3.1 │ The introduction of Hy-line brown roosters with ALV-J significantly increased the positive rate of ALV in the flock
Before the introduction of Hy-line brown roosters, the positive rate of virus isolation and p27 in the albumens in the flock was within 1% for two consecutive generations, and the peak egg production was about 70%. However, after the introduction of the roosters, the positive rate of virus isolation and p27 in the albumens increased to 5.4% (5/92) and 7.6% (7/92), respectively (Table 2). The peak egg production dropped to about 65% from 75%. Two breeding eggs from each positive hen were chosen for virus isolation with albumen, and only one albumen showed positive result (1/10).