Animal Effectiveness
The salinomycin NADA (128-686)
established that salinomycin 40 to 60 g/ton (0.0044 - 0.0066%) is a safe and
effective aid "for the prevention of coccidiosis in broiler chickens
caused by Eimeria tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti,
and E. mivati."
NADA 46-920 established the effectiveness
of bacitracin zinc (from Baciferm) for use in broiler rations for increased
rate of weight gain and improved feed efficiency. The present NADA (139-235)
establishes that the addition of bacitracin zinc to rations containing salinomycin
increased rate of weight gain. Data provided in this submission demonstrate
that rations containing bacitracin zinc and salinomycin are effective when
used at levels of 0.0011% to 0.0055% (10-50 g/ton) for bacitracin zinc and
0.0044% to 0.0066% (40-60 g/ton) salinomycin and are indicated for the prevention
of coccidiosis in broiler chickens caused by Eimeria tenella, E. necatrix,
E. acervulina, E. maxima, E. brunetti, and E. mivati; for increased
rate of weight gain.
A. Summary of Drug Noninterference
Studies
Two-week old, Hubbard x Hubbard,
broiler chickens were used in adequate, well-controlled, 2-week, battery studies
with approved protocols and were conducted in a uniform environment with continuous
artificial illumination to test for noninterference of bacitracin zinc with
the effectiveness of salinomycin. Recent field strain isolates collected from
various broiler-producing regions of the United States were used. For each
study, combinations of E. mivati, E. brunetti, and E. necatrix,
or E. acervulina, E. maxima, and E. tenella were used. This
arrangement facilitated identification of lesions.
These studies (Tables I and II)
were conducted by using the lowest approved level of salinomycin (40 g/ton).
The experimental treatment groups included uninfected unmedicated controls,
infected unmedicated controls, infected groups receiving 40 g/ton of salinomycin
with and without 100 g/ton bacitracin zinc, and 100 g/ton bacitracin zinc
alone. the protocols were designed to test for "noninterference"
of each component with the other for the bacitracin zinc-salinomycin combination.
In each of these studies, all
pens were preselected, birds were randomized by weight and assigned to cages
with 10 birds/cage with 4 replicates being used per treatment group. Medication
was initiated 2 days prior to laboratory infection. Evaluations were by lesion
scores (analysis was performed on preselected birds from each pen), dropping
scores, weight gains, and feed conversions.
These studies demonstrate that
there is "noninterference" of bacitracin zinc with the effectiveness
of salinomycin. The combination was compatible.
The investigators were as follows:
Shi E. Cheng, D.V.M., Ph.D.
A. H. Robins Co., Inc.
1405 Cummings Drive
P. O. Box 26609
Richmond, VA 23261-6609
Michael D. Sims, B.S.
A. H. Robins Co., Inc.
1405 Cummings Drive
P. O. Box 26609
Richmond, VA 23261-6609
Patricia C. Gerber, A.A.S.
A. H. Robins Co., Inc.
1405 Cummings Drive
P. O. Box 26609
Richmond, VA 23261-6609
B. Floor-Pen Studies
Three adequate and well-controlled
floor-pen studies using approximately 3312 broiler chickens (equal number
of male and female), were conducted under simulated actual use to determine
the growth promoting and feed efficiency effects of bacitracin
(Eds. note: The following
table consists of 13 columns.)
