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https://doi.org/10.1177/1098612X17710842
Journal of Feline Medicine and Surgery
1 –7
© The Author(s) 2017
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DOI: 10.1177/1098612X17710842
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Introduction
The popularity of grain-free pet diets has increased in
recent years. From 2012–2014, the percentage of grain-
free cat food purchased more than doubled, going from
4% to 9% of total cat food purchased.1 Based on our per-
sonal experience, as well as from discussions with other
veterinarians, this percentage has likely continued to
increase since 2014. Reasons for this increase are unknown
but may be related to manufacturers’ marketing efforts
and unsubstantiated consumer beliefs about the role of
grains or carbohydrates in pet foods and the ability of
cats to metabolize carbohydrate. Instead of grains, grain-
free diets typically contain alternate carbohydrate sources
such as white potato, peas and other legumes, sweet
potato or tapioca. It is unclear whether grain-free diets
differ in their total carbohydrate content compared with
grain-containing diets. Information on carbohydrate con-
tent, which is not found on the label, must be obtained
from manufacturers and may be based on total starch,
total sugars or, more commonly, nitrogen-free extract
Comparison of carbohydrate
content between grain-containing
and grain-free dry cat diets and
between reported and calculated
carbohydrate values
Lori R Prantil*, Cailin R Heinze and Lisa M Freeman
Abstract
Objectives The aim of this study was to compare the carbohydrate content of grain-containing and grain-free dry
cat diets and compare major protein and carbohydrate sources of these diets.
Methods This was a cross-sectional study of 77 randomly selected dry cat diets (42 grain-containing, 35 grain-
free). Reported carbohydrate values were compared between grain-containing and grain-free cat diets. A subset
of 25% of diets from each category (grain-containing and grain-free) was analyzed and nitrogen-free extract was
calculated as an estimate of carbohydrate content. These calculated values were compared with reported values
from the manufacturer. Animal- and plant-sourced ingredients were also compared between grain-containing and
grain-free diets.
Results Mean reported carbohydrate content of the grain-free diets (n = 35) was lower than the grain-containing
diets (n = 41; 64 ± 16 vs 86 ± 22 g/1000 kcal; P <0.001). Reported carbohydrate values were higher than
analyzed nitrogen-free extract (n = 20; 79 ± 30 vs 73 ± 27 g/1000 kcal; P = 0.024). Poultry (P = 0.009) and soy
(P= 0.007) were less common in grain-free diets than in diets containing grain. The alternative carbohydrate
sources of chickpeas, lentils, peas, potato, sweet potato and cassava/tapioca were more common (P <0.05) in
grain-free diets than in diets containing grain.
Conclusions and relevance This sample of grain-free diets had lower mean reported carbohydrate content than
grain-containing diets, but there was considerable overlap between groups and individual diets’ carbohydrate/
nitrogen-free extract content varied widely.
Accepted: 27 April 2017
Department of Clinical Sciences, Cummings School of Veterinary
Medicine, Tufts University, North Grafton, MA, USA
* Current address: VCA South Shore Animal Hospital, 595
Columbian Street, South Weymouth, MA 02190, USA
Corresponding author:
Cailin Heinze VMD, MS, DACVN, Department of Clinical Sciences,
Cummings School of Veterinary Medicine, Tufts University, 200
Westboro Road, North Grafton, MA 01536, USA
Email: cailin.heinze@tufts.edu
710842JFM0010.1177/1098612X17710842Journal of Feline Medicine and SurgeryPrantil et al
research-article2017
Original Article
2 Journal of Feline Medicine and Surgery 00(0)
(NFE). NFE is calculated by subtracting the measured per-
cent crude protein, crude fat, crude fiber, moisture and ash
from 100 and assuming the remainder is carbohydrate.
In addition to concerns regarding carbohydrates,
some cat owners have reported to the authors that they
choose grain-free diets because of the perception that
food allergies are common in cats and that grains are a
common allergen. In fact, food allergies are reported to
be uncommon in cats.2 When they do occur, they are
most commonly associated with an animal-source pro-
tein such as beef, chicken, fish or dairy protein rather
than to plant ingredients such as wheat, corn or rice.3,4
Whether grain-free diets contain fewer of the most com-
monly reported food allergens in cats (ie, beef, fish,
chicken or dairy) has not been reported.
