Effect of dietary protein content on behavior in dogs

Abstract

To determine the effect that feeding diets containing a low (17%), medium (25%), or high (32%) protein content would have on behavior in dogs.
Prospective, controlled study.
12 dogs with dominance aggression, 12 dogs with hyperactivity, 12 dogs with territorial aggression, and 14 control dogs without behavioral problems.
Dogs were fed each of the diets for a 2-week period, and owners were instructed to score their dogs' behavior on a daily basis.
Behavior of the dogs with dominance aggression, dogs with hyperactivity, and control dogs was unchanged by the dietary manipulations. Territorial aggression was significantly reduced when dogs were fed the low- or medium-protein diet, compared with territorial aggression when fed the high-protein diet. Post hoc analysis indicated that this effect was attributable to a marked reduction in aggression in a subset of the group (n = 7) in which territorial aggression was a result of fear.
Results of this study suggest that a reduction in dietary protein content is not generally useful in the treatment of behavior problems in dogs, but may be appropriate in dogs with territorial aggression that is a result of fear.

Full text

Repnnted from
(he:
;OCR:\AL
OF THE
A~IERIC.\~
\
'ETER1~ARY
\IED1C.-\L
.-\SSOCL-\
7':C\';.
Vol.
~08.
~o.
:-
?:2C=S
376-
~;9
'American
Vetennary
\lc:di~JJ
Assoc.anon.
J996. AU Rights
Reser-ed.
--
Effect
of
dietary
protein
content
on
behavior
in
dogs
Nicholas H. Dodman.
B\I'"\-[S;
llana Reisner,
D\")..[;
louis
Shuster. PhD; William Rand, PhD;
LT.
Andrew Luescher,
Dv~L
PhD;
Ian Robinson,
PhD~
Katherine
A. Houpt.
v:vID,
PhD
Objective-To
deterrmr
e
tne
effect
that feeding
diets
containing
a
low
(17~1,),
meciurn
(25~1cJ),
or
high
(32~1,)
protein
content
would
have
on
behavior
in dogs.
Design-Prospec:ive.
ccrurctled
stucv.
Animals-12
dogs
",vith
ccrninance
aggression,
12
ccqs
with
hyperactivity, 12
cccs
wrth
territorial
aggression,
and
14
control
dogs
witncut
oenaviora:
problems.
Procedure-Dogs
were
:ec
eacn of the
diets for
a 2-
week
period. and
owners
'Nere
instructed
:0
SC8re
their
dogs'
behavior
on
a
daiiy
cas.s.
Results-Behavior
of the
cccs
with
ccrmnaoce
aggres-
sion.
docs
with
hvoeracnvirv.
ana
ccntrci
cogs
'Nas
un-
chanced-
by
the
dietary
~ar.iculalions
.
Territorial aggres-
sion
~as
significantly
recccsc when
dogs
'Nere
fee
the
lcw-
or
medium-protein
cie;
ccrncareo
'.tVrtr.
territcnai ag-
cression
wnen
fee
tne
rucr-crote.n
ciet.
P8S~
nee
analy-
s;s
indicated
that :his
effes: ','las
artnouracre
:0
a
~arked
reduction .n accress.cn
:r.
=
sccse:
of tne creve
in =
7)
.n
'Nhich
~errirorlai
aggres3:c~
'Nas
3
result of
~e3r
.
Clinical
lrnplications-c-Resutts
of
this stucv
succest
that a
recucnon
in cietarv
crctein
content
is not ge!ieraily
useful
in the
treatment
of cer.avicr prcclerns in cccs. but
may
be appropriate in dogs ·
..
vith
terntoriai aggression that
is a result of fear.
