INFLUENCE OF GROWTH SELECTION IN TURKEYS ON RESISTANCE TO PASTEURELLA-MULTOCIDA

Four lines of turkeys, a randombred control (RBC2) started in 1966 and three sire lines (F, A, and B), were challenged with a field isolate of Pasteurella multocida (capsular serogroup A, somatic serotype 3, 4) at 6 wk of age. Line F, a subline of the RBC2 line, was selected for 28 generations for increased 16-wk BW and Lines A and B were primary b reeding sire lines from two commercial breeders. Each bird was inocula ted subcutaneously in the back of the neck with 1.2 x 10(7) washed bac teria. Mortality following challenge with P. multocida was higher in t he sire lines (54 to 65%) than in the RBC2 line (26%). There was no si gnificant difference in mortality among sire lines following challenge . These results suggest that the increased susceptibility to P. multoc ida in the F line in comparison to its control may be due to genetic c hanges resulting from selection for increased BW in this line.