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Title: EFFECTS OF COMBINED TREATMENT WITH RECOMBINANT BOVINE SOMATOTROPINTM AND IMMUNIZATION WITH LIVE OOCYSTS ON PERFORMANCE OF BROILER CHICKS RAISED IN COCCIDIA-SEEDED FLOOR PENS

Author
item Allen, Patricia
item Danforth, Harry
item COMENS-KELLER, PATRICIA - MONSANTO CO, ST.LOUIS, MO

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Coccidiosis costs the American poultry industry approximately $350 million a year. Control has been primarily through the prophylactic use of anticoccidial drugs. Because many coccidia species have developed strains resistant to a large number of these drugs, new methods of control are being sought. Vaccination is an appropriate alternative control measure, and there are several live oocyst vaccines available. However, these may fail where strains of coccidia not included in the vaccines are prevalent. Use of a non-specific immunostimulant might overcome this problem. We have tested recombinant bovine somatotropin (rbST) as a non-specific immunostimulant in an experiment where broiler chicks were immunized with live oocysts and grown out in a coccidia- seeded floor pen, an environment simulating a commercial poultry house. Treatment (.09 mg/chick subcutaneous injection at hatch) with rbST alone was protective of weight gain as illustrated by mean final body weight, suggesting that rbST stimulated immunity gained from ingesting oocysts from the seeded litter. Although the mean final body weight of chicks treated both with rbST and live vaccine was lower, chicks in this group has lower lesion scores upon challenge suggesting that this treatment elicited more specific immunity but at the expense of weight gain. The results indicate that rbST has a good potential for use against coccidiosis as a nonspecific immunostimulant in combination with live vaccines.

Technical Abstract: In our laboratory, preliminary studies have indicated that recombinant bovine somatotropin (rbST), given subcutaneously at hatch at a dose of 0.09 mg/chick) 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. non-immunized, non-rbST-treated, 3. non- immunized, rbST-treated, 4. immunized, non-rbST-treated, 5. immunized, rbST-treated. Each Treatment consisted of 4 pens of 25 chicks each. At the end of the grow out period (7 wk) the chicks in Treatment 1 (medicated controls) had the highest mean body weight, but mean body weights 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 the untreated chickens (Treatment 2). However, when challenged at 3 wk the chicks in Treatment 5 had lower lesion scores over all than chicks on the other Treatments, indicating they had developed a higher degree of specific immunity, but at the expense of weight gain. The results suggest that rbST has a good 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.