(J
Am
\ie~
Meo
Assoc
1996;208:376-
379)
M
any
dog
trainers
and
veterinarians
believe
that
the
disposition
of
aggressive
or hyperactive dogs
can
be
improved
by
changing
from
a
high-protein
diet
(28 to
32~b
protein.
on a
dry
matter
basis) to
a
low-
protein
diet
(16
to
20~b
protein.
on
3
dry
matter
basis),
bv chansinz from
beef-
and
chicken-based
diets
to
~
b
~
h
lamb-based
diets
and
by
changing
from a
diet
t
at
con-
tains
artificial
preservatives
(eg,
ethoxyquin)
[0
one
that
contains
natural
prese:-vatives (eg,
vitamins
C
and
E),
l.~-<i
Bv \vav of
conlr:ct.
1
report:
suggests
that
changing
fro~
a lo\v- to
J
high-protein
diet
may calm
overly
active
dogs. Hov..-e':e:. it
is
uncertain
\vhemer
dietarv
chanaes
have
anv
~tTect
on
beha\ior,
especiallv
;
~.
.
bec3use
dietary
changes
Jre
often
combined
\\ith
be-
havior
modification
or
a
c~3nge
in the o\vner's routine.
It
has
been
ShO\VTI
that
50me
amino
acids in the
diet
influence
brain
acti\-;tv b\'
enhancing
or
reducing
the
r3te
of
svt1thesis of
ditfe~e:l[
neurotransmitters.)
Thus~
protein
~ay
\vell play a
role
in
regulating
beha\ior.
From the
Departm~nt
of
Surge:;;.
St:nool
uf
\'c:tennJ~
·
\ledicine.
Tufts
University.
North GrJfton,
\1.-\
01536
(Dodman):
th~
Depart-
mentS of
Ph~~acology
\ShUSh~:"~
and
Cummunlty
Health
dtJnd)
,
~
.1.
., .,1 ...
r
\ .f ...
A.,...~o
T"rh~
I
·""-'P1""C.HV
Rt1c:;.rnn_
~I&-\
U~ll
L
th~
De-
St:hool of
~tedicine.
Tufts
L'nl\'ersuy.
Boston.
~
A
0_
11:
th~
Ue-
partment of
Physiology.
College of Vetennary
~tedicine.
Cornell
Cniversitv.
Ithao.
NY
1-+853
~R~lSner,
Houpt):
th~
Deparunent of
Popula[i~n
~(edicine.
Ontario
\"etennary
College.
Unl\Oersuy
of
Guelph. Ont:lrio NIG
~\V1
Cluescher);
:lnd
the
\V:lhham
C~nLre
ror
Pet
~utri[ion.
Ldce5tershire.
E:lgbnd
LEl-+
-+RT
(Robinson).
But to
our
kno\\'le::ge.
reports
of
conrrolled
trials
of
the
.e~fect
of
amount
of
protein,
type
of
protein.
or
food
additives
on
beha:~cr
in
dogs
have
not
been
published.
The
purpose
of
the
study
reported
here
was
to
deter-
mine
what
effect.
i any,
dietary
protein
content
had
on
aggression
and
~vDerJ.ctivi(V
in
doss
.4.
,
~
•
Materials
and
Methods
Dogs-Fifty
d
,og~
.:omprising 3
test
groups of 12 dogs
each and
1
COntrOL
~:u!J
of
1-+
doss were included in the
study. All 36 dogs
.r;
the
test
groups
had been examined
because
their
owners considered
them
to have a behavioral
problem~
Gr.o~p
1 ccns.sted of dogs whose primary problem,
a~
'p~rcel\'e~
ov the cwners. was aggression toward people
visiung
th,e
nome
,
~
e
:-:-:
:
o
n
a
l
aggression): group 2 consisted
of dogs wnose pnn:.1;-:
?roble~
was aggression directed to-
ward the
O\\'11e~
or
:.:l::-_:1~:
members
(dominance aoaression
.':
~
. •
-.
::>0
grouP
.)
consisted cr
:cgs
whose prirnarv problem was
hv-
peracnvirv. Group
>
.::~[rol
group} consisted of dogs whose
owners thougnt that
:..~~:r
dogs did nor have behavio'l-al prob-
lems. Owners of grou;_..: dogs were recruited from
the
staff
at
the
Waltham
C~:1~~
.or Pet Nutriuon.
