A survey of foal rejecting mares

Full text

424 EQUINEVETERINARYJOURNAL
Equine vet. J. (1998) 30
(5)
424-428
Prevalence and characteristics of foal rejection in Arabian
mares
SORAYA V. JUARBE-OIAZ, KATHERINE A.
HOUPT
and R. KUSUNOSE*
Department
of
Physiology, College
of
Veterinary Medicine, Cornell University, Ithaca,
New
York 14850, USA
and
ffrEquine
Research Institute,
Japan
RacingAssociation, 321-4 Tokemi-cno. Utsunomiya, Tochigi 320, Japan.
Keywords: horse: foal rejection, Arabian mares, maternal behaviour, aggression
Summary
Separate
surveys of
Thoroughbred,
Paint,
and
Arabian
mare
owners revealed ahigher
than
expected
rate
of foal
rejection in .
Arabian
mares. A
behavioural
history form was
submitted
by owners of foal rejecting
and
nonrejecting
Arabian
mares,
and
maternal
behaviour
and
management
practices compared.
Four
generation pedigrees of rejecting
and
nonrejecting
Arabian
mares
were also examined. Foal
rejecting mares were more likely to avoid, threaten, squeal
at,
chase, bite,
and
kick
their
foals post partum
than
nonrejecting mares. Nonrejecting
mares
were more likely to
lick,
nicker
and
defend
their
foals post partum
than
rejecting mares. No statistically significant relationship was
found between foal rejection
and
the type of breeding
method
(natural
vs, artificial insemination), the presence of
people at birth. the presence of
nearby
horses at
birth,
or
assistance of the first
nursing
bout.
The
presence at least
once of 1 of 2 related sires was statistically higher in
the
pedigrees of rejecting vs, nonrejecting mares. Inherited
and
learned or environmental factors
are
likely to affect
the
expression of foal rejection behaviour,
Introduction
The
exact prevalence
of
foal rejection is not known. Foal
rejection is defined as refusal to allow sucking and aggression
towards the foal. Foal rejection presents unique problems that
can
be time consuming and costly to resolve. Nutritional and
behavioural needs
of
the foal must be met. with particular
attention given to the timely delivery and consumption
of
an
adequate volume of good quality colostrum.
In a review
of
135rejection cases,
75CJc
of the rejectors were
primiparous mares, and the majority
of
rejectors (52%) were
Arabian
mares
(Houpt
and
Lieb
1994). It
could
not be
determined from the review if Arabian mares were at a
higher
risk of rejecting their foals. if there
was
aregional popularity
of
the breed. or if Arabian horse
owners
were more likely to
seek
help for this problem.
The
survey discussed in this article was
initiated to determine if the high prevalence of foal rejection in
A
__
L :
••.
__
.J.
__
•
__
L .J •• _
.~
L..
__
"'"",,...~_IO
Tl..
.....
Arabian mares was due to
chance
or
due
to other factors.
The
prevalence was determined in 3separate surveys: 2 in the United
States comprising Arabian and Paint horses and one in
Japan
involving
Thoroughbred
horses.
Materials and methods
Names and addresses
of
the owners
of
800
Arabian
and 800 Paint
horses. who had registered a foal born in 1993.
were
selected
randomly from lists provided by the Arabian Horse Registry
of
America
I
:\HR.-\)
and
American
Paint
Horse
Association
(APHA). respectively. T.Je
dam's
registered name. number. and
pedigree were obtained. Each
owner
was assigned anumber. A
letter was mailed to 800 Arabian and 800 Paint horse owners
asking if the registered
:'031
had been rejected by its
dam.
Owners
were instructed to report on a particular
mare'
sstatus. even if
several broodmares were on the premises.
4~
self-addressed and
stamped postcard
\\1a5
;;ro\'ided for the owners to return with a
yes or no reply. Owners who did not respond to the first letter
within one month were sent a second letter requesting the
same
information
..
