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Title:Peptides and Nitrogen-Free Analogs as Substitutes for Dietary Amino Acids: Significance in the Nutriture of Chicks and Rats
Author(s):Boebel, Katherine Pigg
Department / Program:Animal Science
Discipline:Animal Science
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Health Sciences, Nutrition
Abstract:Chick and rat bioassays were conducted to establish quantitative efficacy values (slope-ratio procedure) for the D-isomer, the (alpha)-keto analog and the D- and L-(alpha)-hydroxy analogs of phenylalanine (Phe), leucine (Leu), isoleucine (Ile) and valine (Val). D-Phe was well utilized by both chicks (75%) and rats (68%). L-phenyllactic acid (L-PLA) had an efficacy value of 67% for chicks and 46% for rats. D-PLA had no growth-promoting activity for either chicks or rats. KMV, (alpha)-keto-(beta)-L-methylvaleric acid (60%, chicks; 38%, rats) was markedly inferior to L-(alpha)-hydroxymethylvaleric acid, L-HMV (84%, chicks; 65%, rats), as a source of dietary Ile for both chicks and rats. D-HMV had no growth-promoting activity for either chicks or rats. D-Val was well utilized by chicks (72%) but had only marginal Val bioactivity for rats (16%). Efficacy values of the isomers of (alpha)-hydroxyisovaleric acid (HIV) for the chick were: L-HIV, 82% and D-HIV, 66%. KIV, 49%; L-HIV, 54%; and D-HIV, 46%, had comparable efficacy values for the rat. Efficacy values of the isomers of Leu and (alpha)-hydroxyisocaproic acid (HIC) and (alpha)-ketoisocaproic acid (KIC) for the rat were: D-Leu, 48%; KIC, 56%; L-HIC, 58%; and D-HIC, 41%.
Four chick bioassays were conducted to assess the efficacy of DL-2-hydroxy-4-methylthiobutyrate in both the calcium salt (OH-M) and free-acid (OH-MFA) forms, and a freeze-dried preparation of OH-methionine free acid polymers (OH-MFAP) relative to DL-methionine (DL-M). Whether fed as a source methionine in a chemically defined diet (CD) or a semipurified feather meal diet (FM), all analog forms were inferior to DL-M in growth-promoting capacity. Efficacy values were: OH-M, 87% (CD), 84% (FM); OH-MFA, 78% (CD), 77% (FM); and OH-MFAP, 69% (CD), 54% (FM).
Additional chick growth assays were used to evaluate the efficacy of poly-L-methionine, DL/LD methionylmethionine and DD/LL methionylmethionine. The polypeptide possessed no bioefficacy. The DL/LD dipeptide exhibited growth-promoting ability equal to that of DL-methionine itself.
Glutathione (GSH) administered orally was found fully capable of providing bioavailable cysteine activity for chick growth. Whole-blood GSH was unresponsive, but liver GSH increased as dietary cysteine increased from a deficient level to the required level in the diet. Excess levels of dietary cysteine elicited no further increase in hepatic GSH. Plasma cystine concentration increased markedly and in a linear fashion while plasma cysteine increased only modestly as dietary cysteine level increased.
Issue Date:1982
Description:109 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
Other Identifier(s):(UMI)AAI8218433
Date Available in IDEALS:2014-12-15
Date Deposited:1982

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