A different veter.narv
beha\
'io~st
5uoerv1.sed each
group. For each
deg.
:..~e
beha\ioral diagnosis was confirmed
by an
interview
between
J
behaviortst-
and the
des
O\\'11er.
D
.
I
d , . .
e
ogs were mciu
e~:r:
.ne test zrouos onlv
if
results of
CBC
and
serum bioche:-:uc:i Jnalyses,:)and'piasma
triiodothvronme
and thyroxine
conceacauon,
were within reference limits
prior to enro
i!me~1t
:::
:.~e
study. the dogs were adult
(>
1
year old).
ana
the
0W"7:e:s
agreed to avoid
ensazins
in be-
havior modificJtion
it:::ng
the
penod of
the
5t~d~.
For
doss
in
group 1 (rerruorui rggresston) and
:7TOUD
2
(dominan~e
.
,
.
,:)
.
aggression., me unwanted behavior had to be evident at
J
sufficient .Irequencv .cr
.:hanges
to be observed during the
study,
ThIS
frequenc.
'.\'3.5
arbitrarilv
determined
to be a min-
imum of
:2
episodesw;
.n the 3
months
orecedins the studv.
L'nneutered dogs
J~C
':cgs that were considered to be dan-
gerous
\Ve:-e
ex~l~cie.':.::-~m
group 2.
Dogs
in the hyperactive
group
\\'ere
\Velgn~~
:y.
referring
ve[e~narians,
Dogs in
Jll
other
groups
"~'ere
·.~·e:g~ed
at the study
centers. using
JC-
curate
e!ec:ronlc
SCJles
.
Study
protocol-:'uring
the
firSt
2 weeks of the stud\".
dogs
were
fed their
~~ic:ll
diets. These were
all
commercialh,
available diets
\\ith
\'Jr.Jole
protein content.
O\\<71ers
of
doos
in groups 1. 3. Jnd
~
'·\'e:-e
instructed to assess the
beha\i~r
of their dogs
~n
J
daliy Jasis and to assign daily a score from
o
to
LO
to
the~r
dog.:r:
?ch
of
-+
Jre:ls:
territorial aggression
t
.O
=
dog
do~
not
:3:-~
or
adopt
menaCln
a
postures \\'hen
.
~
strangers Jpproacn
2f
~:1ter
the house:
10
=
dog uncontrol-
lably
aggressive \vhe::
~~r::lngers
attempt to enter the house).
dominance Jggresslcn ..
0
=
dog never
gro\\tls
at. lifts its lip
at. thre:ltens. snaps
JL
:'ltes.
lunges
Jt.
or chases familv
mem-
bers: 10
=
dog bites. lunges at. or
chases
familY
members
V~l';'.
~v
-
uV5
Ull~.
~uU5C:>
.u.
VI
l.HOC>C::~
ItJIUUV
lUCUlUCl:::'
repeatedly in many
~:rc:.unstances
Jnd becomes
\~orse
\vhen
owners attempt to
dis:~pline
the dog). exciubility (0
=
dog
sleeps most of the orne dUring the
day,
does not react to
doorbell
or noises
outside the house, lags behind when out
on
walks.
and settles
jC\\"t1
immediately Jfter stimulation: 10
370
Original
Study
SCientific
Rrports
j.-\\
'\L-\~
Vol 208, No.
3.
February
1.
1996

L
~_
Dietary
protein
content
:ol'Quanntv
OT
:000
oifereoNas
':3Ic:;:ate-:
:n
:~e
::as:s
Ji
:~e
:clloWIr.g
e,=~a~jon:
:aliv
~nerg'f
recuirement
:,kcall
=
125
.;bcov
'Ne~C;:':t
',
k
g
l
~
:
,
Results
T() confirm thJt dogs
\Vere
consuming different
quantities
of
prote~n
\vhen fed eJch
of
the different
diets. me:ln
daily
c2rs~mption
of protein
(glkg
of
body
\veighr) \vas
c31c'Ji~red
for e:lcn
test group in
e:.lch
phase of the study
:T
Jble
2
~.
