|JOHNSON, J. - Purdue University|
|SAPKOTA, A. - Purdue University|
|Lay Jr, Donald|
Submitted to: Joint Abstracts of the American Dairy Science and Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 3/26/2015
Publication Date: N/A
Technical Abstract: Heat stress (HS) reduces livestock welfare and productivity and can negatively impact pig health. The study objective was to determine the effects of two HS recovery methods (rapid vs. gradual cooling) on pig welfare after acute hyperthermia. In four repetitions, 36 barrows (88.7 ± 1.6 kg BW) were exposed to thermoneutral conditions (TN; n = 3/rep; 19.5 ± 0.1°C) for 6h, or HS (36.4 ± 0.1°C) for 3h, followed by a 3h recovery period of rapid cooling (HSRC; n = 3/rep; immediate TN exposure and water dousing) or gradual cooling (HSGC; n = 3/rep; gradual decrease in HS room temperature to TN). To evaluate heat dissipation, a thermal circulation index was calculated using gastrointestinal tract (TGI), ambient (TA), and skin (TSKIN) temperatures collected every 15 min [TCI; (TSKIN - TA)/(TGI - TSKIN)]. In repetitions 1 and 2, blood was collected at 60, 180, 210 and 240 min for lipopolysaccharide (LPS) analysis, and then pigs were euthanized at 360 min and duodenum, ileum and colon tissue was collected to determine intestinal morphology. HS treatment reduced (P < 0.02) TCI in HSRC (-0.69) and HSGC pigs (-0.64) compared to TN controls (1.31); however, during recovery HSRC reduced TCI (P < 0.01; 53.5%) compared to HSGC and TN treatments. In the duodenum and ileum, HSRC and HSGC treatment reduced villus height (P < 0.01; 29.4 and 21.1%, respectively) and increased crypt depth (P < 0.01; 56.9 and 32.2%, respectively) and villus width (P < 0.01; 30.5% and 32.5%, respectively) compared to TN controls. In addition, HSRC reduced duodenal and ileal villus height (P < 0.01; 27.6 and 38.2%, respectively) and increased crypt depth (P < 0.01; 43.8 and 35.2%, respectively) compared to HSGC pigs. While no colon crypt depth differences were observed for HSRC and HSGC pigs (156.8 µm), crypt depth was reduced (P < 0.01; 37.1%) in HSRC and HSGC pigs compared to TN controls. During HS, circulating LPS was similar for all treatments (P < 0.57; 56.2 EU/mL); however, during recovery HSRC pigs had increased circulating LPS (P < 0.05; 68.5 and 52.4%, respectively) compared to TN and HSGC pigs. In summary, rapid cooling after acute hyperthermia reduces heat dissipation capacity, damages intestinal tissue, and increases circulating LPS compared to gradual cooling.