Katz and L. R. Fina
E. E. Bartley, T. G. Nagaraja, E. S. Pressman, A. D. Dayton, M. P.
Effects of Lasalocid or Monensin on Legume or Grain (FeedLot)
J ANIM SCI
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LASALOCID OR MONENSIN ON BLOAT 1401
is particularly true of legume bloat studies.
Susceptible bloaters will usually continue to
bloat if they are fed bloat provocative diets. In
our experience drugs are best tested by alternat-
ing control and treatment periods in any given
animal. Treatment was not started on an animal
until it had bloated (bloat score of 2.0 or
higher) for 3 consecutive days. Treatment
periods were 7 d or less if there were 3 consecu-
tive days without bloat. Following drug treat-
ment, the animal was not treated again until it
had bloated for 3 consecutive days. All animals
in this study returned to a bloating condition
after drug treatment. The mean of the bloat
score for the last 2 d of the pretreatment
control period and last 2 d of the treatment
period was used for analysis. The animals used
in these studies were the 12 most bloat suscep-
tible animals among a group of 27 rumen
fistulated animals tested over a 2 yr period for
susceptibility to either legume or grain bloat.
The experimental designs were Latin square
(Exp. 1, 3, 5), switch-back (Exp. 2, 4, 6, 9) or
split-plot (Exp. 7, 8). The animal and period
variations were removed in the normal analysis
used with these designs. Except for treatments
and experimental designs, Exp. 2, 3 and 4
were conducted like Exp. 1, and Exp. 6, 7, 8
and 9 were conducted like Exp. 5.
Exp. 1. Four rumen-fistulated, bloat-suscep-
tible adult cattle were used. Cattle were pastured
on irrigated lush prebloom alfalfa for about
1 h in the morning and 1 h in the evening (11 h
intervals between pasturing). Previous experi-
ence has demonstrated that the degree of bloat
is increased if cattle are pastured for short
periods. The cattle were strip grazed to provide
bloat provacative forage at all times. When
cattle were not grazing, they were confined in
drylot with shade, salt and water available.
Bloat was scored in one-half units by using
the scale developed (Bartley, 1965) for scoring
bloat in rumen-fistulated cattle: 0 = no froth,
no abdominal distention; 1 = slight froth, no
6 Lasalocid premix contained 15% lasalocid sodium
and 85% rice hulls (Hoffmann LaRoche, Inc., Nut-
7 Rumensin 60 contained 60 g monensin sodium/
454 g premix (Elanco Products Co., Indianapolis, IN).
aBloat Guard contains 53% poloxalene and 47%
inert carrier and is the product of Smith Kline Health
Products, Philadelphia, PA.
9Thiopeptin is a sulfur-containing peptide anti-
biotic from Fujisawa, Tokyo, Japan.
abdominal distention; 2 = definite froth with
sufficient pressure to expel froth; 3 = definite
froth, distention of left side; 4 = definite froth,
distention of left and right sides, animal dis-
tressed; 5 = definite froth, severe distention of
left and right sides, animal in severe distress,
terminal unless relieved.
A 2 • 2 Latin square was used to test two
treatments with two groups (two animals/
group). Treatments were .66 mg lasalocid 6 or
monensin 7/kg body weight administered via the
rumen fistula before the morning grazing
period. Following trial 1 a second trial was
conducted similar in all respects to the first
except that 1.32 mg of lasalocid or monensin
Exp. 2. Because monensin was more effective
than lasalocid in preventing alfalfa bloat, mon-
ensin at a dose of .99 mg/kg body weight was
compared with poloxalene. Poloxalene was
given via the rumen fistula once daily in the
form of Bloat Guard s at the Food and Drug
Administration's approved dose of 44 mg/kg
body weight (Feed Additive Compendium,
1981). A switch-back design was used, with two
groups each containing three bloat-susceptible,
rumen-fistulated adult cattle. The treatment
sequence for the three periods for Group I was
monensin, poloxalene, monensin; for Group II,
poloxalene, monensin, poloxalene.
Exp. 3. Because monensin and lasalocid had
demonstrated some degree of bloat prevention,
combinations of antibiotic with poloxalene
were tested to determine if effective bloat
prevention would result with less than recom-
mended quantities of poloxalene. In a first trial,
.66 mg lasalocid or monensin/kg body weight
was tested alone or in combination with 11 or
22 mg poloxalene/kg body weight. The dosages
of poloxalene tested were 25 or 50% of the
recommended dose. Twelve bloat susceptible,
rumen-fistulated adult cattle (assigned to two 6
x 6 Latin squares) were used to compare the
six treatments (table 3). In a second trial, the
dose of lasalocid was increased to .99 mg/kg
weight and tested in combination with 11 or 22
mg poloxalene. Six bloat-susceptible, rumen-
fistulated adult cattle (assigned to two 3 • 3
Latin squares) were used to compare the three
treatments (table 3).
Exp. 4. Four rumen-fistulated, bloat-suscep-
tible adult cattle were used to test the effect of
thiopeptin 9 on alfalfa bloat. When the cattle had
a bloat score of 2.75 or higher, they were given
.66 mg thiopeptin/kg body weight for 7 d.
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1402 BARTLEY ET AL.
