J APPL POULT RES 2009. 18:458-464. doi:10.3382/japr.2008-00093
© 2009 Poultry Science Association
Evaluation of live oocyst vaccination or salinomycin for control of field-strain Eimeria challenge in broilers on two different feeding programs
J. T. Lee*,
C. Broussard
,
S. Fitz-Coy,
P. Burke,
N. H. Eckert*,
S. M. Stevens*,
P. N. Anderson*,
S. M. Anderson* and
D. J. Caldwell*,1
* Poultry Science Department, Texas A&M University, College Station 77843; |and Schering-Plough Animal Health, NJ556 Morris Avenue, Summit, NJ 07901
1 Corresponding author: caldwell{at}poultry.tamu.edu
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SUMMARY
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Live oocyst vaccination as a method for coccidiosis control in broiler production is currently receiving heightened interest from producers and integrators, who have historically relied heavily on anticoccidial use to control infection. Reasons for this elevated level of interest include increased emergence of drug-resistant field strains of Eimeria, bans in the European Union on the use of continuously fed antimicrobials, and consumer pressure within the United States to remove antimicrobial feed additives from poultry diets. This pen study was designed to compare the live oocyst coccidiosis vaccine Coccivac-B with the ionophore salinomycin (Bio-Cox) for controlling field-strain Eimeria in broilers reared on 2 different dietary rations varying mostly in protein concentration. Broilers were reared to 50 d on a 4-phase feeding program. Both experimental diets evaluated in this study were formulated to simulate the diets of a local commercial integrator by season. The dietary protein profile for diet A was 21.5% (starter), 20% (grower), 16.5% (finisher), and 15.75% (withdrawal), whereas diet B had a profile of 22% (starter), 19.6% (grower), 17.8% (finisher), and 17.5% (withdrawal). On d 14 of grow out, field-strain Eimeria oocysts collected from commercial broiler farms in Texas were spray-applied to the litter in all pens. Significant differences in final BW were not observed with regard to diet or anticoccidial control method. Broilers fed diet B had improved (P < 0.05) mortality-corrected FCR during the starter and finisher phases of rearing. Broilers fed salinomycin had lower (P < 0.05) mortality-corrected FCR for the starter and grower phases, whereas vaccinated broilers had lower (P < 0.05) mortality-corrected FCR during the withdrawal period. Cumulative FCR for the entire grow-out period were similar (P > 0.05) for all groups. These results suggest that feeding an appropriately formulated diet while vaccinating broilers as an alternative to the use of an ionophore can result in at least equivalent performance in the presence of a field-strain Eimeria challenge during grow out.
Key Words: Eimeria • protein • vaccination • broiler
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DESCRIPTION OF PROBLEM
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Coccidiosis is recognized as the parasitic disease with the greatest economic impact on poultry production [1]. Infection with coccidian parasites has been calculated to cost the US poultry industry between $450 million [1] and $1.5 billion [2] annually, with approximately 80% of these costs attributable to decreased performance in the presence of drug treatment strategies [3]. Several species of Eimeria cause coccidiosis in chickens, with the most prevalent being Eimeria acervulina, Eimeria maxima, and Eimeria tenella. All Eimeria species parasitize epithelial cells of the intestinal lining, causing pathological changes varying from local destruction of the mucosa to systemic effects such as blood loss, shock, and death [3]. Infection leads to economic losses resulting from malabsorption of nutrients, which causes decreased BW gain, poorer FCR, and possibly increased mortality. Historically, poultry industry personnel have prevented and controlled coccidiosis with the inclusion of anticoccidial feed additives. Despite the implementation of rotation and shuttle programs in which anticoccidial feed additives are strategically varied in diets, drug-resistant strains continue to emerge across the United States and the world, forcing considerable interest in the development of alternative methods of control [4].
