Post-weaning coccidiosis in beef calves in the dry tropics: Experimental control with continuous monensin supplementation via intra-ruminal devices and concurrent epidemiological observations


Parker, R.J.; Jones, G.W.; Ellis, K.J.; Heater, K.M.; Schroter, K.L.; Tyler, R.; Holroyd, R.G.

Tropical Animal Health and Production 18(4): 198-208

1986


Post-weaning Eimeria zuernii coccidiosis in beef calves was treated prophylactically with monensin from intra-ruminal continuous release devices. The evaluation of four treatments during three consecutive years also allowed observations on the epidemiology of this disease to be made. Monensin was an effective prophylactic and the intra-ruminal devices were a convenient method of continuous administration over a one to two month period. The three years of the trial included two characteristically very dry and one unusually wet weaning period. Coccidiosis was more severe in the dry years suggesting that oocyst challenge was less important than the immunodepressive effect of weaning and dietary stress in precipitating disease. Severe disease also occurred in calves subsequent to elimination of oocyst shedding by monensin during the initial treatment trial. The occurrence of disease in conditions inimical to oocyst survival and development and after treatment suggested a role for arrested endogenous stages.

Trop.
Mint.
lath
Prod.
(1986)
18,
198-208
POST
-WEANING
COCCIDIOSIS
IN
BEEF
CALVES
IN
THE
DRY
TROPICS:
EXPERIMENTAL
CONTROL
WITH
CONTINUOUS
MONENSIN
SUPPLEMENTATION
VIA
INTRA-RUMINAL
DEVICES
AND
CONCURRENT
EPIDEMIOLOGICAL
OBSERVATIONS
R.
J.
PARKER%
G.
W.
JoNEs
l
,
KEITH
J.
ELus
2
,
K.
M.
HEATER
S
,
K.
L.
SCHROTER
I
,
R.
TYLER
3
and
R.
G.
HOLROYD
3
Queensland
Department
of
Primary
Industries,
l
Oonoonba
Veterinary
Laboratory,
P.O.
Box
1085,
Townsville,
Queensland
4810,
Australia;
3
Swan's
Lagoon
Beef
Cattle
Husbandry
Research
Station,
Millaroo,
Queensland
4807;
2
CSIRO
Division
of
Animal
Production,
Private
Mail
Bag,
Armidale,
New
South
Wales
2350.
SUMMARY
Post
-weaning
Eimeria
zuernii
coccidiosis
in
beef
calves
was
treated
prophylactically
with
monensin
from
intra-ruminal
continuous
release
devices.
The
evaluation
of
four
treatments
during
three
consecutive
years
also
allowed
observations
on
the
epidemiology
of
this
disease
to
be
made.
Monensin
was
an
effective
prophylactic
and
the
intra-ruminal
devices
were
a
convenient
method
of
continuous
administration
over
a
one
to
two
month
period.
The
three
years
of
the
trial
included
two
characteristically
very
dry
and
one
unusually
wet
weaning
period.
Coccidiosis
was
more
severe
in
the
dry
years
suggesting
that
oocyst
challenge
was
less
important
than
the
immunodepressive
effect
of
weaning
and
dietary
stress
in
precipitating
disease.
Severe
disease
also
occurred
in
calves
subsequent
to
elimination
of
oocyst
shedding
by
monensin
during
the
initial
treatment
trial.
The
occurrence
of
disease
in
conditions
inimical
to
oocyst
survival
and
development
and
after
treatment
suggested
a
role
for
arrested
endogenous
stages.
INTRODUCTION
Post
-weaning
diarrhoea
has
been
seen
for
several
years
in
beef
cattle
grazing
pasture
on
several
farms,
including
Swan's
Lagoon
Beef
Cattle
Research
Station,
in
the
sub
-coastal
dry
tropics
of
northern
Queensland,
Australia.
During
1980
approximately
10
of
300
calves
died
at
Swan's
Lagoon
following
an
outbreak
of
post
-weaning
diarrhoea;
coccidiosis
was
suspected.
An
investigation
in
1981
showed
increased
oocyst
shedding
during
the
period
of
diarrhoea
and
confirmed
Eimeria
zuernii
coccidiosis
as
the
cause
of
severe
cases
(Parker,
Boothby,
Polkinghorne
and
Holroyd,
1984).
Precipitation
of
disease
by
weaning
stress
rather
than
a
heavy
new
oocyst
challenge
was
suggested.
Early
weaning
is
recommended
in
northern
Queensland
mainly
as
a
means
of
reducing
breeder
mortalities
(Holroyd,
1985).
Early
weaning
is
being
widely
practised
in
northern
Queensland
and
is
frequently
followed
by
diarrhoea
in
the
calves
with
some
deaths
(B.
Frank
pers.
comm.).
Coccidiosis
has
been
confirmed
in
some
of
these
outbreaks
(R.
J.
Parker
unpub.).
The
clinical
signs
of
bovine
coccidiosis
are
associated
with
the
fi
nal
stages
of
the
eimerian
life
-cycle
and
commence
shortly
prior
to
oocyst
shedding.
