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Relationship of Restricted Feeding and Medication to Coccidiosis Control
ENVIRONMENT AND HEALTH Relationship of Restricted Feeding and Medication to Coccidiosis Control M. D. RUFF and M. B. CHUTE United States Department of Agriculture, Science and Education Administration, Agricultural Research, Animal Parasitology Institute, Beltsville, Maryland 20705 (Received for publication May 21,1979)
1980 Poultry Science 59:697-701 INTRODUCTION
Many producers of broiler breeder flocks use restricted feeding (RF) programs to reduce the weight of breeders and to delay the onset of maturity. Although the effects of such regimens on the subsequent laying performance have been investigated in several studies (Fuller et al, 1969,1973; Voitle et al, 1970), the effects of such regimens on anticoccidial efficacy and development of coccidial immunity have not been investigated. The purpose of this study was 1) to determine the relationship between feeding regimen and efficacy of anticoccidial drugs and 2) to determine if the feeding regimen affects the development of coccidial immunity after multiple exposure to coccidia. MATERIALS AND METHODS Pullets and Feed. In each of four trials, 240 pullets (Hubbard breeders) were used. The experimental design is shown in Figure 1. Pullets were obtained at 1 day of age, raised in heated brooder batteries with wire floors, and fed a complete pullet starter ration ad libitum. This ration was either unmedicated or con-
tained .0125% amprolium, .0125% clopidol, or .0110% monensin. At 16 days of age, the pullets were weighed, banded, and grouped on a weight basis within medication. For each trial, 120 pullets were placed in floor pens, and the other 120 were transferred to suspended wire-floored cages. In all but one trial, the average weight had reached 275 g, and all groups designated for the restricted feeding (RF) regimen were thereafter fed weighed amounts of ration as recommended in the Hubbard pullet management guide (Hubbard Farms, 1977). Basically, this was a feeding rate of 80 g/bird every other day at the start of restriction reaching a rate of 95 g/bird every other day at 7 weeks. Pullets in the other trial reached an average of 275 g at 18 days of age and were placed on the RF regimen at that time. A sample of the pullets was weighed twice weekly (a minimum of 12 pullets/regimen), and feed was adjusted according to table recommendations. The ad libitum (AL) regimen was continued with the other pullets. Coccidia. Four trials were conducted, each following the same design of feeding regimen, medication, and time of coccidial exposure but involving different species of coccidia as
697
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ABSTRACT Hubbard breeder pullets were fed a complete pullet developer ration on an ad libitum (AL) or restricted feeding (RF) regimen. The ration either was unmedicated or contained .0125% amprolium, .0125% clopidol, or .0110% monensin. The relationship between the feeding schedule and coccidial infection was determined on the basis of 1) efficacy of the medication in controlling a single infection in susceptible pullets and 2) the development of immunity to subsequent challenge inoculation after a series of immunizing inoculations. Cage-reared, susceptible pullets were inoculated with sporulated oocysts of either Eimeria tenella, 2 strains of E. acervulina, or E. maxima. With all three medications, the infection with at least one species was more severe, as measured by intestinal lesion score, in the RF pullets than in the corresponding AL pullets. Other pullets were kept for three weeks in floor pens that contained coccidial oocysts to allow natural infection and immunity to develop. The pullets were then transferred to suspended cages to prevent reinfection and fed an unmedicated ration. After one week, the pullets were challenged with the same coccidial strain as that used for immunizing. All pullets initially exposed to coccidia and given no medication were resistant to challenge inoculation. Control pullets not exposed to coccidia during rearing were susceptible to challenge. The administration of anticoccidial drugs (especially monensin) by ad libitum feeding interfered with development of immunity under these conditions, but, when the same drugs were given with a restricted feeding regimen, they did not interfere with development of immunity.
RUFF and CHUTE
698
EXPERIMENTAL DESIGN ACTION
TIME (DAYS)
Fed Medicated or unmedic;] ted feed Ad libitum
Pullets (240)
Floor pens (120)
Weigh, group Restricted feeding (RF) Ad libitum feeding (AL)
1 -wire floored brooders
< \|/
'(60)
Cages (120)
(60)
(60)
—I RF (60)
21 U (20)
I (20)
U (20)
I (20)
28
Weigh, kill, lesion score
35
\/
v/
(Immunized)
Immunity Challenge, weigh
(Immunized)
(Unimmunized Unmedicated Controls)
I U (20)
is
I (40)
if
U (20
I (40)
v
is
Weigh, kill, lesion score
U (10) I (10)
i
I
I
I
U (10) I (10) 42
i
I
49 FIG. 1. The experimental design of studies on feeding regimen, anticoccidial efficacy, and development of immunity. Numbers in parentheses indicate the number of pullets in each group.