TABLE 1
Anticocicdial Activity of Salinomycin and Salinomycin in Combinationion withZinc Bacitration
Against a mixed Eimeria Infection in 2-Week-Old Chicks Experiment 84-034
Average
Coccidiosis- Dropping -----------Weight Gain (g)---------- Average Live- Feed Conversion
Treatment Medication Induced Score* Bird Weight Total Lesion
Group Infection g/ton Mortality D4-D8 Day 5 Day 6 Day 7 Day 14 on Day 14 Day 7 Day 14 Scores**
I None 0 0/40 0.O 1803a 2227ab 2525a 6131a 944a 1.44b 1.45d 0.0c
Uninfected
II None 0 8/40 2.4 879d 559d 533c 3750c 702c 2.77a 2.10a 5.7a
Mixed
III Salincomycin 40 0/40 0.5 1880a 2214ab 2637a 6309a 958a 1.52b 1.52cd 1.3b
Mixed
IV Zinc Bacitracin 100 5/40 2.0 1083c 769d 746c 3950c 733c 2.57a 1.93b 5.2a
Mixed
V Saliomycin + 40 0/40 0.6 1918a 2390a 2625a 6320a 957a 1.5lb 1.50cd 0.9b
Zinc Bacitracin 100
Mixed
NOTE: Comparisons are based on Duncan's Multiple Range Test at the 0.05 level of
significance. For a given column, any means not followed by the same letter are
siginficantly different.
* Pen dropping scores assigned using a scale of 0 to 4 (Morehouse and Baron,
1970).
** Lesion scores assigned using a score of O to 4 (Johnson and Reid, 1917) for
each area of the small intestine and ceca
(Eds. note: The following table
consists of 11 columns.)
Table II
Anticoccidial Activity of Salinomycin and Salinomycin in Combination with
Zinc Bacitracin Against a Mixed Eimeria Infection in 2-Week-Old Chicks (Pooled
Studies 84-035 and 84-110)
Average Dropping
Score*
Coccidiosis- -----D4-D8------ Weight Gain (g) Feed Conversion
Treatment Medication Induced Total
Group Infection g/ton Mortality 84-035 84-110 Day 7 Day 14 Day 7 Day 14 (g) Lesion Scores**
I None O 0/80 O.O 0 2236 5138 1.50 1.55 O.OOd
Uninfected
II None 0 11/80 1.1 1.7 1698 4902 1.91 1.79 5.62a
Mixed
III Salinomycin 40 3/80 O.7 1.6 1876 4793 1.79 1.71 2.08bc
Mixed
IV Zinc Bacitracin 100 10/80 1.3 2.1 1700 4737 1.82 1.75 5.46a
Mixed
V Salinomycin + 40 3/80 0.9 1.5 1740 4891 1.84 1.71 2.21bc
Zinc Bacitracin
Mixed
Note: Comparisons are based on Duncan's Multiple Range Test at the O.O5 level
of significance. For a given column, any means not followed by the same
letter are significantly different.
* Pen dropping scores assigned using a scale of 0 to 4 (Morehouse and Baron,
1970).
** Lesion scores assigned using a score of 0 to 4 (Johnson and Reid, 1970) for
each area of the small intestine and ceca.
(cont'd) zinc in the presence of
salinomycin. All diets were balanced to provide adequate levels of nutrients
(protein, energy, minerals, etc.). The same general experimental design was
used in all studies. All chickens were maintained from one day of age to market
weight. The studies were conducted in 3 geographical areas.
In these studies, pens were randomly
assigned to treatment within blocks, 50-60 birds (one-half male; one-half
female) were selected at random and assigned to pens; 6-8 replicates were
used per treatment group. Salinomycin at 60 g/ton (.0066%) and bacitracin
zinc at 0, and 50 g/ton was used on all studies. Studies were designed to
simulate varying conditions, to include geographical locations, differences
in climate, changes in weather, differences in management practices, and degree
of disease contamination of the premises.
Data were collected of the evaluation
of bacitracin zinc for increasing rate of weight gain and improving feed efficiency
in the presence of the highest recommended approved use level of the anticoccidial
drug (salinomycin, .0066%). Parameters of evaluation included mortality, body
weight gain and feed to body weight gain ratio.
Birds medicated with the combinations
were healthy throughout the study periods as evidenced by a survival rate
of over 98% for all studies. There were no adverse drug effects observed.