Specific
anti-coccidial
treatment
after
diagnosis
on
faecal
examination
is
therefore
unlikely
to
be
effective
(Hammond,
1964)
and
treatment
of
individual
calves
is
generally
considered
impractical.
We
therefore
tested
an
experimental
prophylactic
treat
-
198
PROPHYLAXIS
OF
COCCIDIOSIS
IN
BEEF
CALVES
199
ment
of
all
calves
at
weaning
during
1982,
1983
and
1984
to
protect
them
against
clinical
coccidiosis
for
the
subsequent
one
or
two
months.
These
experiments
also
allowed
further
observations
on
the
epidemiology
of
this
disease.
MATERIALS
AND
METHODS
Swan's
Lagoon
is
a
beef
cattle
research
station
of
36,000
ha
at
Millaroo
(20°4'S
147°10'E)
maintained
by
the
Queensland
Department
of
Primary
Ind-
ustries.
It
is
situated
in
a
dry
tropical
area
with
a
mean
annual
rainfall
of
900
mm
most
of
which
falls
during
the
summer
months
of
December
to
February.
Cattle
graze
predominantly
native
pastures
at
a
stocking
rate
of
one
adult
animal
per
four
hectares.
The
approximately
3,000
cattle
on
Swan's
Lagoon
are
managed
extensively.
Breeding
is
controlled
and
300
to
600
calves
of
1/2
and
3/4
Brahman
and
1/2,
3/4
and
high
grade
Sahiwal
are
born
between
November
and
January
each
summer.
Calves
are
weaned
between
April
and
June
depending
on
seasonal
and
management
factors.
Weaning
is
followed
by
10
days
in
yards
during
which
they
are
branded
and
vaccinated
with
5
in
1
clostridial
vaccine
(Vaxall
5
vaccine,
Arthur
Webster).
In
the
yards
the
calves
are
fed
hay
from
racks.
Weaners
are
subsequently
grazed:apart
from
adult
cattle.
Calves
were
observed
during
four
post
-weaning
periods
during
1982,
1983
and
1984
(Table
I).
In
1982
calves
were
weaned
in
two
batches
six
weeks
apart
to
investigate
correlations
between
weaning
time
and
coccidial
activity.
A
che-
motherapeutic
trial
was
conducted
on
each
occasion.
Female
calves
from
the
herd
were
grouped
by
weight
and
genotype
and
either
dosed
with
monensin
or
acted
as
untreated
controls.
Identification
codes
for
groups
comprised
the
year,
fi
rst
or
TABLE
I
The
experimental
design
showing
the
compositions
of
groups
and
their
treatments.
First
weaning
Second
weaning
1982
Group
designation
82(i)T60
82(i)U
82(ii)T60
82(ii)u
Number
of
calves
31
32
32
32
Weaning
date
22-4-1982
22-4-1982
1-6-1982
1-6-1982
Monensin
dose
60
mg/day
untreated
60
mg/day
untreated
and
duration
30
days
30
days
Average
weight
138
kg
135
kg
155
kg
155
kg
and
range
75-174 78-184
95-213
86-178
1983
Group
designation
83T40
83T20
83T10
83U
Number
of
calves
30
30
30
30
Weaning
date
19-4-1983
19-41983
19-4-1983
19-4-1983
Monensin
dose
40
mg/day
20
mg/day
10
mg/day
untreated
and
duration
60
days
60
days
60
days
Average
weight
130
kg
130
kg
129
kg
130
kg
and
range
115-146
114-145
113-142
108-145
1984
Group
designation
84T25
84U
Number
of
calves
40
40
Weaning
date
6-6-1984
6-6-1984
Monensin
dose
and
duration
25
mg/day
60
days
untreated
Average
weight
150
kg
151
kg
and
range
126-190
125-189
200
PARKER
ET
AL.
second
weaning
(1982
only),
U
or
T
for
untreated
or
treated
and
a
fi
gure
indicating
dose
rate.
For
example:
82(ii)T60
=
1982,
second
weaning,
treated
with
monensin
at
60
mg
per
day.
Calves
were
identified
as
individuals
and
group
members
by
numbered,
coloured
ear
-tags
and
were
grazed
and
mustered
with
the
rest
of
the
calf
herd.
Apart
from
sample
collections
at
each
muster
the
selected
calves
were
treated
identically
to
other
herd
members.
The
herd
was
observed
in
the
paddock
at
least
every
second
day.
Monensin
(Monensin
sodium,
Elanco)
a
well-known
coccidiostat
was
selected
as
the
prophylatic
drug
because
of
favourable
reports
of
its
control
of
experimen-
tal
E.
bovis
coccidiosis
in
calves
(Fitzgerald
and
Mansfield,
1973;
McDougald,
1978)
and
its
suppression
of
oocyst
production
in
naturally
infected
lambs
(Calhoun,
Carroll,
Livingstone
and
Shelton,
1979).
Its
thermal
stability
suited
administration
by
slow
release
intra-ruminal
devices.
Spring
loaded
plastic
capsules
(Laby,
1978)
were
administered
by
a
modified
balling
gun.
