QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Baker, D. H. Articles by Han, Y. Search for Related Content PubMed PubMed Citation Articles by Baker, D. H. Articles by Han, Y.

Bioavailable Level and Source of Cysteine Determine Protein Quality of a Commercial Enteral Product: Adequacy of Tryptophan but Deficiency of Cysteine for Rats Fed an Enteral Product Prepared Fresh or Stored Beyond Shelf Life¹

Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Young rats were used in bioassays designed to assess the protein quality and tryptophan as well as cystine adequacy of the enteral product TwoCal-HN® that was either freshly prepared or had been stored (nonrefrigerated) in a warehouse for 10 mo (i.e., beyond shelf life). Based upon supplementation studies, cystine was observed to be the first-limiting amino acid in both fresh and expired TwoCal-HN, and tryptophan was not second limiting. Protein efficiency ratio (PER) of expired, but not fresh, TwoCal-HN was lower than that of the casein control diet, but with cystine supplementation, PER of the TwoCal-HN products was equal to or greater than the PER of the casein control. With a diet containing 10 g protein/100 g that also contained energy-furnishing ingredients simulating TwoCal-HN, maximal growth enhancement occurred with a supplement of 1 g cystine/kg diet. Both glutathione and N-acetyl-L-cysteine were observed to be equivalent to an isomolar level of L-cystine in stimulating growth. Using a chemically defined amino acid diet that was singly deficient in tryptophan, bioavailability of tryptophan was determined for casein, fresh TwoCal-HN, expired TwoCal-HN and D-tryptophan. Slope-ratio bioefficacy values relative to L-tryptophan (weight gain regressed on supplemental tryptophan intake) indicated that none of the experimental sources of tryptophan had bioavailabilities different from 100%. The results indicated that tryptophan did not deteriorate, as measured analytically or biologically, as a result of storing TwoCal-HN beyond shelf life. Adding bioavailable sources of cysteine activity to casein-based enteral products markedly improves protein quality when these products are fed to young rats.

KEY WORDS: • rats • tryptophan • cystine • enteral formula • glutathione

¹ Appreciation is expressed to Ross Laboratories, Columbus, OH for financial support of this work.

² To whom correspondence should be addressed: 328 Mumford Hall, 1301 W. Gregory Dr., Urbana, IL 61801.

Manuscript received 31 August 1992. Revision accepted 30 October 1992.

This article has been cited by other articles:

				R. N. Dilger and D. H. Baker Oral N-acetyl-L-cysteine is a safe and effective precursor of cysteine J Anim Sci, July 1, 2007; 85(7): 1712 - 1718. [Abstract] [Full Text] [PDF]

				D. H. Baker Comparative Species Utilization and Toxicity of Sulfur Amino Acids J. Nutr., June 1, 2006; 136(6): 1670S - 1675S. [Abstract] [Full Text] [PDF]

				A. K. Shoveller, J. A. Brunton, O. Brand, P. B. Pencharz, and R. O. Ball N-Acetylcysteine is a Highly Available Precursor for Cysteine in the Neonatal Piglet Receiving Parenteral Nutrition JPEN J Parenter Enteral Nutr, March 1, 2006; 30(2): 133 - 142. [Abstract] [Full Text] [PDF]