Camila Goloni

Implications of obesity and weight loss (WL) for energy and protein metabolism are not fully understood, particularly in senior dogs. This study evaluated changes in body composition, energy expenditure (EE), protein turnover (PT), and voluntary physical activity (VPA) in senior dogs in maintenance and after 10% and 20% WL. Twenty obese, neutered, client‐owned dogs without comorbidities (8.05 ± 0.44 years, 33.41 ± 1.79 kg, body condition score [BCS] median 8/9; range: 8–9) received the same diet (3.2 kcal/g; per 100 kcal: 10.4 g protein, 4 g fat, 7.8 g fibre), with intake adjusted (±5%–10%) to maintain a WL rate of 1%–2%/week. At baseline, after 10% WL, and after 20% WL, body composition and EE were assessed using the doubly labelled water, and PT was measured using the ¹³ C‐leucine method. VPA was evaluated at baseline and after 20% WL using triaxial accelerometers. Data were analysed by repeated measures ANOVA. Dogs achieved a final BCS of 6 (5–6) ( p < 0.01) but exhibited a lower WL rate in the second phase of WL (0.85 ± 0.05% vs. 0.70 ± 0.04%/week; p < 0.05). Fatty mass (FM) decreased from 40.57 ± 1.23% to 310.1 ± 1.50%, while lean mass (LM) increased from 59.43 ± 1.23% to 68.90 ± 1.5% ( p < 0.01). LM (kg) decreased in the first phase ( p < 0.05) but was preserved thereafter ( p > 0.05). Energy intake from food decreased over time (from 61.09 ± 2.06 to 52.95 ± 1.3 kcal/kg ^0.75 /day; p < 0.001), whereas EE increased during WL (from 98.23 ± 5.1 to 111.26 ± 4.18 kcal/kg ^0.75 /day; p < 0.01), raising the caloric deficit from 37% to 58% ( p < 0.05). PT rates declined by 20%–27% when expressed per kg ^0.75 or kgLM ^0.75 ( p < 0.05), while VPA remained unchanged ( p > 0.05). A progressive predominance of fatty over lean tissue oxidation may explain the increasing need for energy restriction and the reduced WL rate as WL progresses, despite higher EE in dogs. Strategies to preserve LM and protein metabolism are warranted to optimise WL in dogs.

Energy requirements (ER) are known to decline as dogs age into the senior stage. However, the implications of body composition and physical activity (PA) on this parameter remain poorly investigated. The aim of this study was to evaluate ER, body composition, water turnover rate (WTR), and voluntary PA by triaxial accelerometers in adults (5.2 ± 1.75 years; 11.8 ± 0.65 kg; body condition score (BCS) 5 ± 0.2/9) and old Beagle dogs (14.2 ± 2.65 years; 12.5 ± 0.37 kg; BCS 5 ± 0.31/9). The ER were assessed by the food intake to constant body weight (FI), ¹³ C‐Bicarbonate ( ¹³ C‐Bic) and doubly labelled water (DLW) methods. Animals were fed to maintain a constant body weight for 30 days. Food intake was recorded, and the diet's metabolisable energy was determined via total faecal collection method. Masks were used to measure ¹³ C in expired air after ¹³ C‐Bic enrichment. Body water was enriched with ² H and ¹⁸ O, and isotopes elimination was evaluated after 7, 10, and 15 days. ER was similar between methods ( p = 0.99), but 30% higher for adult (511.9 ± 4.72 kJ/kg ^0.75 /day) than old dogs (389.0 ± 5.07 kJ/kg ^0.75 /day; p < 0.001). WTR was higher for adult (134.58 mL/kg ^0.75 /day) than old dogs (106.51 mL/kg ^0.75 /day; p = 0.005). Despite similar BCS, old dogs showed lower lean and higher fat mass, suggesting sarcopenia ( p < 0.01). Old dogs presented lower PA ( p < 0.01), which, may have contributed to their lower lean mass, ER and WTR. Considering that ¹³ C‐Bic and DLW resulted in similar estimations of energy expenditure to the FI method, the most appropriate approach might depend on experimental conditions and objectives. The implications of reduced ER on food and nutrient intake and its relationship with lower WTR, sarcopenia and obesity development, highlight the need for targeted nutritional recommendations for ageing dogs.

