Essential fatty acid metabolism in dogs and cats

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© 2008 Sociedade Brasileira de Zootecnia
Revista Brasileira de Zootecnia
© 2008 Sociedade Brasileira de Zootecnia
ISSN impresso: 1516-3598 R. Bras. Zootec., v.37, suplemento especial p.20-27, 2008
ISSN on-line: 1806-9290
www.sbz.org.br
Essential fatty acid metabolism in dogs and cats
J John E. Bauer, DVM, PhD, DACVN
College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4474 USA
Dietary Fats: Facilitative and
Functional
Are there good fats and bad fats for dogs and cats?
Although the concept of good fats and bad fats
has been used in human nutrition, dogs and cats are not
as susceptible to coronary artery diseases and can
therefore consume greater amounts of saturated fats
which are considered “bad” fats for humans. The
reason for this is that dogs and cats have more good
cholesterol (HDL) than bad cholesterol (LDL) no matter
what types of fat they eat (1). Thus it is not
advantageous to categorize different types of fats as
either good or bad for these animals. Cats are likely
similar to dogs in this regard although definitive data
other than the fact that cats have high HDL cholesterol
has not been obtained. In view of these metabolic
differences, the author prefers to categorize the various
types of dietary fats for dogs and cats as either
‘functional’ or ‘facilitative’.
Facilitative fats
It is recognized that fat adds palatability and
acceptable textures to food. Adding palatability
demonstrates how fats can be facilitative because they
help assure the intake of the necessary calories for well
being. Beef tallow, primarily composed of saturated
and monounsaturated fatty acids, is one of the most
palatable fats for dogs, cats. Thus, tallow is not a bad
fat for companion animals; instead it is facilitative. In
dogs and cats, the amounts of tallow that may be fed
without imposing a health risk would likely be
detrimental to a human consuming a similar amount on
a daily basis. Hence it is considered a ‘bad’ fat for
humans; but merely facilitative for dogs and cats.
The saturated fat present in tallow is additionally
facilitative for dogs and cats by contributing a high
calorie fuel to the animal body providing energy to
work, regulate body temperature, grow, reproduce, or
simply survive. These fats are also facilitative because
they can be stored in adipose tissues for future
mobilization and used for energy when needed.
Facilitative fats can be present in relatively large
amounts in dog and cat diets without health risks except
perhaps with respect to obesity where high fat diets,
containing too many calories are overfed.
One additional way in which dietary fats are
facilitative is because they assist the proper digestion
and absorption of fat soluble vitamins from mixed
micelles in the gastrointestinal tract. Because fats and
fat soluble vitamins are insoluble in water, they must
first be emulsified into smaller droplets by becoming
dispersed with bile salts so that digestive lipases can
break them into their digestible forms for absorption.
Thus dietary fats facilitate the absorption of the fat
soluble vitamins. In summary, a facilitative fat is one
that has one or more of the following properties:
1.) adds palatability and acceptable texture to
food
2.) is a dense source of dietary calories and
energy
3.) promotes the absorption of fat soluble
vitamins
4.) can be present in reasonably large amounts in
dog and cat diets
Included in the facilitative fat category are dietary
saturated fats such as palmitic and stearic, the
monounsaturated fatty acid, oleic, and the trans fatty
acids. These fats do not promote cholesterol elevations
per se in dogs and cats as they do in humans. While

Essential fatty acid metabolism in dogs and cats
© 2008 Sociedade Brasileira de Zootecnia
21
they may be considered ‘bad’ for humans, they are
simply facilitative in dogs and cats.
.
Functional fats
The first functional fat to be discovered was
linoleic acid, an omega-6 fatty acid. It was found to be
an essential dietary component necessary for growth
and prevention of skin lesions of dogs and other
species. More recent studies have shown that both
omega-6 and omega-3 fatty acids are essential. Both
types can be converted to longer chain polyunsaturated
fatty acids that have additional functions namely as
precursors of the eicosanoids which are powerful
physiological mediators of cell functions. These
findings have added new complexities to the functional
fatty acid category even though only modest amounts
need to be included in the diet in order to meet tissue
needs.
For the most part, the functional fatty acids that
are also essential are all polyunsaturated by nature.