Preliminary
trials
showed
that
calves
could
be
expected
to
retain
the
capsules
for
several
months.
The
slow
-release
intra-ruminal
devices
were
prepared
by
one
of
us
(K.J.E.)
and
pilot
capsules
were
tested
for
monensin-release
rates
in
fi
stulated
cattle
at
the
Commonwealth
Scientific
and
Industrial
Research
Organisation
(CSIRO)
laboratory,
Armidale
and
at
Swan's
Lagoon.
The
dose
rate
of
60
mg
per
day
used
in
1982
was
based
on
published
recommendations
(Fitzgerald
and
Mansfield,
1973)
but
reduced
because
of
the
greater
efficiency
of
utilisation
of
drugs
from
the
intra-ruminal
capsules
(Lehane,
1982).
The
duration
of
30
days
of
drug
release
in
1982
calves
was
selected
to
cover
the
expected
period
of
coccidial
activity.
The
1983
dose
rates
of
10,
20
and
40
mg
per
day
and
the
1984
dose
rate
of
25
mg
per
day
each
for
60
days
were
based
on
previous
results.
The
capsules
were
administered
to
calves
during
handling
for
the
fi
rst
sample
collections.
Faecal
samples
were
collected
one
or
two
days
after
weaning,
at
the
end
of
the
yard
period
(10
days
after
weaning)
and
at
two
weekly
intervals
thereafter
for
11
weeks
in
1982
and
for
15
weeks
in
1983
and
1984.
The
initial
sampling
at
weaning
was
omitted
in
1984.
Calves
were
weighed
at
each
muster.
Faecal
samples
were
collected
from
the
rectum
and
liquid
and
dysenteric
samples
noted.
Faeces
were
examined
using
a
modified
McMaster
salt
fl
otation
technique
and
a
Whitlock
universal
0.5
ml
counting
chamber.
Coccidial
oocysts
and
helminth
eggs
were
recorded
at
a
sensitivity
of
100
per
g.
Coccidial
oocysts
were
identified
by
comparing
their
morphology
with
published
descriptions
(Davies,
Joyner
and
Kendall,
1963;
Pellerdy,
1974;
Anon,
1977).
Subsequently
oocyst
counts
of
species
that
reached
counts
?--5,000
per
g
were
'scored'
to
eliminate
the
effects
of
individual
very
high
counts
on
group
average
results.
The
scoring
system
was
as
follows:
1
=
1,000
to
4,900;
2
=
5,000
to
9,900;
3
=
10,000
to
99,000
and
4
=
100,000.
Environmental
contamination
by
oocysts
was
investigated
by
collecting
samples
of
hay
-rack
-trough
contents
and
yard
fl
oors
at
the
end
of
the
10
days
following
weaning.
They
were
treated
by
washing
and
sieving
followed
by
alternate
centrifugation
in
water
and
saturated
sodium
chloride
solution
to
collect
particles
(including
coccidial
oocysts
and
helminth
eggs)
of
specific
gravity
between
FO
and
F2.
These
were
fi
nally
concentrated
in
water
and
examined
microscopically.
The
sizes
of
the
samples
and
the
details
of
their
handling
varied
according
to
the
type
of
sample
and
its
composition
but
the
sensitivity
of
the
technique
was
considered
to
be
better
than
one
per
gram.
The
weather
and
environmental
conditions
were
visually
assessed
for
their
suitability
for
oocyst
survival
and
development.
PROPHYLAXIS
OF
COCCIDIOSIS
IN
BEEF
CALVES
201
RESULTS
The
results
are
presented
in
four
sections.
The
fi
rst
presents
general
results
applicable
to
all
three
years;
the
other
three
sections
present
the
results
of
the
three
years
of
study
in
chronological
order
and
concentrate
on
E.
zuernii
coccidiosis,
the
effect
of
monensin
medication
and
climatic
differences.
General
results
for
1982,
1983
and
1984
No
difficulties
were
encountered
in
administering
the
capsules.
They
were
swallowed
readily
by
the
calves
without
apparent
discomfort
and
apparently
retained.
Capsules
tested
each
year
in
fi
stulated
cattle
released
their
contents
evenly
and
became
empty
within
two
days
of
the
intended
times.
The
pattern
of
oocyst
shedding
was
similar
in
untreated
calves
on
all
occasions.
Both
the
number
of
calves
shedding
oocysts
and
the
average
oocyst
counts
increased
until
three
to
fi
ve
weeks
after
weaning
and
subsequently
declined.
Although
calves
shed
oocysts
of
the
nine
species
previously
recorded
in
this
region
(Parker
et
al.,
1984;
Jones
and
Parker
1985)
oocyst
counts
a-5.0
x
10
3
per
g
were
recorded
for
only
three
species
E.
ellipsoidalis,
E.
subspherica
and
E.
zuernii.
It
was
considered
that,
although
there
was
an
increase
in
the
number
of
calves
shedding
small
numbers
of
oocysts
of
the
other
six
species,
these
were
unlikely
to
have
contributed
significantly
to
severe
diarrhoea.
