Lucas Bassi Scarpim

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.

In aquaculture, feed production influences nutrition, performance, water quality, and overall profitability. This study evaluated the effects of three levels of internal fat (IF), resulting from the inclusion of 0%, 2%, or 4% fat in the preconditioner during extrusion, and their interaction with two extruder screw configurations: medium-shear (MS) and high-shear (HS), on kibble physical quality and extrusion parameters. Increasing IF resulted in a quadratic increase in amylose–lipid complexation under the HS configuration (p = 0.030; r2 = 0.9) and a linear reduction (p < 0.001) in specific mechanical energy (SME) with a strong negative Pearson correlation (r −0.9; p = 0.009) in both configurations. Fat inclusion also reduced mass temperature and die pressure (p < 0.05), leading to lower starch gelatinization degree (p < 0.05) from 87.9 ± 0.6% to 83.4 ± 0.3% in MS configuration and 95.6 ± 0.7 to 86.3 ± 0.8% in HS configuration, increased bulk and piece density (p < 0.001), and reduced radial expansion (p < 0.001). These changes decreased floatability (p < 0.05) and water stability, increasing mushiness (p < 0.01). Increased shear partially improved SME transfer, starch cooking, expansion, floatability, and mushiness; however, the negative effects of 4% IF could not be fully mitigated. Overall, higher IF compromised kibble structure, starch gelatinization, and floatability, while screw configuration resulted in only a limited compensatory effect.

Determining protein requirements (PRs) for dogs remains a longstanding challenge. During growth, the rapid rate of protein deposition increases the demand for amino acids. In adult dogs, differences in overall diet digestibility and lower energy requirements of domestic dogs have led to discrepancies between the minimum crude protein (CP) value proposed by the National Research Council (NRC; 80 g of CP/kg of diet) and the 180 g of CP/kg of diet proposed by the European Pet Food Industry Federation (FEDIAF) and the Association of American Feed Control Officials (AAFCO), although most commercially available adult dog feeds offer protein levels that exceed both recommendations. In elderly dogs, physiological changes such as sarcopenia and reduced energy intake indicate a potential increase in PR, although evidence remains scarce. A similar gap exists for pregnant and lactating bitches, since most recommendations rely on extrapolations from growth studies. Classical PR recommendations were based on body weight gain and nitrogen balance (NB), methods that present important limitations. Due to this, stable isotope methods—including ¹³C-leucine, ¹⁵N-glycine, and ¹³C-phenylalanine—have emerged as precise methodological tools, enabling a detailed and dynamic assessment of whole-body protein metabolism, protein quality, and more accurate determination of PR and recommended allowance across different life stages.

Determining protein requirements (PR) for dog maintenance using welfare-conscious methods is challenging. This study aimed to establish a minimally invasive and efficient protocol for applying the indicator amino acid oxidation (IAAO) technique using L-[1-13C] phenylalanine (13Phe), while minimizing animal handling and cost (through lower isotope doses and fewer meals) and eliminating the need for respiration chambers. Two diets were extruded: a complete and balanced for maintenance based on poultry by-product meal (PBM) with 28% crude protein (CP); a low-protein formulation where PBM was replaced by maize starch (SBD) with 6% CP (DM basis). Ingredients were analyzed, and the SBD was supplemented so both formulations presented 22 g/kg of phenylalanine + tyrosine (DM basis). The dilution technique was applied to create five levels of CP: 6%, 8%, 10%, 12%, and 14% (DM basis). A sixth diet with 11% CP was used in the adaptation period. To test three feeding, isotope-enrichment, and sampling protocols (P1, P2, and P3), a block design was used with 10 dogs assigned to each protocol (14.8 ± 1.1 kg; 5.8 ± 2.0 years). After two days of adaptation (11% CP), the daily dog food was divided into 10 (P1), 7 (P2), or 5 (P3) meals. A priming dose (PD) of 0.18 mg/kg of 13C-Bicarbonate (13Bic) and 0.66 mg/kg of 13Phe were offered on the fourth, sixth, or fifth meal, followed by six, four, and four subsequent doses of 1.33 mg/kg of 13Phe in capsules every 30 min (P1, P2, and P3, respectively). Two basal samples of expired air were collected using an adapted mask, and after PD, eight samples were collected, starting 30 (P1), 90 (P2), and 90 (P3) min after enrichment. The CO2 volume was measured by the 13Bic method using masks. The time required to reach isotopic steady state (ISS) and the accuracy of measurements varied across protocols. P1 required the longest time to reach ISS (183.7 ± 8.4 min) and showed lower accuracy (r2 = 0.39; mean absolute percentage error [MAPE] = 17.1%; P < 0.05). P3 reached ISS more quickly (105.4 ± 6.1 min) but demonstrated moderate accuracy (r2 = 0.67; MAPE = 7.1%; P < 0.05). P2 represented an intermediate condition, reaching ISS at 170.6 ± 6.7 min while providing higher accuracy (r2 = 0.81; MAPE = 1.26%; P < 0.05). It was concluded that P2 is a minimally invasive and efficient protocol for IAAO application in dogs, potentially providing valuable insights for future research involving dogs living outside of a laboratory setting.

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.

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.

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.

Fermentable fibres are used in commercial dog food to promote intestinal health by providing substrates for better metabolic activity of the gut microbiota. Brazil is the world’s largest producer of oranges, from which it is possible to obtain fibre with a relevant soluble fraction. The present study compared the effects of two inclusions of orange fibre (1% and 3%, on as fed basis) with a negative control (without addition of fibre source) and two positive controls, beet pulp (3%) and purified inulin (1%), totalling five extruded diets for dogs. The experiment followed a randomised block design with 4 blocks of 10 dogs, 2 dogs per food in each block, totalling 8 dogs per diet. The apparent total tract nutrient digestibility was determined by total faecal collection. Faecal pH and fermentation product content were also measured. The digesta mean retention time (DMRT) was evaluated using plastic markers. The inclusion of a 3% fibre source in diets with 3% orange fibre and beet pulp reduced DM, OM, and energy digestibility (p < 0.05). Diets with 3% orange fibre, beet pulp and 1% inulin presented lower crude protein digestibility than the control (p < 0.05). Dietary fibre digestibility was higher for orange fibre-supplemented diets than inulin (p < 0.05). Beet pulp and 3% orange fibre inclusions resulted in increased moisture content in the faeces of dogs (p < 0.05) but did not alter DMRT. Total short-chain fatty acids were higher than the control in the faeces of dogs fed both orange fibre levels and the beet pulp-supplemented diet (p < 0.05), and the inulin diet-fed dogs presented intermediate values. Butyrate was higher in the faeces of dogs fed the diets supplemented with 1% and 3% orange fibre (p < 0.05), and similar values to the control were observed for beet pulp- and inulin-fed animals. Thus, it was concluded that orange fibre presented higher apparent total tract dietary fibre digestibility than beet pulp and had a fermentation profile in the colon that promoted the generation of butyrate, an effect not observed for inulin and beet pulp.