Lysine, threonine and tryptophan postprandial metabolism in LPS challenged growing pigs

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 repeatedinjections of Escherichia coli lipopolysaccharide (LPS) on lysine, threonine and tryptophan postprandialmetabolism. Fourteen growing pigs fitted with a jugular catheter were housed in a temperature-controlledroom in which ambient temperature was maintained constant at 24°C. The experimental period lasted 17 daysthat was subdivided in a seven days period before and a 10 days period during the inflammatory challengethat consisted in five repeated injections of LPS at two days intervals. The initial dose of 30 μg/kg of bodyweight was increased by 12% at each subsequent injection to circumvent adaptive endotoxin resistance tothe repeated inflammatory stimuli. Before the LPS- challenge (baseline), and 24h after the second (T1) andthe fourth (T2) LPS injections, 300 g of feed was given to pigs previously fasted overnight and serial bloodsamples were taken over four-hours to measure plasma amino acids concentrations. Amino acids postprandialconcentrations were analyzed using the linear MIXED procedure of SAS including the fixed effects of timepoints (baseline, T1 or T2). Relative to baseline, postprandial concentrations of lysine were lower at T1and greater at T2. In addition, the LPS-challenge induced a long-lasting (at T1 and T2) reduction in plasmapostprandial concentrations of threonine and tryptophan. Firstly, these results suggest a short-term increasedutilization of lysine to be used as energy source during the LPS-challenge. Then, lysine demand decreasesin association with a lower protein synthesis for growth. Secondly, they evidence an increased threonineand tryptophan metabolic demand to support the requirements of the immune response. For instance, theimmune system activation induces the synthesis of acute phase proteins that, in turn, have greater amounts ofthreonine and tryptophan in their compositions. Finally, our evidences that an inflammatory challenge causedby LPS leads to significant changes on amino acids metabolism and partitioning. induces significant changesin the postprandial metabolism of growing pigs. These findings may contribute to redefine pigs nutritionalrequirements during inflammatory and/or immune challenges

Effects of ambient temperature on the postprandial metabolism of limiting essential amino acids in growing pigs

High ambient temperature is one of the major environmental factors limiting animal production in tropical and subtropical areas. Pig production is particularly affected because of the high sensitivity of pigs to high ambient temperatures due to their limited capacity to dissipate heat and the high metabolic heat production of modern genotypes. The consequences of high temperature on pigs include the well described reduction in voluntary feed intake and growth but also changes on hormones and nutrients metabolism. In this regard, the objective of this study was to evaluate the effects of ambient temperature on lysine, threonine and tryptophan postprandial metabolism. Twenty-eight growing pigs equipped with a jugular catheter were divided into two groups and housed in thermo-neutral (TN, 24ºC) or high (HT, 30ºC) ambient temperature-controlled rooms. Pigs remained in the temperature-controlled rooms for a period of 21 days divided in a 14 days adaptation period and a subsequent seven days experimental period (from day 1 to 7). On day 4, all the animals received 300 g of feed after a fasting period overnight, and serial blood samples (4 mL) of each animal were collected over a period of four hours in order to measure plasma amino acids concentrations. Amino acids postprandial concentrations were analyzed using the linear MIXED procedure of SAS including the fixed effects of ambient temperature. A similar response profile was observed for the three evaluated amino acids (lysine, tryptophan and threonine) in which plasma concentrations increased immediately after the meal intake, reached peak values between 40 and 70 minutes, and decreased thereafter. According to our results, ambient temperature did not affect the postprandial profiles of the amino acids (P > 0.05) suggesting that pigs kept at 30°C had rather close metabolic statuses to those kept at 24°C in terms of lysine, tryptophan and threonine utilization