For
Jil
~
groups.
dJily
protein consumpticn
\\I"hen
dogs
\\'e~e
fed the lo\v-pro-
tein diet \vas significJntly less than
daily
protein con-
sumption
\vhen
ecgs
were fed the medium-protein
diet. and daily protein consumption \\'hen dogs \vere
fed the medium-pre-tein diet \vas significJnrly less thJn
daily protein
con~umption
\vhen dogs \vere fed the
high-protein diet.
For dogs \\it:t territorial aggression (group
1'.
me:ln scores for te:-:-:torial aggression \vere signific:lntly
(P
=
0.035)
IO\\'e:-
\\"hen dogs
\Vere
fed the lo\v- and
medium-protein
die!.S
than when
fed
the high-protein
d~et
(F~g
1).
During behavioral intenie\vs \vith o\vners
dIet (Flg
i).
LJunng
oenavlorallnlerYle::\v~
\\Il111
-U\~llCl:)
of dogs
in
this group.
it
had
been found. on the
basis
of responses to a dominance profile questionnaire, that
5 dogs in
this
group had pronounced dominant ten-
under all circumstances:
10
=
dog shows signs of extreme
fear when challenged
by
any strange person. situation. or
experience).'
O\VTIerS
of dogs in group 2
were
instructed to
assess
the
behavior
of
their
dogs
on
J
dally basis. but to
assign
J
score onlv for dominance aggression.
Following
this
iruual period. each
dogwas
fed
speciallv
prepared
diets'
COn[J.l~.lI~g
low, medium. or
high
protein
con-
lent
(Table 1),
A.
codmz
svstern was
used
to
identify each
diet. The
protein
source
~n
'each diet
\\iJS
poultry by-product
meal and dried egg: none of the diets contained
ethoxvquin
.
Fat
content
of
each die:
was
modified
so
mat
e~ergy
densities
and carbohvdrate contents of the 3 diets were similar
Each
of
the
test
diets
was
fed for
J
2-\\"eek
period. and
owners scored their dogs behavior daily during each 2-\veek
penod.
Diets were
fed
~
_
n
J.
repeated
Linn
square design so
that all cornbmauons
',) 1
.he
3 diets were covered in ail the
groups,
Owners
were
instructed
to
measure
intake
as
JCCU-
ratelv as possible.
USir:g
J
250-ml measure. and to record
dailv the volume consumed. The
QUaOllC"
offered was cal-
culated
on
the
basis
Ji
each
dog's'
body
'weight.
using
the
following equauon:
daiiv energv
requirement
(kcal)
=-
125
x
body weight (kg
.'"
" .
~one
of the owners
were
told
which
diet
was
being fed
dur.ng
each phase of
the
study. and
the
veterinarians
sunervtsinz
zrouos
2
and 3 were
unaware
of
the coding of
th~
diets.
"ji~ts
were phased in gradually over
3
davs to minirruze
Jr.
...
::sk of zastromtestinal disturbances.
Owners
were
cornac.ec
Je~\vee;
the chases of the studv to
address
anv
concerns
. ·
Statistical analvsis-e-Dailv
SCQr~s
:cr the different be-
haviors were surnrnec .cr each week for
~:1C~
dog
..
All
-+
be-
nJVIOrS
were recorder; :·cr dogs in
grou~s
1. 3, and
~:
oniv
dominance was recorcec for dozs in
~rOUD
2. Total weeklv
scores were anaivcec
:\'
use of
~\"o-\\;\'
:~::\O\'_\.
~
A
mixed
model design
\V3S
usee, with diet as
J
·h.'(ed
factor and dog
JS
a
random
factor.
