Objective The avian leukosis (AL) eradication protocol in yellow feather breeders was evaluated and the effects of different albumen samples from the same breeder chickens on the results of avian leukosis virus (ALV) detection were compared.

Method A total of 2 691 albumen samples collected from a yellow feather breeders of Guangdong Province were tested using ALV p27 antigen ELISA.Seventy plasma samples were collected from corresponding hens based on the different S/P intervals results for virus isolation in CEF and DF-1 cells respectively, and the results were analyzed.PCR was used to identify subgroup.

Result and conclusion A total of 243 positive samples were detected in this local breeder flock, and the ALV p27 positive rate was 9.03%(243/2 691).The virus isolation ratios (VIR) at different S/P intervals were found as follows: both 100% VIR in CEF and DF-1 cells of hens' plasma samples with albumen S/P ≥2.0; both 88.9%VIR with 1.5≤S/P < 2.0; both 85.7% VIR with 1.0≤S/P < 1.5; 60%-75%(CEF)and 40%-50%(DF-1) with 0.2≤S/P < 1.0;62.5%(CEF)and 50% (DF-1) with 0.1≤S/P < 0.2; 27.2%(CEF)and 9.1% (DF-1) with S/P < 0.1. The PCR detection showed that six of seven CEF⁺DF-1^- proviral DNA were positive with endogenous ALV-E and one positive with ALV-J.The results indicated that in albumen ELISA detection, the higher S/P value of positive albumen samples, the more likely exogenous ALV viremia positive in their corresponding hens. The corresponding hens of low S/P value of positive albumen samples were caused by a certain proportion of endogenous virus; it is noteworthy that exogenous ALV can still be isolated from some ELISA negative chickens at the beginning of eradication. This study suggests some "misdiagnosed" and "missed" chickens may be caused by using only one method of albumen p27 antigen ELISA.