Protein hydrolysates may contain bioactive peptides that influence metabolic and physiological responses. This study evaluated the effects of hydrolysed poultry byproduct meal (HPM), replacing conventional poultry byproduct meal (PBM), on selected antioxidant, inflammatory and metabolic parameters in dogs. Four extruded diets were formulated: a control diet with PBM as the protein source and diets replacing 25%, 50%, and 100% of PBM protein with HPM protein. Thirty‐two Beagle dogs were included (eight dogs per diet) and were fed the respective diets for 32 days. Outcomes assessed included total cholesterol and lipoprotein fractions, oxidative stress markers, serum angiotensin‐converting enzyme (ACE) activity, systemic blood pressure, urinary parameters, renal electrolyte excretion, serum cytokines, phagocytic activity of neutrophils and monocytes, and faecal IgA levels. Data were analysed using ANOVA, with means compared through polynomial contrasts based on HPM inclusion levels ( p < 0.05). Diet had no effect on blood pressure, ACE activity, serum triglycerides, phagocytic index, or oxidative parameters ( p > 0.05). However, urine sodium concentration and renal excretion increased linearly, while urine pH decreased quadratically with HPM inclusion ( p < 0.01). Serum cholesterol decreased quadratically ( p < 0.01), and LDL cholesterol was lower in dogs fed 100% HPM compared to control diet ( p = 0.030). Dogs fed 100% HPM had lower IL‐2 and TNF‐α levels than dogs fed other diets ( p < 0.05), and their IL‐6 and IL‐10 levels were lower than those of dogs fed 25% and 50% HPM ( p < 0.05). Faecal IgA increased linearly, with the highest value observed in dogs fed 100% HPM ( p = 0.048). In conclusion, HPM intake modulated serum cytokines and faecal IgA concentrations, suggesting an impact on inflammatory and immune responses, while also increasing renal sodium excretion and reducing serum cholesterol. These physiological effects warrant further exploration in dogs with specific disease conditions.

Cashew nut is a co-product of the cashew (Anacardium occidentale) industry, with high fat (40%) and protein (23%) contents. During processing, the nuts can break down, generating the cashew nut granules (CNG). Considering the effort for rational use of food resources, the present study investigated the use of CNG as an ingredient in extruded dog diets. Four formulations with similar chemical compositions were used, a control (CO) based on poultry by-product meal and poultry fat, and three inclusion levels of CNG as protein and fat source: 2.5%, 5%, and 10% (on an as-fed basis). Due to its high fat content, the implications of CNG to the extrusion process was investigated. Twenty-four beagle dogs were used to determine total tract apparent digestibility (TTAD), faeces characteristics and fermentation products, and a panel of 39 dogs were used for palatability comparisons. The results of extrusion, TTAD, and faecal traits were submitted to variance analysis and means compared by polynomial contrasts according to the CNG inclusion level (p < 0.05). In the palatability test, the first intake was compared by the Qui-square test and the intake ratio by the Student's t-test (p < 0.05). The CNG addition increased the internal fat content of the raw material mixture from 9.5% to 12.6%. This induced a linear reduction in mechanical energy transference, which in turn reduced mass pressure and temperature at extrusion (p < 0.01), which compromised kibble formation with lower expansion and higher density (p < 0.01). Starch gelatinisation did not reduce but in fact increased, explained by a linear increase in thermal energy application (p < 0.01). The TTAD of nutrients did not differ between diets (p > 0.05). Faeces pH, production and score did not differ among treatments (p > 0.05). Acetate, butyrate, and lactate increased quadratically (p < 0.01) in the faeces, with higher values for animals fed the 2.5% CNG feed. In the palatability test, only CO, 2.5% CNG and 5% CNG treatments were compared, and diets with CNG had higher preference than CO (p < 0.01). By conclusion, up to 10% inclusion of CNG did not alter TTAD of nutrients or faeces formation and increased diet palatability, supporting the use of this co-product in extruded diets for dogs.