Live oocyst vaccination is currently a realistic alternative to the use of anticoccidial drugs for coccidiosis control in broilers. Vaccines have been used in the poultry industry for more than 50 yr, primarily in broiler breeder and replacement layer flocks [5]. The basis for vaccine use in the host is immunity that develops, affording the animal protection against subsequent infections by the same species [2]. Live oocyst vaccination has been shown to be an effective tool for the generation of immunity and protection against subsequent Eimeria challenge, as evidenced by increased BW gain [6–8], reduced FCR [7], and reduced lesion development [6–8] in vaccinated chickens compared with nonvaccinated chickens. To date, aside from complexes raising broilers for prolonged grow-out periods, there has been a general reluctance to implement vaccination programs in large-scale US broiler production facilities because of reports of reduced performance [1]. Because nonattenuated vaccines are designed to introduce a controlled subclinical infection early during grow out for immunity development, they have often been shown to decrease BW gain and increase FCR in broilers when compared with medicated birds during the starter period [4, 6]. Other researchers have reported negative effects on cumulative broiler performance when using live oocyst vaccines compared with anticoccidial use, as evidenced mainly by reduced final BW [9, 10] and increased FCR [10, 11]. Other investigations, however, contradict these cited reports, indicating that vaccinated broilers have performed similarly to, if not better than, medicated broilers [6, 12], and that vaccination can lead to significantly lower mortality rates compared with medication [11]. Previous research has indicated that varying dietary protein levels can positively influence performance during clinical coccidial infection [13]. Despite this potential involvement of dietary protein in ameliorating clinical Eimeria infection, there is a lack of research to date focusing on the relationship between dietary protein levels and broiler performance when using a live oocyst vaccination program.
Therefore, the objective of the current study was to compare performance and level of control of field-strain Eimeria challenge in broilers grown in floor pens either medicated with salinomycin (Bio-Cox, 60 ppm) [14] or vaccinated with Coccivac-B (full dose) [15]. The experimental approach for this trial included a comparison of the efficacy of both coccidiosis control measures when broilers were fed 1 of 2 different diets that varied in protein concentration.
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MATERIALS AND METHODS
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A 2 x 2 factorial-based design comparing 2 diets (Table 1
) with 2 anticoccidial control measures (ionophoric chemotherapy or vaccination) was used to investigate broiler performance as measured by BW and feed conversion. The dietary program consisted of 4 dietary phases: starter (1 to 14 d of age), grower (15 to 29 d of age), finisher (30 to 40 d of age), and withdrawal (41 to 50 d of age). The dietary protein profile for diet A was 21.5% (starter), 20% (grower), 16.5% (finisher), and 15.75% (withdrawal), whereas diet B had a profile of 22% (starter), 19.6% (grower), 17.8% (finisher), and 17.5% (withdrawal). Salinomycin was included at a rate of 60 g/ton for the starter and grower diets and was reduced to 50 g/ton in the finisher diet. The withdrawal diet did not include salinomycin. Specific details related to the dietary formulation of each diet are presented in Table 1.
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Table 1. Calculated nutrient concentrations of experimental diets fed to broilers given 1 of 2 coccidiosis control measures (salinomycin or Coccivac-B)1
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Straight-run Cobb [16] x Ross [17] broiler chicks were placed in a total of 40 floor pens (10 replicates/treatment) with dimensions of 6 x 6 ft. With 1 ft2 allowed for feeder space in each pen, 35 ft2 of total rearing space was present in each pen. With a placement density of 0.8 ft2/bird, 43 birds were placed per individual pen on the day-of-hatch. The total number of birds placed in this trial was 1,720. Every attempt was made throughout this study to allow pens to be representative of industry operations. Each pen included one 30-lb tube feeder, a nipple drinker system, and fresh pine shavings as the litter material. Broiler chicks were provided age-appropriate supplemental heat and given access to feed and water ad libitum. All animal husbandry procedures were conducted in accordance with an animal use protocol approved by the Texas A&M University Laboratory Animal Care Committee, and grow-out facilities were thoroughly cleaned and sanitized before the initiation of the trial.