follows: Trial 1, a laboratory strain of Eimeria tenella maintained in our laboratory for over 30 years; Trial 2, a field strain of Eimeria acervulina from Georgia (strain #1); Trial 3, a laboratory strain of Eimeria acervulina (strain #2); Trial 4, a laboratory strain of Eimeria maxima. The last two strains were originally isolated by S. A. Edgar (Auburn University, Auburn, AL). Drug Efficacy, After the caged pullets were maintained on RF or AL regimens for 7 days, they were inoculated with 1 X 10 5 E. tenella, 2 X 10 s E. maxima, or 1 X 10 6 E. acervulina sporulated oocysts/pullet (Fig. 1). Ten pullets from each feeding regimen and each medication were inoculated with each species individually. Uninoculated controls were also maintained. Seven days later, the pullets were weighed, killed, and the severity of lesions was scored according to the method described by Johnson and Reid (1970). Immunity Challenge. The pullets placed in the floor pens were used to evaluate the development of immunity to coccidiosis. Five
Weigh, kill, lesion score
days before the start of the trial these floor pens had been seeded with coccidial oocysts by introducing seeder birds that had been inoculated 5 days previously with sporulated oocysts of E. tenella, E. maxima, or E. acervulina. Immediately before the pullets were introduced, these seeder birds were removed. The pullets were kept in the floor pens for an additional 21 days to allow immunity to develop. During this time, pullets were fed a ration containing the desired medication and on the RF or AL regimens. The litter was kept moist throughout the experimental period to promote sporulation of the oocysts. The pullets were then transferred to suspended cages, and all pullets were placed on unmedicated feed for 1 week to allow the clearing of any residual coccidial infections that might influence the subsequent scoring of immunity challenge infections. The AL and RF regimens were continued. After this 1-week period, the pullets were challenged with the same single species used to immunize. The challenge dosages were the same as those used in the drug efficacy trials. The 40 pullets that
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Efficacy Test weigh, Inoculated (I) Uninoculated (U)
Randomize Cage, weigh, Unmedicated feed
14
RESTRICTED FEEDING IN COCCIDIOSIS CONTROL were used as inoculated and uninoculated controls (Fig. 1) had been previously maintained in cages and had been neither immunized nor medicated. One week later, all pullets were weighed, killed, and lesions were scored. RESULTS
the RF regimen was used. Results were similar with clopidol and monensin against strain #1 of E. acervulina and with monensin against E. maxima where no lesions were found in the AL pullets but were found in the RF pullets. Immunity Challenge. As in the drug efficacy trials, weight gain was a valid parameter for coccidial infection in only the AL pullets. There was a marked depression of weight gain in the unmedicated, nonimmunized control birds inoculated with E. tenella and E. maxima. Pullets with all combinations of anticoccidials and species had sufficient immunity to protect against a weight depression in the AL regimens, with the exception of the previously monensinmedicated birds against E. tenella, which gained only 66% as much weight as the unchallenged controls. Lesion score was a more sensitive parameter for measuring immunity and was markedly affected by feeding regimen. In both the AL and RF pullets, the challenge infection failed to produce visible lesions in the immunized unmedicated pullets except for a few lesions in the RF-£. tenella group (Table 3). Conversely, in the previously medicated AL pullets, lesions were found with some species such as E. tenella and strain #2 of E. acervulina. No lesions, however, were found in the challenged pullets on the RF regimen. There were severe lesions in the digestive tract in the unmedicated nonimmunized control pullets on both the AL and RF regimens. No residual lesions were found in the immunized nonchallenged controls.
DISCUSSION The efficacy of the anticoccidials tested was related to the feeding regimen used. The RF
TABLE 1. Weight gain (x + SEM, g/bird, 3rd to 4th week) of 4-week-old broiler breeder pullets fed ad libitum inoculated with coccidial oocysts when 3 weeks old Weight gain (g) Eimeria E. tenella E. acervulina #1 E. acervulina #2 E. maxima
Uninfected control
No medication
Amprolium
Clopidol
Monensin
392 ± 25 432 ±41
219 ± 15* 402 ±15
409 ± 13 454 ± 10
425 ± 13 479 ± 20
387± 11 465± 20
379 ± 8
295 ±20*
361 ±16
411 ± 8
331± 47
506 + 17
489 ± 9
430 ± 12
487 ± 11
455± 17
'Significantly different from corresponding control value (P<.05).