Hydrolysed proteins are of interest owing to their potential effects on metabolic and physiological responses, low allergenicity and high digestibility. This study aimed to evaluate the use of hydrolysed poultry byproduct meal (HPM) as a replacement for conventional poultry byproduct meal (PBM) as a protein source and to study its effects on serum cytokines, angiotensin‐converting enzyme (ACE) activity, serum antioxidant parameters, blood pressure, and urinary parameters in cats. The replacement of PBM with HPM was evaluated using five formulations with similar chemical compositions: control (PBM as the sole protein source) and the inclusion of 5%, 10%, 20%, and 30% HPM (on an as‐fed basis). Thirty cats were distributed into two randomised blocks of 15 cats, with 3 cats per diet in each block, totalling 6 cats per food. After 10 days of diet adaptation, the urine of the cats was quantitatively collected from Days 11 to 15, and on the day 21 blood samples were collected and blood pressure was evaluated. Data were subjected to analysis of variance and the means were compared by polynomial contrasts. Non‐parametrically distributed variables were compared using the Kruskal–Wallis test (p < 0.05). All the cats remained healthy throughout the study period. Diet did not affect urine volume; intake and excretion of sodium, potassium, and chloride; blood pressure; ACE plasma activity; or serum triglyceride and cholesterol levels (p > 0.05). Among the oxidative parameters, there was a quadratic increase in lipid peroxidation and glutathione S‐transferase (higher values at 10% HPM) (p < 0.05). A quadratic increase was observed for steam cell factor, interferon‐γ, IL‐4, and IL‐8 (p < 0.05), with higher values for cats fed 5% and 10% HPM diets. A nonparametric distribution with higher values for cats fed the 5% HPM diet was observed for monocyte chemoattractant protein‐1; tumour necrosis factor‐α; IL‐2; and regulated upon activation, normal T cell expressed and secreted (RANTES) (p < 0.05). In conclusion, we observed that the intake of diets containing 5% and 10% HPM stimulated the antioxidant system and the secretion of several cytokines involved in the preparation and function of the immune system, suggesting potential biological functions with implications for cat health deserving further investigation.

Stable isotope methods have been used to study protein metabolism in humans; however, there application in dogs has not been frequently explored. The present study compared the methods of precursor (13C-Leucine), end-products (15N-Glycine), and amino acid oxidation (13C-Phenylalanine) to determine the whole-body protein turnover rate in senior dogs. Six dogs (12.7 ± 2.6 years age, 13.6 ± 0.6 kg bodyweight) received a dry food diet for maintenance and were subjected to all the above-mentioned methods in succession. To establish 13C and 15N kinetics, according to different methodologies blood plasma, urine, and expired air were collected using a specifically designed mask. The volume of CO2 was determined using respirometry. The study included four methods viz. 13C-Leucine, 13C-Phenylalanine evaluated with expired air, 13C-Phenylalanine evaluated with urine, and 15N-Glycine, with six dogs (repetitions) per method. Data was subjected to variance analysis and means were compared using the Tukey test (P0.05). However, only 13C-Leucine and 13C-Phenylalanine (expired air) presented an elevated Pearson correlation and concordance. This suggested that caution should be applied while comparing the results with the other methodologies.

