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Amino Acid Composition and Digestibility of Four Protein Sources for Dogs



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Amino Acid Composition and Digestibility
of Four Protein Sources for Dogs1
Veterinary Faculty, State University B43 Sart Tllman, 4000 Liege, Belgium
Indexing Key Words:
•symposium •dogs •dietary protein •protein di
Protein in dog diets can be either of animal source
or of vegetable origin. Dietary protein must supply 10
essential amino acids (EAA).Protein quality is depen
dent on the concentration of EAA and their availabi
lity. Quality is also influenced by digestibility. The
digestibility varies with processing and with the pres
ence of other components such as carbohydrates or
fiber. The purpose of the present study was to compare
amino acid (AA)composition and protein digestibility
in four diets containing four different protein sources.
Materials and methods. Three animal-protein
sources (lung, tripe, minced meat) and one vegetable-
protein source (soybean meal) were used. The lung,
tripe and minced meat were raw. They were incor
porated into a basic diet composed of cooked rice, corn
oil, minerals and vitamins. Four young adult Beagles,
two males and two females, were fed daily 550 kj me-
tabolizable energy (ME)/kg BW075. Protein was cal
culated to provide 20% of the ME. All four dogs were
fed the same diet during the same period. After a tran
sition period of 1 wk, each diet was tested during a 4-
wk period, at the end of which digestibility was mea
sured during 7 d. Feces were collected daily along with
food samples for analysis of dry matter (DM), ash and
ether extract (EE). The AA composition was deter
mined by capillary gas chromatography. Digestibility
of each protein source was calculated by difference,
assuming a digestibility for rice of 89% for DM, 91%
for organic matter (OM), 84% for crude protein (CP)
and 75% for EE. For corn-oil digestibility of DM, OM
and EE was estimated at 98%. Means among the pro
tein sources were compared by analysis of variance.
Results and discussion. Daily AA consumption
is given in Table 1. Difficulties were encountered in
the determination of the concentrations of Cys, Met
and Trp. Since the concentrations of the other AAs
were quite similar to reported data, these three values
have been taken from published data. The AA profiles
were similar in the four diets. Although soybean meal
is known to provide less sulfur-containing AAs, such
as Cys and Met, as well as His, the daily consumption
of these AAs with the diet based on soybean meal was
quite comparable to their consumption with the diets
based on animal protein. The diet based on lung, how
ever, provided less Met-Cys, His and Trp than the
other three diets. The concentration of Arg was low
in the diet with the minced meat. In the diet containing
tripe, concentrations of all AAs were fairly high, es
pecially the sulfur-containing AAs, due to the fact that
tripe was only washed so that the keratinized papillae
remained. The utilization of these AAs is, however,
assumed to be low since the proteolytic enzymes of
the dog and its intestinal microbes cannot digest kera
tin. The concentration of Leu was, on the contrary,
quite low in this diet. Regardless of these differences,
the concentrations of the EAAs in the four diets were
greater than the minimum requirements for mainte
nance according to the National Research Council (1).
They were still sufficient if the requirement was in
creased by 40% to compensate for impaired availabi
lity and digestibility (2). It should be noted that the
protein concentration in the diets was quite high (20%
1Presented as pan of the Waltham International Symposium on
Nutrition of Small Companion Animals, at University of California,
Davis, CA 95616, on September 4-8, 1990. Guest editors for the
symposium were James G. Morris, D'Ann C. Finley and Quinton
R. Rogers.
2To whom correspondence should be addressed: Veterinary Fac
ulty, State University B43 Sart Tilman, 4000 Liege, Belgium.
0022-3166/91 $3.00 ©1991 American Institute of Nutrition. J. Nutr. 121: S64-S65, 1991.
by guest on January 5, 2012jn.nutrition.orgDownloaded from
of the ME) to avoid any influence by protein deficiency
on digestibility and nitrogen balance.