When
the
oocyst
counts
for
E.
ellipsoidalis,
E.
subspherica
and
E.
zuernii
were
scored
and
compared
with
faecal
consistency
an
association
was
often
seen
between
high
E.
zuernii
oocyst
scores
and
liquid
faeces.
Liquid
faeces
were
never
associated
with
high
counts
of
E.
ellipsoidalis
and
E.
subspherica.
Disease
was
associated
only
with
E.
zuernii
particularly
with
oocyst
counts
.?
-40.0
x
10
3
per
gram.
Of
fi
ve
calves
seen
with
counts
a740.0
x
10
3
two
had
dysentery,
two
appeared
clinically
dehydrated
and
one
died.
The
highest
nematode
egg
counts
(up
to
2.0
x
10
3
per
g)
were
seen
within
two
weeks
of
weaning.
This
corresponded
to
the
period
when
faeces
were
dry
and
solid
faecal
components
and
contents
would
have
been
concentrated.
Counts
subsequently
declined
and
stabilised
in
the
low
hundreds.
There
was
no
association
between
the
highest
count
and
liquid
faeces.
Monensin
had
no
effect
on
nematode
egg
count.
Results
for
1982
A
period
of
very
dry
sunny
weather
preceded
weaning
and
the
yards
were
dry
and
dusty.
Pasture
herbage
was
minimal
and
there
was
no
surface
water
or
mud.
The
calves
were
thin
with
rough
coats.
Calves
in
the
second
weaning
were
in
better
condition
than
the
fi
rst,
they
were
approximately
19
kg
heavier
at
weaning
and
maintained
this
advantage
during
the
period
of
observation.
A
little
light
rain
fell
during
the
weeks
following
weaning
but
it
was
insufficient
to
relieve
the
hot
dry
sunny
conditions.
Supplementary
feeding
with
molasses
and
urea
was
commenced
immediately
after
the
calves
left
the
yards
10
days
after
weaning.
Widespread
diarrhoea
occurred
four
to
fi
ve
weeks
after
each
weaning.
More
than
90%
of
calves
had
faeces
-soiled
tails
and
hocks
indicating
recent
loose
to
fluid
faeces.
Apart
from
clinical
depression
and
dehydration
associated
with
severe
diarrhoea
in
some
calves
no
other
signs
of
disease
were
seen.
Faecal
samples
were
frequently
of
fi
rmer
consistency
than
indicated
by
the
soiled
tails
and
hocks.
This
indicated
that
diarrhoea
was
of
either
short
duration,
intermittent
or
both.
Faecal
202
PARKER
ET
AL
samples
were
usually
fi
rm
to
soft,
but
hard
dry
samples
were
common
immediately
after
weaning.
Similar
numbers
of
calves
in
monensin
treated
and
control
groups
passed
liquid
faeces
during
the
treatment
period.
However,
following
cessation
of
treatment
there
was
an
increase
in
the
number
of
liquid
samples
collected
with
the
increase
being
greater
in
the
treated
groups
(Fig.
1).
Seven
and
19
untreated
calves
were
shedding
oocysts
at
the
fi
rst
and
second
weanings
respectively
with
average
counts
of
0.5
x
10
3
oocysts
per
g
increasing
to
30
calves
and
18.0
x
10
3
oocysts
at
three
to
fi
ve
weeks
after
each
weaning.
Five
E.
zuernii
counts
_ _‘
5.0
x
10
3
per
g
were
seen
in
untreated
calves:
in
group
82(i)U,
14.0
x
10
3
and
15.0
x
10
3
at
week
fi
ve
and
31.0
x
10
3
and
40.0
x
10
3
at
week
seven
and
in
group
82(ii)U,
47.0
x
10
3
at
week
fi
ve.
The
highest
two
counts
were
associated
with
dysentery.
Oocyst
shedding
rapidly
declined
in
the
treated
groups
and
was
almost
eliminated
by
week
three.
Shedding
had
resumed
at
week
fi
ve
with
high
counts
being
seen
at
weeks
nine
and
11
(five
to
seven
weeks
after
30•
10.
Calves
passing
oocysts
w
Calves
passing
Ezuernil
cacY.ts••1
82
(
i
)
U
Gahm
passing
liquid
ih0.-gaqrnil
score
1
30•
Number
of
calves
and
E.zuernil
10*
score
82(i)180
Hammen
30.
20
10-
30
82(ii)U
20-
10.
82(ii)T60
Aleneesle
1.5
3
5
7
9
11
13
15
Weeks
after
weaning
FIG.
1.
1982.
The
numbers
of
calves
passing
E.
zuernii,
other
oocysts
and
liquid
faeCes,
and
E.
zuernii
scores.
PROPHYLAXIS
OF
COCCIDIOSIS
IN
BEEF
CALVES
203
cessation
of
treatment).
In
group
82(i)T60,
E.
zuernii
counts
of
11.0
x
10
3
and
223.0
x
10
3
were
seen
at
week
11,
and
in
group
82(ii)T60,
17.0
x
10
3
and
513.0
x
10
3
at
week
nine.
The
two
highest
counts
were
associated
with
dysentery.
