Mainland Poultry has isolated over 550,000 free-range hens as a precautionary measure after New Zealand's first two cases of the H5N1 bird flu strain were detected last week. Photo / 123rfMainland Poultry has isolated over 550,000 free-range hens as a precautionary measure after New Zealand’s first two cases of the H5N1 bird flu strain were detected last week. Photo / 123rf