Pre.irrunarv
anaivsis
indicated
that there
was no consistent
~~Te:::
of week and. therefore. successive
\veeklv
measure:n~~:s
were used as
re:>licHes
. For
eJc~
group'. mean scores :'or
~3ch
phase uf
the
s~udy
\\"ere com-
Dared
bv
use of
th~
\e·.\tman-K~'Jis
tesl
;~;,1t
J
significJoce
ieve!
of
·O.uS)
'.vhe~e·:e:-
~he
_-\:"iO\-.-\
was signific3nl. Effects
of Jge. \veight. Jrnour:t
0f
protein fed, Jnd-
die~
order
\\"ere
~xplored
by usc of .
.l..:\C'V.-\
and
.-\:\CO\-.-\.
:\0
attempt
'\\,3:5
made to analv:e for
~reed
or sex
diffe:e~ces.
because dogs
of multiple breeds
Jr:c
Doth sexes
\ve:-e
included in
e3;~
group. precluding
m~:::Lngful
analysis.
; I
I 1
i ;
i
i
~
2 : 1:
:.0 :
1~
I
i
.~
:
).;
~;
:
i:
Hign-orotein
ciet
•
:~
:G"
;.: : 1:
~:
: 1:
.1
.: :
).~
~.5
:
1:
~eoium-orotein
diet
•
Daiiv
protem
censumcncn
"
:g/kg
of
~odV
'NeigmJdl
.;.._ : 'J
.,
:.3 :
1:
2.3 :
1:
2,~
: J.:
tow-oroten
diet
Dietary
constituent/energy
leve'
Low
(17~)1
Medium
12S~,,1
High
132~,,1
Preoicred
metaoolizaole
energy
Ikcal
i1QO
gl
36.1
35j
)JJ
?rotein
i9l1.000
kcaH
~9
.5
70.3
?2.3
Carbohydrate
1911
.000
kcaj)
i26.3
~2:,2
~2::.3
Fat
\911.000
(cail
!J.3
36.3
.. 1 . .-
..\rgiOlne
'91'.000
kcall
2.~
:;'92
:
.~g
Histidine
i9l1.000
(cat)
195
L~l
~.~
.1
'soieucme
i
gJ
l.000
~caJ)
',~3
2.:5
12::
leucine
!
91
1
.000
kcal)
j.:6
7
,00
3.6i
lysine
!g;1.000
<cal)
~,
?
3
2.9B
1.33
Methionine
~
91
1
.
0
0 0
kC311
lSJ
~
.30
l.U
?henyialanine
19It.OOO
(call
2
.Q3
3.09
.1
,02
Threonine
!
91
',
OO
O
kcall
1.::
2.~
2.95
'/aiine
igJU)OO
kcal)
2,
:1
3.17
i
,C5
Senne
'91
l..
JOO
kcall
:.08
3.06
~
.O2
Giutamlc
.ic:d
;9/1.000
<call
3.~3
~2.~5
~6.:?
Proune
!911.DOO
kcall
3.;~
:.u:
~.'J3
Giye,"e
:g;1.000
kcal)
:.37
~
.S6
:.:
I
C,/stine
!g,
·1.000
(caD
1:5
17.1
:.0.1
Tvrcsine
~g;1.000
~C3i)
~.~i
:11
2
.:.1
i
ryptoonan
I
g;1
.000
kcal)
1:8
),.1J
1~
GrOUD
~5
j
!
i
:41
I
~
;2--:
2;
i
~
I
;
:)
I
:E
I
:o~
I
!
i
I
•
15"
I
I
-'-
i
16
1
'-OW
i
erntcnar
:~~reS510n
)om:nance
3qgression
nvcerac::v1r
..