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Drug Efficacy. Weight gain was a valid parameter for the measurement of coccidial infection in only those pullets fed AL. The weight gain of the RF pullets was already depressed to the level recommended in the Hubbard guide (Hubbard Farms, 1977) and subsequent coccidial infection often produced no additional depression. There were no significant differences in weight between medicated and unmedicated, uninoculated controls in either the AL or RF regimes. In unmedicated pullets infected with E. tenella and strain #2 of E. acervulina, weight gain of the AL pullets was markedly less than that of the uninoculated AL controls (Table 1). Conversely, with E. maxima of strain #1 of E. acervulina, no subsequent weight depression was seen in unmedicated AL pullets even though lesions were found in the intestine. Medication protected against the weight depression with E. tenella or strain #2 of E. acervulina, Lesion score was an excellent parameter to measure drug efficacy. With both feeding regimens, severe coccidial lesions were found in the digestive tract of the unmedicated inoculated control pullets. The feeding regime had a marked effect on the ability of some of the anticoccidials to reduce or eliminate the lesions produced by some of the coccidia (Table 2). For example, all three anticoccidials eliminated lesions of E. tenella when the AL regimen was used, but clopidol and monensin did not when
699
700
RUFF and CHUTE TABLE 2. Lesion score (x ± SEM) in 4-week-old broiler breeder pullets inoculated 7 days previously with coccidial oocysts Lesion score
Feeding regimen
Eimeria
None
Amprolium
Clopidol
Monensin
Ad
E. E.
2.8 ± . 2 a 4.0 ± 0 a
Ob 3.0 ±
Ob 0C
Ob 0C
libitum
Restricted
tenella acervulina
3.8 ±
.2a
2.0 ± 0 b
2.4 ± . 2 a 2.2 ± . 2 a 4.0 ± 0 a
2.4 ± 0b 3.6 ±
.2
3.4 ±
.2a
2.2 ±
2.2 ±
.2ab
2.4 +
1.4 ±
.2a
.2C
1.6 ±
.2bc
2.2 ± . 2 a 2.0 ± 0 a 1.0 ± . 3 b
0b .6 ± . 4 b .6 ± . 6 b
.2b
2.0 ± 0 b
1.8 + . 2 b
.2a
2.6 ±
a
.2a
1.8 ± . 2 b
' ' Values within a regimen and species not followed by a common letter are significantly different (P=S.05).
regime allowed a significant increase in the severity of coccidial infection (as measured by lesion score) with two of the species and strains tested when compared with that seen in the AL regimen pullets. The intermittent cycling of the medication evidently gives levels that are inadequate to control heavy infections of coccidia. Thus, if we are to prevent coccidial outbreaks, the use of the RF regimen in the field should be closely monitored where the birds may be exposed to heavily contaminated litter or resistant strains. Three predominant methods are used for the control of coccidiosis in breeder and laying birds. One involves the use of anticoccidial medication during the growing period and continuous use of an approved "no withdrawal" anticoccidial during the production period. A second method involves the use of anticoccidials for protection during the growing period but in such a way that natural immunity to coccidiosis develops. This immunity is relied upon for protection during the production period. The third method relies on planned immunity (CocciVac) 1 and uses therapeutic medication only when needed. Although broilers rather than breeders were used in recent studies by Karlsson and Reid (1978),
1 Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the US Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be available.
results indicate that with the second method, anticoccidials that are extremely effective may not allow adequate development of immunity by the time medication is withdrawn. The results of the present study confirm these findings in AL fed pullets but not in RF pullets. Medication with 1) amprolium, 2) clopidol, or 3) monensin AL during the immunizing period allowed only partial immunity to develop in pullets exposed, respectively, to 1) E. tenella, 2) E. tenella or strain #2 of E. acervulina, and 3) E. tenella, strain #2 of E. acervulina, or E. maxima. Conversely, the same combinations of medication and coccidia in RF pullets allowed complete development of immunity, and no lesions were produced by subsequent challenge. In the AL pullets, four combinations of the effectiveness of coccidiosis control and subsequent development of immunity are indicated by the results in Tables 2 and 3. The first combination was one in which the organism produced an infection in the medicated pullets which gave complete immunity to subsequent challenge infection. Examples would be pullets given amprolium or clopidol and immunized and challenged with E. maxima and pullets given amprolium and immunized and challenged with E. acervulina (Tables 2 and 3). The second combination was one in which complete control was obtained by the medication (no lesions observed) yet complete immunity developed. Examples would be pullets medicated with clopidol and monensin and immunized and challenged with strain #1 of E. acervulina.
