Effects of combined treatment with recombinant bovine somatotropin and immunization with live oocysts on performance of broiler chicks raised in coccidia-seeded floor pens.
In our laboratory, preliminary studies have indicated that recombinant bovine somatotropin (rbST) can stimulate protective immunity against coccidia infection. A floor pen trial on coccidia-seeded litter was run to further test its activity as an adjuvant during immunization of chicks with a live oocyst vaccine. Five hundred day-old male broiler strain chicks were randomly assigned to five experimental Treatments: 1, medicated controls; 2, unimmunized, not treated with rbST; 3, unimmunized, rbST-treated; 4, immunized, not treated with rbST; 5, immunized, rbST-treated. Each treatment consisted of four pens of 25 chicks each. At the end of the growout period (7 wk), the chicks in Treatment 1 (medicated controls) had the highest mean BW, but mean BW of chickens in Treatment 3 (rbST treatment only) were not significantly less. On the other hand, the mean weights of chicks in Treatments 4 (immunized only) and 5 (immunized plus rbST) were significantly reduced, and not different from those of the untreated chickens (Treatment 2). However, when challenged at 3 wk, the chicks in Treatment 5 had a mean combined total lesion score that was significantly lower than that from Treatment 3, indicating that they had developed a higher degree of specific immunity, but of the expense of weight gain. The results suggest that rbST has a potential for use as an adjuvant with live oocyst vaccination, but that the ratio between rbST dose and numbers of oocysts in the live vaccine needs to be carefully controlled.
Allen
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USDA, Agricultural Research Service, Beltsville, Maryland, USA.
Danforth
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D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D002417:Cattle; D002645:Chickens / Q000254:growth & development* / Q000276:immunology / Q000469:parasitology*; D003048:Coccidiosis / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D004539:Eimeria / Q000276:immunology* / Q000302:isolation & purification / Q000502:physiology; D013006:Growth Hormone / Q000494:pharmacology*; D006799:Housing, Animal; D008297:Male; D011201:Poultry Diseases / Q000276:immunology / Q000503:physiopathology / Q000517:prevention & control*; D016052:Protozoan Vaccines / Q000008:administration & dosage / Q000276:immunology; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000276:immunology
D000913:Antibodies, Protozoan; D016052:Protozoan Vaccines; D011994:Recombinant Proteins; D014613:Vaccines, Attenuated; D013006:Growth Hormone