Among this group are linoleic acid (LA), α-linolenic
acid (ALA), and under certain conditions
docosahexaenoic acid (DHA) and arachidonic acid
(AA). By contrast, conjugated linoleic acids may also
fit into the functional category as new research is
completed on their specific effects in companion
animals. However, they do not have the requisite
methylene interrupted sequence and thus are not
essential. Also medium chain fatty acids are neither
polyunsaturated nor essential but may be functional
under some conditions. In summary, a functional fat is
one that:
1. usually, but not always, an essential fatty acid
or is derived from an essential fatty acid
2. participates in either an important structural
and/or functional cellular process per se
3. or is converted to an important derivative that
regulates cell function
Definition of essential fatty acids
The essential nature of a fatty acid is primarily
due to an animal’s inability to synthesize it in sufficient
quantities to meet its metabolic needs. However, at the
molecular level, important functional and structural
characteristics both contribute to their essential nature.
Functionally, the fatty acid must contribute in some
significant way to health and well being. Structurally, it
must contain at least two double bonds, the location of
which must be in what is known as a methylene
interrupted cis, cis-configuration. This precise
molecular configuration enables the particular fatty acid
to fold upon itself three dimensionally so that it can
participate in cell membrane and physiologic events
important for normal health. Once esterified into
phospholipids these essential fatty acids significantly
affect many membrane properties such as fluidity,
compressibility, permeability, and fusion. Both
omega-6 and omega-3 fatty acids meet these criteria.
Figure 1 shows a comparison of selected
saturated, monounsaturated, and polyunsaturated fatty
acids all of which have the requisite methylene
interrupted sequence.
Figure 1 - Structural formulas of the saturated,
monounsaturated, and polyunsaturated fatty acids also
showing the methylene interrupted sequence of the
polyunsaturated acids.
As a matter of contrast, conjugated linoleic acid,
which contains two double bonds does not qualify as an
essential fatty acid because its double bonds are
“conjugated” instead of methylene interrupted. A
comparison of the methylene interrupted sequence and
the conjugated sequence of double bonds is shown in
Figure 2. Both LA and ALA have methylene
interrupted double bonds and are essential fatty acids.
In addition, each serves as precursor of unique
eicosanoids which are powerful physiological mediators
of cell functions in numerous tissues. These derived
long chain PUFA are also important because under

Bauer, J John E.
© 2008 Sociedade Brasileira de Zootecnia
22
some conditions or life stages, there may not be
adequate conversion of the precursor 18 carbon acids
making them conditionally essential.
C-C=C-C-C=C-C
methylene-interrupted double bonds
-C-C=C-C=C-C-
conjugated double bonds
Figure 2 - Comparison of methylene interrupted fatty acid
sequence (essential) and conjugated sequence (non-
essential but potentially functional, e.g CLA, conjugated
linoleic acid). Note the presence of the carbon atom
between the double bonds in the methylene interrupted
sequence.
The Unique Fatty Acid Requirements of Cats
Omega-6 Fatty Acids and Adult Maintenance
In the 1970s experiments on feline essential fatty
acid (EFA) metabolism reported that domestic cats
could not convert linoleic acid to arachidonate. This
finding suggested that cats do not possess the necessary
Δ6 desaturase to perform this conversion (2-4) (Figure
3). These observations were confirmed and extended
by Sinclair et al (5) who concluded that while cats did
not have significant Δ6 desaturase activity they did
possess both Δ5 and a Δ8 desaturases. These and other
authors (6, 7) thus proposed an alternative pathway to
arachidonic acid synthesis in cats (Figure 3). Indeed
subsequent studies found that when cats were fed diets
rich in linoleic acid, both plasma and liver amounts of
arachidonic acid were similar to when the diet also
contained tuna oil (8). Thus cats appear to be able to
synthesize arachidonic acid from linoleic acid at least to
some extent and that an alternate pathway for its
synthesis may exist. More recently, evidence of
limited Δ6 desaturase activity in cat liver and brain has
been confirmed by using sophisticated stable isotope
techniques combined with gas chromatography and
mass spectrometry (9) appearing when a diet
completely devoid of arachidonate was fed. However,
these data do not rule out the existence of the alternate
pathway in cat tissues.
Figure 3: Pathways of synthesis of arachdonic acid from
linoleic acid showing an alternate scheme involving Δ8-
and Δ5-desaturation and by-passing the Δ6 desaturation
step.
Omega-6 Fatty Acids, Growth, and Reproduction in
cats
One study by Macdonald etal (10) found that
male cats fed a linoleic acid deficient diet resulted in
tubular degeneration of the testes. The fatty acid profile
of testicular phospholipids had higher arachidonate
concentrations when linoleic acid was present compared
to the deficient group. By contrast, queens did not bear
live kittens when fed the deficient diet. It was
concluded that linoleic acid appears to meet the
requirement for spermatogenesis but that arachidonate
was necessary for reproduction in queens.
