Electronically controlled cooling pads can improve litter growth performance and indirect measures of milk production in heat-stressed lactating sows

Authors: Johnson, Jay; JANSEN, TAYLOR - Purdue University; GALVIN, MICHAIAH - Purdue University; FIELD, TYLER - Purdue University; GRAHAM, JASON - Purdue University; STWALLEY, ROBERT - Purdue University; SCHINCKEL, ALLAN - Purdue University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2021
Publication Date: 2/1/2022
Citation: Johnson, J.S., Jansen, T.L., Galvin, M., Field, T.C., Graham, J.R., Stwalley, R.M., Schinckel, A.P. 2022. Electronically controlled cooling pads can improve litter growth performance and indirect measures of milk production in heat-stressed lactating sows. Journal of Animal Science. 100(2). Article skab371. https://doi.org/10.1093/jas/skab371.
DOI: https://doi.org/10.1093/jas/skab371

Interpretive Summary: Pork consumption is projected to increase substantially and is one of the most widely consumed meats in the world. However, pork production occurs in warm climates and in locations that have seasonal heat stress, which can negatively impact pig health, productivity, and welfare. This is because heat stress (HS) causes decreased swine growth performance, reproductive efficiency, and in severe cases, mortality, leading to reduced productivity and financial losses for the swine industry. Lactating sows are especially sensitive to the negative effects of HS due to greater feed intake and increased metabolic heat production as a result of milk production. As a result, heat stress reduces sow milk production, which can negatively impact piglet growth and health. To address this issue, various cooling methods have been developed and implemented. In particular, floor cooling pads that remove excess heat improve the ability of lactating sows to maintain a normal body temperature under heat stress conditions. However, it is currently unknown whether the use of cooling pads during times of heat stress can promote improved sow and litter performance. It was determined that sow cooling pads were effective in improving piglet growth performance and that this was associated with increased sow milk production independent of an increase in sow feed intake. In addition, the cooling pads allowed the sows to maintain a normal body temperature under heat stress conditions. These data indicate that the use of floor cooling pads are an effective mitigation tool to improve lactating sow welfare and performance under heat stress conditions.

Technical Abstract: Heat stress (HS) decreases lactation output in sows due to an attempt to reduce metabolic heat production. However, this negatively affects litter growth performance. Therefore, the study objective was to determine whether electronically controlled cooling pads (ECP) would improve indirect measures of lactation output (e.g., metabolic heat production) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg) and litters were assigned to either an ECP (n = 6) or a non-functional ECP (NECP; n = 6) and placed into farrowing crates within indirect calorimeters from d 3.7 ± 0.5 to d 18.7 ± 0.5 of lactation. Litters were standardized across all sows (11.4 ± 0.7 piglets/litter), and sows were provided ad libitum feed and water. All sows were exposed to cyclical HS (28.27 ± 1.42°C nighttime to 35.14 ± 0.70°C daytime). On d 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine total heat production (THP). Body temperature (TB) was measured hourly using vaginal implants, and respiration rate (RR) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Litter weights were obtained at birth and weaning. An overall decrease (P < 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40°C) was observed in ECP versus NECP sows. An increase in THP (P < 0.01; 20.4%) and THP/kg0.75 (P < 0.01; 23.1%) was observed for ECP when compared to NECP sows and litters. Litter growth rate was increased (P < 0.01; 20.8%) in ECP versus NECP sows. In summary, the use of ECP improves litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical HS.