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

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., total heat production [THP]) and litter growth performance in HS exposed sows. Over two repetitions, 12 multiparous (2.69 ± 0.85) lactating sows (265.4 ± 26.1 kg body weight [BW]) and litters were assigned to either an ECP (n = 3/repetition) or a non-functional ECP (NECP; n = 3/repetition) and placed into farrowing crates within indirect calorimeters from days 3.7 ± 0.5 to 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 ± 0.26 °C nighttime to 33.09 ± 0.19°C daytime). On days 4, 8, 14, and 18 of lactation, indirect calorimetry was performed on each individual sow and litter to determine THP and THP/kg BW0.75. Body temperature (TB) was measured hourly using vaginal implants, and respiration rate (RR; breaths per minute [bpm]) was measured daily at 0700, 1100, 1300, 1500, and 1900 h. Sow feed intake (FI) was assessed daily. Litter weights were obtained at birth, on days 4, 8, 14, and 18 of lactation, and at weaning. Data were analyzed using PROC GLIMMIX with sow and/or litter as the experimental unit. An overall decrease (P < 0.01; 25 bpm) in RR and maximum daily TB (P = 0.02; 0.40 °C) was observed in ECP vs. NECP sows. An increase in THP (P < 0.01; 20.4%) and THP/kg BW0.75 (P < 0.01; 23.1%) was observed for ECP when compared with NECP sows and litters. Litter average daily gain and weaning weight were increased (P < 0.05; 25.0 and 19.2%, respectively) for ECP vs. NECP litters. No FI differences were observed (P = 0.40) when comparing ECP (5.66 ± 0.31 kg/d) and NECP (5.28 ± 0.31 kg/d) sows. In summary, ECPs improve litter growth, thermoregulatory measures, and bioenergetic parameters associated with greater milk production in lactating sows exposed to cyclical HS.

Keywords: cooling pad; heat stress; lactation; mitigation; pigs; sows.

Figure 1.

Effects of an ECP and NECP on the RR of lactating sows exposed to cyclical HS over a 16-d period. Data are presented as LSM ± SE. Letters^a,b,c,d,e indicate ECP treatment by study day differences (P < 0.01).

Figure 2.

Effects of an ECP and NECP on the T_B of lactating sows exposed to cyclical HS over a 16-d period. Data are presented as LSM ± SE. No ECP treatment by study day differences (P > 0.05) or tendencies (P > 0.10) were observed.

Figure 3.

Effects of an ECP and NECP on the (A) THP and (B) THP/kg BW^0.75 of lactating sows and their litters exposed to cyclical HS on lactation days 4, 8, 14, and 18. Data are presented as LSM ± SE. No ECP treatment by lactation day differences (P > 0.05) or tendencies (P > 0.10) were observed for THP or THP/kg BW^0.75.

Figure 4.

Effects of an ECP and NECP on the BW of piglets exposed to cyclical HS from lactation days 3.7 ± 0.5 until weaning (days 18.7 ± 0.5). Data are presented as LSM ± SE. Birth weight was used as a covariate and birth weight data are included for descriptive purposes only. Letters^a,b,c,d,e indicate ECP treatment by lactation day differences (P < 0.01). Symbols^{&,@,^,#,~} indicate overall lactation day differences (P < 0.01). An asterisk* indicates overall ECP treatment differences (P < 0.01).