Table 1.
Lactation diet composition (as-fed basis).
Fig 1.
Temperature, dew point, and relative humidity during experiments.
Experimental phase 1 (A) and phase 2 (B) hourly room temperature (solid green line) and dew point (orange line) recorded by temperature loggers in experimental room, and air temp (dotted green line) as recorded by the weather station in West Lafayette, Indiana. Phase 1 (C) and phase 2 (D) hourly relative humidity (% rh) recorded by temperature loggers. Black bars on the x-axis represent the dark phase while the white bars represent the light phase of the 16 h light and 8 h dark cycle.
Table 2.
Multiple reaction monitoring for data acquisition of cortisol and melatonin saliva concentrations.
Fig 2.
Effect of Cooling on RR and RT.
The effect of cooling (blue) and H(red) on mean (open circles) RR (A) and RT (B) and the fit to sine and cosine curves (solid line) over 48 h. Black bar on the x-axis represent the dark phase while the white bars represent the light phase.
Fig 3.
Cooling on HS sow eating, standing, laying and nursing behaviors.
Effect of cooling (C) (blue) and heat stressed (H) (red) on eating (A), standing (B), laying (C), and nursing (D) behaviors over 24 h from time slice analysis. Black bar on the x-axis represents the dark phase while the white bar represents the light phase. * indicates results from time slice analysis on treatment by time interaction with significance at P < 0.05, and + indicates a significant tendency at P < 0.1.
Fig 4.
The relationship between eating behavior to RT increment in HS sows.
The rectal temperature (RT) were fitted to the Fourier series and eating in the previous 2 h included as a linear covariate. The RT (bold smooth line) and a 2 h lag in the time of eating (circled line) of heat-stressed group (H) over a 48 h period indicate a second peak of RT in dark phase, and corresponds to the increased eating 2 h prior. The x-axis has a black bar representing the dark phase and a white bar representing the light phase.
Fig 5.
Effect of cooling on circadian rhythms of salivary cortisol and melatonin concentration.
Effect of cooling (blue) or H (red) on sow salivary cortisol (A) and melatonin (B) concentrations over 48 h and the fitting to sine and cosine curves. The black bar on the x-axis represents the dark phase, while the white bar represents the light phase.
Fig 6.
Impact of cooling on diurnal salivary cytokine levels.
The effect of cooling (blue) HS (red) sows on the relative abundance of cytokines. Levels are relative to average densitometry of positive control spots on the array. IL-1a_Interleukin 1 alpha; IL-1b_Interleukin 1 beta; IL-1Ra_Interleukin 1 receptor antagonist; IL-10_Interleukin 10; IL-12 p70_Interleukin 12; IL-15_Interleukin 15; NCAM-1_Neural cell adhesion molecule 1; TGF beta 1_Transforming growth factor beta 1; TNF alpha 1_ Tumor necrosis factor alpha 1.
Fig 7.
Schematic of proposed mechanism of cooling ameliorations of heat stress.
Cooling represses alterations in daily patterns of respiration rate, rectal temperature, timing of feed intake, and salivary melatonin concentrations. We propose that cooling reduces the shift in feeding time, which likely increases daytime melatonin release from the gut, raising daytime salivary melatonin levels and decreasing oxidative stress and salivary inflammatory cytokines. These effects mitigate negative heat stress responses, thereby supporting the positive impact of cooling on circadian rhythms. The figure also suggests that changes in feeding time can influence rectal temperature and vice versa.