High starch intake favours body weight control in neutered and spayed cats living in homes fed ad libitum.

Different starch-to-protein ratios were compared among neutered and spayed domiciled cats. Male and female obese and non-obese cats were fed kibble diets ad libitum for 4 months high in starch (HS (38 % crude protein (CP)): starch 32 %, protein 38 %; DM basis) or high in protein (HP (55 % CP): starch 19 %, protein 55 %) but similar in energy and fat in a crossover design. Physical activity was evaluated using an accelerometer, and body composition (BC), energy expenditure (EE) and water turnover (WT) using the doubly labelled water method. Results were compared in a 2 diet × 2 sex × 2 body condition factorial arrangement. Cats fed the HS (38 % CP) diet maintained a constant body weight, but lean mass (LM) tended to be reduced in female obese but to be increased in male non-obese (P < 0·08) and increased in female non-obese cats (P = 0·01). The HP (55 % CP) diet induced an increase in cat body weight and LM (P < 0·05) without altering BC proportion. EE tended to be higher in males (351 (se 8) kJ/kg0·67/d) than females (330 (se 8) kJ/kg0·67/d; P = 0·06), was unaffected by diet or BC, decreased as age increased (R 2 0·44; P < 0·01) and increased as physical activity increased (R 2 0·58; P < 0·01). WT was higher for the HP (55 % CP) diet (P < 0·01) and increased with EE (R 2 0·65; P < 0·01). The HS (38 % CP) diet favoured body weight control during 4 months of ad libitum feeding. Caution is necessary to balance protein in diets of female obese cats over 5 years, as they may have low energy and food intake, with LM loss.

Intake of energy, protein, amino acids and minerals by dogs under energy restriction for body weight loss when fed with commercial weight loss diets.

This retrospective study evaluated energy and nutrient intake of dogs in a weight loss programme. Ninety-four obese dogs were divided into three groups: G5-15: from 5% to 15% body weight (BW) loss (n = 55); G155-25: from 15.1% to 25% BW loss (n = 29); and G > 25: more than 25.1% BW loss (n = 10). Five brands of kibble diets designed for weight loss were analysed for crude protein, amino acids, fat, dietary fibre, and minerals. The food metabolizable energy (ME) was estimated (NRC, 2006). Data were compared inside each group using the paired t test and between groups with analysis of variance and Tukey tests (p < 0.05). The BW loss (weeks in regimen) was: G5-15, 9.8% ± 2.7% (13.5 ± 5.7 weeks); G15-25, 17.5% ± 2.7% (22.6 ± 11.9 weeks); G > 25, 30.0% ± 2.1% (50.4 ± 17.4% weeks; p < 0.01). The mean weekly BW loss rate was similar between groups (0.8% ± 0.3%; p > 0.05) but was higher during the first (0.96.6% ± 0.5%) than in the second (0.64% ± 0.4%) half of the regimen (p < 0.01). At beginning ME intake for BW loss did not differ (251.6 ± 32.2 kJ/kg0.75 /day), but it was lower for G > 25 in the second half of the regimen (230.3 ± 44.3; p = 0.02). Considering the observed ME intake of each dog, depending on the commercial product, intake below recommended for maintenance was verified for crude protein in 1%-20% of the dogs, methionine in 4%-38% of dogs, methionine plus cystine in 4%-22% of dogs, tryptophan in 7%-93% of dogs, potassium in 2%-85% of dogs and magnesium in 1% up to 95% of dogs. Although the diets presented elevated nutrient concentrations per MJ, due to the reduced energy allowance, the estimated intake of several nutrients was lower than the recommendations, highlighting the importance of changing the formulation perspective, which must prioritize the actual nutrient intake per kg of BW during the energy deficit.

Energy expenditure of red-footed tortoises (Chelonoidis carbonaria) fed kibble diets with high levels of fibre, starch, or fat.

Knowledge of energy requirements is necessary to optimise the nutritional management of animals. For tortoises, very little is known about their nutrient and energy requirements. Data on substrate oxidation and the implications of starch or fat intake on the energy metabolism are lacking. The present study compared the daily energy expenditures (DEE) of red-footed tortoises (Chelonoidis carbonaria) that were fed three extruded diets: a control diet high in fibre and two test diets, one with high starch content and another with high fat content. A total of 18 tortoises (5.5 ± 1.18 kg) were used in a completely randomised design, with 6 animals per diet. After 14 months of experimental diet intake and 48 h of preliminary fasting, the animals were kept for 12 h in 70-l respiratory chambers. An open "push mode" system was used to determine the carbon dioxide production and oxygen consumption levels for the subsequent calculations of DEE. The data were analysed with ANOVA, and the means were compared by using Tukey's test (p < 0.05). The body weights, chamber temperatures and food intakes of the tortoises were similar among the treatments (p > 0.05). There were no significant differences in oxygen consumption (21.7 ± 3.16 ml · kg-1 · h-1), carbon dioxide production (18.1 ± 1.96 ml · kg-1 · h-1), or DEE (9.7 ± 1.04 kJ · kg-1 d-1) between diets or sex (p > 0.05). The respiratory quotients (0.84 ± 0.11) were also similar among the diets (p > 0.05). The DEE of red footed tortoises did not differ after a long-term starch or fat intake.

Efficiency of methionine and cystine utilization by broiler chickens using stable isotopes.

The aim of this study was to develop a method to determine the efficiency of utilization of Met and Cys using stable isotopes in order to reduce the number of sacrificed animals relative to the comparative slaughter technique. Met and Cys efficiencies were obtained separately and as total SAA values. Twenty-one 14- to 28-day-old broiler chickens were fed experimental diets containing different Met:Cys ratios (44:56, 50:50 and 56:44). Birds were given diets with daily supplements of L-(15 N) Met (60 mmol/kg) or L-(15 N2 ) Cys (35 mmol/kg) throughout the entire experimental period. Excreta were collected daily, and birds were euthanized at the end of the trial to collect feather-free bodies and feathers. Samples were analysed for 15 N and 15 N-Met content. The utilization efficiency for Met, Cys and Met + Cys for feather-free bodies was 55%, 75%, and 60%, while the efficiencies for feathers were estimated at 96%, 77% and 84% respectively.

Methionine to cystine ratio in the total sulfur amino acid requirements and sulfur amino acid metabolism using labelled amino acid approach for broilers.

BACKGROUND: Assuming that part of Methionine (Met) is converted into Cystine (Cys), but ignoring the rates with which such phenomenon occurs may lead to an excessive supply of Met in poultry diets. Such inconvenient could be easily avoided with the knowledge of the ideal Met:Cys/Total sulfur amino acids (TSAA) ratio and the rates of Met conversion into Cys. RESULTS: Met sources did not affect performance. Met:Cys/TSAA ideal ratio was determined using curvilinear-plateau regression model. Both optimum body weight gain and feed conversion ratio were estimated in 1007 g/day and 1.49, respectively, at 52% Met/TSAA ratio. Feed intake was not affected by Met:Cys/TSAA ratios. In the labelled amino acid assay, the rates with which Met was converted into Cys ranged from 27 to 43% in response to changes in Met:Cys/TSAA ratios, being higher at 56:44. CONCLUSION: Based on performance outcomes, the minimum concentration of Met relative to Cys in diets for broilers from 14 to 28 d of age based on a TSAA basis, is 52% (52:48 Met:Cys/TSAA). The outcomes from labelled amino acid assay indicate that highest the Met supply in diets, the highest is its conversion into Cys.