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E. acervulina #2 E. maxima E. tenella E. acervulina #1 E. acervulina #2 E. maxima
.2b
RESTRICTED FEEDING INCOCCIDIOSIS CONTROL
701
TABLE 3. Lesion score (x ± SEM) in 7-week-old broiler breeder pullets previously exposed to coccidia (2nd to 5th week) and challenged at 6th week Lesion score Feeding regimen Ad
libitum
Restricted
No medication
tenella acervulina
3.3 ± . 3 a 3.1 ± . l a
0C
acervulina maxima tenella acervulina
3.1 + . 2 2.4 ± . 3 a 2.0 ± . 2 a
0
.4 + .3b Ob
acervulina
3.3 ± . 2 a
maxima
2.9 ± . 3 a
Eimeria E\ E. #1 E. #2 E. E. E. #1 E, #2 E.
Amprolium
Clopidol
Monensin
Ob
1.2 ± .4b Ob
1.9 ± . 2 b Ob
2.1 ± ,2b Ob
3.8 ± . l a
0C
0C
1.5 ± . 2 b
2.9 ± .2b
a
C
OC
OC
Ob Ob
Ob Ob
1.4 ± . 3 b Ob Ob
Ob
Ob
Ob
Ob
Ob
Ob
Ob
Ob
a,b,c.Values within a regimen and species not followed by a common letter are significantly different (P=S.05).
T h e third c o m b i n a t i o n was organisms that produced s o m e lesions in t h e intestine of medicated pullets a n d , u p o n s u b s e q u e n t challenge, showed only a partial i m m u n i z a t i o n . Examples would be pullets medicated with clopidol and monensin and i m m u n i z e d and challenged with strain # 2 of E. acervulina. T h e fourth c o m b i n a t i o n was o n e in which lesions were entirely controlled in t h e initial infection and, as a result, only partial i m m u n i t y developed t o subsequent challenge. Examples would be all medications in pullets immunized and challenged with E. tenella and pullets medicated with monensin and immunized and challenged with E. maxima. In the last t w o c o m b i n a t i o n s , the c o m p l e t e i m m u n i t y that developed in t h e RF-fed pullets was probably related t o t h e reduced control of t h e initial immunizing infections in t h e R F pullets w h e n compared with greater c o n t r o l o b t a i n e d with those drugs in t h e A L pullets. T h u s , t h e R F regimen was often more conducive t h a n t h e A L regimen t o t h e d e v e l o p m e n t of i m m u n i t y in medicated pullets. Under field conditions, t h e initial exposure t o coccidia would probably n o t be as severe as t h a t e n c o u n t e r e d in these studies. A less severe exposure would allow for b e t t e r control of coccidiosis with t h e A L regimen which, in t u r n , would increase t h e likelihood of t h e pullets being susceptible t o infection after withdrawal of medication. Under these conditions t h e R F
regimen would have an even greater impact o n t h e d e v e l o p m e n t of a practical i m m u n i t y t o coccidiosis. ACKNOWLEDGMENTS T h e a u t h o r s wish to express appreciation to Gary Wilkins, Lawrence Spriggs, and J o h n Billhimer for their assistance in conducting these studies. T h e a u t h o r s also t h a n k T. J . S e x t o n for his advice on t h e restricted feed program.
REFERENCES Fuller, H. L., W. M. Kirkland, and L. W. Chaney, 1973. Methods of delaying sexual maturity of pullets. 2. Restricting energy consumption. Poultry Sci. 52:228-237. Fuller, H. L., D. K. Potter, and W. M. Kirkland, 1969. Effect of delayed maturity and carcass fat on reproductive performance of broiler pullets. Poultry Sci. 48:801-809. Hubbard Farms, 1977. Management guide for the Hubbard breeder pullet. Hubbard Farms, Walpole, NH. Johnson, Joyce, and W. M. Reid, 1970. Anticoccidial drugs: Lesion scoring techniques in battery and floor-pen experiments with chickens. Exp. ' Parasitol. 2 8 : 3 0 - 3 6 . Karlsson, T., and W. M. Reid, 1978. Development of immunity to coccidiosis in chickens administered anticoccidials in feed. Avian Dis. 22:487—495. Voitle, R. A., H. R. Wilson, and R. H. Harms, 1970. The effect of body weight restriction of broiler breeder pullets on subsequent performance. Poultry Sci. 49:1448.
