Heat Stress Reduces Metabolic Rate While Increasing Respiratory Exchange Ratio in Growing Pigs

Abstract

Heat stress (HS) diminishes animal production, reducing muscle growth and increasing adiposity, especially in swine. Excess heat creates a metabolic phenotype with limited lipid oxidation that relies on aerobic and anaerobic glycolysis as a predominant means of energy production, potentially reducing metabolic rate. To evaluate the effects of HS on substrate utilization and energy expenditure, crossbred barrows (15.2 ± 2.4 kg) were acclimatized for 5 days (22 °C), then treated with 5 days of TN (thermal neutral, 22 °C, n = 8) or HS (35 °C, n = 8). Pigs were fed ad libitum and monitored for respiratory rate (RR) and rectal temperature. Daily energy expenditure (DEE) and respiratory exchange ratio (RER, CO2:O2) were evaluated fasted in an enclosed chamber through indirect calorimetry. Muscle biopsies were obtained from the longissimus dorsi pre/post. HS increased temperature (39.2 ± 0.1 vs. 39.6 ± 0.1 °C, p < 0.01) and RER (0.91 ± 0.02 vs. 1.02 ± 0.02 VCO2:VO2, p < 0.01), but decreased DEE/BW (68.8 ± 1.7 vs. 49.7 ± 4.8 kcal/day/kg, p < 0.01) relative to TN. Weight gain (p = 0.80) and feed intake (p = 0.84) did not differ between HS and TN groups. HS decreased muscle metabolic flexibility (~33%, p = 0.01), but increased leucine oxidation (~35%, p = 0.02) compared to baseline values. These data demonstrate that HS disrupts substrate regulation and energy expenditure in growing pigs.

The Effect of Heat Stress and Vitamin and Micro-Mineral Supplementation on Some Mineral Digestibility and Electrolyte Balance of Pigs

“…However, our results suggest otherwise-although such losses did not significantly affect all the studied parameters. Acute and chronic HS reduces metabolic rate, causes metabolism disorders, acute phase response, and respiratory alkalosis that might affect the electrolyte balance of pigs [11,[46][47][48]. The concentration of plasma Cl − obtained from pigs under HS + fed basal diet (HC) was significantly reduced (p < 0.01) and is below the reference range in pigs (94-106 mmol/l) [49], regardless of the duration of exposure, which is in contrast to the results observed by Pearce et al [5] in pigs exposed to acute HS (2-6 h).…”

The Effect of Supplementation with Betaine and Zinc on In Vitro Large Intestinal Fermentation in Iberian Pigs under Heat Stress

“…Pigs are highly susceptible to HS because of their scattered sweat glands and elevated metabolic rate [ 2 ]. The negative impact of HS on pig growth has been shown in cosmopolitan pigs [ 3 ] and also in purebred Iberian pigs [ 4 ]. The exact mechanisms of heat stress-induced reactions in productivity are unknown but might be partially mediated by its effects on intestinal integrity.…”

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

“…It has been reported that heat stress plays a negative role in animal welfare and animal production, especially in broilers (Soravia et al, 2021). During heat stress, energy metabolism is reduced, leading to poor organ development and decreased mass gain (Fausnacht et al, 2021). It has been reported that energy metabolism and immunity are related (Wang et al, 2020).…”