The need for dietary arachidonate for successful
reproduction in queens was recently revisited by
feeding one of three diets containing either 1% corn oil;
3 % corn oil; or 1% corn oil plus 0.02% arachidonate
before mating and throughout pregnancy (11). All
animals became pregnant but a high incidence of
congenital defects and low viability was found in the
1% corn oil group. By contrast, the diet containing 3%
corn oil without arachidonate supported reproduction.
This study showed that queens are incapable of
effective reproduction when maintained on a diet low in
polyunsaturates including linoleic acid but that addition
of small amounts of arachidonate restored this function.
However, because the diet containing 3 % corn oil
without arachidonate also supported reproduction, it
was concluded that other dietary factors may be
involved. Of additional interest is that neonatal
kittens from queens fed arachidonate in this study
were found to also synthesize it from labeled linoleic
acid precursor (12).

Essential fatty acid metabolism in dogs and cats
© 2008 Sociedade Brasileira de Zootecnia
23
Morris et al recently reported the effect of
arachidonate depleted diets on both male and female
feline reproduction (13). They confirmed their earlier
finding that male cats fed diets containing linoleic acid,
but not arachidonate, are fertile. In their study, 5 male
cats fed hydrogenated vegetable oil containing diets
devoid of arachidonate were mated with queens either
individually or in small groups. The queens had been
given commercial dry-type diets. Of the 13 queens
mated, 12 conceived and with litter sizes ranging from 3
to 8 kittens. All kittens were observed to be clinically
normal although of the 67 live kittens born 4 of them
from 3 litters died after one day of age for unspecified
reasons. Nonetheless the litter size exceeded the colony
average of their laboratory using commercial diets.
From this study, it was concluded that arachidonic acid
is not an essential fatty acid for male cats for
reproduction.
The reproductive outcome of 4 queens fed the
hydrogenated vegetable oil diet all entered estrus,
mated, and had subsequent body weight gains
consistent with pregnancy (13). However, most of the
kittens born live were eaten after birth with the
proportion observed being much higher than the
historical normal for this colony. Following this study,
2 of the queens were supplemented with 0.5 ml of
arachidonic acid and two were given 1.0 ml once
weekly for 10 weeks using a fungal derived oil
containing 40.7% arachidonic acid and again bred.
However, none of the queens conceived after this
supplement. It was concluded that some other fatty
acid(s) whether alone or in combination with
aracidonate may be necessary for successful
reproduction. Which fatty acid this may be is presently
unknown.
Omega-3 Fatty Acids in Cats
The effects of vegetable-based α-linolenic acid on
reproduction of queens fed one of two levels of linseed
oil (50 and 150 g /kg diet) was compared to a safflower
oil (50 g/kg diet)control diet (14) (3 queens per group).
In the 50 g/kg linseed group, the 3 queens gave birth to
litters of 3-4 kittens. One queen had a second litter of 2
kittens both of which died. The other 2 queens did not
have any further litters. In the 150 g/k linseed oil group
only one queen gave birth to one kitten which also died.
Cats fed the linseed oil diets ultimately lost body
weight. Their tissues were found to contain low
concentrations of long chain omega-6 acids and they
developed signs of EFA deficiency. Because the
limited feline Δ6 desaturase competes for both ALA and
LA, high dietary ALA may preclude the conversion of
linoleic acid to arachidonate. Hence excessive amounts
of omega-3 acids relative to omega-6 fatty acids may be
contraindicated in feline species.
Regarding the conversion of vegetable based
omega-3 fatty acids to longer chain forms, adult cats
were found to produce eicosapentaenoic acid (20:5n-3)
and docosapentaenoic acid (22:5n-3) in liver and
plasma and docosahexaenoic acid 22:6n-3 and 22:5n-6
in brain (11, 12). Of particular interest from these
findings is that the final step of desaturation to form
DHA appears to occur only in the nervous tissues, and
not liver, of cats.
Independent of site of tissue synthesis, the
important clinical question is whether the synthetic
capacities of cats for the long chain omega-3 fatty acids
are adequate under various life stages. Following their
earlier study, Pawlosky et al. (12) fed diets with various
amounts of corn oil and hydrogenated coconut oil prior
to mating, during pregnancy, and subsequent lactation.