A detailed statistical examination
of the 3 studies was conducted. Data were combined over 3 locations and an
analysis of variance (weighted by location) conducted according to block design,
and mean differences separated using the least significant difference test
(P<.05). The combined analysis of variances demonstrated significant bacitracin
effects, i.e., that the 50 g/ton treatment was significantly better for increased
rate of weight gain (P<.01), while in the presence of salinomycin. The
combined individual treatment means (Table IV and V) illustrates the responses
from the combination.
(Eds. note: The following
table consists of 5 columns.)
Table III
Location and Design Study Information
Trial Study Study Pens/ Birds/
Location No. Investigator Trt. Pen
Colorado C878 Dr. C.L. Quarles 6 50
Oklahoma C880 Dr. R.G. Teeter 8 50-60
Georgia C905 Dr. R.B. Davis 8 58
(Eds. note: The following table
consists of 3 columns.)
Table IV
Mean Body Weight, Kg
Trial Treatments in the Presence of 60 g/ton Salinomycin
0 g/ton 50 g/ton
Bacitracin Zinc Bacitracin Zinc
C878 1.816 1.862
C880 1.513 1.582
C905 1.942 1.960
Average 1.757 1.801
Percent
Improvement -- 2.5
(Eds. note: The following table
consists of 3 columns.)
Table V
Feed Efficiency (F/G)*
Treatments in the Presence of 60 g/ton Salinomycin
0 g/ton 50 g/ton
Trial Bacitracin Zinc Bacitracin Zinc
C878 2.002 1.983
C880 2.016 1.866
C905 2.025 1.968
Average 2.014 1.939
Percent
Improvement -- 3.7
*F/G: Feed consumed per body weight gain
These studies demonstrate that there
is "non-interference" of bacitracin zinc with the effectiveness of
salinomycin. Bacitracin zinc is compatible with salinomycin.
The above data satisfy the requirement
for evaluation of an application under the CVM Policy outlined in the guidelines
for combination drugs revised October 1983. The policy provides for the granting
of a range approval for production drugs in combination when the maximum level
tested for the claim(s) is demonstrated to make a significant benefit to the
combination. The range approval according to the revised policy is from 50
g/ton to the minimum level approved for bacitracin zinc in the parent application.
A minimum use level of 10 g/ton was used in establishing the feed stability
data for this combination. Accordingly, 10 g/ton of bacitracin zinc is the
minimum approvable level. Therefore, use levels approvable for this application
are 10-50 g/ton of bacitracin zinc and 40-60 g/ton of salinomycin in broiler
rations.
The investigators were as follows:
Dr. Cary L. Quarles
Colorado Quality Research, Inc.
2629 Redwing Road
Creekside Two, Suite 315
Fort Collins, Colorado 80526
Dr. Robert G. Teeter
Department of Animal Science
Oklahoma State University
Stillwater, Oklahoma 74078
Dr. Richard B. Davis
4785 Lexington Road
Athens, Georgia 30605
The original approved NADA's
for bacitracin zinc (NADA 46-920) and salinomycin (NADA 128-686) contained
adequate data to establish the safety of each drug for broiler chickens.
The safety of a combination of
the 2 drugs was demonstrated in the drug residue elimination study, the floor-pen
studies and the compatibility battery studies described in this document.
Birds in the drug elimination studies were in good health throughout the study
and did not have any gross pathology at sacrifice. The birds in the floor-pen
and battery studies were healthy throughout the experimental periods. Mortality
in each study was within an acceptable range for each facility, and there
was no evidence that drug was the cause of any death.
Based on the data in the parent
NADAs, the compatibility battery studies, the drug elimination residue study,
and the floor-pen studies, we conclude that the combination is safe to be
fed to broiler chickens as indicated by the label.
The data provide evidence for
the combination of bacitracin zinc 10-50 g/ton and salinomycin at 40-60 g/ton
in the feed of broiler chickens that is consistent with and fulfills all the
requirements for a combination drug for animals as follows:
A. Each drug component makes
a contribution to the claimed effects.
B. The dosage of each drug component
are such that the combination is safe and effective.