To begin to address these issues, the first objective of
this study was to determine whether the manufacturer-
reported carbohydrate content of grain-free dry cat diets
was lower than that of grain-containing diets, with the
hypothesis that there would be no difference in the carbo-
hydrate content between grain-containing and grain-free
diets. Second, since carbohydrate values reported by
manufacturers could encompass a number of different
types of assays and methods, reported carbohydrate val-
ues were compared with calculated NFE in a subset of
grain-free and grain-containing cat diets. Our hypothesis
was that there would be no significant difference between
reported carbohydrate and calculated NFE values.
Finally, animal-sourced and plant-sourced ingredients
were compared between grain-free and grain-containing
diets, with the hypothesis that there would be no signifi-
cant difference in the most commonly reported food
allergens in grain-free vs grain-containing diets.
Materials and methods
Diet selection
A list of dry cat diet manufacturers was created from all
diets offered for sale on two popular internet pet food
retailers’ websites (petfooddirect.com; chewy.com). For
the purposes of the study, an individual manufacturer
was defined by having a unique main corporate address,
which was assumed to have common management and
manufacturing sites, even if they produced multiple prod-
ucts sold under different names. All manufacturers with
corporate headquarters outside of the USA were excluded.
Since some manufacturers sell both mass-market and
‘premium’ brands of diets (which may use different ingre-
dients and formulations), we recorded whether each man-
ufacturer had diets sold on the mass market (eg, grocery
stores, superstores/big-box stores), only in specialty
stores (eg, pet supply stores, pet boutique stores) or both.
Procedures
For each manufacturer, a list of all flavors and varieties
of dry adult cat diets that were available for sale on the
sites was compiled. The list included all diets that were
marketed as being for adult maintenance and included
diets with an Association of American Feed Control
Officials (AAFCO) nutritional adequacy statement indi-
cating that the diet had passed feeding trials or was for-
mulated to meet the AAFCO Nutrient Profile for adult
cat maintenance or all life stages.5 Diets that were mar-
keted specifically for kittens were excluded. Any diets
with labels that contained wording implying special
needs, such as ‘indoor’, ‘urinary tract health’, ‘breed spe-
cific’ or ‘hairball control’ were also excluded. The final
list included 224 diets.
Ingredient lists of all eligible diets were reviewed and
grains were defined as any food made from wheat, rice,
oats, corn, barley or another cereal grain. As per the US
Department of Agriculture definition of the word ‘grain’,
this included both the whole-grain products (which
include the entire grain kernel of the bran, the germ and
the endosperm), as well as refined-grain products that
have been milled to remove the bran and germ.6 The
diets were categorized as containing grains if there was a
grain or grain-derived product in the ingredient list
(grain-containing group) and as ‘grain-free’ (grain-free
group) if they did not contain any recognizable grains or
grain-derived ingredients on the ingredient list or were
marketed as being ‘grain-free’ by the manufacturer, even
if there was a grain in the ingredient list.
Of the 224 diets identified, some were from the same
manufacturer. To ensure that one manufacturer’s diets
were not over-represented, a computerized randomiza-
tion scheme was used to select one diet from each manu-
facturer for each diet group (grain-free vs grain-containing).
In addition, if a manufacturer sold diets in both mass-
market and specialty stores, one diet from each of these
categories was selected in the grain-containing and grain-
free groups. Therefore, from an individual manufacturer,
between one (one grain-containing or one grain-free) and
four (two grain-containing and two grain-free) diets were
selected for the study for a total of 77 diets.
For each diet included in the study, manufacturers’
customer service lines were contacted and asked to pro-
vide ‘carbohydrate content’ on a metabolizable energy
basis (in g/1000 kcal). If the manufacturer could only
provide the carbohydrate content on an as-fed percent
basis, the energy density (kcal/kg) was also obtained
from the manufacturer and the as-fed carbohydrate
content was converted to a g/1000 kcal value. If the
manufacturer could only provide the carbohydrate
content on a dry matter basis, the moisture content was
obtained and the carbohydrate content was converted
to g/1000 kcal.
From the complete list of diets included in the study
(n = 77), a subset of approximately 25% (n = 20) was
selected using a random number generator from the
grain-containing and grain-free diet groups (grain
Prantil et al 3
group: n = 11; grain-free group: n = 9). Each of these
diets was purchased online. Each diet was mixed thor-
oughly, and 250 g samples were removed, repackaged
and coded so that the laboratory personnel were blinded
to the identity of the samples during diet testing. All of
the diet samples were shipped to a commercial labora-
tory (Midwest Laboratories, Omaha, NE, USA) regularly
used by the pet food industry for diet analysis. A single
proximate analysis that included moisture, crude fat,
ash, crude protein and crude fiber was run on each diet
sample. The percentage NFE was then calculated by the
laboratory using the formula NFE = 100 – (crude protein
+ crude fat + crude fiber + moisture + ash). The energy
density of the diet was calculated using modified
Atwater factors and used to convert these values to
g/1000 kcal.7 The NFE values were then compared with
the manufacturer-reported carbohydrate content.