Two reference diets also were evaluated containing AA
and DHA. The corn oil diets were capable of
maintaining AA concentrations in the developing retina
and brain but only those diets containing DHA could
support the high concentrations of DHA generally
found in these tissues. Low concentrations of 22:5n-6
were also found suggesting that kittens have a low
capacity to produce this omega-6 fatty acid as well as
DHA. Differences in electroretinograms were observed
in the LCPUFA deficient diet groups compared with
control animals as an index of neural development.
The LCPUFA deficient diets of Pawlosky et al
did not provide kittens with an adequate supply of n-3
fatty acids for proper accumulation of neural and retinal
DHA during development and thus were inadequate for
support of optimal visual function (12). Conversion of
either the n-6 or n-3 18-carbon precursors may simply
not occur to the extent needed in developing or
immature cats. Finally, where practical diets are
concerned, the presence of small amounts of dietary
AA, EPA, and DHA (i.e., 0.14 %, 0.02 %, and 0.03%,
as-is basis) in combination with high LA (i.e., 4.2% as
is) resulted in insignificant conversion of ALA to

Bauer, J John E.
© 2008 Sociedade Brasileira de Zootecnia
24
LCPUFA when supplied as 0. 88% (as is) in the diets
of 19- to 20- month old cats (15).
Summary and Conclusion
Cats do not synthesize linoleic acid and require a
dietary supply. Cats also have a limited capacity to
synthesize arachidonic acid and an alternative pathway
for it may exist. For maintenance needs, male, female,
and neutered cats may be able to meet their
requirements at very low levels of dietary inclusion of
this fatty acid. A summary of the essential and
conditionally essential fatty acids of cat is presented in
Table 1. Specific recommended allowances for each
life stage have been made as part of the 2006 NRC
Nutrient Requirements for Dogs and Cats document
from the National Research Council (16).
Table 1 - Summary of the Essential and Conditionally
Essential Fatty Acids for Dog and Cat Life Stages.
a) X, Essential fatty acid; C, Conditionally
essential for the respective life stage.
b) Recommended but no requirement
established
c) Many n-3 LCPUFA sources contain both
EPA and DHA; EPA should not exceed 60%
of EPA + DHA total.
Male cats may be able to synthesize enough
arachidonate for reproduction. However, queens
require an exogenous source of arachidonate for
successful pregnancies and normal litters although for
conception per se to occur arachidonate may not be
needed.
For the omega-3 fatty acids, high dietary amounts
of α-linolenic acid relative to linoleic acid may be
contraindicated leading to EFA deficiency signs. As
with the omega-6 acids, adult cats can synthesize small
amounts of long chain omega-3 acids from precursors.
Nonetheless, in order to support the high retinal and
nervous tissue concentrations of DHA needed for
development, kittens may require this fatty acid as
conversion of precursors may be insufficient to meet
this need.
Recent Studies on Omega-3 Fatty Acid
Effects in Canine Species
Several questions relating to omega-3 fatty acid
metabolism have been studied in our laboratory. These
include the following:
• Adults
o Can adult dogs convert α-linolenic acid
(ALA, 18:3n-3) to eicosapentaenoic acid
(EPA, 20:5n-3) and docosahexanenoic
acid (DHA, 22:6n-3)?
o Can ALA help improve skin and hair
coat?
o Can adult dogs synthesize enough EPA
to affect the inflammatory response?
• Gestation/Lactation
o Is ALA incorporated into canine milk?
o Is DHA present in canine milk when
only ALA is fed?
• Puppy Growth
o Can puppies synthesize enough DHA to
optimally support early neurological
development?
o Is dietary DHA more efficient than ALA
in this regard?
Skin and hair coat:
The first study we conducted compared
supplementation of a complete and balanced
commercial, dry-extruded type diet using whole ground
sunflower seed (rich in omega-6 linoleic acid, LA) with
whole ground flaxseed (rich in omega 3, ALA) (17).
Two groups of dogs were fed a commerical diet
supplemented with the respective ground oilseeds (3%
Nutrient Cats
Growth Adult Gest/Lact
Omega-6
LA X X X
AA C -- C
Omega-3
ALA Recb -- Recb
EPAc -- -- --
DHAc C Recb C

Essential fatty acid metabolism in dogs and cats
© 2008 Sociedade Brasileira de Zootecnia
25
by weight) for 84 days. Blood samples were obtained
and plasma fatty acid profiles of phospholipid fractions
were determined. The sunflower diet contained 9.3 %
of calories as LA and 0.4 % calories as ALA while the
flaxseed diet had 7.3% of calories as LA and 2.5% of
calories as ALA. Results showed a rapid accumulation
of EPA (at 4 days) reaching a steady state plasma
concentration at 28 days. In addition, docosapentaenoic
acid (22:5n-3, DPA) a DHA precursor was also found.
