Diets with different protein and carbohydrate proportions for cats: effects on energy metabolism, oxalate production and methods of study energy expenditure

Abstract

Gats are carnivore animals, with high protein requirements. Carbohydrate metabolism and use by cats has been studied, but several aspects remain unknown. The present study will evaluate the consumption of diets with different proportions of protein and carbohydrates over the energy and protein metabolism, and oxalate formation and urinary excretion. Additionally, methods for energy requirements estimations will be studied. The experiment will follow a two 4x4 Latin square design, each one with four foods, four cats, and four periods of seven weeks, totaling eight cats per food. Extruded foods with different proportions of protein (CP) and carbohydrats (CHO) will be used: 20% of CP and 48.5% of CHO; 34% of CP and 33.5% of CHO; 48% of CP and 18.5% of CHO and 62% of CP and 3.5% of CHO. Cats will be fed the experimental diets during seven weeks, and the following parameters will be evaluated: body composition by deuterium oxide (lean body mass and fatty body mass); nutrient and energy digestibility of the diets; daily food intake, food intake pattern, and satiety; protein metabolism through nitrogen balance, 24h urinary excretion of urea, muscular catabolism (measuring urinary 3-methyl-histidin), and lean body mass amount; 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; comparison of tradition methods to study energy requirements, specifically energy intake to maintain constant body weight and respirometry measurements, with the double labeled water aiming to develop a toll to study energy expenditure in owned cats; urinary oxalate excretion, organic oxalate balance, and calcium oxalate urinary superssaturation. Data will be evaluated by polynomial contrasts, except food intake pattern that will be evaluated by repeated measures (P<0.05). The methods of study energy expenditure will be evaluated by Pearson correlation. (AU)