Control
Table
l-Composition
of the 3
diets
used
in a
study
of
the
effect
of
dietary
protein
intake
on behavior -n oogs
=
dog
is
Jhvays pacing and panting
dunng
the day. becomes
uncontrollablY excited \vhen hears the doorbell or noises
outside the
h~use.
is uncontrollable on \valks. and never set-
tles do\vnL and fearfulness (0
=
dog is relaxed and
happy
Ficure
l-rvlean
terrnoriai
aggression
scores
for 12
dogs
with
:erritoriai
aggression
fea ciers
'Nlth
a
low.
rnedium.
or hiah
proteIn
content.
Scares
recorded
'Nr.en
dcgs
were-
fed
a
low-
or
mecil,;m-proteln
die!
'Nere
indisi:Jr~
auishable,
but
\Nere
Sicn,f:cantlv
lower
than sc::xes re-
corded
when
dogs
vvere
fed
the
hign-protein
diet.
Bars
represent
SEi'v1.
I
acre
2-\tlean
=
SE\tl
S2::V
crcten
ccnsurrcncn
fer
coos
witn
vanous oenav.cre:
ciscrcers
;ed
sceca.lv
are-
parec
ciets
ccntairunc
varcus
crcte.r
ccntents
JA\t~L-\.
Vol
108,
No. 3.
F~bruary
1. 1996
Scientific Reports
Ongtnal Study
3-;-;

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LOW
·Jec
:u~
.•
-
fGrl
:)le:ar,
::rc:e
~n
ccmeru
~
:gure
2-iVlean
territoria: aggressicn
SC8res
fer 5 cccs
:Nlth territorial
accressicn
re.atec :c
acminance
(.)
one
':cr
7
docs
with
-territoriai
accress.cn
retatec to fear (
.
~
,
fed diets
with
a
low,
mec:um.
or high protein content.
Scores did
not
vary significantly \N;tn
die!
fer the dorm-
nant dogs.
but
did for the fearfui dogs. See r:gure 1 ':cr
<e«.
:5--------------------
•
!
1
•
•
i
!
lJ..,.1
---------.-----
...
cw
Ficure
3-Mean
ocmmerce
accress.cn scores tor 12
cccs with
dominance
accression
fed ciets
with
a tow.
medium,
or high protein C:ntent. Scores did net vary s;g-
nificantly
with
diet. See ;::gure 1 for key.
dencies
and
the remaining 7 dogs were primarily of J
fearful disposition. Post hoc analysis indicated [hat ter-
ritorial aggression scores for the 5 dominant dogs did
not
vary significantly with changes in protein intake
(P =
0.054):
territorial :lggression scores for the fearful
dogs did (P < 0.0001: Fig 2). Fearfulness scores in
group 1,
however,
did
not
change significantly (P =
0.97)
with
diet for the
group
as J whole. nor did thev
change in either of the 2 subgroups tP = 0.32 for the
fearful dogs:
P = 0.10 for the dominant dogs).
For dogs
with
dominance
aggression (group 2).
mean scores for dominance aggression did not vary
sicrnificantlv (P
= 0.5)
with
protein content of the diet
::>lVllU,l\..6olUL1V
\C -
V.J/
n
LU&'
t'
.. ""..._
....
--"
---'----
- - ,
(Fig
3).
The
responses of individual dogs appeared
random
and inconsistent.
For dogs
with
hvperactivity
(group 3L mean ex-
citability scores did
not
vary significantly (P = 0.13)
~:gur~
4--:Nlear..
~x:::abiiity
scores for 10 hyperactive
oogs Tedcrets
'/VIT.":
CON.
medium.
or
hich
orotein content.
Scores did nat
'Ie,:,
s.cruficanuv
with
diet.
See Ficure ,
for key.
...
with protein
C~D(~::[
~f
the diet
when
the group was
analvced as a wnc.e FIg
-+).
Two dogs were eliminated
from the analysis
cecause of owner scoring errors. but
this did
not
chanse
:he
result. No individual ciao was
remarkable in its
~~\Jonse
to the different
die~.:;'
During the
::-~.\-cek
period that dogs were fed their
typical diets. mean .erritorial aggression score for con-
trol dogs (7.0:
5~.
