Threonine Requirement of Neonatal Piglets Receiving Total Parenteral Nutrition Is Considerably Lower than That of Piglets Receiving an Identical Diet Intragastrically

Abstract

Evidence is accumulating that the amino acid requirements for neonates receiving total parenteral nutrition (TPN) are significantly different than those for oral feeding and need to be determined. The parenteral threonine requirement was determined in 3-d-old male Yorkshire piglets (n = 25) by examining the effect of varying dietary threonine intakes [0.05-0.6 g/(kg.d)] on phenylalanine oxidation. The diet included adequate energy, total amino acids and phenylalanine, with excess tyrosine. Phenylalanine kinetics were determined from a primed, continuous intravenous infusion of L-[1-14C]phenylalanine. Phenylalanine oxidation, estimated from the rate of 14CO2 released in expired air during isotope infusion, decreased (P < 0.05) as threonine intake increased from 0.05 to 0.15 g/(kg.d) and was low and constant for threonine intakes >0.15 g/(kg.d). Using breakpoint analysis with 95% confidence interval (CI), mean requirement and safe level of parenteral threonine intake were estimated to be 0.19 and 0.21 g/(kg. d), respectively (equivalent to 13 and 14 mg/g amino acids, respectively). To compare these data with those of orally fed controls, we then repeated the experiment by infusing identical diets intragastrically to piglets (n = 25); the varying dietary threonine intakes were 0.1-1.2 g/(kg.d). Employing identical kinetics and analyses, the mean requirement and safe level of oral threonine intake were estimated to be 0.42 and 0.51 g/(kg.d), respectively (equivalent to 28 and 34 mg/g amino acids, respectively). These data demonstrate that the threonine requirement of neonates during TPN is approximately 45% of the mean oral requirement.

Intestinal development and growth performance of early-weaned piglets fed a low-threonine diet

“…Indeed, compared with the other essential amino acids, threonine requirements for maintenance are high (Fuller et al, 1989) and the intestine seems to contribute extensively to this requirement. In orally fed piglets, threonine requirement, evaluated by the indicator amino acid oxidation technique, is twice as much as that of parenterally fed piglets (Bertolo et al, 1998). Measurement of tissue balance in catheterised animals associated with tracer infusion confirms that dietary threonine is massively extracted by the portal-drained viscera (small and large intestines, pancreas, spleen and stomach).…”

Enteral Tryptophan Requirement Determined by Oxidation of Gastrically or Intravenously Infused Phenylalanine Is Not Different from the Parenteral Requirement in Neonatal Piglets

“…It is important to note that both the University of Alberta and Shooter's Hill Livestock receive their genetic stock from the same source. More detailed descriptions of the surgical procedures can be found elsewhere (3,8). After surgery, all piglets were fitted with a jacket containing an anchoring button as part of a tetherswivel system used to secure and protect the implanted catheters.…”

“…Unlike threonine, which is involved in the production of gut mucins, tryptophan has not been implicated to play a major role in gut function apart from protein synthesis. We hypothesized that unlike threonine, which is disproportionately used by the gut (3,6), the tryptophan requirement in parenterally fed piglets would be similar to or slightly lower than that in enterally fed piglets, proportionate to the decrease in protein synthesis associated with gut atrophy during parenteral feeding (7,18). Our second objective was to determine whether the enteral tryptophan requirement estimate differs if phenylalanine isotope is delivered intragastrically instead of intravenously.…”

Effect of Different Dietary Threonine Levels on Optimal Growth Performance and Intestinal Morphology in 1-14 Days Old Ross 308 Broilers

“…Approximately, 30-50% of arginine, proline, isoleucine, valine, leucine, Met, Lys, phenylalanine, glycine, serine and Thr may be used through the small intestines and as a result would not be available for extra intestinal tissues (Wu, 1998). Not withstanding, several literature references (Stoll et al 1998;Burrin et al 2001;Bertolo et al, 1998) describe that about 40-50% of the threonine intake is used in animal's gut. This implies that a part of threonine requirement is not associated with muscle protein deposition, but is essential for adequate gut functions.…”