The Effects of Recovery Time from Heat Stress on Circulating Bioenergetic Variables and Biomarkers of Leaky Gut

Abstract

The metabolic consequences of heat stress (HS) are atypical (i.e. hyperinsulinemia) considering the animal's nutritional status and a compromised intestinal barrier may initiate the pathophysiological consequences of HS. However, the temporal pattern of metabolic and leaky gut variables during HS recovery is not well‐understood. Female pigs (n=32; 19.5±1.3 kg BW) were sacrificed following exposure to one of four environmental protocols: 1) constant thermoneutral conditions (TN; 24.2°C and 57.2% RH), 2) no TN recovery following 3 d of HS (0d), 3) 3 d of TN recovery post 3 d of HS (3d), 4) 7 d of TN recovery post 3 d of HS (7d). The HS protocol was cyclical (33.6 to 37.4°C, 29.5% RH). All pigs were fed ad libitum. During the heat load, HS increased rectal temperature (P<0.01; 1.0ºC), and respiration rate (P<0.01; 63 bpm), but decreased feed intake (P<0.01; 24%) and growth (P<0.01; 33%) compared to TN controls. Blood glucose was decreased (P<0.05; 10%) for the 0 d pigs, but returned to TN levels by 3 and 7d. Recovery length did not affect circulating NEFA (P>0.73), insulin concentrations or the insulin:glucose (P=0.80). However, the insulin:feed intake was increased in the 0d compared to the TN controls (P=0.06; 49%). Lipopolysaccharide binding‐protein was markedly increased (P<0.05) with advancing recovery time: 67, 110, and 150% in 0, 3, and 7d pigs compared to TN controls, respectively. In summary, HS did not have a lasting effect on energetic variables, but advancing recovery length was associated with progressively increased biomarkers of leaky gut.