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Animals are affected by heat stress (HS) and it results in economical losses, due to an increase respiratory rates and body temperatures, less body weight gains and feed intake. HS can compromise intestinal integrity and induce leaky gut in a variety of species. The main objective of this study was to determine if heat stress (HS) directly or indirectly (via reduced feed intake) increases intestinal permeability and markers of intestinal stress in growing pigs. It was hypothesized that an increased heat-load would cause physiological alterations to the intestinal epithelium, resulting in compromised barrier integrity, altered intestinal function and metabolism. A total of 48 crossbred gilts (43 ± 4 kg BW) were housed in individual pens with constant climate controlled rooms and exposed to 1) thermal neutral (TN) conditions (20°C, 35–50% humidity) with ad libitum intake, 2) HS conditions (35°C, 20–35% humidity) with ad libitum feed intake, or 3) pair-fed in TN conditions (PFTN) to eliminate confounding effects of dissimilar feed intake. All animals where fed a complete diet and monitored continuously for signs of distress such as excessively high core temperature (>41°C), weight loss, and complete loss of appetite. Pigs were sacrificed at 1, 3,or 7 d of environmental exposure and jejunum samples were mounted into modified Ussing chambers for assessment of trans-epithelial electrical resistance (TER) and intestinal fluorescein isothiocyanate (FITC)-labeled lipopolysaccharide (LPS) permeability (expressed as apparent permeability coefficient, APP). Further, gene and protein markers of intestinal integrity and stress were assessed.
Irrespective of d of HS exposure, plasma endotoxin levels increased 45% (P < 0.05) in HS compared with TN pigs, while jejunum TER decreased 30% (P < 0.05) and LPS APP increased 2-fold (P < 0.01). Furthermore, d 7 HS pigs tended (P = 0.06) to have increased LPS APP (41%) compared with PFTN controls. Lysozyme and alkaline phosphatase activity decreased (46 and 59%, respectively; P < 0.05) over time in HS pigs.
These results indicate that both HS and reduced feed intake decrease intestinal integrity and increase endotoxin permeability. This may partially be attributed to the reduced nutrient intake, as seen in the PFTN pigs, or as a consequence of potential changes in digesta flow rates and motility as a result of this reduced feed intake.
Pearce, S.C., Mani, V.,Weber, T.E., Rhoads, R. P., Patience, J. F., Baumgard, L. H. and Gabler N. K. 2013. Heat stress and reduced plane of nutrition decreases intestinal integrity and function in pigs. J. Anim. Sci. 2013.91:5183–5193. doi:10.2527/jas2013-6759