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Caged control
1980 Poultry Science 59:697-701 INTRODUCTION
Many producers of broiler breeder flocks use restricted feeding (RF) programs to reduce the weight of breeders and to delay the onset of maturity. Although the effects of such regimens on the subsequent laying performance have been investigated in several studies (Fuller et al, 1969,1973; Voitle et al, 1970), the effects of such regimens on anticoccidial efficacy and development of coccidial immunity have not been investigated. The purpose of this study was 1) to determine the relationship between feeding regimen and efficacy of anticoccidial drugs and 2) to determine if the feeding regimen affects the development of coccidial immunity after multiple exposure to coccidia. MATERIALS AND METHODS Pullets and Feed. In each of four trials, 240 pullets (Hubbard breeders) were used. The experimental design is shown in Figure 1. Pullets were obtained at 1 day of age, raised in heated brooder batteries with wire floors, and fed a complete pullet starter ration ad libitum. This ration was either unmedicated or con-
tained .0125% amprolium, .0125% clopidol, or .0110% monensin. At 16 days of age, the pullets were weighed, banded, and grouped on a weight basis within medication. For each trial, 120 pullets were placed in floor pens, and the other 120 were transferred to suspended wire-floored cages. In all but one trial, the average weight had reached 275 g, and all groups designated for the restricted feeding (RF) regimen were thereafter fed weighed amounts of ration as recommended in the Hubbard pullet management guide (Hubbard Farms, 1977). Basically, this was a feeding rate of 80 g/bird every other day at the start of restriction reaching a rate of 95 g/bird every other day at 7 weeks. Pullets in the other trial reached an average of 275 g at 18 days of age and were placed on the RF regimen at that time. A sample of the pullets was weighed twice weekly (a minimum of 12 pullets/regimen), and feed was adjusted according to table recommendations. The ad libitum (AL) regimen was continued with the other pullets. Coccidia. Four trials were conducted, each following the same design of feeding regimen, medication, and time of coccidial exposure but involving different species of coccidia as
697
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ABSTRACT Hubbard breeder pullets were fed a complete pullet developer ration on an ad libitum (AL) or restricted feeding (RF) regimen. The ration either was unmedicated or contained .0125% amprolium, .0125% clopidol, or .0110% monensin. The relationship between the feeding schedule and coccidial infection was determined on the basis of 1) efficacy of the medication in controlling a single infection in susceptible pullets and 2) the development of immunity to subsequent challenge inoculation after a series of immunizing inoculations. Cage-reared, susceptible pullets were inoculated with sporulated oocysts of either Eimeria tenella, 2 strains of E. acervulina, or E. maxima. With all three medications, the infection with at least one species was more severe, as measured by intestinal lesion score, in the RF pullets than in the corresponding AL pullets. Other pullets were kept for three weeks in floor pens that contained coccidial oocysts to allow natural infection and immunity to develop. The pullets were then transferred to suspended cages to prevent reinfection and fed an unmedicated ration. After one week, the pullets were challenged with the same coccidial strain as that used for immunizing. All pullets initially exposed to coccidia and given no medication were resistant to challenge inoculation. Control pullets not exposed to coccidia during rearing were susceptible to challenge. The administration of anticoccidial drugs (especially monensin) by ad libitum feeding interfered with development of immunity under these conditions, but, when the same drugs were given with a restricted feeding regimen, they did not interfere with development of immunity.
RUFF and CHUTE
698
EXPERIMENTAL DESIGN ACTION
TIME (DAYS)
Fed Medicated or unmedic;] ted feed Ad libitum
Pullets (240)
Floor pens (120)
Weigh, group Restricted feeding (RF) Ad libitum feeding (AL)
1 -wire floored brooders
< \|/
'(60)
Cages (120)
(60)
(60)
—I RF (60)
21 U (20)
I (20)
U (20)
I (20)
28
Weigh, kill, lesion score
35
\/
v/
(Immunized)
Immunity Challenge, weigh
(Immunized)
(Unimmunized Unmedicated Controls)
I U (20)
is
I (40)
if
U (20
I (40)
v
is
Weigh, kill, lesion score
U (10) I (10)
i
I
I
I
U (10) I (10) 42
i
I
49 FIG. 1. The experimental design of studies on feeding regimen, anticoccidial efficacy, and development of immunity. Numbers in parentheses indicate the number of pullets in each group.
