Effects of cooling systems on physiological responses and intestinal microflora in early gestating sows exposed to high-temperature stress

This study was conducted to investigate the effect of cooling systems on reproductive performance, body temperature, blood metabolites, and the intestinal microbiome in early gestating sows exposed to high ambient temperature.In total, 39 pregnant sows (Landrace × Yorkshire; 2 parities) were randomly assigned to and maintained in the following three treatment groups (13 sows per group) over days 0 to 35 of pregnancy: (i) air cooling (AC; 26.87 ± 1.23℃), (ii) water-drip cooling (WC; 28.81 ± 0.91℃), and (iii) a lack of cooling with heat stress (HS; 30.72 ± 0.70℃).Backfat thickness was measured before and after HS.Feces were collected on day 0 and 35 d of the trial for microbiome analysis, whereas blood was taken at day 35 of pregnancy and analyzed.Reproductive performance and physiological responses were identified at day 35.Respiration rate along with rectal and skin temperatures were lower (p < 0.05) in the AC group than in the HS and WC groups.Serum blood urea nitrogen values were increased (p < 0.05) in the WC group compared with those measured in the AC and HS groups.Triiodothyronine was found at greater levels (p < 0.05) in the AC than in the HS group.Reproductive performance was not affected by the cooling systems.At the phylum level, fecal pathogenic Spirochaete and Euryarchaeota were found in higher numbers (p < 0.05) in all groups after HS.Similarly, at the genus level, the amount of Treponema was greater (p < 0.05) in all groups after HS.In conclusion, our results suggest that AC or WC can ameliorate or mitigate the adverse effects of HS on the physiological parameters of pregnant sows reared under high temperatures.