The
numbers
of
calves
in
each
group
shedding
E.
zuernii
and
other
oocysts
and
the
associated
E.
zuernii
scores
are
shown
in
Fig.
1.
The
average
weight
of
calves
decreased
by
three
to
four
kg
during
the
11
week
trial
period.
Losses
of
2:10
kg
occurred
between
consecutive
weighings
in
three
treated
and
six
untreated
calves
during
the
treatment
period
and
in
four
treated
and
three
untreated
calves
after
cessation
of
treatment.
Two
of
these
calves
in
the
treated
groups
had
E.
zuernii
oocyst
counts
of
223.0
x
10
3
and
513.0
x
10
3
and
associated
rapid
weight
losses
of
31
and
11
kg,
respectively.
Both
survived
the
acute
disease
but
one
became
progressively
more
emaciated
and
died
eight
weeks
later.
The
other
failed
to
regain
the
lost
weight
before
the
end
of
the
trial.
Approximately
10%
of
the
ungrouped
calves
at
Swan's
Lagoon
suffered
sudden
weight
loss
of
10
to
30
kg
between
one
and
two
months
after
weaning
and
then
maintained
their
new
weight.
The
yard
floor
consisted
of
sand
and
dust.
Heavy
faecal
contamination
was
obvious
both
grossly
.
and
in
the
characteristic
smell
and
colour
of
dust
clouds.
The
troughs
beneath
hay
racks
contained
short
fi
bres
from
the
hay,
dust
and
dried
faeces.
The
recognisable
dried
faeces
accounted
for
30%
by
weight
of
the
trough
contents;
however,
most
of
the
dust
appeared
to
be
of
faecal
origin
and
it
is
estimated
that
faeces
made
up
at
least
70%
of
the
trough
contents.
No
coccidial
oocysts
or
nematode
eggs
were
recovered
from
the
yards
or
troughs
but
bodies
tentatively
identified
as
damaged
oocysts
were
occasionally
seen.
Results
for
1983
Dry
weather
preceded
weaning
but
unseasonal
heavy
rain
commenced
six
days
after,
producing
areas
of
deep
mud
and
water
in
the
yards;
herbage
became
abundant.
Calves
were
approximately
six
kg
lighter
at
weaning
than
the
fi
rst
weaned
group
in
1982.
As
in
1982
a
period
of
widespread
diarrhoea
occurred
with
faeces
soiled
tails
and
hocks
being
common.
Clinical
disease
was
not
noticed.
Herbage
growth
was
rapid
and
the
calves
were
turned
out
onto
good
pasture.
Subsequent
frequent
rain
maintained
herbage
growth
and
maintained
large
areas
of
very
shallow
water
in
the
paddocks.
As
in
1982
fewer
fl
uid
faecal
samples
were
collected
than
expected.
During
the
treatment
period
fl
uid
faeces
were
reduced
in
the
40
mg
and
10
mg
per
day
groups
compared
to
the
untreated
group
(Fig.
2).
There
was
no
increase
in
the
number
of
liquid
faecal
samples
collected
after
the
cessation
of
treatment.
The
number
of
untreated
calves
shedding
oocysts
and
their
average
counts
increased
from
15
and
11
x
10
3
oocysts
per
g
at
weaning
to
23
and
2.1
x
10
3
respectively
at
three
to
seven
weeks.
Four
E.
zuernii
counts
x
10
3
were
seen,
in
the
untreated
group
(83U),
a
count
of
409.0
x
10
3
per
g
at
week
three,
and
counts
of
22.0
x
10',
9.0
x
10
3
and
56.0
x
10
3
per
g
at
week
seven.
Three
of
these
had
severe
diarrhoea
and
one
died.
Oocyst
shedding
was
reduced
in
the
treated
groups
with
an
average
of
nine
calves
shedding
oocysts
and
an
average
count
of
0.2
x
10
3
oocysts
per
g
at
week
three.
The
number
of
calves
shedding
oocysts
and
the
average
counts
rose
throughout
the
treatment
period
to
be
similar
to
the
untreated
group
by
week
11.
At
week
11
approximately
70%
of
calves
were
shedding
oocysts
with
average
counts
around
0.5
x
10
3
per
g.
E.
zuernii
counts
were
generally
low
in
treated
calves
but
rose
throughout
the
treatment
204
PARKER
ET
AL.
30•
10•
Number
of
calves
and
E.zuernil
1
score
Cate.a
gigs
asing
." "all
Exuer
t
:
83U
Cowes
iu
1
----"-
Ocleysts
CltiV00
passing
&mkt
Issas3-41
lib—E.zuent4111C010
83T40
MoneasM
10-
30.
20.
10•
83T20
83710
MertensIn
1.1
N
1.5
3
5
7
9
11
13
15
Weeks
after
weaning
FIG.
2.
1983.
The
numbers
of
calves
passing
E.
zuernii,
other
oocysts
and
liquid
faeces,
and
E.
zuernii
scores.
period
in
common
with
overall
counts.
Three
counts
above
1.0
x
10
3
were
seen
at
week
seven
with
one
of
8.1
x
10
3
.
At
week
nine
counts
of
9.6
x
10
3
and
53.2
x
10
3
were
seen,
the
latter
associated
with
dysentery.