follows: Trial 1, a laboratory strain of Eimeria tenella maintained in our laboratory for over 30 years; Trial 2, a field strain of Eimeria acervulina from Georgia (strain #1); Trial 3, a laboratory strain of Eimeria acervulina (strain #2); Trial 4, a laboratory strain of Eimeria maxima. The last two strains were originally isolated by S. A. Edgar (Auburn University, Auburn, AL). Drug Efficacy, After the caged pullets were maintained on RF or AL regimens for 7 days, they were inoculated with 1 X 10 5 E. tenella, 2 X 10 s E. maxima, or 1 X 10 6 E. acervulina sporulated oocysts/pullet (Fig. 1). Ten pullets from each feeding regimen and each medication were inoculated with each species individually. Uninoculated controls were also maintained. Seven days later, the pullets were weighed, killed, and the severity of lesions was scored according to the method described by Johnson and Reid (1970). Immunity Challenge. The pullets placed in the floor pens were used to evaluate the development of immunity to coccidiosis. Five
Weigh, kill, lesion score
days before the start of the trial these floor pens had been seeded with coccidial oocysts by introducing seeder birds that had been inoculated 5 days previously with sporulated oocysts of E. tenella, E. maxima, or E. acervulina. Immediately before the pullets were introduced, these seeder birds were removed. The pullets were kept in the floor pens for an additional 21 days to allow immunity to develop. During this time, pullets were fed a ration containing the desired medication and on the RF or AL regimens. The litter was kept moist throughout the experimental period to promote sporulation of the oocysts. The pullets were then transferred to suspended cages, and all pullets were placed on unmedicated feed for 1 week to allow the clearing of any residual coccidial infections that might influence the subsequent scoring of immunity challenge infections. The AL and RF regimens were continued. After this 1-week period, the pullets were challenged with the same single species used to immunize. The challenge dosages were the same as those used in the drug efficacy trials. The 40 pullets that
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on June 24, 2015
Efficacy Test weigh, Inoculated (I) Uninoculated (U)
Randomize Cage, weigh, Unmedicated feed
14
RESTRICTED FEEDING IN COCCIDIOSIS CONTROL were used as inoculated and uninoculated controls (Fig. 1) had been previously maintained in cages and had been neither immunized nor medicated. One week later, all pullets were weighed, killed, and lesions were scored. RESULTS
the RF regimen was used. Results were similar with clopidol and monensin against strain #1 of E. acervulina and with monensin against E. maxima where no lesions were found in the AL pullets but were found in the RF pullets. Immunity Challenge. As in the drug efficacy trials, weight gain was a valid parameter for coccidial infection in only the AL pullets. There was a marked depression of weight gain in the unmedicated, nonimmunized control birds inoculated with E. tenella and E. maxima. Pullets with all combinations of anticoccidials and species had sufficient immunity to protect against a weight depression in the AL regimens, with the exception of the previously monensinmedicated birds against E. tenella, which gained only 66% as much weight as the unchallenged controls. Lesion score was a more sensitive parameter for measuring immunity and was markedly affected by feeding regimen. In both the AL and RF pullets, the challenge infection failed to produce visible lesions in the immunized unmedicated pullets except for a few lesions in the RF-£. tenella group (Table 3). Conversely, in the previously medicated AL pullets, lesions were found with some species such as E. tenella and strain #2 of E. acervulina. No lesions, however, were found in the challenged pullets on the RF regimen. There were severe lesions in the digestive tract in the unmedicated nonimmunized control pullets on both the AL and RF regimens. No residual lesions were found in the immunized nonchallenged controls.
DISCUSSION The efficacy of the anticoccidials tested was related to the feeding regimen used. The RF
TABLE 1. Weight gain (x + SEM, g/bird, 3rd to 4th week) of 4-week-old broiler breeder pullets fed ad libitum inoculated with coccidial oocysts when 3 weeks old Weight gain (g) Eimeria E. tenella E. acervulina #1 E. acervulina #2 E. maxima
Uninfected control
No medication
Amprolium
Clopidol
Monensin
392 ± 25 432 ±41
219 ± 15* 402 ±15
409 ± 13 454 ± 10
425 ± 13 479 ± 20
387± 11 465± 20
379 ± 8
295 ±20*
361 ±16
411 ± 8
331± 47
506 + 17
489 ± 9
430 ± 12
487 ± 11
455± 17
'Significantly different from corresponding control value (P<.05).