8.1)
was significantlv less than
mean territorial
3.~gression
score for
group-l
dogs
l20.8: SD.
1.7';.
men
dominance aggression score for
control dogs (0.3:
~u.
0.6) was significantlv less than
mean dominance ;ggression score for group-2 dogs
(.16.5: SD. 7.5).
anc
mean excitabilitv score for
con[r~l
dogs (18.1: SD. 3.'; was significantly less than mean
excitability score :cr group-3 dogs (29.2: SD.
10.1~.
For the control
~cgs
(group
-+).
mean territorial
ag-
gression. excitabiii:v. dominance aggression.
and
fear-
fulness scores die not vary significantly
with
protein
content of the die:
:~P
= 0.39 for the territorial ag-
gression scores . P
= 0.51 for the excitabilirv scores
....
P
=
0.2-+
for the dcrainance aggression scores. and P =
0.61 for the Iearfu.aess scores).
Discussion
In this study. .at. rather than carbohydrate. con-
tent was modifiec :0 accommodate
chano~s
in dietary
protein content. cecause fat was
thoushtless
likelv
to
~
.
have an influence on behavior.
..
A computer-based
search of articles cublished between 1990
and
199-+
failed to reveal anv relevant publications on the effect
of fat on
behavior.
Jut
it has been suggested that CJr-
bohvdrate intake
zm
influence
behavior.'
The lower
territorial
a~reSS~L'n
scores in the 7
doss
with terri-
~~ ~
torial aggression .!::d a fearful disposition. when fed
the low-protein
~i~:.
therefore. were most likelv a re-
sult of low dietarv ?rotein intake.
Low dietary protein
intake may
facilitate transportation of the amino acid
1 • _ L _ ,",1 _ _ ...J L n _
~
_ L
__
.: _ _ __ _L ; _ L
tryptophan across the blood-brain barrier. which
would result in .1:1 increase in serotonin formation.
5
Low brain serotonin concentration has been implicated
in aggression in clinical and preclinical studies in hu-
378 Original Study
Scientific Reports
J:~\"\L-\.
Vol 208. No
.3.
February
1. 1996

man beings:
0
Tryptophan competes with other large.
neutral amino acids for transportation across the
blood-brain barrier.P" and because the tryptophan
content
of dietary proteins is low, plasma concentra-
tions of these other large, neutral amino acids increase
to a greater degree than does plasma tryptophan con-
centration following the ingestion of a high-protein
meal.
5 This leads to a decrease in tryptophan entering
the brain and a reduction in serotonin svnthesis. In
addition, tryptophan use
by the liver is
in~re3sed
dur-
ing protein
synthesis following a dietary load of amino
acids." which would decrease plasma tryptophan con-
centration even further.
Behaviors other than aggression may be affected
b~"
dietary protein intake. .o
.n.»
However, in this study.
we failed to demonstrate a reduction in excitabilitv
when low-protein diets were fed or an increase in
ex'-
citabiliry when high-protein diets were fed. This could
be because owner-reported excitability is affected
by a
number
of factors that are not sensitive to dietary pro-
tein intake. or because the protein contents of the diets
fed to dogs in this study were not sufficiently extreme
to permit demonstration of an
effect."
Results of this study suggest that a reduction in
dietary protein content
is not generally useful in the
treatment of behavior problems in dogs, but
may be
appropriate in dogs with territorial aggression that is
a result of fear. There are problems in attempts to es-
timate the proportion of dogs that may have this prob-
lem. as
any studv is likeiv to include bias. A recent
literature
revie\vi~
indicated that of
5.7-+8
behavior
problems reported by owners of dogs examined for
nonbehavioral reasons, 307
(5.3~b)
could be described
as territorial aggression, However. some owners may
have been prompted.
by being asked to indicate prob-
lems from a checklist. and it was nor possible to de-
termine the severity or cause of the problem (fear vs
dominance).
-Kilcommons B. Family Dcg. Littletovvn.