To assess ingredients, each diet’s ingredient list was
reviewed and major animal and plant sources of protein
and carbohydrate in the diet were recorded. Fats such as
fish oil, animal fat and vegetable oils were not included
in the analysis. Ingredients that followed the vitamins
and minerals in the ingredient list were deemed to be
present in only trace amounts and were also excluded.
To facilitate analysis, some of the animal-sourced ingre-
dients were grouped into larger categories if they were
rare (eg, calamari was grouped with clam in the seafood
category), if they were derived from the same proteins
(eg, cheese and yogurt both coming from milk) or if it
was not clear which specific species were contained in
each ingredient (eg, ‘poultry’ or ‘fish’ or ‘meat’ could
include multiple species that were all individually
included in other diets). As such, the ‘poultry’ category
included the following ingredients: poultry, chicken, tur-
key, pheasant and duck. The ‘fish’ category included the
following ingredients: fish, salmon, whitefish, ocean
fish, trout, herring, menhaden and tuna. The ‘dairy’ cat-
egory included the following ingredients: whey, yogurt,
milk, cheese and cottage cheese. The ‘seafood’ category
included the following ingredients: mussel, crab, clam
and calamari. The ‘meat’ category included the follow-
ing ingredients: meat, meat meal and animal digest.
Overall, there were 12 animal-sourced ingredients or cat-
egories. There were 42 different major plant-sourced
ingredients and these were not further grouped. These
main protein categories and individual carbohydrate
ingredients were compared between grain-containing
and grain-free diets.
Statistical analysis
Data distributions were evaluated graphically, and since
all data were normally distributed, data are presented
as mean ± SD. The carbohydrate content reported by
manufacturers was compared between grain-containing
and grain-free diets using an independent t-test. For the
subgroup of diets that underwent nutrient analysis, the
calculated NFE vs reported carbohydrate content was
compared using a paired t-test. Major protein catego-
ries and carbohydrate ingredients in each diet were
compared between grain-containing and grain-free
diets using χ2 tests. Data were analyzed with commer-
cial statistical software (Systat 13.0 [Systat Software]
and SPSS version 22 [IBM]), and P <0.05 was consid-
ered significant.
Results
Of the 77 diets included in the study, three manufactur-
ers were unable to provide information on carbohydrate
content on an energy basis. Two of these manufacturers
provided dry matter carbohydrate values from a typical
analysis (average dry matter carbohydrate content or
maximum dry matter carbohydrate content) and aver-
age moisture levels from which carbohydrate content on
an energy basis was calculated. The third manufacturer
did not respond to repeated requests over several
months to provide the carbohydrate content of the diet,
resulting in a total study population of 76 diets for the
carbohydrate content comparison between grain-
containing and grain-free diets. When the subset of diets
was randomly selected for diet analysis, in anticipation
of being able to get the requested information from all
manufacturers, this diet was counted in the calculation
of the 25% subset of grain-containing diets. Without
reported carbohydrate content, this product could only
be included in the ingredient evaluation as an ingredient
list was available on the manufacturer’s website.
Therefore, a total of 77 diets were included in the ingre-
dient comparison portion of the study.
The manufacturer-reported carbohydrate content of
the grain-containing diets (n = 41; 86 ± 22 g/1000 kcal)
was significantly higher than that of the grain-free group
(n = 35; 64 ± 16 g/1000 kcal [P <0.001]; Figure 1). When
diets typically sold in specialty stores were compared
with mass-market diets, reported carbohydrate content
was higher in the mass market (n = 12, 93 ± 17 g/1000
kcal) than in the specialty diets (n = 64, 72 ± 22 g/1000
kcal; P = 0.003), all inclusive of grain-free and grain-
containing diets (Figure 2).
For the subgroup of 20 grain-containing and grain-
free diets for which NFE content was calculated from
analysis, the reported carbohydrate content (79 ± 30
g/1000 kcal) from the manufacturers was significantly
higher than the NFE calculated from analysis (73 ± 27
g/1000 kcal; P = 0.024) The calculated NFE content of
the grain-containing diets (n = 11; 90 ± 19 g/1000 kcal)
was higher than that of the grain-free diets (n = 9; 52 ±
20 g/1000 kcal; P <0.001).