Oocyst
shedding
did
not
increase
after
the
cessation
of
treatment
and,
except
for
a
count
of
10.7
x
10
3
at
week
13,
E.
zuernii
counts
remained
low.
The
numbers
of
calves
in
each
group
shedding
E.
zuernii
and
other
oocysts
and
the
associated
E.
zuernii
scores
are
shown
in
Fig.
2.
After
an
initial
loss
of
around
5
kg
by
week
three
the
average
weight
of
the
calves
increased
throughout
the
period
of
observation
to
be
12
kg
above
the
weaning
weight
by
week
15.
The
calf
in
the
untreated
group
that
died
lost
15
kg
and
was
not
seen
or
mustered
after
week
three.
Approximately
10%
of
the
calves
at
Swan's
Lagoon
failed
to
maintain
their
weaning
weight
and
one
ungrouped
calf
lost
21
kg
suddenly
and
died.
Of
the
grouped
calves
six
failed
to
regain
their
weaning
weight
but
suffered
no
sudden
losses.
These
comprised
three
untreated
calves,
two
treated
calves
in
group
83T10
and
one
in
83T20.
PROPHYLAXIS
OF
COCCIDIOSIS
IN
BEEF
CALVES
205
The
yards
initially
dry
and
dusty
became
muddy
and
water-logged
after
heavy
rain.
The
contents
of
troughs
below
hay
racks
became
a
slurry
of
mud
and
hay
fi
bres.
One
sporulated
E.
ellipsoidalis
oocyst
and
several
nematode
eggs
were
recovered
from
a
sample
of
trough
contents.
No
oocysts
or
eggs
were
recovered
from
samples
of
yard
mud
or
water.
Results
for
1984
The
dry
and
dusty
conditions
with
no
surface
water
closely
resembled
those
seen
in
1982.
A
period
of
diarrhoea
was
seen
around
week
fi
ve
but
was
less
widespread
than
in
the
previous
two
years.
Calves
with
faeces
-soiled
tails
and
hocks
were
in
the
minority.
Supplementary
feeding
with
molasses
and
urea
commenced
immediately
after
the
calves
left
the
yards
10
days
after
weaning.
Fewer
than
half
as
many
liquid
faecal
samples
were
collected
from
the
treated
compared
to
the
untreated
group
(Fig.
3).
There
was
no
increase
in
liquid
samples
collected
after
cessation
of
treatment.
The
number
of
untreated
calves
shedding
oocysts
and
their
average
counts
increased
from
19
and
0.3
x
10
3
oocysts
per
g
at
weaning
to
34
and
1.9
x
10
3
respectively
at
three
to
fi
ve
weeks.
Four
E.
zuernii
counts
x
10
3
were
seen
all
at
week
three.
These
were
one
of
6.4
x
10
3
in
the
treated
group
(84125)
and
three
in
the
untreated
group
(84U)
of
25
x
10
3
,
6.0
x
10
3
and
7.9
x
10
3
.
Liquid
faeces
were
associated
with
the
highest
count.
Oocyst
shedding
was
reduced
in
the
treated
group
with
nine
calves
shedding
oocysts
and
an
average
count
of
0.07
x
10
3
oocysts
per
g
at
week
seven;
during
weeks
nine
to
15
the
number
of
Number
of
calves
and
E.zuernii
score
Calves
passing
comets
---9
Calves'peastng
soeysts
Calves
passing
liquid
laiscas--.-1
84U
30
-
40-
30-
20-
84T25
Monensin
110—
.zt
g_ilt
i
score
1.5
3
5
7
9
11
13
15
Weeks
after
weaning
Fto.
3.
1984.
The
numbers
of
calves
passing
E.
zuernii,
other
oocysts
and
liquid
faeces,
and
E.
zuernii
scores.
206
PARKER
ET
AL.
calves
shedding
oocysts
and
the
average
counts
remained
lower
than
in
previous
years.
During
this
time
between
15
and
50%
of
calves
passed
oocysts
with
average
counts
in
the
low
hundreds.
The
number
of
calves
shedding
E.
zuemii
and
other
oocysts
and
the
associated
E.
zuernii
scores
are
shown
in
Fig.
3.
The
average
weight
of
calves
decreased
to
fi
ve
kg
below
weaning
weight
by
week
11
and
then
increased
to
approximately
three
kg
above
weaning
weight
by
week
15.
Two
untreated
calves
lost
11
and
18
kg
by
week
fi
ve.
Four
ungrouped
calves,
one
female
and
three
males
also
lost
>10
kg.
Yard
and
trough
conditions
were
dry
and
dusty
resembling
conditions
in
1982.
No
oocysts
or
nematode
eggs
were
recovered
from
yards
or
troughs.
DISCUSSION
Coccidiosis
is
clearly
a
potential
hazard
for
early
weaned
beef
calves.
This
is
probably.
greater
in
very
dry
seasons
when
earlier
weaning
is
economically
attractive
but
may
subject
the
weaned
calves
to
additional
dietary
hardship.