Apparent digestibility coefficients of the compo
nents of the diets and the protein sources are given in
Table 2. The digestibility of DM was similar for the
diets based on animal protein and was ~90.36%. It
was significantly lower (P < 0.001) with the diet con
taining soybean meal (73.86%). The OM digestibility
was on average 3.31% units higher than the DM val
ues. High digestibility coefficients were observed for
CP (91.22%) and EE (96.79%) for the diets based on
animal protein. The corresponding figures were signi
ficantly lower (P < 0.001) when soybean meal was
When the digestibility of each protein source was
calculated by difference, coefficients differed only
slightly between protein sources and whole diet with
the animal proteins. For soybean meal the protein di
gestibility (CP) was rather low and similar to that of
the diet (76.33%) while DM and OM digestibility were
reduced to a large extent. The negative value for di
gestibility of EEis due to the low EEcontent of soybean
meal. Similar findings have been reported by Kendall
and Holme (3).
It appears from the present data that the three an
imal-protein sources did not differ to a large extent in
terms of AA profiles and digestibility. Animal protein
is generally well digested even if differences can be
found depending on the connective tissue (lung) or
carbohydrates (glycogen). Digestibility was lower in
the soybean-meal diet than in the animal-protein diets,
indicating that although the AA profile was compa
rable, the availability of the AA was lower in the soy-
Daily consumption of essential amino acids (EAA)
from four diets with different protein sources
Minced Soybean
Diet Tripe Lung meat meal Requirements'
Apparent digestibility coefficients of diets and
of protein sources1'1
Available amino acid based on 1985 NRC.
1Four dogs were fed each of the 4 diets.
2Abbreviations: CP, crude protein; DM, dry matter; EE, ether
extract; OM, organic matter; SED, standard error of the difference.
bean-meal diet. Proteins of plant origin generally have
a lower digestibility than animal proteins because plant
fiber or carbohydrates lower digestion due to a reduced
degradation rate of nutrients in the gut and an in
creased bacterial activity (4). In most commercial dog
foods both animal and vegetable proteins are used.
This combination raises the protein quality by com
plementation of EAA and increases the palatability of
the food (5).
The most interesting findings in the present trial
were the similarity in the EAA composition between
vegetable and animal protein, opposed to the reduced
digestibility of the vegetable protein. Further research
needs to be done with a lower level of protein in the
1. NATIONALRESEARCHCOUNCIL. (1985) Nutrient Requirements
of Dogs. National Academy Press, Washington, DC.
2. SHEFFY,B. A. (1989) The 1985 revision of the National Research
Council nutrient requirements of dogs and its impact on the
pet food industry. In: Nutrition of the Dog and Cat, pp. 11-26,
(I. H. Burger & J. P. W. Rivers, eds.), Cambridge University
Press, London.
3. KENDALL,P. T. & HOLME,D. W. (1982) Studies on the diges
tibility of soya bean products, cereals, cereal and plant by-pro
ducts in diets of dogs. /. Sci. Food Agrie. 33: 813-822.
4. MEYER,H. (1984) Nutrient digestibility and its relationship to
alimentary disorders in dogs. In: Nutrition and Behaviour in
Dogs and Cats, pp. 55-69, (R. S. Anderson, ed.), Pergamon Press,
5. BROWN,G. R. (1989) Protein in dog foods. Can. Vet. ]. 30: 528-
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... Table 3 shows the inclusion levels of both soybean meal and poultry offal meal as well as other protein ingredients evaluated in the studies. Only two [28,30] of the 17 studies did not provide this information. The processing of the ingredient and diet was only documented by two authors [3,22]. ...
... As regards the digestibility coefficient (Table 5), in most studies, the inclusion of soybean meal reduced the ADC of DM [9,13,22,28,30,32], EE [3,27,28,30] and GE [22,27,30] and increased the ADC of CP [3,24,27,29]. Of the 13 articles cited, 7 [10,22,24,26,27,32,34] presented the metabolizable energy (ME) values of the diet and, within these studies, soybean meal inclusion reduced ME. ...
... As regards the digestibility coefficient (Table 5), in most studies, the inclusion of soybean meal reduced the ADC of DM [9,13,22,28,30,32], EE [3,27,28,30] and GE [22,27,30] and increased the ADC of CP [3,24,27,29]. Of the 13 articles cited, 7 [10,22,24,26,27,32,34] presented the metabolizable energy (ME) values of the diet and, within these studies, soybean meal inclusion reduced ME. ...