Exp. 5. Six rumen-fistulated adult cows with
a history of susceptibility to grain bloat were
used. Each was housed in a separate stall and
fed twice daily a bloat-producing diet (Bartley
et al., 1975) in amounts to meet daily nutrient
requirement. The diet consisted of 60% cracked
sorghum grain (IFN 4-O8-139i, 22% dehydrated
alfalfa (IFN 1-00-023), 16% soybean meal (IFN
5-04-604), 1% salt and 1% dicalcium phosphate
The animals were divided into three groups
on the basis of bloat susceptibility. A 3 x 3
Latin square design was used to test three poly-
ether antibiotics for bloat prevention. The
antibiotics (monensin, lasalocid or X-14,547 A)
were provided in the concentrate diet at 1.32
mg antibiotic'kg body weight-I'd -1. Each
treatment lasted 14 d, followed by a 14-d
interval when no drug was given. The cattle
were scored for bloat 3 h after the morning
feeding by using the scale described in Exp. 1.
Exp. 6. To determine whether lasalocid
could sustain a bloat-preventive effect, even
after continuous feeding for a long period (60
d), two adult, rumen-fisulated cows were fed
1.32 mg lasalocid'kg body weight-I'd -1. Bloat
was scored for 4 d before initiating drug feeding
for 60 d, and for 23 d after drug feeding had
ceased. The latter period was used to evaluate
drug response and carryover affects of the drug.
Exp. 7. Six rumen-fistulated adult cows, all
of which were bloating at the initiation of the
study, were divided into two groups on the
basis of their previous bloat potential. One
group was fed lasalocid at .66 mg'kg body
weight -i'd -1 and the other group at 1.32 mg.
Each period lasted 7 d without drug, 21 d with
drug and 21 d after drug feeding had ceased.
Exp. 8. In the previous experiments, the
antibiotics were evaluated in animals that were
already bloating. In this experiment, the
effectiveness of lasalocid was tested at two
dosages (.66 or 1.32 mg/kg body weight daily)
when given to nonbloating animals fed hay and.
then gradually changed to the all-concentrate,
bloat-producing diet. Six adult, rumen-fistulated
cows were used. The animals were fed alfalfa
hay (IFN 1-00-063) ad libitum for 14 d; then
454 g of the bloat diet was substituted for 454
g hay daily (change-over accomplished in 14 d).
Lasalocid feeding was initiated when concentrate
feeding was started by mixing the drug in the
Exp. 9. Two adult, rumen-fistulated cows,
both bloating at the initiation of the experi-
ment. were fed salinomycin at 1.32 mg'kg
body weight -1 "d -1. The duration of the periods
was 3 d without drug, 12 d with drug and 7 d
R esu Its
Exp. 1. Only the 1.32-mg dose of monensin
significantly reduced the bloat score (table 1).
Both drugs reduced bloat scores to zero in
some animals, whereas others continued to
bloat. This effect is demonstrated by the wide
range in bloat scores observed (table 1).
Exp. 2, Because poloxalene is the most
widely used drug for bloat prevention in the
USA, the effect of poloxalene at the FDA-
TABLE 1. EFFECT OF TWO DOSAGES OF LASALOCID OR
MONENSIN ON ALFALFA PASTURE BLOAT (EXP. 1)
.66 mg/kg body wt
1.32 mg/kg body wt
30.0 a 16.1 b
aMeans between lasalocid and monensin do not differ (P>.IO).
b'CMeans between lasalocid and monensin differ (P<.02).
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LASALOCID OR MONENSIN ON BLOAT
TABLE 2. EFFECT OF MONENSIN OR POLOXALENE ON
ALFALFA PASTURE BLOAT (EXP. 2)
bloat score Treatment
a'bMeans between poloxalene and monensin differ (P<.O01).
approved dosage (44 mg/kg body weight; Feed
Additive Compendium, 1981) was compared
with .99 mg monensin/kg weight (200 mg
monensin daily is maximum FDA-approved
dose for cattle on pasture or .66 to .99 mg/kg
body weight for 200- to 300-kg cattle). Poloxa-
lene, as demonstrated
1965), was 100% effective in preventing bloat
(table 2), whereas monensin was 67% effective.
More importantly, however, poloxalene effec-
tively prevented bloat in all animals, whereas
monensin was effective in some animals and not
in others, as illustrated by the wide range in
bloat scores (table 2).
Exp. 3. In the first trial, .66 mg monensin
was more effective in reducing the degree of
bloat than was .66 mg lasalocid (table 3).
However, the difference between lasalocid and
monensin was not significant. There were
incremental and significant increases in the
reduction of bloat with monensin in combina-
tion with either 11 or 22 mg poloxalene.
Though the reduced dosages of poloxalene (11
or 22 rag) increased bloat reduction with both
lasalocid and monensin, the combination effect
did not give 100% bloat reduction, as obtained
with 44 mg poloxalene alone (Exp. 2). Because
.99 mg monensin had been tested in Exp. 2, .99
mg lasalocid was tested with and without
poloxalene in Exp. 3, trial 2. The effect on
bloat of .99 mg lasalocid in combination with
poloxalene was similar to that of .66 mg
TABLE 3. EFFECT OF LASALOCID OR MONENSIN WITH OR WITHOUT
POLOXALENE ON ALFALFA PASTURE BLOAT (EXP. 3)
(dose/kg body wt)
pretreatment Bloat score
-- % --
.66 mg lasalocid
.66 mg lasalocid + 11 mg poloxalene
.66 mg lasalocid + 22 mg poloxalene
.66 mg monensin
.66 monensin + 11 mg poloxalene
.66 monensin + 22 mg poloxalene
.99 mg lasalocid
.99 mg lasalocid + 11 mg poloxalene
.99 mg lasalocid + 22 mg poloxalene
a'b'CMeans in column with unlike superscripts differ (P<.01).
d'eMeans in column with unlike superscripts differ (P<.05).
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