Monensin
reduced
the
severe
diarrhoea
and
dysentery
associated
with
E.
zuernii
but
it
apparently
did
not
reduce
the
incidence
of
mild
diarrhoea.
Coccidiosis
is
probably
only
a
minor
contributor
to
this
condition
and
cases
of
severe
and
fatal
post
-weaning
E.
zuernii
coccidiosis
have
been
recorded
in
the
absence
of
widespread
mild
diarrhoea
(R.J.
Parker
unpub.).
The
mild
diarrhoea
is
probably
caused
by
bovine
parvovirus
infection
which
was
demonstrated
at
Swan's
Lagoon
in
the
post
-weaning
period
of
1981
(Durham,
Johnson,
Isles,
Parker,
Holroyd
and
Goodchild,
1985).
Nevertheless
an
association
was
observed
between
post
-weaning
disease
and
E.
zuernii
coccidiosis.
The
several
severe
cases
recorded
had
high
oocyst
counts,
diarrhoea
or
dysentery
and
sudden
weight
loss.
Obtaining
these
data
was
fortuitous
because
of
the
short
duration
of
high
oocyst
counts
(Stockdale,
Bainborough,
Bailey
and
Niilo,
1981;
R.J.
Parker
unpub.)
and
the
sampling
intervals
used.
Diarrhoea
and
disease
were
apparently
more
widespread
than
was
indicated
by
the
consistency
of
collected
samples
and
sudden
weight
loss
during
the
periods
of
coccidial
activity
affected
up
to
10%
of
calves.
This
evidence
suggested
widespread
E.
zuernii
coccidiosis
with
approximately
10%
of
calves
suffering
clinical
disease.
Some
of
these
calves
subsequently
became
"poor
-doers"
and
failed
to
regain
rapidly
lost
weight.
Apart
from
E.
zuernii
only
E.
ellipsoidalis
oocysts
were
present
in
sufficient
numbers
to
indicate
a
potential
problem.
E.
ellipsoidalis
has
been
associated
with
diarrhoea
(Gobzem
and
Nazarov,
1978;
Hammond,
Sayin
and
Miner,
1962)
but
no
association
between
this
species
and
disease
was
recorded
during
this
study.
The
association
between
weaning
and
a
subsequent
rise
in
coccidial
oocyst
shedding
was
confirmed
by
the
similar
pattern
recorded
in
both
weaning
groups
in
1982.
However,
the
rise
in
oocyst
counts,
and
more
importantly
the
cases
of
E.
zuemii
coccidiosis,
were
a
week
or
two
later
than
expected
from
previous
work
(Parker
et
al.,
1984).
Disease
was
unlikely
to
have
resulted
from
oocyst
accumulation
in
1982
and
1984.
Sporulated
oocysts
were
difficult
to
fi
nd
in
the
environment
and
apparently
never
abundant
despite
obvious
faecal
contamination.
Although
a
similar
rise
in
faecal
oocyst
counts
occurred
each
year
of
the
trial,
disease
was
more
severe
in
environmental
conditions
apparently
hotter,
drier
and
sunnier
than
those
considered
suitable
for
oocyst
survival
and
sporulation
(Marquardt,
1957,
1960;
Marquardt,
Senger
and
Seghetti,
1960).
In
1983
yard
conditions
favoured
oocyst
PROPHYLAXIS
OF
cocamosss
IN
BEEF
CALVES
207
development,
calves
weighed
four
and
20%
less
than
those
in
1982
and
subsequently
grazed
in
paddocks
that
were
wet
for
long
periods
but
fewer
had
high
E.
zuernii
counts.
Although
two
deaths
were
attributed
to
coccidiosis
in
1983
no
calves
lost
weight
and
became
"poor
-doers".
The
various
psychological,
social
and
environmental
stresses
associated
with
weaning
are
known
to
be
immunodepressive
(Kelley,
1980,
Stephens,
1980)
and
could
precipitate
recrudescence
of
latent
infections.
Evidence
for
such
latent
infections
has
been
found
in
E.
zuernii
(Niilo,
1970)
and
proof
has
been
demonstrated
in
E.
nieschulzi
infections
(Marquardt,
Osman
and
Muller,
1984).
Disease
precipitated
from
latent
infection
by
immunodepression
could
explain
coccidiosis
in
conditions
inimical
to
oocyst
survival
and
development.
The
intra-ruminal
controlled
release
capsules
were
a
convenient
and
effective
method
of
medicating
weaner
calves
continuously
for
one
to
two
months.
Treatment
with
monensin
reduced
oocyst
shedding
and
had
the
greatest
effect
at
the
highest
dok
rate;
however,
it
is
difficult
to
explain
the
rises
in
E.
zuernii
oocyst
counts
which
followed
the
60
mg
per
day
treatment
and
were
accompanied
by
the
most
severe
cases
of
clinical
coccidiosis
seen.
In
contrast
in
1983
oocyst
shedding
increased
throughout
the
treatment
period
to
be
similar
to
that
of
the
untreated
group
when
medication
ceased.
It
is
possible
that
high
doses
of
monensin
prevented
the
infection
from
undergoing
primary
schizogony
and
becoming
active
while
lower
doses
allowed
slow
development.