Athird mailing was sent to owners
who
failed to
respond to the first 2 letters
..
Alack
of
reply to the third letter was
considered anonresponse to the survey. The
Chi-square
test was
used to compare the prevalence
of
foal rejection rates
of
Arabian
and Paint mares.
The
pedigree of all Arabian mares that were reported as
having rejected their rcais was downloaded from the AHRA's
computer
database.
Mares
belonging
to
owners
listed
immediately before and
mer
the owners of rejecting mares in the
responding-owner list were used as controls. In cases in which
this selection process yie.ded a mare whose pedigree already had
been obtained. either
~~
arejector or as a control. the next
immediate previous or
:-\."ilowing
nonrecruited
owner
name was
used to obtain 3centroipedigree. Pedigrees furnished by the
Arabian Horse Registry \.'I.-\merica include
-I-
generations.
The pedigrees were .nspected visually for the recurrence of
any sires or dams in :x'th rejectors and nonrejector lineages.
Because stallions CJl1 produce numerous offspring per breeding
season. whereas mares typically produce a single offspring.
statistical analysis WJ.i- performed on
data
generated
from
pedigrees containing recurring sires' names. For sires that were
found commonly in the pedigrees. Chi-square analysis was used to
compare the proportion
"'T
rejector vs. nonrejector mares that had
the sire's name appearing Jt least once in the mare's pedigree.
In the second
half
,-'Ithe survey. behavioural history forms
~ere
maii~d
(~~
.~rabLm
horse
o~vners
~~~ho
had
indicated
that
they had 3foal-rejecting mare. Behavioural history forms were
also mailed
(0
the owners
of
nonrejecting (control) mares. A
comparison
\.)f.
management
practices and
maternal
behavioural

Soraya
V.
Juarbe-Diazet al. 425
Results
TABLE 1: Comparison of
statistical
tests
and percentages of
mares
displaying
behaviours
towards
their
foals
in the
post
partum
period
All tests are Fisher's exact test
except
those indicated
tChi-square
test. ·Comparison of natural
breeding
vs. AI.
iPlacentas
were
removed by people within 10 min of expulsion in 31 and
26~~
of
cases of rejecting and nonrejecting
mares
respectively.
1.93
Paint
6
5.13
5
UJ 4
0
'0 3
Q)
.~
2
~
0
aArabian
80
control
mares were
examined.
4
sires
were
found
to
appear
frequently in
over
a
~uarter
of
the
mares'
pedigrees.
For
each
of
these
sires.
Chi-square
analysis
was
used
to
determine
if it was
equally
likely for the
sire's
name
to be
found
in a
rejector's
pedigree
as it was to be found in the
pedigree
of
anonrejector.
For
these 4it was found that the
appearance
at
least
once
of
either
of
:2
related sires
was
determined
to be
significantly
higher
in
the
pedigrees
of
rejecting
vs.
nonrejecting
mares
(Chi-square
=28.706. d.f. =1.
P<O.OO
1).
The
related
sires were
sire
and offspring.
History forms were
returned
by 16 (44.4%)
rejecting
mare
owners
and
by 38
1':-
.5% )
nonrejecting
mare
owners.
Figure 2
shows
the ages
of
rejecting and
nonrejecting
mares
-
median
age
was
7
years
for rejecting
and
6
years
for
nonrejecting
mares.
Figure
3
shows
the
;arity
of
rejecting
and
nonrejecting
mares:
the
majority
(50C1
)of rejecting mares
were
primiparous.
Among
control
mares
32CC
were
primiparous.
Statistical
analysis
revealed
no significant
difference
(Chi-square
=1.638. d.f. =1.
P=
0.20
ILbut 3 foals
born
to
primiparous
mares
and
one foal
born
to a multiparous :nare in the
nonrejector
control
group
were
partially rejected foais.