~Y:
Personal
cornrnu-
nication, 1992.
°Fisher
GT.
Canine
Behavior
Service Inc.
\lanchesrer.
:\H
: Per-
sonal
communication.
1992.
-Duford D.
Lessard
C.
Gemini
Dog
Training.
Groton. Mass: Per-
sonal
communication.
1992.
-Bicks
J.
Fauna
Foods.
Long
Island.
~Y:
Personal
Cornrnuruca-
uon. 1991.
c:Copies
of the
cornpiete
scoring
systems
are available from the
authors
on
request.
'Diets
were
produced
by
Waltham
Inc.
Vernon
. Calif.
-Csing
Number
Cruncher
Stausncal
Svstern.
Version
5.03. Dr.
jerrv
Hintze.
Kaysville. Ltah. '
"Hamdi .-\. Onaivi ES. Farooqui 5. et al.
Levei
of protein In diet
modulates
dopamine
receptor
(abstr
..
FASEB
J 1991 :5:.-\853.
References
1.
Mugford
R..\. The influence of
nutrition
on
canine
behav-
iour. JSmall .-\nim
Praa
1987:28:10~(r.1()55.
2.
Campbell
\\
c.
~utri[ion
and
behavior. In:
Pratt
P\\·. ed.
BdlQ\'ior
problt7n5
in
dogs
2. Goleta. Calif: American Vetennarv
Publications
Inc.
1992:l~:--1-+9.
.
3. Pitzalis G. Vania
_-\.
Morin 5. et
at
Nutnuon
and behavior
in pediatrics
..
\tiner.
·a Petiuur
1990:~2:20'-21~.
..;..
Wurtman
RJ.
:-!e:n
F. Melamed E. Precursor control vi
neu-
rotransmitter
synthesis.
?~armacol
Rc.'"\·
1981 :32:315-330.
5. Kanarek
RB.
Marks-Kaufman
R.
~·ucriClon
and
bdlQ\·ior
new
?aspccri\"es.
New
York
Van
Nostranr
Reinhold. 1991 :229.
6. Miller HL. Delgado PL.
Salomon
R'vl. e; Ji
..
Acute trvoro-
pnan
depletion:
J
method
of studvmg anndepressanr .icnon. Jelin
Psychjac~:
1992:53:28-35.
7. Fernstrom JD. ..l.c.rte and
chronic
effects wl
orotein
Joe car-
bonvdrate ingestion on
:T31n
tryptophan leveis Jnci serotorun svn-
thesis.
Suer
Rev
1986:~:25-36.
.
8.
Lester
\IL.
Fisbein DH.
~utntion
and childhood neuro-
psvchoiogical
disorders.
::1:
Tarter
RE. Van Thiei
JH.
Edwards
~L.
eds
..
\lldical
neuropsychoiv~"
New York:
Plenum
Press. 1988 :29
t-
335.
9.
\\"unman
RJ.
\\-:Jrtman
JJ.
Do carbohvdrates affect
feed
in-
take via
neurotransmitter
acnvirv? .:
~t'De[ice
1988:l1
:~2-l7.
10.
Harndi
A.
Onaivi
ES. ·Pras;ci C.
A.
low protem-high car-
~o~ydnte
diet decreases
)2
dopamine receptor densirv in
r:l~
brain.
Li}e
Sci 1992:50:
1529-:53-+.
11.
Yokogoshi
H.
\\·unman
RJ. Meal
comoosinon
and
oiasrna
amino acid
ratios: eflec: Ji various
proteins
or
~3rooh\"drJte.
·Jnd
of
various
protein
concenrrauons.
~Ie[aboii.sm
1986:35:d3;-
-342.
12. Beaver Bv. Cwner complaints about carune behavior. r Am
Vee
\1{Q Assoc
199-+:2C~
::
953-1955.
~
J.-\
v
~L-\.
Vol 208,
~o.
3. February 1. 1996
SCientific
Reports
Original Study 379