When laying hens do not appear to be in good health or show behavioural changes, steps shall be taken to establish the cause and appropriate remedial action shall be taken, e.g. treatment, isolation, culling or correction of environmental factors. If the cause is traced to an environmental factor in the production unit which it is not essential to remedy immediately, remedial action shall be taken as soon as practicable and in any event when the accommodation is next emptied and before the next batch of laying hens is put in.