On the day of placement, chicks in the vaccinated groups were vaccinated by spray application of the commercially available live oocyst coccidiosis vaccine Coccivac-B [15], using a Spraycox II [15] machine at the hatchery. Chicks were allowed to preen for at least 1 h before placement on litter in the floor pens. On d 14, the litter in all pens was contaminated with field-strain Eimeria by using a garden sprayer. The inoculum, consisting of E. acervulina, E. maxima, and E. tenella with a target dose of 40,000 oocysts/chick, was prepared from oocysts previously isolated from commercial broiler houses in Texas. Seven days (d 21) post spray application of oocysts, the oocyst uptake was confirmed microscopically by collecting fresh fecal samples from a representative sample of pens.
Body weights and FCR were determined on days of diet changes during grow out. As such, all birds and feed were weighed on the day of placement and then on d 14, 29, 40, and 50 of grow out to calculate performance parameters related to the experimental objective of the trial.
Statistical Analysis
Statistical analysis was performed using the GLM procedure of SPSS version 11.0 [18]. Data were analyzed using a 2 x 2 factorial ANOVA with differences in main effects deemed significant at P 
0.05. A significant interaction was present between diet and anticoccidial control method for d-14 BW; thus, these data were analyzed using a 1-way ANOVA. Means were separated using Duncan’s multiple-range test, with a significance value of P 0.05.
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RESULTS AND DISCUSSION
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BW
With respect to vaccination, BW of broilers fed diet B were heavier (P < 0.05) than broilers fed diet A on d 14 of age. A direct comparison was performed on d 14 because a significant interaction was present between the anticoccidial prevention method and diet. Broilers medicated with salinomycin fed both diets A and B were similar (P > 0.05) to both vaccinated treatments on d 14 (Table 2). Throughout the remainder of the study, BW were similar between the 2 coccidiosis control methods. With respect to diet, broilers fed diet B were heavier (P < 0.05) on d 40, but these differences did not persist through d 50 because both diets yielded similar BW at the completion of grow out. At the conclusion of the trial on d 50, no significant effect (P > 0.05) on BW was observed relative to the anticoccidial control measure or diet.
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Table 2. Body weights (kg) of broilers fed 2 diets varying in protein level with 2 control methods for coccidiosis
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Mortality-Corrected FCR
Differences were observed in mortality-corrected FCR during the starter period with respect to both diet and anticoccidial control measure (Tables 3 and 4). Medicated broilers had an improved (P < 0.05) FCR during the starter period compared with vaccinated broilers, and broilers fed diet B had an improved (P < 0.05) FCR compared with broilers fed diet A. During the grower period (d 14 to 29), medicated broilers yielded an improved (P < 0.05) FCR compared with vaccinated broilers, although no differences were observed with respect to diet. During the finisher period (d 29 to 40), broilers fed diet B yielded an improved (P < 0.05) FCR compared with broilers fed diet A, whereas no differences were observed during the finisher period with respect to the coccidial control measure. During the withdrawal period (d 40 to 50), vaccinated broilers had an improved (P < 0.05) FCR compared with broilers fed the medicated diet. This elevation in FCR in the latter group is likely due to removal of salinomycin during the withdrawal phase. No dietary effects were observed within the withdrawal period.
