Viremia, PCR results, and the influence of ALV-J infection on the body weights of birds (X±SE). (A) Influence of the viral infection on the body weights of birds. Each mean body weight, followed by a different lower-case letter, was significantly different (P < 0.05) based on Duncan's multiple range test. (B) ALV-positive identification by ALV P27 antigen ELISA; an S/P value greater than or equal to 0.2 was regarded as positive. (C) PCR was used to identify the ALV-J in the samples of 10 birds. The results showed that all ALV-positive samples were ALV-J; C1-C4, PCR results of 28, 56, 77, and 175 d samples. M, DL2000 DNA marker; +, DF-1 cells infected with GX14YYA1 used as positive control; -, uninfected DF-1 cells used as a negative control; 1-10, samples. Abbreviation: ALV-J, avian leukosis virus of subgroup J.