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Soybean meal and poultry offal meal are protein ingredients commonly used in the formulation of commercial diets for dogs. However, there remains great variability in the data on the digestibility of each protein source. This systematic review study aimed to examine the intake, apparent nutrient digestibility coefficients and fecal output of protein sources (soybean meal and poultry offal meal) in adult dog food as reported in published studies. The article search was conducted in August 2018 in the PUBMED, SciELO, Science Direct and AGRIS indexing databases. The literature search was performed using "digestibility", "source protein" and "dog" as the main key terms combined with sub-terms to broaden the scope of the search. Criteria were defined for readability, exclusion and inclusion of articles. Results were organized in groups according to the search in the indexing databases, totaling 1,414 articles. After the works were selected following the inclusion criteria, 17 articles were evaluated in this review. According to most studies, plant-based ingredients have a less variable nutritional composition than animal-derived ingredients and poultry offal meal increases the digestibility coefficients of nutrients and energy and reduces fecal dry matter production. Factors inherent to raw-material origin, ingredient and food processing, as well as the high heterogeneity of the methodologies evaluated in the studies are directly related to the obtained results. To ensure a more accurate evaluation of the quality and of effects on the digestibility of protein sources, we recommended that articles include ingredient processing data and that the variables be evaluated under standardized study conditions.
... The digestibility of amino acids in food is dependent not only on the protein source, but also on the way the food is processed and on the presence of other components in the food. It remains to be investigated how the composition of diets can influence blood amino acid profiles in dogs with impaired hepatic function (Neirinck et al., 1991;de-Oliveira et al., 2012;Hendriks et al., 2015). ...
... Some commercial pet foods have been found not to provide some essential elements (Gosper, Raubenheimer, Machovsky-Capuska, & Chaves, 2016;Zafalon et al., 2020) and macronutrients (Hewson-Hughes et al., 2011). Furthermore, the proteins in pet foods can be derived from both animal and plant sources, but plant proteins have lower digestibility (Kanakubo, Fascetti, & Larsen, 2015;Neirinck, Istasse, Gabriel, Van Eenaeme, & Bienfait, 1991), lower bioavailability (Zafalon et al., 2020) and a less complete amino acid profile (Donadelli, Aldrich, Jones, & Beyer, 2019) than animal proteins. Cats also have specific behavioral needs, and encouragement of physical activity and reproduction of natural feline behavior in the home environment is important for preventing negative states such as boredom and frustration (Tan et al., 2020). ...
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Domestic cats (Felis catus) that roam outdoors have increased exposure to hazards to their health and welfare. Outdoor cats can themselves present a hazard to biodiversity conservation and wild animal welfare. Approaches to reducing predation of wildlife by cats might also bring benefits to cats by reducing their roaming and associated risks. We investigated ranging behaviors of domestic cats that regularly captured wild prey, and that had restricted or unrestricted outdoor access. We tested whether interventions aimed at reducing predation also affected their spatial behavior. We evaluated cat bells, Birdsbesafe collar covers, using a “puzzle feeder”, provision of meat‐rich food, object play, and a control group. Seventy‐two cats in 48 households in England completed the 12‐week trial in spring 2019. Home ranges were small (median AKDE95 = 1.51 ha). Cats with unrestricted outdoor access had 75% larger home ranges, 31% greater daily distances traveled, and reached 46% greater maximum distances from home, than cats with restricted outdoor access. None of the treatments intended to reduce predation affected cat ranges or distances traveled. While owners might use interventions to reduce predation, the only effective means of reducing cat roaming and associated exposure to outdoor hazards was restriction of outdoor access. While some interventions, like object play and dietary changes, can reduce domestic cat predation of wildlife, we found that these measures do not affect cat roaming behavior. Restricting access to the outdoors, even partially, does reduce the extent of cat ranging and likely reduces associated exposure to outdoor hazards.
... Furthermore, the protein in pet foods can be derived from both animal and plant sources. Plant protein sources have lower digestibility (Neirinck et al. 1991, Kanakubo et al. 2015, lower bioavailability (Zafalon et al. 2020), and a less complete profile of amino acids (Donadelli et al. 2019) than animal proteins. Therefore, it is possible that domestic cats that hunt wild prey are attempting to address some nutritional shortfall, though their success in so doing will clearly depend on successfully hunting, killing, and ultimately consuming their prey. ...