Owners
reported
that
these
~
mares
required
restraint \\'!L1 a
halter
and
lead
rope
before
the foals
could
nurse.
One
foal was
accepted
after
24 h
and
2 foals were
accepted
after
..+8
h. T:1e fourth foal
was
born
to a multiparous
mare
that had 3standing history
of
requiring
restraint
with a
halter
and
lead rope :·
...
""f 2
days
before
allowing
the
foal to nurse
freely.
These
mares
-quealed
and
threatened
to bite when the
foals
attemped
to nurse. No
other
aggressive
behaviour
was
displayed
toward
the
:·\.
...
al. All
of
the
mares
defended
their foals
when
approached
by other horses. If
these
4
mares
are
counted
among
the primiparous foal rejectors
and
the
statistical test is
calculated
anew.
j
significant
difference
is
revealed
(Chi-square
=0.7.1
S:.
d.f. =1. P=
0.007).
Median
number
..
."1' people present at
birth
was 2 for both
rejecting and nonrejecting mares, with
ranges
1-3
and
1-7.
respectively. Rejection. either as refusal to
allow
sucking. as
aggression directed
:11
:he foal or as both.
occurred
at birth for 9
(56%)
foals.
2-12
h_:'(lSl partum for 5 (31
%)
foals. between 12
and
2~
h for one foal I
~·c)
and one
between
24 h
and
48 h for one
foal (60C)'
Of
these.
_:
foals were
eventually
accepted
by their
darns and the remainder were not.
Of
the
rejected
foals. 10were
raised on bottles or
~uckets
by owners.
one
was injured but
recovered and was thea raised by hand.
and
2
were
killed by their
dams. For this sample. .he prevalence
of
mortality
was
6l}
l2J36).
Fig I: Prevalence rare; for foal rejection in
/993
(Arabian and Paint
mares).
1.000
0.007
0.947
t
1.000
0.591
0.704
0.723t
0.003
0.003
0.002t
0.000
0.000
o.oost
0.000
0.001
0.000
89
24
55
16
11
76
55
82
74
76
5
5
39
o
11
3
82
60
56
6
12
88
50
38
38
31
56
75
81
44
56
81
0/
0rejectors %nonrejectors Pvalue
traits
was
made
to
determine
which.
if any.
were
associated
with foal rejecting
behaviour
in
mares.
In
addition.
breeding
methods
were
compared
to
determine
if
type
of
breeding
method
(artificial
insemination
vs.
natural
cover)
affected
foal
rejection
rates. The
Chi-square
test
was
used
to
compare
the
frequencies
of
the
characteristics
of
interest
in
rejecting
and
nonrejecting
mares.
The
Fisher"s
exact
test
was
used
when
cell
frequencies
were less
that
5.
Student
Systat1
was
used
for
statistical
analysis.
An
evaluation
of
foal
rejection
prevalence
rates
in
Thoroughbred
mares was made by
surveying
28
breeding
farms
in
Japan
in 1993 and 1994.
Twenty-one
farms
returned the
questionnaire
and information
from
371
mares
which
foaled in
1993
and
~
II
mares in
199.1
was
used
to
determine
foal
rejection
prevalence rates.
Responses
were received fron
720
(90%)
Arabian
and 657
(820/0)Paint horse owners.
Of
these.
702
(88%)
and
621 (789c).
respectively. provided
information
that fitted the yes or no
answer
criteria. Thirty-six
Arabian
horse
owners
(5.13~)
and 12
(1.93%)
Paint horse owners
reported
that
their
mare
had
rejected
her foal.
This
difference
between
rejection rates
of
Paint
and
Arabian
mares (Fig I) was found to be statistically significant
(Chi-square
=9.625. d.f. =1. P<O.05).
