The effects of hydrolyzed protein on macronutrient digestibility, fecal metabolites and microbiota, oxidative stress and inflammatory biomarkers, and skin and coat quality in adult dogs.

Research on protein hydrolysates has observed various properties and functionalities on ingredients depending on the type of hydrolysate. The objective of this study was to evaluate the effects of hydrolyzed chicken protein that was incorporated into diets on digestibility, gut health, skin and coat health, oxidative stress, and intestinal inflammation markers in healthy adult dogs. Five complete and balanced diets were manufactured: (1) CONd: 25% chicken meal diet; (2) 5% CLHd: 5% chicken liver and heart hydrolysate plus 20% chicken meal diet; (3) CLHd: 25% chicken liver and heart hydrolysate diet; (4) 5% CHd: 5% chicken hydrolysate plus 20% chicken meal diet; (5) CHd: 25% chicken hydrolysate diet. A replicated 5 × 5 Latin square design was used which included 10 neutered adult Beagles. Each of the 5 periods consisted of a 7-d washout time and a 28-d treatment period. All diets were well accepted by the dogs. Fecal butyrate concentration was higher while fecal isovalerate and total phenol/indole were lower in dogs fed CLHd than CONd (P < 0.05). Dogs fed CHd had higher fecal immunoglobulin A concentration when compared with CLHd (P < 0.05); however, both groups were comparable to the CONd. There was no difference among groups in serum cytokine concentrations, serum oxidative stress biomarkers, or skin and coat health analyses (P > 0.05). Fecal microbiota was shifted by CLHd with higher abundance in Ruminococcus gauvreauii group as well as lower Clostridium sensu stricto 1, Sutterella, Fusobacterium, and Bacteroides when compared with CONd (P < 0.05). There was also a difference in beta diversity of fecal microbiota between CLHd and CHd (P < 0.05). In conclusion, chicken protein hydrolysate could be incorporated into canine extruded diets as a comparable source of protein to traditional chicken meal. The test chicken protein hydrolysates showed the potential to support gut health by modulating immune response and microbiota; however, functional properties of protein hydrolysates are dependent on inclusion level and source.

Research has been exploring various functional properties of hydrolyzed protein to benefit the health of animals. However, the functionality of a hydrolyzed protein depends on the type of hydrolysate. Therefore, this study was conducted to evaluate the effect of hydrolysates from chicken meat and hydrolysates from chicken heart and liver on digestibility, gut health, skin and coat health, oxidative stress, and inflammation in healthy adult dogs. Five canine diets were manufactured with similar ingredients except for the test protein sources. The control diet was formulated with chicken meal, a traditional protein source in pet food, and the other diets had a partial or complete substitution from the chicken meal with the two types of protein hydrolysate. The diets were all well accepted by the dogs and all dogs maintained healthy throughout the study. Dogs fed the hydrolysate from chicken meat showed lower inflammatory biomarkers in the feces. On the other hand, dogs fed the hydrolysate from chicken liver and heart demonstrated a shift in gut microbiota with more abundant beneficial bacteria. In conclusion, poultry-originated protein hydrolysates showed the potential in making positive changes in inflammatory state, immune response, and microbiota in healthy adult dogs.

Effects of hydrolyzed chicken liver on digestibility, fecal and urinary characteristics, and fecal metabolites of adult dogs.

High-protein low-carbohydrate diets have been widely used for adult maintenance dogs, as well as in specific weight loss diets and maintenance programs. However, increasing dietary protein may increase undigested protein in the hindgut, modifying intestinal fermentation and fecal metabolite concentrations. The aim of this study was to evaluate the effects of protein source and concentration on apparent total tract digestibility (ATTD) of nutrients, metabolizable energy (ME), fecal and urinary characteristics, and fecal metabolites of dogs. Twelve healthy adult dogs were distributed into six treatments (n = 6 per diet) in a balanced incomplete Latin square design consisting of three periods of 30 days each. Six diets, varying in protein source [poultry byproduct meal (PBPM) and hydrolyzed chicken liver powder (HCLP)] and concentration [24, 32, and 40% crude protein (CP) on dry matter (DM) basis] were tested: PBPM24 (PBPM based diet with 24% CP); PBPM32 (PBPM with 32% CP); PBPM40 (PBPM with 40% CP); HCLP24 (HCLP based diet with 24% CP); HCLP32 (HCLP with 32% CP); HCLP40 (HCLP with 40% CP). The ATTD of CP was greater in dogs-fed HCLP and higher protein concentrations diets (P < 0.05). However, dogs-fed HCLP diets had lower ATTD of fat and carbohydrates, and ME (P < 0.05). Similarly, high-protein diets reduced the ATTD of DM, OM, fat, carbohydrates, and energy (P < 0.05). High-protein diets increased the daily fecal output and moisture (P = 0.004 and P < 0.05, respectively), as well as the fecal score (P < 0.0001), verified as soft, moist stools, but still within the ideal range. Fecal valerate concentration was greater in dogs-fed PBPM at 32% CP (P = 0.007). Fecal isobutyrate tended to increase in dogs-fed PBPM and high-protein diets (P < 0.10). Also, dogs-fed PBPM and high-protein diets had greater fecal concentrations of isovalerate, branched-chain fatty acids (BCFA), and ammonia (P < 0.05). Finally, the fecal lactate concentration increased in dogs-fed HCLP and high-protein diets (P < 0.05). The HCLP increased the ATTD of CP, being a highly digestible protein. Although the inclusion of HCLP slightly increased fecal score and moisture, it decreased the amount of fecal metabolites of protein fermentation ammonia and BCFA, both of which are associated with proteolytic fermentation in the colon.