The grain-containing diet group contained eight cat-
egories of animal-sourced ingredients and 35 unique
plant-sourced ingredients. In the grain-free diet group,
4 Journal of Feline Medicine and Surgery 00(0)
10 categories of animal-sourced ingredients and 32
unique plant-sourced ingredients were identified, one of
which was a grain by the US Department of Agriculture
definition.6 Tables 1 and 2 show ingredients that were
present in more than one diet of the total 77 diets. Other
ingredients – venison, bison, avocado, apricot, artichoke,
chia, papaya and zucchini – were each only present in
either one grain-free diet and no grain-containing diets
or one grain-containing diet and no grain-free diets and
were excluded from statistical analysis. The most com-
mon animal-sourced ingredient category in the grain-
containing diets was poultry, while poultry and fish tied
as the most common ingredients in the grain-free foods.
The most common plant-sourced ingredients in the
grain-containing diets were rice, flax and cranberry vs
pea, cranberry and potato in the grain-free diets. Poultry
(P = 0.009), which included chicken, a commonly
reported food allergen, was significantly more common
in the grain-containing diets than in the grain-free diets.
For the plant-sourced ingredients, all grains and soy
were significantly more common (P <0.05) in grain-con-
taining diets than grain-free diets, while chickpea, lentil,
pea, potato, sweet potato and cassava/tapioca were sig-
nificantly more common (P <0.05) in the grain-free diets.
Figure 1 Boxandwhisker plot of the carbohydrate content
of grain-free and grain-containing dry feline diets. Each box
represents the interquartile range (25th–75th percentiles), the
horizontal line in each box represents the median value, the
whiskers indicate the range of observed values that fall within
± 1.5 times the interquartile range, and circles represent
outliers
Figure 2 Boxandwhisker plot of the carbohydrate content
of dry feline diets available in mass market retailers as
compared with specialty retailers. Each box represents the
interquartile range (25th–75th percentiles), the horizontal
line in each box represents the median value, the whiskers
indicate the range of observed values that fall within ± 1.5
times the interquartile range, and circles represent outliers
Table 1 Comparison of animal-sourced ingredients in grain-containing (n = 42) and grain-free (n = 35) dry cat diets
Protein source Number of grain diets Number of grain-free diets P value
Beef 0 2 0.203
Dairy* 4 5 0.724
Egg 26 17 0.259
Fish†30 25 1.000
Lamb 3 0 0.246
Meat‡3 0 0.246
Pork 2 4 0.402
Poultry§40 25 0.009
Rabbit 0 2 0.203
Seafood¶4 1 0.369
*Included whey, yogurt, milk, cheese and cottage cheese
†Included fish, salmon, whitefish, ocean fish, trout, herring, menhaden and tuna
‡Included meat, meat meal and animal digest
§Included poultry, chicken, turkey, pheasant and duck
¶Included mussel, crab, clam and calamari
Prantil et al 5
Discussion
The mean manufacturer-reported carbohydrate content
of the grain-free diets was 25% lower than the reported
carbohydrate content of the grain-containing diets,
which did not support our hypothesis. However, there
was considerable overlap between the two groups, and
within each group, individual diets varied widely in car-
bohydrate content.
The physiological and clinical relevance of this 25%
difference is unclear since, while cats do have some met-
abolic differences related to carbohydrate metabolism
compared with many other species, they are able to
digest and metabolize carbohydrates. Cats have low
hepatic glucokinase activity, which is the primary
enzyme used by most animals to phosphorylate glucose
inside hepatic cells as the first step in glycolysis when
blood glucose levels are high, such as after meals con-
taining carbohydrates.8 Adult cats, as well as many other
mammals, have no dietary requirement for carbohy-
drate.9 In one study, cats preferred to consume a diet
containing about 8 g carbohydrate daily, and were reluc-
tant to consume more than 20 g of carbohydrate daily.
