title: Sulfur amino acid requirements of immature Beagle dogs.
abstract: The methionine and total sulfur amino acid requirements of growing Beagle dogs were determined using diets containing purified L-amino acids as the sole nitrogen source. In the presence of 0.60% dietary L-cystine, optimal growth, feed efficiency, and nitrogen retention were attained in dogs fed diets containing 0.20% or more L-methionine. Two additional experiments revealed that maximal growth, feed efficiency, and nitrogen retention occurred in growing dogs fed diets containing 0.20% L-methionine and supplemented with 0.15% or more L-cystine. Therefore, the total sulfur amino acid requirement was estimated to be 0.39% methionine. Cystine, on an isosulfurous basis could effectively supply up to approximately 50% of the total sulfur amino acid requirement. In crystalline amino acid diets, D-methionine, DL-methionine, N-acetyl-L-methionine and methionine hydroxy analogue were effective in replacing the L-methionine requirement of growing Beagles. N-acetyl-D-methionine, however, was not efficiently utilized as a substitute for dietary methionine.
mesh_terms: D000603:Amino Acids, Sulfur / Q000502:physiology*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003553:Cystine / Q000008:administration & dosage; D004032:Diet; D004285:Dogs / Q000254:growth & development*; D004435:Eating / Q000187:drug effects; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D009747:Nutritional Physiological Phenomena; D009751:Nutritional Requirements
chemical_list: D000603:Amino Acids, Sulfur; D003553:Cystine; C006379:N-acetylmethionine; D008715:Methionine; D009584:Nitrogen