However, no accumulation of DHA was seen. This
study was the first to establish that EPA could be
synthesized by dogs after ALA feeding although the
amount of conversion appeared small. Additional
questions remained, however, such as whether the
derived EPA might help modify the inflammatory
response or whether skin and hair coat benefits might
exist .
Skin and hair coat condition scoring was
conducted during the above study with improvements
of skin and hair coat seen in both groups after 28
days.. However, differences due to diet were not seen
and improvements were not sustained thereafter likely
due to diet adaptation. Of particular interest, however,
was that animals fed the flaxseed diet accumulated
more LA than the sunflower group even though the
sunflower diet contained more LA overall. We
postulated that a sparing effect of ALA on LA with
resultant skin and hair coat improvement may have
occurred as well as the possbility of a total fat effect.
Our later studies on skin and hair coat would observe a
similar result.
A second skin and hair coat study compared 3 dry
diets (19,20). Diet A contained adequate amounts of
EFAs (2.5% energy LA, 0.2% energy ALA) and dietary
zinc (120mg/kg). Diet B contained 8.8% energy LA
and 0.2 % energy ALA while Diet C had 8.8% energy
LA plus 1.6% energy ALA and increased zinc (both
Diets B and C, 350 mg zinc/kg). Total dietary fat of all
diets was approximately 13% (as-is); the diets were
isocaloric at 3800 kcal/kg and formulated to be
complete and balanced. Compared to a 9% total fat
acclimation diet, all three diets improved skin and hair
coat scores and the improvement was statistically
significant after 7 weeks of feeding. The most dramatic
differences seen were increased hair coat glossiness and
softness. Fatty acid profiles of plasma phospholipids
fractions again showed a sparing effect of ALA on LA.
The improvements observed appeared to be due, at least
in part, to the higher total dietary fat concentrations of
the diets compared to the acclimation diet rather than
differences due to polyunsaturated fat types. Indeed,
Diet A contained higher amounts of saturated fat
compared to Diets B and C while dietary total fat was
similar, yet hair coat scores were improved in all
groups. Some additional benefits were seen with the
polyunsaturated fat diets but the most dramatic skin and
hair coat difference was due to total fat rather than fat
type. It should be noted, however, that the appropriate
balance of polyunsaturated fatty acids provides
additional benefits beyond skin and hair coat. Thus
these findings do not preclude their presence in modern
commercial diets.
Of additional interest in this study were changes
in the major lipid fractions from hair lipid extracts
samples quantified after thin layer chromatography and
densitometry with external standardization. Statistically
significant increases in hair total cholesteryl ester (CE)
concentrations were found in all three experimental diet
groups at the end of the feeding period. It is unknown
at this time whether this lipid alteration may correlate
with skin and hair coat improvements. Nonetheless
these preliminary data suggest a possible relationship
when higher fat diets are fed. Should a positive
correlation exist between these two parameters, hair
lipid analysis may provide a useful, non-invasive
technique to quantify dietary effects on skin and hair
coat. Consistent with this possibility is that an earlier
study also demonstrated increased sebum CE fraction in
dogs fed diets containing increased total fat (21)
Furthermore, our laboratory has previously shown that
diets increased in total fat also elevate plasma CE in
dogs (22).
Inflammatory response:
Long chain n-3 PUFA from fish oil or other
marine sources seem to be especially capable of
modifying inflammatory and immune responses. Diets
containing only ALA as n-3 source or mixtures of ALA
and fish oil may not perform as effectively in this
regard when included on an equivalent weight basis
(23-25) One reason for this is the inefficient rate of
conversion of ALA to EPA (26). To confirm this
possibility, a comparison of dietary ALA and EPA was
conducted in our laboratory resulting in changes in

Bauer, J John E.
© 2008 Sociedade Brasileira de Zootecnia
26
neutrophil structure and function (232). In these studies,
fish oil (i.e. containing EPA and DHA) outperformed
linseed oil (i.e. containing ALA) at the same omega-
6/omega-3 ratio showing significantly different
enrichment of EPA and DPA over AA, increased
neutrophil membrane fluidity, decreased superoxide
dismutase activities, and ex vivo phagocytosis. In
addition, greater leukotriene B5 (LTB5) and lower
leukotriene (LTB4) production consistent with less
inflammation were found. Another recent study
described similar blunting of ex vivo neutrophil LTB4
production when dogs were fed a high n-3 PUFA diet
using marine sources compared with corn oil (mg/kg diet
amounts of the n-3 PUFA not specified) (27). These
findings are consistent with earlier reports that diets
containing high marine source n-3 PUFA were
particularly adept at modifying neutrophil and
inflammatory skin responses of healthy dogs (24).
