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The objective of this study was to evaluate the performance and thermoregulatory responses during acclimation to high ambient temperature (Ta) of pigs from two lines selected for high (RFI) or low (RFI) residual feed intake with the hypothesis that RFI pigs producing less heat would better tolerate high Ta. Pigs (50 kg initial body weight; 17 per line among which 10 of them were catheterized) were individually housed in a climatic-controlled room where Ta was maintained at 24.2 ± 0.4 °C during 7 days and thereafter at 30.4 ± 0.7 °C during 14 days. Irrespective of Ta, RFI pigs had lower feed intake (ADFI) and similar average daily gain (ADG) than RFI pigs. Whatever the line, ADFI, ADG, and feed efficiency decreased with increased Ta. Overall, the Ta increase resulted in an increase in rectal temperature (RT), skin temperature (ST), and respiratory rate (RR) within the first 24-48 h and, subsequently, in a decrease followed by stabilization. The RT decrease during acclimation occurred 24 h earlier in RFI pigs than in RFI. Thyroid hormones and cortisol decreased at high Ta and it was similar in both lines. Based on performance and RT, ST, and RR responses, it seems that selection for low RFI tends to ameliorate pigs' tolerance to high Ta. Nevertheless, this selection does not induce significant differences between lines in endocrine and metabolite responses during thermal stress. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Pig production has increased in hot climate countries over recent years, but the effect of exposure to high temperatures on the health status of farm animals has not been investigated thoroughly. It is not clear how the ambient temperature (Ta) might influence responses to inflammatory challenge in pigs. The aim of the present study was to evaluate the effects of high Ta on performance and physiological parameters of growing pigs, subjected to repeated administration of Escherichia coli lipopolysaccharide (LPS). Thirty-seven pigs, each fitted with a jugular catheter, were assigned to one of two Ta conditions: thermo-neutral (TN, 24 °C) or high (HT, 30 °C). After a 14-day adaptation period, and a 7-day measurement period, pigs were administered five repeated injections of LPS at 48 h intervals. Irrespective of Ta, the LPS chal-lenge reduced feed consumption and increased plasma pro-inflammatory cytokines, haptoglobin and Cortisol. However, the extent of these responses was greater in pigs at TN than HT. In both groups, plasma thyroxine and triiodothyronine concentrations decreased, following the first LPS injection and thereafter returned to baseline, which occurred faster at HT than at TN. Moreover, the LPS challenge decreased growth and feed efficiency in pigs kept at TN, which was not observed in pigs kept at HT. The results suggest a greater capacity of pigs to limit the physiological and metabolic disturbances caused by inflammatory challenge, when kept at HT, compared to TN. [ABSTRACT FROM AUTHOR]