Although
other
pathogens
were
undeniably
present
severe
disease
and
death
were
associated
only
with
E.
zuernii
coccidiosis
or
with
signs
identical
to
those
seen
in
calves
with
proven
E.
zuernii
coccidiosis.
Monensin
prophylaxis
reduced
the
incidence
of
disease
but
the
increase
in
disease
following
high
dose
rates
in
1982
requires
further
investigation
before
it
can
be
confidently
recommended.
As
post
-weaning
coccidiosis
appears
to
be
a
disease/physiology/nutrition
interaction
adequate
nutrition
for
early
weaned
calves
might
be
expected
to
reduce
the
severity
of
disease.
ACKNOWLEDGEMENTS
The
authors
are
grateful
to
the
staff
of
Swan's
Lagoon
and
CSIRO,
Armidale
for
their
support
and
assistance
without
which
this
work
would
have
been
impossible.
We
are
also
grateful
to
the
Elanco
Products
Company
of
West
Ryde,
NSW
for
their
generous
gift
of
monensin.
Accepted
for
publication
January
1986
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COCCIDIOSE
D'APRES
VELAGE
CHEZ
LES
VEAUX
DE
BOUCHERIE
DANS
LES
TROPIQUES
SECS:
CONTROLE
EXPERIMENTAL
PAR
SUPPLEMENTATION
CONTINUE
DE
MONENSIN
A
L'AIDE
DE
DISPOSITIFS
INTRA-RUMINAUX
ET
OBSERVATIONS
EPIDEMIOLOGIQUES
CONCOMITTANTES
Résumé
-La
prophylaxie
de
la
coccidiose
d'apres
sevrage
it
Eimeria
zuernu
des
veaux
de
boucherie
a
Ete
mise
en
place
avec
des
dispositifs
intra-ruminaux
delivrant
de
la
monensin
de
manure
continue.
L'ivaluation
de
4
traitements
pendant
3
annees
consecutives
a
permis
l'obtention
d'observations
dpidemiologiques.
La
monensin
s'est
montree
etre
une
substance
prophylactique
efficace
et
les
dispositifs
intra-ruminaux
un
moyen
efficace
d'administration
continue
sur
une
periode
de
1
a
2
mois.
Les
3
annees
de
la
duree
de
l'essai
ont
porte
sur
2
periodes
caracteristiquement
tits
seches
et
sur
une
periode
anormalement
humide.
La
coccidiose
a
ete
plus
severe
pendant
les
annees
seches,
suggerant
que
la
pression
due
aux
ookystes
est
moins
importante
que
l'immunodepression
due
au
sewage
et
le
stress
alimentaire
pour
faire
eclore
la
maladie.
Pendant
le
traitement
initial,
une
maladie
severe
s'est
declaree
chez
les
veaux
apres
arret
de
l'elimination
des
ookystes
par
la
monensin.
L'apparition
d'une
maladie
dans
des
conditions
defavorables
a
la
survie
et
au
dCveloppement
des
ookystes,
et
apres
traitement,
suggere
un
role
de
stades
endogenes
retardes.
COCCIDIOSIS
POSTDESTETE
EN
TERNEROS
PARA
LA
PRODUCCION
DE
CARNE
EN
EL
TROPICO
SECO:
CONTROL
EXPERIMENTAL
CON
EL
SUMINISTRO
CONTINUO
INTRARUMINAL
DE
MONENSINA
Resumen-Se
trat6
la
coccidiosis
clinica
postdestete,
por
Eimeria
zuernii,
en
terneros
para
la
produccidn
de
came,
mediante
el
siministro
intraruminal
de
monensina.
La
aplicacien
de
la
droga
se
hizo,
mediante
combinaciones
farmaceuticas
que
permiten
la
liberacion
continua
de
la
droga.
La
evaluaci6n
de
cuatro
tratamientos
durante
tres
afios
consecutivos,
permiti6
tambien
la
observaci6n
sobre
la
epidemiologia
de
la
enfermedad.
La
monensina
actu6
efectivamente
como
droga
profilactica
y
las
combinaciones
farmaceuticas
utilizadas,
permitieron
la
administracion
continua
de
la
misma
por
periodos
de
rads
de
uno
y
dos
meses.
Los
tres
arios
del
ensayo,
incluyeron
dos
periodos
de
destete
en
la
estacidn
seca
y
uno
en
la
liuviosa.
La
coccidiosis
fi
re
xnas
severa
en
la
estacion
seca,
sugiriendo,
que
la
descarga
de
ooquistes
fue
menos
importante
como
causal
de
la
enfermedad,
que
el
estres
del
destete.
La
enfermedad
tambien
se
present6
en
forma
severa,
en
los
temeros
que
eliminaron
ooquistes
despues
del
suministro
de
monensina,
en
los
ensayos
de
tratamiento
iniciales.
La
ocurrencia
de
la
enfermedad
en
condiciones
imprdpias
para
la
supervivencia
de
los
ooquistes
y
despues
del
tratamiento,
sugieren
la
acci6n
de
los
estados
latentes
del
parisito.