These
numbers
may not
include
foals that died due
(0
rejection
or
other
causes
before
being
registered. but it is
assumed,
for the
purpose
of
this
comparison.
that neonatal
death
rates
due
to aetiologies
other
Characteristic
Natural cover'
Primiparous
Birth observed
Mares
licks placentat
Mare flehmens
Horses nearby
Nursing assisted
Mare licks foal
Mare nickers to foal
Mare defends foal
Mare avoids foal
Mare threatens foal
Mare squeals at foal
Mare
chases
foal
Mare bites foal
Mare kicks foal
th'~n_f,...,,1
..
~;~
.....
:.,~
.. __, ..
:_~~1",_
...__
L.._.L
L.
...J~
"'t...,~~
~
••
_L.
.
__
.,
than
foal rejection are similar
tor
both
breeds.
These
numbers
also
may
under-represent the true
prevalence
of
foal rejection in
both
breeds.
When
the pedigrees
of
the
~6
rejecting
Arabian
mares and
The
Chi-square
tc':-:t was used to
determine
if there
W3S
3
difference in the
management
practices
and
behaviours
of
rejector
vs. non rejectors. Table I
summarises
results
for the
characteristics
that were
evaluated
based
on the
responses
given

Foal rejection in Arabian mares
oRejectors
• Non rejectors
UNK
6+
4 5
Parity
3
2
12
10
8
6
4
2
o
UJ
e
tU
E
(5
ci
z
oRejectors
• Non rejectors
6 7 8 9 10 11+ UNK
Age in years
5
426
18
16
14
012
Q)
(ij 10
E8
-0 6
0
z4
2
034
Fig 2: Comparison
af
the ages
of
rejecting and nonrejecting Arabian
mares. UNK -unknown. Fig 3: Comparison
of
the
partity
c:(rejecting and non rejecting Arabian
mares. UNK -unknown,
in the
history
forms by
owners
of
rejecting
and
nonrejecting
Arabian mares.
There
was no statistical difference
found
in this
sample
between
rejecting and
nonrejecting
mares
with respect to
breeding
method
(Fisher's
exact
test. 2-tJil. P=1.000),
presence
of
people
during
foaling
(Chi-square
=
0.004.
d.f. =1. P =
0.947).
presence
of
horses
within
sigh:
of
the foaling
mare
(Fisher's
exact
test. 2-tail. P=0.7041. or
human
assistance to
facilitate the first nursing
bout
(Chi-square
=
0.125.
d.f. =1.
P=0.723).
Foal
rejecting
mares
were
more
likely to
avoid
(Fisher's
exact
test. 2-tai1.
P<O.OO
ILthreaten
(Fisher's
exact
test. 2-taiL P<O.OOI). squeal at
(Chi-square
=
7.871.
d.f. =1.
P=
0.005),
chase
(Fisher's
exact
test. 2-tai1. P<O.OOI), bite
(Fisher's
exact
test. 2-tail. P=
D.DO
1:. or kick
their
foals
(Fisher's
exact
test. 2-tail. P<O.OOI).
~vnrejecting
mares
v.'ere
more likely to lick their foals at birth
(Fisher's
exact
test. 2-tail,
P=
0.003).
nicker
(Fisher's
exact
test. 2-tail. P=0.003).
and
defend
their
foals (Chi-square =
9.806.
d.f. =1. P=0.002).
Twenty-one
out
of
28
(759c)
surveyed
Thoroughbred
breeding
farms
in
Japan
participated
in the
maternal
behaviour
study. In this
convenience
sample
(Huliey et al. 1988)
of
21
Japanese
Thoroughbred
breeding
farms. foal rejection rates
were
extremely
10\\':
09C
(no rejections in 3
~
I roalings) for 1993
and
0.5% (2 rejections in 411 foalings) for 1994
were
all
managed
by
commercial
breeders. The
mares
in the
Japanese
survey
were not
randomly
selected
and
these
figures cannot,
therefore.
be
analysed
with
the rest of the data.