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on June 24, 2015
Drug Efficacy. Weight gain was a valid parameter for the measurement of coccidial infection in only those pullets fed AL. The weight gain of the RF pullets was already depressed to the level recommended in the Hubbard guide (Hubbard Farms, 1977) and subsequent coccidial infection often produced no additional depression. There were no significant differences in weight between medicated and unmedicated, uninoculated controls in either the AL or RF regimes. In unmedicated pullets infected with E. tenella and strain #2 of E. acervulina, weight gain of the AL pullets was markedly less than that of the uninoculated AL controls (Table 1). Conversely, with E. maxima of strain #1 of E. acervulina, no subsequent weight depression was seen in unmedicated AL pullets even though lesions were found in the intestine. Medication protected against the weight depression with E. tenella or strain #2 of E. acervulina, Lesion score was an excellent parameter to measure drug efficacy. With both feeding regimens, severe coccidial lesions were found in the digestive tract of the unmedicated inoculated control pullets. The feeding regime had a marked effect on the ability of some of the anticoccidials to reduce or eliminate the lesions produced by some of the coccidia (Table 2). For example, all three anticoccidials eliminated lesions of E. tenella when the AL regimen was used, but clopidol and monensin did not when
699
700
RUFF and CHUTE TABLE 2. Lesion score (x ± SEM) in 4-week-old broiler breeder pullets inoculated 7 days previously with coccidial oocysts Lesion score
Feeding regimen
Eimeria
None
Amprolium
Clopidol
Monensin
Ad
E. E.
2.8 ± . 2 a 4.0 ± 0 a
Ob 3.0 ±
Ob 0C
Ob 0C
libitum
Restricted
tenella acervulina
3.8 ±
.2a
2.0 ± 0 b
2.4 ± . 2 a 2.2 ± . 2 a 4.0 ± 0 a
2.4 ± 0b 3.6 ±
.2
3.4 ±
.2a
2.2 ±
2.2 ±
.2ab
2.4 +
1.4 ±
.2a
.2C
1.6 ±
.2bc
2.2 ± . 2 a 2.0 ± 0 a 1.0 ± . 3 b
0b .6 ± . 4 b .6 ± . 6 b
.2b
2.0 ± 0 b
1.8 + . 2 b
.2a
2.6 ±
a
.2a
1.8 ± . 2 b
' ' Values within a regimen and species not followed by a common letter are significantly different (P=S.05).
regime allowed a significant increase in the severity of coccidial infection (as measured by lesion score) with two of the species and strains tested when compared with that seen in the AL regimen pullets. The intermittent cycling of the medication evidently gives levels that are inadequate to control heavy infections of coccidia. Thus, if we are to prevent coccidial outbreaks, the use of the RF regimen in the field should be closely monitored where the birds may be exposed to heavily contaminated litter or resistant strains. Three predominant methods are used for the control of coccidiosis in breeder and laying birds. One involves the use of anticoccidial medication during the growing period and continuous use of an approved "no withdrawal" anticoccidial during the production period. A second method involves the use of anticoccidials for protection during the growing period but in such a way that natural immunity to coccidiosis develops. This immunity is relied upon for protection during the production period. The third method relies on planned immunity (CocciVac) 1 and uses therapeutic medication only when needed. Although broilers rather than breeders were used in recent studies by Karlsson and Reid (1978),
1 Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the US Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be available.
results indicate that with the second method, anticoccidials that are extremely effective may not allow adequate development of immunity by the time medication is withdrawn. The results of the present study confirm these findings in AL fed pullets but not in RF pullets. Medication with 1) amprolium, 2) clopidol, or 3) monensin AL during the immunizing period allowed only partial immunity to develop in pullets exposed, respectively, to 1) E. tenella, 2) E. tenella or strain #2 of E. acervulina, and 3) E. tenella, strain #2 of E. acervulina, or E. maxima. Conversely, the same combinations of medication and coccidia in RF pullets allowed complete development of immunity, and no lesions were produced by subsequent challenge. In the AL pullets, four combinations of the effectiveness of coccidiosis control and subsequent development of immunity are indicated by the results in Tables 2 and 3. The first combination was one in which the organism produced an infection in the medicated pullets which gave complete immunity to subsequent challenge infection. Examples would be pullets given amprolium or clopidol and immunized and challenged with E. maxima and pullets given amprolium and immunized and challenged with E. acervulina (Tables 2 and 3). The second combination was one in which complete control was obtained by the medication (no lesions observed) yet complete immunity developed. Examples would be pullets medicated with clopidol and monensin and immunized and challenged with strain #1 of E. acervulina.