Feeding companion animals with high-protein diets has been a demand of the market and pet owners. However, the protein quality and quantity consumed can interfere with the amount of undigested protein that reaches the hindgut and be fermented. Intestinal fermentation can be desired when well controlled. This study tested two protein sources (hydrolyzed chicken liver and poultry byproduct meal) combined at three dietary protein concentrations (24, 32, and 40% crude protein on dry matter basis) and their effects on the apparent total tract digestibility (ATTD), fecal and urinary characteristics, and fecal metabolites of healthy adult dogs. In summary, diets containing higher inclusion of hydrolyzed chicken liver had improved protein ATTD. However, the same diets impaired the ATTD of fat and carbohydrates and decreased metabolizable energy. High-protein diets retained more water in the feces and increased the fecal output. Fecal consistency was affected, scored as soft and moist stools, but remained within an acceptable score. Dogs-fed poultry byproduct meal diets had greater concentrations of fecal protein fermentation metabolites, such as ammonia and branched-chain fatty acids, possibly related to a greater amount of undigested protein that reached the hindgut and was fermented.

Standardized amino acid digestibility and protein quality in extruded canine diets containing hydrolyzed protein using a precision-fed rooster assay.

Protein hydrolysate has become a choice of alternative protein source in canine diets as it showed greater digestibility, lower allergenic responses, and various functional properties when compared with intact proteins. The objective of the study was to determine the effect of hydrolyzed protein inclusion on amino acid digestibility and protein quality in extruded canine diets when compared with a traditional protein source for adult dogs. Five treatment diets were formulated to have similar compositions except for the main protein source. The control diet was formulated with chicken meal (CM) as the primary protein source. Test hydrolyzed proteins, chicken liver and heart hydrolysate (CLH) and chicken hydrolysate (CH) were used to partially or completely substitute CM. The diets were: CONd: CM (30%) diet; 5%CLHd: 5% CLH with 25% CM diet; CLHd: CLH (30%) diet; 5%CHd: 5% CH with 25% CM diet; CHd: CH (30%) diet. A precision-fed rooster assay was used to determine standardized amino acid digestibility for the ingredients and diets. In addition, Digestible Indispensable Amino Acid Score (DIAAS)-like values were calculated for the protein ingredients. All protein ingredients had higher than 80% of digestibility for all indispensable amino acids with no difference among sources (P > 0.05). From the DIAAS-like values referencing AAFCO nutrient profile for adult dogs, CLH and CH did not have any limiting amino acid; on the other hand, CM has a lower DIAAS-like value (93.3%) than CLH and CH (P < 0.05) with tryptophan being the first-limiting amino acid. The DIAAS-like values were often lower when the amino acid combinations methionine + cysteine and phenylalanine + tyrosine were included in the calculation. When referencing NRC recommended allowances and minimal requirements, methionine was the first-limiting amino acid for all protein sources. Amino acid digestibility was mostly above 80% and comparable among the treatment diets. Regarding the digestible indispensable amino acid concentrations in the diets, all of them met the AAFCO nutrient profile for adult dogs at maintenance. In conclusion, both protein hydrolysates were highly digestible, high-quality protein sources, and a full substitution from CM to protein hydrolysate could result in greater protein quality, according to the DIAAS-like values of the ingredients, when compared with CM in extruded canine diets.

Hydrolyzed protein has been more commonly used in the pet food industry recently to increase digestibility, decrease allergenic responses, and for other health benefits (such as anti-inflammation and anti-oxidation) in companion animals. The study was designed to determine the protein quality of two protein hydrolysates for incorporating into dry dog foods. Chicken meal (CM) was chosen to be the control protein source as it is a high-quality protein source and has been widely used in pet foods. The test hydrolyzed proteins were made from chicken liver and heart or mechanically separated chicken. The current study aimed to compare the test hydrolyzed proteins, which are usually highly digestible, with a traditional high-quality protein to examine if the hydrolyzed proteins were comparable with CM or of higher quality. Five treatment diets were formulated with CM and/or hydrolyzed proteins. Cecectomized roosters were used in the assay to determine the amino acid digestibility and protein quality of the ingredients and treatment diets. It was shown that all ingredients and diets were highly digestible. The protein hydrolysates were of higher protein quality that better met the animals' needs. Conclusively, the test protein hydrolysates are suitable protein sources in canine diets to create high-value and specialty foods.

Hydrolyzed chicken liver used as single source of animal protein in diet and its effect on cytokines, immunoglobulins, and fecal microbiota profile of adult dogs.

Dogs with food allergies and enteropathies may require hydrolyzed diets to prevent or reduce clinical signs, therefore the protein sources used in these diets must be previously characterized and evaluated in healthy dogs. This study aimed to investigate the effects of a hydrolyzed chicken liver powder-based diet (HCLP) versus a poultry by-product meal and bovine meat and bone meal-based diet (Control), on complete blood count (CBC), cytokine, immunoglobulins responses (assessed on days 0, 15, 30 and 45), and fecal microbiota (assessed on day 45) in healthy adult dogs. The CBC did not differ between diets (P>0.05), remaining within reference range. Total plasma IL-4 concentrations were decreased over time independent of the dietary treatment (P<0.001). Total plasma IgA decreased on day 30 compared to days 0 and 45 in dogs fed the control diet (P<0.001). Total plasma IgE concentrations were reduced on days 30 and 45 in dogs fed the control diet, and on days 15 vs 30 and 15 vs 45 in dogs fed HCLP diet (P = 0.001). The 16S rRNA gene sequencing showed similar species richness and abundances of phyla and genera between diets (P>0.05). ß-diversity principal coordinate analysis plots demonstrated that HCLP group had a higher similarity than control. Based on our results, healthy adult dogs fed a HCLP based diet maintained normal values for hematological and immunological characteristics, and fecal microbiota after 45 days of feeding.