Factors Affecting Deficiency and Toxicity of Sulfur-Containing Compounds
Dilger, Ryan Neil
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https://hdl.handle.net/2142/83602
Description
Title
Factors Affecting Deficiency and Toxicity of Sulfur-Containing Compounds
Author(s)
Dilger, Ryan Neil
Issue Date
2007
Doctoral Committee Chair(s)
Baker, David H.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Culture and Nutrition
Language
eng
Abstract
Comparative studies were conducted to determine the relative effects of excess dietary sulfur amino acid (SAA) compounds in chicks, rats, and pigs. When included in nutritionally adequate diets, 2.5% or more supplemental cysteine (Cys, reduced form), but not cystine (oxidized form), was lethal when consumed by chicks. While growth was severely depressed by such excesses in young rats and pigs, mortality did not occur in either of these species. Studies with chicks suggested this species had minimal capacity to resist disruption of acid-base balance. Thus, excess Cys led to metabolic acidosis within 12 hours of feeding and was ultimately lethal. The growth depressive and lethal effects observed in chicks consuming 2.5% excess Cys were ameliorated through provision of dietary potassium bicarbonate and hydrogen peroxide, respectively. Chicks were also used to investigate efficacy and safety of SAA precursor products, namely N-acetyl-L-cysteine (NAC) and 2-keto-4-(methylthio)butyric acid (Keto-Met). Addition of NAC to a Cys-deficient diet resulted in linear (P < 0.01) increases in growth performance, and it was concluded that NAC was 100% effective as a source of dietary Cys. However, dietary NAC was unable to ameliorate lipopolysaccharide-induced effects on chick feeding behavior and indices of oxidative stress. Addition of Keto-Met to either purified or practical-type Met-deficient diets fed to chicks elicited marked responses in growth performance, and it was concluded that Keto-Met was 92% bioavailable relative to L-Met. Moreover, provision of Keto-Met above the chick's Met requirement was no more noxious than L-Met or DL-Met. When included in a severely Met-deficient practical-type diet, growth responses to both L-Met and DL-Met were negatively impacted by modest excesses of dietary cyst(e)ine. Because weight gain was depressed by 0.2% cyst(e)ine, but body weight gain was unaffected, it was concluded that Cys had caused a nutritional imbalance in the chick. Finally, data suggested that Met and betaine have minimal choline-sparing activity in chicks fed purified diets devoid of preformed choline. However, in the presence of minimal dietary choline (i.e., 150 mg/kg), addition of betaine allows a marked reduction in the total dietary choline requirement.
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