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E. acervulina #2 E. maxima E. tenella E. acervulina #1 E. acervulina #2 E. maxima
.2b
RESTRICTED FEEDING INCOCCIDIOSIS CONTROL
701
TABLE 3. Lesion score (x ± SEM) in 7-week-old broiler breeder pullets previously exposed to coccidia (2nd to 5th week) and challenged at 6th week Lesion score Feeding regimen Ad
libitum
Restricted
No medication
tenella acervulina
3.3 ± . 3 a 3.1 ± . l a
0C
acervulina maxima tenella acervulina
3.1 + . 2 2.4 ± . 3 a 2.0 ± . 2 a
0
.4 + .3b Ob
acervulina
3.3 ± . 2 a
maxima
2.9 ± . 3 a
Eimeria E\ E. #1 E. #2 E. E. E. #1 E, #2 E.
Amprolium
Clopidol
Monensin
Ob
1.2 ± .4b Ob
1.9 ± . 2 b Ob
2.1 ± ,2b Ob
3.8 ± . l a
0C
0C
1.5 ± . 2 b
2.9 ± .2b
a
C
OC
OC
Ob Ob
Ob Ob
1.4 ± . 3 b Ob Ob
Ob
Ob
Ob
Ob
Ob
Ob
Ob
Ob
a,b,c.Values within a regimen and species not followed by a common letter are significantly different (P=S.05).
T h e third c o m b i n a t i o n was organisms that produced s o m e lesions in t h e intestine of medicated pullets a n d , u p o n s u b s e q u e n t challenge, showed only a partial i m m u n i z a t i o n . Examples would be pullets medicated with clopidol and monensin and i m m u n i z e d and challenged with strain # 2 of E. acervulina. T h e fourth c o m b i n a t i o n was o n e in which lesions were entirely controlled in t h e initial infection and, as a result, only partial i m m u n i t y developed t o subsequent challenge. Examples would be all medications in pullets immunized and challenged with E. tenella and pullets medicated with monensin and immunized and challenged with E. maxima. In the last t w o c o m b i n a t i o n s , the c o m p l e t e i m m u n i t y that developed in t h e RF-fed pullets was probably related t o t h e reduced control of t h e initial immunizing infections in t h e R F pullets w h e n compared with greater c o n t r o l o b t a i n e d with those drugs in t h e A L pullets. T h u s , t h e R F regimen was often more conducive t h a n t h e A L regimen t o t h e d e v e l o p m e n t of i m m u n i t y in medicated pullets. Under field conditions, t h e initial exposure t o coccidia would probably n o t be as severe as t h a t e n c o u n t e r e d in these studies. A less severe exposure would allow for b e t t e r control of coccidiosis with t h e A L regimen which, in t u r n , would increase t h e likelihood of t h e pullets being susceptible t o infection after withdrawal of medication. Under these conditions t h e R F
regimen would have an even greater impact o n t h e d e v e l o p m e n t of a practical i m m u n i t y t o coccidiosis. ACKNOWLEDGMENTS T h e a u t h o r s wish to express appreciation to Gary Wilkins, Lawrence Spriggs, and J o h n Billhimer for their assistance in conducting these studies. T h e a u t h o r s also t h a n k T. J . S e x t o n for his advice on t h e restricted feed program.
REFERENCES Fuller, H. L., W. M. Kirkland, and L. W. Chaney, 1973. Methods of delaying sexual maturity of pullets. 2. Restricting energy consumption. Poultry Sci. 52:228-237. Fuller, H. L., D. K. Potter, and W. M. Kirkland, 1969. Effect of delayed maturity and carcass fat on reproductive performance of broiler pullets. Poultry Sci. 48:801-809. Hubbard Farms, 1977. Management guide for the Hubbard breeder pullet. Hubbard Farms, Walpole, NH. Johnson, Joyce, and W. M. Reid, 1970. Anticoccidial drugs: Lesion scoring techniques in battery and floor-pen experiments with chickens. Exp. ' Parasitol. 2 8 : 3 0 - 3 6 . Karlsson, T., and W. M. Reid, 1978. Development of immunity to coccidiosis in chickens administered anticoccidials in feed. Avian Dis. 22:487—495. Voitle, R. A., H. R. Wilson, and R. H. Harms, 1970. The effect of body weight restriction of broiler breeder pullets on subsequent performance. Poultry Sci. 49:1448.
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Caged control