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Table 3. Cumulative mortality-corrected FCR of broilers fed 2 diets varying in protein level with 2 control methods for coccidiosis
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Table 4. Dietary period mortality-corrected FCR of broilers fed 2 diets varying in protein level with 2 control methods for coccidiosis
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When evaluating cumulative FCR during grow out, vaccinated broilers were associated with an elevated (P < 0.05) FCR compared with medicated broilers at d 29, whereas no dietary effects were observed. On d 40, significant differences were observed with respect to both experimental factors. Broilers fed diet B had an improved (P < 0.05) FCR compared with broilers fed diet A, and medicated broilers had an improved (P < 0.05) FCR compared with vaccinated broilers. At the conclusion of grow out (d 50), there were no differences between coccidiosis control methods, although diet B yielded an improved (P < 0.05) FCR compared with diet A. The use of the coccidiosis vaccine as a coccidiosis control measure resulted in broilers with equivalent performance parameters compared with salinomycin-fed broilers, regardless of dietary regimen.
The effectiveness of live oocyst vaccination in the generation of immunity and protection against subsequent Eimeria infection has been well documented [6–8]. The reluctance to implement vaccination programs within the US broiler industry to date is likely due to reports of reduced performance associated with vaccination [1]. The results of the current study indicate that vaccination with a nonattenuated, live oocyst vaccine for the control of coccidiosis does not result in rearing broilers with diminished growth parameters compared with broilers fed salinomycin, provided vaccination is coupled with an appropriate dietary program. These results are in agreement with the report of Williams and Gobbi [12], although these authors observed that vaccination significantly increased broiler BW compared with a medication shuttle program. Body weights of vaccinated broilers were numerically higher in the current study at the termination of the trial, although statistical significance was not observed. Danforth [6] also observed similar cumulative growth parameters in vaccinated roasters compared with roasters fed a medicated diet with a shuttle program composed of nicarbazin and narasin, although vaccination reduced BW until d 35 of age. Waldenstedt et al. [10] also observed significant reductions in BW and elevated FCR of vaccinated broilers compared with medicated broilers at 36 d of age.
Other reports have indicated reduced BW and elevated FCR of vaccinated chicks compared with medicated chicks during the starter period [4, 6]. A postvaccination decline in BW gain during the starter period was not observed in this study, with vaccinated broilers fed either dietary regimen having similar BW at d 14 compared with medicated broilers, although an elevation in FCR was observed during the starter period in vaccinated chicks compared with salinomycin-fed chicks. This elevation in FCR caused by vaccination was also observed during the grower period; however, the improved performance observed during the withdrawal period resulting from vaccination offset these differences by the conclusion of grow out. Removal of salinomycin from the withdrawal diet of medicated broilers resulted in an elevated FCR, presumably because of Eimeria exposure combined with the lack of immunity present in medicated broilers. Body weights of vaccinated broilers on d 14 indicate that vaccine-induced reductions in early BW can be overcome by dietary modulation. In vaccinated broilers, the increased protein level in diet B resulted in higher BW compared with broilers fed diet A on d 14, although this difference did not persist throughout the trial.
The general trend of reduced implementation of coccidiosis vaccination programs within mainstream US broiler production is likely a result of reduced performance, leading to an increased cost of production. After analysis of the 2 dietary programs evaluated in this study, which included costs of the anticoccidial control measure, differences were not observed with respect to the cost of production per kilogram of live broiler weight (Table 5). This lack of difference in costs was evident in spite of the increased costs attributable to elevated protein level in diet B compared with the lower dietary protein level included in diet A. The results of this study suggest that substitution of ionophoric chemotherapy by a vaccination program does not reduce the performance or increase the production cost of broilers reared under simulated industry conditions in the presence of field-strain Eimeria when an appropriate dietary program is used to ensure early vaccine establishment within the starter period of grow out.
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Table 5. Production cost1 including the dietary and anticoccidial control cost per kilogram of live broiler weight of broilers fed 2 diets varying in protein level with 2 control methods for coccidiosis
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CONCLUSIONS AND APPLICATIONS
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- Increased dietary protein (diet B) improves cumulative FCR.
- The early check in broiler weight commonly associated with live oocyst vaccination can be alleviated with increased dietary protein in the starter diet.
- The use of a live oocyst vaccine can result in broilers with cumulative performance parameters equal to broilers medicated with salinomycin.
