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The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days −7 to −1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days −4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature.

Pigs reared in commercial conditions are often exposed to sanitary challenges. Consequently, the immune system interacts with regulatory and metabolic mechanisms to maintain animal homeostasis and integrity. For instance, a redistribution of nutrients from growth to the immune responses have been widely reported in challenged animals including pigs. However, little is known on the effects of imune system activation on amino acids metabolism in growing pigs. The aim of this study was then to evaluate the effects of an inflammatory challenge caused by repeated injections of Escherichia coli lipopolysaccharide (LPS) on the branched-chain amino acids leucine, isoleucine and valine. Fourteen growing pigs fitted with a jugular catheter were housed in a temperature-controlled room in which ambient temperature was maintained constant at 24°C. The experimental period lasted 17 days that was subdivided in a seven days period before and a 10 days period during the inflammatory challenge that consisted in five repeated injections of LPS at two days intervals. The initial dose of 30 μg/kg of body weight was increased by 12% at each subsequent injection. Before the LPS-challenge (baseline), and 24h after the second (T1) and the fourth (T2) LPS injections, 300 g of feed was given to pigs previously fasted overnight and serial blood samples were taken over four-hours to measure plasma amino acids concentrations. Amino acids postprandial concentrations were analyzed using the linear MIXED procedure of SAS including the fixed effects of time points (baseline, T1 or T2). According to our results, pigs had lower (P < 0.05) postprandial concentrations of leucine, isoleucine and valine during than before the LPS challenge. The lower plasma concentrations of the branched-chain amino acids might be associated to their increased transamination and oxidation to be used as energy source during the inflammatory challenge to support the synthesis of immune system compounds and others immune actions such as the fever response. These results suggest that the requirements for branched-chain amino acids is increased in response to inflammatory stimuli and that the supplementation of these amino acids might be advantageous in pigs exposed to immune and/or sanitary challenges.

Sanitary challenges and/or immune system activation are associated with decreased voluntary feed intake, increased metabolic rate and energy expenditure, and alterations on nutrient utilization in growing pigs. As a consequence, animals weight gain and feed efficiency are negatively impacted in such conditions. The aim of this study was then to evaluate the effects of an inflammatory challenge caused by repeated injections of Escherichia coli lipopolysaccharide (LPS) on lysine, threonine and tryptophan postprandial metabolism. Fourteen growing pigs fitted with a jugular catheter were housed in a temperature-controlled room in which ambient temperature was maintained constant at 24°C. The experimental period lasted 17 days that was subdivided in a seven days period before and a 10 days period during the inflammatory challenge that consisted in five repeated injections of LPS at two days intervals. The initial dose of 30 μg/kg of body weight was increased by 12% at each subsequent injection to circumvent adaptive endotoxin resistance to the repeated inflammatory stimuli. Before the LPS- challenge (baseline), and 24h after the second (T1) and the fourth (T2) LPS injections, 300 g of feed was given to pigs previously fasted overnight and serial blood samples were taken over four-hours to measure plasma amino acids concentrations. Amino acids postprandial concentrations were analyzed using the linear MIXED procedure of SAS including the fixed effects of time points (baseline, T1 or T2). Relative to baseline, postprandial concentrations of lysine were lower at T1 and greater at T2. In addition, the LPS-challenge induced a long-lasting (at T1 and T2) reduction in plasma postprandial concentrations of threonine and tryptophan. Firstly, these results suggest a short-term increased utilization of lysine to be used as energy source during the LPS-challenge. Then, lysine demand decreases in association with a lower protein synthesis for growth. Secondly, they evidence an increased threonine and tryptophan metabolic demand to support the requirements of the immune response. For instance, the immune system activation induces the synthesis of acute phase proteins that, in turn, have greater amounts of threonine and tryptophan in their compositions. Finally, our evidences that an inflammatory challenge caused by LPS leads to significant changes on amino acids metabolism and partitioning. induces significant changes in the postprandial metabolism of growing pigs. These findings may contribute to redefine pigs nutritional requirements during inflammatory and/or immune challenges.