title: Cats are able to adapt protein oxidation to protein intake provided their requirement for dietary protein is met.
abstract: Cats require more dietary protein than noncarnivorous species. Earlier work showed that cats lack the ability to regulate hepatic urea cycle enzymes in response to dietary protein concentration. We thus hypothesized that cats are unable to fully adapt protein oxidation to protein intake, particularly at low-protein concentrations. We used indirect respiration calorimetry to assess cats' ability to adapt substrate oxidation to diets containing different concentrations of protein, including 1 below their protein requirement. Nine cats (5 males and 4 females; 2.7 +/- 0.5 y; 4.49 +/- 0.19 kg) consumed each of 4 semipurified diets containing 7.5% [low protein (LP(3))], 14.2% [adequate protein (AP)], 27.1% [moderate protein (MP)], and 49.6% [high protein (HP)] of metabolizable energy from protein in a modified crossover design, beginning with the MP diet and then consuming the remaining diets in random order. After adaptation to each diet, cats completed a 5-d nitrogen balance trial and at least 2 12-h indirect calorimetry measurements. There was a significant effect of diet on protein oxidation (P < 0.0001), which measured 10.4 +/- 0.5, 14.1 +/- 1.0, 25.0 +/- 1.7, and 53.2 +/- 1.7% of total energy expenditure for the LP, AP, M,P and HP diets, respectively. The ratio of protein oxidation:protein intake was higher with the LP diet (1.39 +/- 0.07) than the other 3 diets (AP, 1.00 +/- 0.07; MP, 0.93 +/- 0.06; HP, 1.07 +/- 0.03; P < 0.0001), indicating a net loss of protein with the LP diet. Thus, cats are able to adapt protein oxidation to a wide range of dietary protein concentrations, provided their minimum protein requirement is met.
authors.affiliation: Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616-8741, USA.
authors.forename: Alice S
authors.initials: AS
authors.lastname: Green
authors.forename: Jon J
authors.initials: JJ
authors.lastname: Ramsey
authors.forename: Cecilia
authors.initials: C
authors.lastname: Villaverde
authors.forename: Danny K
authors.initials: DK
authors.lastname: Asami
authors.forename: Alfreda
authors.initials: A
authors.lastname: Wei
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Fascetti
mesh_terms: D000596:Amino Acids / Q000097:blood / Q000652:urine; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002415:Cats / Q000378:metabolism*; D018592:Cross-Over Studies; D004032:Diet / Q000662:veterinary; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D013047:Specific Pathogen-Free Organisms
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D009584:Nitrogen