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Diets with different protein and carbohydrate ratios for cats: effects on energy and protein metabolism and methods to evaluate energy expenditure


Cats are carnivores with a high requirement for nitrogen and amino acids Starch digestion and metabolism of these animais has been studied, however important aspects are not completely understood, especially the effects of protein to starch ratios on feline energy and protein metabolism. This is important to promote long-term health benefits and as a potential tool to prevent obesity development. The study FAPESP (2013/20340-0) is evaluating the consumption of diets with different proportions of protein and carbohydrates on energy and protein metabolism, oxalate formation and urinary excretion. Additionally, methods for estimating energy requirements will be studied. Extruded diets with different proportions of protein (CP) and starch (CHO) will be used: 25% of CP and 47% of CHO; 37% of CP and 32% of CHO; 50% of CP and 19% of CHO and 60% of CP and 8% of CHO. Cats will be fed the experimental diets for 7 weeks, and the following parameters will be evaluated: a) body composition by deuterium oxide (Iean body mass and fat mass); b) nutrient and energy digestibility of the diets; c) daily food intake, food intake pattern, and satiety; d) protein metabolism through nitrogen balance, 24h urinary excretion of urea, muscle catabolism (measuring urinary 3-methyl-histidine), and lean body mass; e) daily energy expenditure through indirect calorimetry in respirometry chambers, evaluating the maintenance energy requirement, basal metabolic rate, heat increment, and net energy requirement, respiratory quotient to measure protein, carbohydrate and fat oxidation; f) comparison to traditional methods to study energy requirements, specifically energy intake to maintain constant body weight and respirometric measurements, with doubly labeled water aiming to develop a non-invasive tool to study energy expenditure in pet cats; g) urinary oxalate excretion, organic oxalate balance, and calcium oxalate urinary supersaturation. Data will be evaluated by polynomial contrasts, except food intake pattern that will be evaluated by repeated measures (P<0.05). The methods to study energy expenditure will be evaluated by Pearson correlation. Actual and expected results: The experiment with carbohydrate intake and oxalate production is finished and will not be include in this SPRINT proposal. Briefly, carbohydrate intake did not induce increased oxalate production and renal excretion. Protein intake, however, increased urinary production and water intake, diluting the urine and inducing reduction on calcium oxalate urinary supersaturation (P<0.05). The 4 respirometric chambers approved in the project were purchased. Currently, they are under technical evaluation to ensure proper function. Benefits to the research project UC Davis have a long history in study energy and protein metabolism of cats. Prof. Fascetti has several publications on this area, and her participation will facilitate conducting and interpreting the results from the last phase (respirometric analysis, energy, and protein metabolism studies). She is also the Scientific Director of the UC Davis Amino Acid Laboratory in the School of Veterinary Medicine; and can analyze urinary 3-methyl-histidine. With her participation we will increase the project scope, analyzing more aspects of protein metabolism, including other markers of protein turnover and postprandial amino acid concentrations in feline plasma. Academic Gains: The partnership with UC Davis aims to integrate the universities and as a specific objective, improve the evaluation of protein and amino acid metabolism in the current project. The exchange activities will be important to ensure better training of the graduate students and principal investigator on the methods of energy and protein analysis. This training will include exchange visits and seminars conducted by Prof. Fascetti and Prof. Carciofi, increasing the investigators' ability to interpret their findings It will provide the opportunity to utilize the capabilities of the UC Davis Amino Acid Analysis for the study, enlarging the project scope and allowing better use of the grant supported by FAPESP. Another aim is to propose, at the end of this SPRINT, a joint research project to scientific agencies. Funding and Infrastructure: [...] The project does not have funding for mobility ar amino acid analysis. (AU)