Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2003
Publication Date: July 25, 2003
Citation: Peterson, B.C., Bilodeau, A.L. 2003. Effects of recombinant bovine growth hormone on levels of the bacteria edwardsiella ictaluri in channel catfish (ictalurus punctatus). American Society of Animal Science Meeting. Vol. 81(Suppl. 1). p. 299. Technical Abstract: Research was conducted to examine the immunoregulatory role of recombinant bovine growth hormone (rbGH, Posilac) in channel catfish challenged with Edwardsiella ictaluri (E. ictaluri). A total of 240 fish (3.7 +/- .7 g) were assigned randomly to four treatments with three replicates each. The treatments were 1.) Con-Exposed (Sham injected by needle puncture and challenged with E. ictaluri), 2.) Con-Nonexposed (Sham injected by needle puncture and not challenged), 3.) rbGH-Exposed (Posilac, injected at 30 mg/g BW and challenged with E. ictaluri), and 4.) rbGH-Nonexposed (Posilac, injected at 30 mg/g BW and not challenged). Treatments were then randomized to one of each sampling day (1 and 5). Fish were maintained in 24, 120-L tanks (10 fish/tank) for three weeks prior to challenge. During this time, fish were injected (rbGH or sham) and specific growth rates were assessed. Fish were reinjected (rbGH or sham) two days prior to challenge with E. ictaluri. A genetic assay utilizing real-time PCR was used for detection and quantification of E. ictaluri and mortality was recorded daily. Specific growth rate was higher (P = 0.06) in rbGH-treated fish compared to sham injected controls (3.5 vs 3.0) prior to challenge. All non-exposed fish tested negative for the presence of E. ictaluri throughout the trial. On days 1 and 5, rbGH-Exposed fish exhibited lower (P < 0.05) levels of E. ictaluri when compared to Con-Exposed fish (0 vs 3,250 +/- 2,927) (cell-equivalents/100 mL whole blood) and (10,230 +/- 5,813 vs 62,294 +/- 34,315) (cell-equivalents/100 mL whole blood), respectively. Mortality was similar between rbGH-Exposed and Con-Exposed throughout the study. Reduced levels of E. ictaluri in rbGH-Exposed fish suggest an immunoregulatory role for rbGH in channel catfish.