factor to estimate THP of the individual test sows as previously described [12].…”

“…Indirect calorimetry was also conducted on sentinel piglets to measure their THP on days 4, 8, 14 and 18, and detailed in Johnson et al [12]. The sentinel litter data were then used as a correction factor to estimate THP of the individual test sows as previously described [12].…”

“…Greater metabolic rate during lactation due to the intense demand for milk production and litter-rearing [12] increases heat sensitivity [5] and HS risk to a larger extent than other production stages [4]. Therefore, reducing heat production in lactating sows exposed to high environmental temperatures may improve production efficiency and welfare.…”