Considering the differences in molecular structure and function, the effects of β-1,3-glucans from Euglena gracilis and β-1,3/1,6-glucans from Saccharomyces cerevisiae on immune and inflammatory activities in dogs were compared. Four diets were compared: control without β-glucans (CON), 0.15 mg/kg BW/day of β-1,3/1,6-glucans (Β-Y15), 0.15 mg/kg BW/day of β-1,3-glucans (Β-S15), and 0.30 mg/kg BW/day of β-1,3-glucans (Β-S30). Thirty-two healthy dogs (eight per diet) were organized in a block design. All animals were fed CON for a 42-day washout period and then sorted into one of four diets for 42 days. Blood and faeces were collected at the beginning and end of the food intake period and analysed for serum and faecal cytokines, ex vivo production of hydrogen peroxide (H₂O₂) and nitric oxide (NO), phagocytic activity of neutrophils and monocytes, C-reactive protein (CRP), ex vivo production of IgG, and faecal concentrations of IgA and calprotectin. Data were evaluated using analysis of covariance and compared using Tukey’s test (PPP2O₂ than those from the CON and B-Y15 groups (PPex vivo production of NO by monocytes, neutrophil phagocytic index, and serum CRP. Calprotectin and CRP levels did not support inflammation or other health issues related to β-glucan intake. In conclusion, both β-glucan sources modulated some immune and inflammatory parameters in dogs, however, different pathways have been suggested for the recognition and action of these molecules, reinforcing the necessity for further mechanistic studies, especially for E. gracilis β-1,3-glucan.

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/kg^0·67/d) than females (330 (se 8) kJ/kg^0·67/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.

Hydrolysed proteins have been shown to be potential ingredients in cat diets due to their high digestibility, presence of bioactive peptides, and relatively low antigenicity. The effects of the substitution of conventional low ash poultry byproduct meal (PBM) with hydrolysed poultry byproduct meal (HPM) as a protein source were evaluated in extruded cat diets. Five diets with similar nutrient contents were formulated: a control (CO) diet based on PBM and 4 diets with different inclusions of HPM (5%, 10%, 20%, and 30%, on an as-fed basis) replacing PBM as the protein source. The total tract apparent digestibility (CTTAD) of nutrients, faecal characteristics and microbial fermentation products, urine production and pH, nitrogen balance and urea renal excretion were evaluated using 30 healthy cats (15 males and 15 females; 4.18 +/- 0.86 kg; 4.17 +/- 1.38 years old), with 6 cats per diet in a complete randomised block design. When significant differences were found with the F test, the effects were evaluated by polynomial contrasts according to HPM inclusion (p < 0.05). The CTTADs of DM (89 +/- 0.41%), CP (90 +/- 0.36%), fat (93 +/- 0.41%) and gross energy (90 +/- 0.33%) were similar among treatments (p > 0.05). The faecal production, score, short-chain fatty acids and ammonia concentration were similar among treatments (p > 0.05). Isobutyric, isovaleric, valeric, and total branched-chain fatty acid contents increased quadratically (p < 0.05), with the highest level in the faeces of cats fed the diet with 20% HPM. Lactate concentration in faeces increased linearly with the inclusion of HPM (p < 0.05). Urine characteristics and urea renal excretion did not differ among treatments (p > 0.05). At 10% inclusion, HPM tended to increase the nitrogen retention of cats (p = 0.083), which may reflect the higher tryptophan, methionine, lysine, and available lysine contents of HPM in comparison to PBM. The inclusion of up to 30% HPM can be considered in cat formulations without affecting nutrient digestibility or faecal and urine characteristics. HPM tended to increase nitrogen retention and increased branched-chain fatty acids in faeces, aspects which deserves further studies.

Fiber supplemented extruded foods are produced by pet food companies to help with several specific health conditions. The fiber material, however, is difficult to incorporate efficiently into dry kibble diets for dogs. The aim of the study was to evaluate the influence of citrus pulp pellet (CPP), the solid waste part of the production of orange juice characterized by a good proportion of soluble and fermentable fiber, on extrusion traits, kibble macrostructure, starch gelatinization and in vitro digestibility of dog foods. A control formula (CO) was developed for dogs. CPP was added to CO at different inclusion levels: 5%, 10%, 15% and 20%. Foods were extruded in a single screw extruder using two different die diameters (d_d): 5 mm and 7 mm. CPP inclusion with 5 mm d_d did not affect bulk and piece density and resulted in a lower impact on kibble expansion; It also resulted in greater starch gelatinization and kibble expansion compared to the 7 mm d_d configuration (p < 0.01). In addition to the nutritional implications, recycling and proper uses of this material exemplified in the present study by the exploration of CPP as a fiber source to dogs, this method can improve sustainable agriculture by transforming low-quality materials into high-quality foods.