Discussion
In this
random
sample
of
mares.
prevalence
rate
of
foal rejection
for
Arabian
mares was
5.13%.
whereas
foal rejection
prevalence
rates for Paint mares
was
1.93'iC. In a study
of
maternal
behaviour
in Arabian
mares.
Matoock
(1992)
found a foal
rejection
prevalence
rate
of
8.4o/c
with a
sample
size
of
107
Arabian
mares
studied
at
the
Egyptian
Agricultural
Organisation's El-Zahraa
Arabian
Horse
Stud
Farm.
The
survey
of
Thoroughbred
breeding
farms
in
Japan
revealed
even
lower
foal
rejection
rates.
although
it is possible that these figures are
biased by the nature
of
the
sampling
procedure: a
random
sampling
technique
"'as not
used
and
only
professional horse ,
breeders
were
surveyed.
Since
Arabian
and Paint
mare
owners
were
selected
at
random.
the
ratio
of
commercial
to
noncommercial
breeders in the
sample
should reflect this
same
fatiS I·R the D8DuiatiSR of interest. Astronz inherited
component
au tte Ppu au 0
irueresi.
f'\
~uuu~
lUIlClIlCU
~UllIPVll""IIL
to foal
rejection
in
Arabian
mares
must be suspected.
For
Arabian
horse
owners.
the
possibility
that one out
of
20
mares
might
reject
her
newborn
foal
can
add
to the cost
and
hardship
of
breeding
and
raising foals.
In a few
cases.
rejecting
mares
may injure or kill their foals,
creating
a loss
of
time
and
money
for the breeder.
Although
this
behaviour
is
uncommon.
it
can
be
devastating
to both foal and
owner. In this
sample,
3
of
16 (19%) mares that rejected
their
foals injured or killed
them
within
a few days POSI partum.
The
aetiology
of
foal rejection is not well understood.
Hormonal priming
with
progesterone
and oestrogen or oestrogen
alone. olfactory cues.
oxytocin
levels. exposure to neonates, and
previous maternal
experience
all have been
shown
to
playa
role
in the development
of
normal
maternal
behaviour
post partum
(Herrenkohl and
Rosenberg
19-2:
Keverne et al. 1982: Baldwin,
et al. 1986; Kendrick et al. 1987a. 1988: Kendrick and Keverne
1991:
Heming
et al. I
994a.b
)of sheep. rats and mice. Hormonal
priming in conjunction
with
vaginocervical stimulation elicited
maternal
behaviour
in
ovariectornised
nulliparous
and
multiparous
ewes
upon
exposure
to
2-10
day old lambs (Kendrick
and
Keveme
1991).
Increase
in oxytocin release from the
olfactory bulb of
oestrogen
treated mature ewes following
vaginocervical stimulation was similar to that measured during
panurition in sheep
(Kendrick
e: al. 1988). lntracerebroventricular
oxytocin treatment in
oestrogen-primed
ovariectornised
ewes
elicited maternal
behaviour
upon exposure to lambs. but not in the
absence
of
oestrogen
priming
IKendrick et al. 1987). In arecent
study by Brown et al.
(1996).
amutation defect in the immediate
early gene fosB
generated
mice
that lacked anurturing response
toward offspring.
They
noted
that exposure of post panum and
nulliparous wild type females. and
of
young wild type males to
pups induced fosB
expression
in the preoptic area. and also in in
the olfactory bulb
and
the pyriform cortex. suggesting that fosS
may be involved in
processing
of
olfactory stimuli that induce
maternal behaviour.
With
harmonious
conjunction
of
so many
factors required for the
expression
of
normal maternal phenotype.
it is reasonable to
propose
that adeficiency in any of the elements
could lead to
abnormal
nuturing behaviour, or that the deficient
factor may differ from
species
to species.
The possible
effects
of
environment
on the
expression
of
behaviour
cannot
be
discarded.
because
physiological
deficiencies
could
create
a
predisposition
to a
behaviour
abnormality
whose
severity
would
depend
on the
environment's
moludatory effects.