These amounts would be provided by a diet containing
40 g and 100 g of carbohydrate/1000 kcal, respectively,
for a cat consuming 200 kcal.10 However, these results
may be related to the specific diets used in the study, and
may not be generalizable to all cats. Safe upper limits
have been described for some specific types of carbohy-
drates (including glucose, sucrose and lactose) in cat
diets, but not for overall carbohydrate, assuming protein
Table 2 Comparison of plant-sourced ingredients in grain-containing (n = 42) and grain-free (n = 35) dry cat diets
Carbohydrate source Number of grain diets Number of grain-free diets P value
Alfalfa 6 10 0.162
Apple 9 11 0.435
Barley 13 1 0.002
Beet 14 9 0.618
Blackberry 1 2 0.588
Blueberry 13 15 0.344
Broccoli 4 3 1.000
Carrot 16 16 0.643
Cauliflower 0 2 0.230
Celery 2 5 0.235
Chickpea 0 6 0.007
Chicory 9 8 1.000
Corn 12 0 0.000
Cranberry 20 18 0.821
Flax 24 15 0.256
Green beans 0 2 0.203
Kelp 9 4 0.361
Lentil 1 6 0.042
Lettuce 2 4 0.402
Millet 5 0 0.059
Oat 19 0 0.000
Pea 14 32 0.000
Pomegranate 1 1 1.000
Potato 8 17 0.008
Pumpkin 5 5 1.000
Raspberry 1 2 0.588
Rice 34 0 0.000
Sorghum/milo 3 0 0.246
Soy 8 0 0.007
Spinach 9 9 0.788
Sweet potato 7 15 0.021
Tapioca/cassava 0 12 0.000
Tomato 11 7 0.596
Watercress 2 4 0.402
Wheat 7 0 0.014
Yucca 1 1 1.000
6 Journal of Feline Medicine and Surgery 00(0)
and fat needs are met.11 Under the known limits, the data
show that cats can efficiently digest and metabolize car-
bohydrates,12 utilizing enzymes such as hexokinase to
metabolize carbohydrates through the traditional path-
ways of glycolysis through oxidative phosphorylation.
In addition cats can obtain not only energy but other
nutrients, such as fiber, protein, vitamins and minerals
from plant (carbohydrate) ingredients, in their diets.
While differences in postprandial glucose and insulin in
healthy cats fed diets of differing carbohydrate concen-
trations have been reported,13,14 clear clinical conse-
quences to these differences in healthy cats remain
undocumented. Therefore, any clinical implications of
the mean 25% lower carbohydrate content found in the
current study will require additional research.
The current study only looked at the total amount of
carbohydrate, and not the source or type of carbohy-
drate, which also is important as not all carbohydrate
ingredients in pet foods have equivalent nutritional pro-
files or physiologic effects. In addition, dietary carbohy-
drate is not in isolation – processing and interaction with
other diet ingredients can also alter physiologic effects.
Whole grains often contain more protein and less sugar
and simple carbohydrates than common non-grain car-
bohydrate sources used in cat diets such as tapioca and
potatoes. These ingredients may have differing effects
on insulin release, gut function and other metabolic
activities that cannot be predicted based solely on the
total reported carbohydrate content. Evaluation of these
additional factors is warranted in future studies.
Regardless of any potential clinical importance, eval-
uating carbohydrate content in pet diets is a challenge
for not only the pet food consumer, but also for veteri-
nary medical professionals who want to have the most
accurate information available in order to compare and
contrast different pet diets. In comparing the different
tests offered by three different commercial laboratories
that specialize in food/feed nutrient analysis for this
study (Midwest Laboratories, Eurofins Scientific,
Covance), there were no standard analytes that could be
compared across the board; each laboratory had differ-
ent inclusions for tests deemed as ‘carbohydrate analy-
ses’. For example, one laboratory offered 23 different
assays in the category of carbohydrate testing with
almost no overlap of what specific compounds were
being measured, and another manufacturer only offered
NFE. This discrepancy is likely because there are many
types of carbohydrates and it can be difficult and expen-
sive to distinguish the individual components. However,
the type of monosaccharides and the bonds that connect
them are important as the metabolism of the different
carbohydrates depends on them. There is little regula-
tory guidance in this regard currently, although the
AAFCO has organized a carbohydrate working group to
address the matter of carbohydrates in pet food. A stand-
ard method of measuring and reporting carbohydrate
content would be ideal, but owing to the nature of carbo-
hydrates, condensing this information down into one
single value for assessing and reporting accurate carbo-
hydrate content may not be possible.
Currently, the most commonly reported value relating
to carbohydrate content is NFE. As an estimate of carbo-
hydrate content, NFE has a number of limitations. Owing
to the nature of the NFE equation, any errors in analyses
of other nutrients will result in alterations in the NFE.
One example is that the NFE equation uses crude fiber,
which typically underestimates the amount of total fiber
that is present in pet diets and can result in higher calcu-
lated NFE.15 In addition to inaccuracies from the equation
itself, using guaranteed analysis values (minimums and
maximums) rather than average or typical analyses to
estimate NFE will lead to even greater inaccuracies.
