Variation in resistance to Pasteurella multocida among Turkey lines

Previous research has shown that a line (F) of turkeys selected long-term f or increased 16-wk body weight was more susceptible to challenge with washe d Pasteurella multocida than a randombred control line (RBC2), the base pop ulation of F. A previous study also indicated that the mortality of the F l ine following challenge with P. multocida was similar to that of sire lines from two of the three major primary breeders. The purpose of the present s tudy was to compare the resistance of the sire line from the third major pr imary turkey breeder (C) not previously studied with that of the F and RBC2 lines to determine whether there is variation in resistance among the sire lines from the three major primary breeders. The sire lines from all three primary breeders were used in the production of commercial turkeys. Body w eights of the F line were greater than those of the C line at the time of c hallenge with P. multocida. Both the C and F lines were heavier than the RB C2 line. The birds were challenged at 6 wk of age with a field isolate of w ashed P. multocida (1.2 x 10(7) organism per bird of capsular serogroup A a nd somatic serotype 3,4). Mortality was recorded daily for 14 d. Mortality following challenge with P. multocida was higher in the F line than in the C line, and both large-bodied lines had higher mortality than the RBC2 line . Based on the present results and those published in the literature, there may be variation in resistance among commercial sire lines from the three major primary breeders.