The
beneficial
aspects
of
past maternal
experience
also
could
act
to
improve
maternal
performance
over
time (Houpt and Wolski. 1979,. In this
sample.
rejecting mares
had not
experienced
more
than
3foalings
and
half
of
them
were
primiparous.
This
may
be
due
to
owners
opting
not to rebreed a
mare that
previously
had
rejected
a foal.
.I&m
.......
&
.....
,t"'&"""
.'"''''~&J
......
~
"-J--"--
- -
---
-
Anecdotal
evidence
suggests
that
some
management
practices
could
contribute
factors to foal rejection. A
respondent
to the Arabian
mare
owner
survey
speculated
that foal rejection
was likely in
Arabian
mares
bred
by artificial
insemination.
In
this survey. no
relationship
was
found
between
breeding

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IUn
In
.1ng
Soraya
V.
Juarbe-Diaz et at.
method and foal rejection in Arabian, mares. The American
Paint Horse Association allows the registration of foals born
to.
mares bred by artificial insemination. but data on the
percentage of registered foals concei ved by this method was not
obtained. The Jockey Club. the governing body for the
Thoroughbred breed, does not allow registration of the
offspring of mares bred artificially.
No conclusions could be drawn regarding the effect that
people present during foaling may have on foal rejection because
owners did not answer accurately. It should be noted that births
were unobserved for mares foaling at pasture. Of mares foaling
at pasture 3 out of 38 control and 3 out of 16 rejector Arabian
mares rejected their foal in the absence of human observers.
Although the presence of horses in contact or within sight of the
foaling mare was not found to beassociated with foal rejection in
this study, there have been documented cases of mares
redirecting aggression toward their foal that was originally aimed
at another horse that had come too close to the mare and foal
(Houpt 1993). Newborn foals follow any large moving object
that they encounter. and will continue to due so for up to age one
week (Houpt 1991; McCall 1991). For these 1 aforementioned
reasons. it might be desirable to prevent other horses from
coming in physical contact with mares immediately before and
after parturition. Having other horses within sight may not pose
a problem
if
they are at a sufficient distance for the mare not to
feel threatened.
Assistance given to the foal. in the form of light traction.
help when the foal attempted to stand. or help in finding the
udder when it first attempted to suck. was not found to be
associated with foal rejecting behaviour. In the case of foal
rejecting mares. nursing assistance was given to
50lk
of
rejected foals and consisted mostly of guiding the foal to the
udder and restraining the mare with a halter and lead rope.
Halter and lead rope restraint was also performed by many
owners of nonrejecting mares (5Sq.): either because it was
standard farm practice or because the mare. usually
primiparous. would not allow the foal to suck. Unlike foal
rejecting mares. mares in the nonrejecting control group did
not require restraint beyond the first few sucking bouts. with
the notable exception of the
~
mares that partially rejected
their foals but accepted them after amaximum of 2 days of
restraint during nursing.
Foal rejecting mares were less likely to exhibit behaviours
that are pan of the normal post partum maternal pattern. They
exhibited less pOST
partum
licking of and nickering to their foals.
and were less likely to stand between their foals and other horses
or people in a protective fashion. Foal rejectors were also more
likely to move away when their foals approached them. and kept
them at a distance. These mares were more likely
(0
threaten.
squeal at. bite. chase. or kick their foals. Nonrejecting mares were
also observed to squeal and bite at their foals. but this was usually
associated with the first nursing bouts. This is in agreement
with observations made bv other researchers (Crowell-Davis
1985: Houpt 1998:
rviat(h.'~k
1992: Smith-Funk and
Crowell-Davis 1992).
