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SCHERING-PLOUGH ANIMAL HEALTH
technical services bulletin
Clostridium perfringens Type A Toxoid:
Field Efficacy in Broiler Flocks Without Subtherapeutic Antibiotics
Part II: Ionophore Trials
The efficacy of maternal antibodies against the alpha toxin of Clostridium perfringens (Cp) was tested in a series of field trials in the USA. Anovel Clostridium perfringens Type Atoxoid was administered to a total of 863,760 breeder pullets at four complexes belonging to a large broiler integrator. Flocks were vaccinated at 10-12 weeks and again at 18 weeks of age. Vaccination of pullets prior to laying provides passive antibodies for the protection of the progeny.
Three of the complexes were “big bird” operations, growing broilers over 5.5 pounds. One of the complexes grew “small birds” weighing an average of 4.0 pounds.
The integrator maintained replacement pullet flocks of similar age that did not receive the novel treatment. Broiler progeny of those hens served as the controls. Standard ionophore + chemical anticoccidial products were used for coccidiosis control in all flocks, but no growth promotant antibiotics were used in the ration.
Necrotic enteritis (NE) was a sporadic problem on some of the farms, and increased mortality events were routinely treated with therapeutic antibiotics. Over the duration of the trials, there were no changes in the patterns of occurrence of NE in the test farms.
Key Points
Performance of the progeny of C. perfringens Type A Toxoid-vaccinated hens was compared to that of control broilers in four complexes feeding ionophores without subtherapeutic antibiotics.
Progeny of the toxoid-vaccinated hens demonstrated statistically significant improvements in:
• Livability
• Feed Conversion
• Calorie Conversion
• Adjusted Calorie Conversion
• Standard Cost
Test Flocks Matched to Controls
Progeny from toxoid-vaccinated parent flocks and non-vaccinated control parent flocks were placed on grow-out farms according to typical hatch placements.
Following placement, the integrator identified those farms which contained at least 70% of birds from test breeder flock eggs, and compared performance parameters to control farms of similar size and average grower performance during the same processing week.
Live Broiler Performance
Statistical analysis (Paired T-test) was conducted on each individual broiler complex (Table 1, columns A- D). The progeny of flocks vaccinated with C. perfringens Type A toxoid exhibited positive trends in livability, feed conversion, calorie conversion, adjusted calorie conversion and standard cost, with statistically significant improvements in each of these categories at individual complexes.
Table 1 Live Broiler Performance Comparison C. perfringens Type A toxoid progeny vs. Standard Broiler Progeny
Light grey shading indicates numerical difference favorable to Cp type A toxoid flocks Dark grey shading indicates statistically significant difference favorable to Cp type A toxoid flocks * p<0.1; **p<0.5; ***p<0.01
Pooled Complex Results
Researchers pooled the sample data for all complexes to see if the multiple positive trends that failed to demonstrate statistical significance within a single complex would demonstrate significance when all flocks were evaluated together (Table 1, last column).
Data from 193 broiler farms containing at least 70% progeny from breeders vaccinated with C. perfringens Type A toxoid yielded statistically significant improvements in livability, feed conversion, calorie conversion, adjusted calorie conversion and standard cost.
Conclusion
Progeny of parent flocks vaccinated with a C. perfringens Type A toxoid demonstrated improved livability, feed conversion, calorie conversion, adjusted calorie conversion and standard cost in flocks fed standard ionophore + chemical anticoccidial products without growth promotant antibiotics. These improvements may be due to improved control of clinical or subclinical necrotic enteritis in vaccinated flocks.