Because NFE is the most common way of represent-
ing carbohydrates in pet food currently, it is likely that
many manufacturers were providing NFE when asked
for diet carbohydrate content for this study, but this is
not known for sure. The differences seen between manu-
facturer-reported carbohydrate content and calculated
NFE in this study could thus be due to use of different
carbohydrate assays (NFE vs other measurements), vari-
ation in assays for crude protein, moisture, ash, crude
fiber and crude fat from the laboratories used by the
manufacturers to calculate NFE vs the laboratory used
for this study, or to variations in the actual nutrient con-
centrations between batches of diet as only one bag of
each diet was analyzed in this study.
The final objective of this study was to compare ingre-
dients and investigate potential allergens in grain-
containing vs grain-free diets. Although, anecdotally,
many cat owners appear to believe that grains are a com-
mon cause of allergies in cats, studies of food sensitivities
and allergies do not bear this belief out. In one study of
55cats with chronic idiopathic gastrointestinal problems,
only 29% were diagnosed as having food sensitivities.4
Another study of 128 cats with pruritus or gastrointestinal
signs confirmed only 17% as food allergic.16 The rate in
the general cat population would be assumed to be dra-
matically lower than in these two very selected popula-
tions. The most commonly reported allergens in cat diets
are animal protein sources such as beef, dairy, fish,
chicken and lamb, with plant sources such as barley and
wheat less common and other plant-sourced ingredients
even rarer.3 Multiple sensitivities are even more infre-
quent, making claims of allergy to ‘all grains’ an unlikely
scenario for cats.2
In the current study, besides all of the grains (which
was expected), poultry and soy were the only ingredi-
ents that were significantly less common in the grain-
free diets than the grain-containing diets. Chicken has
been reported to be one of the more common causes of
food allergies in cats, but other ingredients such as beef
and dairy products that are also reported to be causes of
Prantil et al 7
food allergies in cats were just as common in grain-free
diets. The greater inclusion of poultry and soy in the
grain-containing vs grain-free diets may reflect current
marketing trends to include more exotic ingredients
than chicken. Several exotic ingredients such as venison,
rabbit and bison were seen in this study only in grain-
free foods. There also seems to be a trend for companies
to specifically advertise that their foods contain no soy.
As such, these differences may reflect the philosophy of
the manufacturer or the desires of the customer base
rather than having any relation to whether the diet does
or does not contain grains.
There are a number of limitations to this study. The
total number of dry cat diets on the market is hard to
define and will vary based on how manufacturers are
selected. This study used online searches of retailers and
it is likely that some manufacturers were excluded
because they are not sold by these online retailers.
Therefore, the population of diets used in this study may
not accurately reflect the total population of dry cat diets
available for sale in the USA. This is particularly likely in
the case of comparing products from pet specialty stores
to those from mass-market channels. Pet foods sold on
the mass market are less likely to be also available online,
which is how the foods in this study were chosen, so the
mass market diets that were included in this study may
not be representative of overall mass market diets. The
study may also not be appropriately powered for detailed
ingredient comparisons between the diets as this was a
secondary aim rather than the primary one. Only one
sample of each diet was analyzed for financial reasons
and while a product with good-quality control should
have a similar analysis from batch-to-batch, inter-batch
variability is certainly possible, especially among brands
with less reliable quality-control measures. A major, but
unavoidable, limitation was the use of the NFE as a sur-
rogate of the carbohydrate content value and the assump-
tion that the manufacturers were providing NFE when
asked for the carbohydrate content. Future studies could
attempt to investigate the specific methods used by each
manufacturer to determine carbohydrate content or
investigate both carbohydrate type and amounts.
Conclusions
The grain-free dry cat diets included in this study had
lower carbohydrate values than the grain-containing
diets, but individual diets varied widely in both type and
amount of carbohydrate ingredients and all of the diets
contained measurable carbohydrates. Although many pet
owners that select grain-free diets may worry about food
allergies, many common allergens were just as frequently
found in the grain-free diets. Selecting a grain-free diet is
thus no guarantee that lower carbohydrate content or
fewer common food allergens are being fed.
Conict of interest The authors declared no potential con-
flicts of interest with respect to the research, authorship, and/
or publication of this article.
Funding Dr Prantil’s residency was funded by VCA Antech
and Mars Petcare. This project was supported by VCA Antech.
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