Thirty-nine percent of owners of nonrejecting mares
reported squealing directed
;l[
foals by their
darns:
tl
C:C
reported that their mares attempted to bite their foals, Most of
the squealing was reported
(0
occur when the foals first
atternnted
to
suck
~nri
":l1h\.':irl~
.i
~ftpr""lrrl
nrp\.':t1m~,hlv
h~r~II":~
attempted to suck and subsided afterward, presumably because
nursing would decrease pressure in the udder and sucking by
the foal was associated with relief of udder discomfort. Biting
or nipping attempts were reported to occur when the foals
427
would bump or tug at the udder with force. Squealing and
nipping are communication signals usually directed at others to
increase the distance between horses; the receiver of the signal
usually moves away. Their use by a mare toward her foal may
be appropriate in certain circumstances when the foal's
behaviour needs to be moderated. A foal that is bumping the
udder too vigorously learns by its darn's reaction to decrease
the strength of its request for nourishment. The findings of this
survey are in agreement with observations previously made of
normal mare and foal interactions (Crowell-Davis 1985:
Matoock
1992~
Smith-Funk and
Crowell-Davis
1992).
Squealing and nipping, in the
above
described
cases.
constitutes maternal behaviour that falls within normal limits.
and usually is minimal during the first 4 weeks pOST
partum
(Crowell-Davis 1985,.
There is a large discrepancy between the percentage of
rejectors vs. nonrejectors that direct kicks towards their
offspring. Kicking is one of the most severe forms of agonistic
behaviours that horses can exhibit. A threat to kick. a lifting and
striking motion with a leg that purposefully does not make
contact with the target, is a powerful visual stimulus that often is
made in lieu of an actual kick. Threats to kick were the form
employed by nonrejecring mares. Rejecting mares were more
likely to kick and aim tohit: one foal was injured by kicking and
2 were killed as the result of kicks delivered by their dams.
Another form of aggressive attack in which the mare grabs
the foal with her teeth. particularly over the dorsal cervical and
shoulder area.. and snakes the foal. was not reported by the
owners in this sample. This behaviour. similar to one shown to
nonrelated foals by some stallions and occasionally geldings.
has been described IHoupt 1984). and it constitutes the most
severe form of foal rejection known.
In this sample. 3significant relationship was found between
the appearance at least once of either of 2 directly related sires
and the likelihood
of
an Arabian mare rejecting her foal. It is
probable that this trait is heavily influenced by inheritance. Yet.
30Ck
of mares with
L.1e
2 sires in their pedigrees did not reject
their foals in the year the survey was taken. Other factors may
modulate the Iikelihood of the mare expressing the foal rejecting
behavioural phenotype. Acombination
of
genetic and
environmental elements. such as incomplete penetrance.
multiple gene aetiology. inexperience
(of
primiparous mares).
and redirected or pain-induced aggression. can render an animal
more or less likely to reject her offspring.
Progesterone serum concentrations.
which
may be
implicated in the aer.ology of rejection. were lower in 8foal-
rejecting Arabian :nares immediately
prepartum
when
compared to serum .evels of 8 normally behaving control
mares (YLY.S. Maroock and K..
~.
Houpt
..
unpublished data LIn
sheep and mice. olfaction, vaginal stimulation. and subsequent
release of oxytocin is believed to play an important role in the
recognition of offspring by the dam (Keverne et al.
1l)8~:
Baldwin et al. 1986:
Kendrick.
et al.
1987.
1988:
Kendrick and
Keverne 1991). but Jsimilar association in horses has not been
made. Further studies to elucidate the roles that oestrogen.
progesterone. and oxytocin may have in the control of
offspring recognition in mares are necessary before further
conclusions are drawn and an appropriate treatment plan can
b~
instituted.
~(anufacturer's
address
'Cour
..
~
Technologies. lnc..
L.Jmhridg~
.
Massachusetts. USA .

428
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1l)9~
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Equus
cabal/us
J
.~
nh mule foals
tEquus
asinus
X
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SC
:l. 33.93-119.
Received
for
pub/ication: i.3.97
Accepted: lB.9.97
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