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Predation of wildlife by domestic cats Felis catus presents a threat to biodiversity conservation in some ecological contexts. The proportions of wild prey captured and eaten by domestic cats and thus the contributions of wild prey to cat diets are hard to quantify. This limits the understanding of any impacts of cats may have on wild animal populations and confounds analyses of the effects of interventions aimed at reducing wildlife killing. We used stable isotope analyses to quantify the relative contributions of wild and provisioned foods to the diets of domestic cats kept as companion animals and which frequently captured wild prey. We tested the effects of treatments aimed at reducing killing upon stable isotope ratios of cat whiskers and, where treatments had significant effects, we estimated variation in the contributions of wild prey to cats’ diets before and during treatment. We evaluated bells, Birdsbesafe collar covers, provision of food in a “puzzle feeder,” provision of food in which meat was the principal source of protein, object play, and a control group. As expected, cat diets consisted primarily of provisioned foods, though the contribution of wild animals to the diets of these cats, all of which regularly caught wild animals, was low (cat food ˜96%, wild animals ˜3–4%). Compared to the pre‐treatment period and control group, cats with a Birdsbesafe collar cover exhibited a significant reduction in nitrogen stable isotope ratios in their whiskers and consumed less wild prey, most likely attributable to effective inhibition of hunting, particularly for birds. Fitting cats with a Birdsbesafe collar cover, therefore, reduced both returns of wild birds and consumption of wild prey. While multiple interventions can significantly affect the numbers of wild animals that cats capture and return home, the remarkably small dietary contributions made by wild animal prey mean dietary change is harder to discern. Domestic cats rely almost exclusively on food provided by people, even when they frequently kill wild animals. This suggests that the hunting behavior of domestic cats may be driven by behavioral motivations, or by a need to address micronutrient requirements, but is unlikely to alter macronutrient intake.
... It remains to be investigated how the composition of diets can influence blood amino acid profiles in dogs with impaired hepatic function. [37][38][39] Our study had some limitations. Only a small number of dogs was included; different small dog breeds were represented and half of the dogs were young at the time of inclusion. ...
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... In the present study, nutrient digestibility and bioavailability were not assessed. However, it is generally recognized that plant protein sources have lower digestibility compared to animal protein [43,60]. Funaba et al. [61] observed in adult cats that a diet in which meat meal was used as a protein source resulted in higher apparent nitrogen absorption and retention, and higher dry matter digestibility when compared to a corn gluten meal based diet. ...
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The objective of this study was to evaluate the macronutrients composition, fatty acid and amino acid profiles, and essential minerals content of all vegan foods for dogs and cats available in the Brazilian market, and to compare results with FEDIAF (2019) and AAFCO (2019) recommendations. Four vegan pet foods were assessed (three for dogs and one for cats). The comparisons were made in a descriptive manner. All foods met the minimum recommendations for macronutrients. Arachidonic acid was not reported in any food label. Regarding the FEDIAF recommendations, one food for dogs had low calcium, another had low potassium and a third had low sodium. The cat food presented potassium content lower than recommended. The Ca:P ratio did not meet the minimum recommendation of FEDIAF (2019) and AAFCO (2019) in any of the dog’s foods analyzed, and the cat food also did not present the minimum recommendation based on FEDIAF (2019). Copper concentrations exceeded the legal limit in all foods. Zinc concentrations exceeded this limit in two foods (one for dogs and one for cats) and iron levels exceeded the legal limit in one dog food. One of the dog foods did not meet the minimum recommendation for methionine and the cat food did not meet the minimum recommendation for arginine. In addition, when the amount of nutrients consumed by animals with low energy requirements was simulated, in addition to the same non-conformities described above, it was observed that the cat food does not meet the minimum recommended of protein and taurine in unit/Kg0.67. It was concluded that all foods analyzed had one or more nutrients below the recommended levels and some presented zinc and copper excess, therefore, these foods should not be recommended for dogs and cats, because dietary deficiencies found may lead to health risks for dogs and cats. Furthermore, manufacturers should review their formulations to ensure the nutritional adequacy of these foods.
... Some feed ingredients used commonly in pet food formulations have been described elsewhere [46,47]. In Costa Rica, the basis for pet food formulations is corn and soybean meal. ...