- The cost of production was unaffected by substituting a live oocyst vaccinate for salinomycin to control Eimeria.
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ACKNOWLEDGMENTS
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The authors thank Phillip Hargis of Hargis and Associates (Springdale, AR) for technical assistance with diet formulation.
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REFERENCES AND NOTES
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- Allen, P. C., and R. H. Fetterer. 2002. Recent advances in biology and immunobiology of Eimeria species and in diagnosis and control of infection with these coccidian parasites of poultry. Clin. Microbiol. Rev. 15:58–65.[Abstract/Free Full Text]
- Yun, C. H., H. S. Lillehoj, and E. P. Lillehoj. 2000. Intestinal immune responses to coccidiosis. Dev. Comp. Immunol. 24:303–324.[CrossRef][Web of Science][Medline]
- Vermeulen, A. N., D. C. Schaap, and T. M. Schetters. 2001. Control of coccidiosis in chickens by vaccination. Vet. Parasitol. 100:13–20.[CrossRef][Web of Science][Medline]
- Williams, R. B. 2002. Anticoccidial vaccines for broiler chickens: Pathways to success. Avian Pathol. 31:317–353.[CrossRef][Web of Science][Medline]
- Chapman, H. D., T. E. Cherry, H. D. Danforth, G. Richards, M. W. Shirley, and R. B. Williams. 2002. Sustainable coccidiosis control in poultry production: The role of live vaccines. Int. J. Parasitol. 32:617–629.[CrossRef][Web of Science][Medline]
- Danforth, H. D. 1998. Use of live oocysts vaccines in the control of avian coccidiosis: Experimental studies and field trials. Int. J. Parasitol. 28:1099–1109.[CrossRef][Web of Science][Medline]
- Crouch, C. F., S. J. Andrews, R. G. Ward, and M. J. Francis. 2003. Protective efficacy of a live attenuated anticoccidial vaccine administered to 1-day-old chickens. Avian Pathol. 32:297–304.[CrossRef][Web of Science][Medline]
- Williams, R. B. 2003. Anticoccidial vaccination: The absence or reduction of numbers of endogenous parasites from gross lesions in immune chickens after virulent coccidial challenge. Avian Pathol. 32:535–543.[CrossRef][Web of Science][Medline]
- Danforth, H. D., E. H. Lee, A. Martin, and M. Dekich. 1997. Evaluation of a gel-immunization technique used with two different Immucox vaccine formulations in battery and floor-pen trials with broiler chickens. Parasitol. Res. 83:445–451.[CrossRef][Web of Science][Medline]
- Waldenstedt, L., A. Lunden, D. Elwinger, P. Thebo, and A. Uggla. 1999. Comparison between a live, attenuated anticoccidial vaccine and an anticoccidial ionophore, on performance of broilers raised with or without a growth promoter, in an initially Eimeria-free environment. Acta Vet. Scand. 40:11–21.[Web of Science][Medline]
- Williams, R. B., W. W. H. Carlyle, D. R. Bond, and I. A. G. Brown. 1999. The efficacy and economic benefits of Paracox, a live attenuated anticoccidial vaccine, in commercial trials with standard broiler chickens in the United Kingdom. Int. J. Parasitol. 29:341–355.[CrossRef][Web of Science][Medline]
- Williams, R. B., and L. Gobbi. 2002. Comparison of an attenuated anticoccidial vaccine and an anticoccidial drug programme in commercial broiler chickens in Italy. Avian Pathol. 31:253–265.[CrossRef][Web of Science][Medline]
- Sharma, V. D., M. A. Fernando, and J. D. Summers. 1973. The effect of dietary crude protein level on intestinal and cecal coccidiosis in chicken. Can. J. Comp. Med. 37:195–199.[Web of Science][Medline]
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- Animal Science Products, Nacogdoches, TX.
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SUMMARY
DESCRIPTION OF PROBLEM