Taking this observation one step further, our work
helped design dietary amounts of menhaden fish oil used by
others in a study on its anti-inflammatory effects in dogs
with osteoarthritis. Affected dogs were randomized to
receive either a fish oil or control oil supplement. The
amount of fish oil used was determined using predictive
equations of fish oil enrichment as a function of dietary
amounts developed in our laboratory (28). Dogs were fed
their respective diets for 63 days and plasma and synovial
fluid was collected and analyzed (29,30). The fish oil diet
resulted in significant increases of EPA and DHA in both
plasma and synovial fluid with concomitant reduction of
arachidonic acid. Also significant reductions in matrix
metalloproteinase-2 and -9 (MMP-2 and MMP-9) activities
which are known to contribute to cartilage destruction as
well as a significant increase in a tissue inhibitor of the
metalloproteinases (TIMP-2) were found. Furthermore
synovial fluid bicyclo-PGE2 was significantly reduced with
fish oil feeding. Of additional interest in this regard is the
observation of Trumble et al in which synovial fluid PGE2
showed positive correlation with clinical variables of pain in
dogs with osteoarthritis further (31) supporting the
physiological significance of findings in these studies.
Gestation, lactation and puppy neurological
development:
DHA appears to be necessary for neurological
development (32). To test this idea, diets varying only
in type/amount of PUFA were fed to female dogs as
sole nutrition source beginning with estrus and
throughout breeding, gestation, and lactation. Puppies
were weaned to the same diets. Diets contained either
low amounts of n-3 fatty acids, Lo n-3; moderate
amounts of fish oil, Mod Fish; high amounts of fish oil,
Hi Fish; or high amounts of vegetable n-3 fatty acids
from flaxseed oil, Hi Flax. Mother’s milk supplied
exclusive nutrition to the puppies during suckling.
Plasma phospholipid fatty acids during both gestation
and lactation significantly reflected the diets fed and n-3
fatty acid dose responses were noted. However, dogs
fed the Hi Flax diet showed no accumulation of DHA
although EPA and DPA were increased as we have
reported previously in non-parous adult dogs fed
ALA (17).
Electroretinograms of puppies at 12 weeks of age
revealed significantly improved visual performance in
the Hi Fish group with superior rod response. Puppies
in the Hi Flax group showed some improvement but not
to the same extent as the Hi Fish group. In addition,
this improvement occurred at a markedly high
concentration of ALA compared to considerably lower
amounts of fish oil (33). Thus preformed dietary n-
3LCPUFA vs ALA is a more effective means of
enriching maternal plasma-DHA resulting in improved
visual performance or puppies. Providing pre-formed
long chain n-3 fatty acids in the diet as a means of
enriching plasma appears to be conditionally essential
especially for growth, development, and reproduction
because slow and inefficient conversion of ALA to
DHA may not be sufficient during these life stages.
Finally, it was of interest to observe that the fatty
acid profiles of canine milk samples of dogs fed the Hi
Flax diet showed enrichment only of ALA and not EPA
nor DHA (34). Thus we were able to investigate
whether puppies suckling this ALA-rich milk
accumulated plasma DHA thereby suggesting its
synthesis. The plasma phospholipid fraction of puppies
during suckling showed not only the expected ALA and
EPA enrichment but DHA was also increased compared
to controls. After weaning, however, DHA content
decreased while ALA and EPA remained elevated.
This latter finding is similar to that seen in adult dogs
(17). Thus, it appears neonatal canines may
preferentially synthesize DHA from ALA at a time of
life when demand for this fatty acid is especially high

Essential fatty acid metabolism in dogs and cats
© 2008 Sociedade Brasileira de Zootecnia
27
(i.e.during suckling) but only for a short time during
this neonatal period. Again it is important to note that
the milk from the Hi Flax diet was markedly enriched in
ALA due to high diet amounts fed compared to the
more modestly omega-3 enriched diets used in the fish
oil groups. It is not known whether lower amounts of
milk ALA would support similar DHA conversion.
Hence the efficiency of including dietary DHA from
fish oil for neonatal development is preferred to feeding
ALA for both practical reasons as well as overall
improvement of canine retinal development and
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