highly significantP<0·001
Nine of 10 birds shed virus after onset of lay compared with only two in the three-and-a-half weeks before, and there was a highly significant increase (P<0·001) in the overall number of virus isolations during this period.
Nine of 10 birds shed virus after onset of lay compared with only two in the three-and-a-half weeks before, and there was a highly significant increase (P<0·001) in the overall number of virus isolations during this period.