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The dog has assumed a prominent role in human society. Associated with that status, diet choices for companion dogs have begun to reflect the personal preferences of the owners, with greater emphasis on specialty diets such as organic, vegan/vegetarian, and omission or inclusion of specific ingredients. Despite consumer preferences and many marketing strategies employed, the diets must ensure nutritional adequacy for the dog; if not, health becomes compromised, sometimes severely. The most frequent consideration of consumers and dog food manufacturers is protein source and concentration with a growing emphasis on amino acid composition and bioavailability. Amino acids in general play diverse and critical roles in the dog, with specific amino acids being essential. This review covers what is known regarding amino acids in dog nutrition.
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Predation by domestic cats Felis catus can be a threat to biodiversity conservation,1, 2, 3 but its mitigation is controversial.⁴ Confinement and collar-mounted devices can impede cat hunting success and reduce numbers of animals killed,⁵ but some owners do not wish to inhibit what they see as natural behavior, perceive safety risks associated with collars, or are concerned about device loss and ineffectiveness.⁶,⁷ In a controlled and replicated trial, we tested novel, non-invasive interventions that aim to make positive contributions to cat husbandry, alongside existing devices that impede hunting. Households where a high meat protein, grain-free food was provided, and households where 5–10 min of daily object play was introduced, recorded decreases of 36% and 25%, respectively, in numbers of animals captured and brought home by cats, relative to controls and the pre-treatment period. Introduction of puzzle feeders increased numbers by 33%. Fitting Birdsbesafe collar covers reduced the numbers of birds captured and brought home by 42% but had no discernible effect on mammals. Cat bells had no discernible effect. Reductions in predation can be made by non-invasive, positive contributions to cat nutrition and behavior that reduce their tendency to hunt, rather than impede their hunting. These measures are likely to find support among cat owners who are concerned about the welfare implications of other interventions.
Full-text available
This study evaluated the nutritional levels, apparent digestibility coefficients, and faecal characteristics of dogs fed with four by-products from bovine slaughter: testicles, residue sirloin steak, trachea, and liver. Ingredients were processed and packed in tins for heat treatment in autoclaves. For the digestibility and faeces quality, ingredients were mixed with a reference diet (commercial food) in the proportion of 30g kg-1 test ingredient and 70g kg-1 reference diet (as dry matter). Ten adult dogs were distributed in double Latin block squares (5x5) with five treatments and five periods, totalling ten repetitions per treatment. The residue sirloin steak presented the highest levels of essential (414.2g kg-1 of dry matter) and non-essential (399.0g kg-1 of dry matter) amino acids in tested ingredients. No differences (P>0.05) were observed in apparent digestibility coefficients of dry matter - ADCDM (907g kg-1), ADCOM (930g kg-1), ADCCP (841g kg-1), ADCAEE (954g kg-1) values, and DE (5069kcal kg-1) and ME (4781kcal kg-1) values between testicle, residue sirloin steak, and liver. The trachea presented lower digestibility and energy values (digestible and metabolizable) than the other ingredients. This lower trachea digestibility resulted in higher faecal volume for natural and dry matter (P<0.05). There was no difference (P>0.05) in faecal score between ingredients. Ingredients tested in this study can be used in feeds for adult dogs; however, their nutritional levels and digestibility values should be considered for correct diet balance.
The apparent digestibility of 21 plant materials was evaluated in dog diets using adult beagles. In most cases the digestibility by difference method was used. Apparent crude protein (N × 6.25) digestibility coefficients for textured soya protein, extracted soya meal, full-fat soya flours and micronised whole soya beans ranged from 0.71 to 0.87. Digestible energy (DE) contents ranged from 14.3 to 20.8 MJ kg DM−1. Samples of wholeground wheat, barley meal and flaked maize were well digested by dogs, as were samples of refined flour, vital gluten, feeding-oat meal and wheat-germ meal; apparent energy digestibility coefficients ranged from 0.72 to 0.96. Wheatfeed and two distillers by-products had lower energy digestibility coefficients (0.39 to 0.59). Other materials with low apparent digestibility in dog diets (probably because of high fibre levels) were walnut meal, almond meal, dried molassed sugar beet pulp and locust bean meal. Gross energy and dry matter digestibility coefficients of below 0.52 were obtained. Data are also presented on the digestibility of samples of rapeseed meal, cassava and dried potato. When comparison was possible, DE values measured for dogs agreed closely with those for pigs for most materials.
The 1985 revision of the National Research Council nutrient requirements of dogs and its impact on the pet food industry.
Nutrient digestibility and its relationship to alimentary disorders in dogs.