C. For a significant animal population
that is affected by a significant disease condition, Eimeria tenella
is a major and widespread etiological organism for coccidiosis and the most
pathogenic Eimeria species for chickens and, as such, possess the potential
of causing extensive economic losses to broiler producers.
D. The label claims are not antagonistic.
A. Data to Support Human Safety
Safety for the approved products
-- bacitracin zinc (Baciferm) and salinomycin (Bio-Cox)--has been established
by data previously submitted in their respective parent NADA's, NADA 46-920,
and NADA 128-686.
Tolerances for residues of bacitracin
zinc in edible tissue of chickens is established at 0.5 ppm (21 CFR Section
556.70). Safe concentrations of salinomycin in the edible tissues of chickens
are 0.6 ppm for muscle, 1.8 ppm for liver and 1.2 ppm for skin/fat.
B. Residue Depletion/Non-Interference
Studies
The residue data supporting the
approved individual uses of bacitracin zinc and salinomycin and their withdrawal
times of zero and zero, respectively, have been submitted in their respective
parent applications (see Part A, above).
The studies indicated below establish
that each drug in the presence of the other does not influence or exceed the
established safe concentration or tolerance at withdrawal and that they do
not interfere in each other's tissue residue assays. Residue depletion studies
conducted on the three-way combination of salinomycin, roxarsone, and bacitracin
were used to support the two way combination of salinomycin and bacitracin
zinc.
Under NADA 128-686, a research
Rm was established for salinomycin from birds dosed with salinomycin only.
Unchanged 14C-Salinomycin was
determined by TLC/radiotracer. After 6 hours withdrawal, unchanged salinomycin
was 0.035 ppm in skin/fat with total salinomycin residues of 0.061 ppm. Using
skin/fat as the target tissue, a ratio of parent drug to total, residue of
0.57 was calculated at zero withdrawal. Thus, the permissible level of unchanged
salinomycin (marker) in skin/fat at zero withdrawal would be equal to the
product of the ratio value and the safe concentration (1.2 ppm) or 0.68 ppm.
Under NADA 135-746, broilers
were dosed for 46 days with the three-way combination of salinomycin (80 g/ton)
/roxarsone (45 g/ton) /bacitracin zinc (100 g/ton). Six birds were sacrificed
at zero withdrawal and skin/fat collected for determination of salinomycin
using a microbiological assay. The average salinomycin concentration in skin/fat
at zero withdrawal was found to be 29.4 ppb +/- 10.1. Thus, the concentration
of parent salinomycin is approximately equal to that found in NADA 128-686
and is below the research Rm of 0.68 ppm.
Another drug residue elimination
study was completed under protocol 84-039 at the A. H. Robins facility in
Ashland, Virginia, examining bacitracin zinc while in the presence of salinomycin
and roxarsone. A total of 30 birds was reared for control tissue (no drug)
and another 30 broilers received the combination of 0.0088% salinomycin plus.
0.011% bacitracin zinc from day 0 to day 41. On day 41 (zero withdrawal) six
birds (3 males, 3 females) were sacrificed from the above combination treatment
group and assayed for bacitracin zinc residue. Edible tissue assayed was muscle.
There was no bacitracin zinc residue found in any of the muscle tissue at
zero day withdrawal.
Reference is also made to A.
H. Robin NADA P-137-536, which indicates that spiking of muscle homogenate
with various combinations of salinomycin and bacitracin zinc do not affect
the size of salinomycin inhibition zones. Therefore, bacitracin zinc does
not interfere with the salinomycin assays.
A non-interference study for
bacitracin zinc was conducted by spiking control muscle tissue with 0.5 ppm
bacitracin zinc and 80 ppb of salinomycin. There were no detectable assay
interferences caused by salinomycin when assaying for bacitracin zinc in chicken
muscle.
A regulatory analystical method
for salinomycin is not required. A practical analytical method for the determination
of tissue residue of bacitracin zinc is available in the Food Additives Analytical
Manual on display in FDA's Freedom of Information Room (Room 12A-30), 5600
Fishers Lane, Rockville, Maryland 20857.
