Peptides and Nitrogen-Free Analogs as Substitutes for Dietary Amino Acids: Significance in the Nutriture of Chicks and Rats
Boebel, Katherine Pigg
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https://hdl.handle.net/2142/69993
Description
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
Issue Date
1982
Department of Study
Animal Science
Discipline
Animal Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(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.
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