Spent layers or Old layers are egg laying birds that are past their prime, whose output is increasingly irregular, rendering them economically inefficient.
As the Poultry Farmer, once your Laying birds or Layers chicken start showing you the following signs below, you just have to know that they are Old Layers or Spent Layers or maybe they are tired of laying eggs and at that point you just have to sell them off as they are no longer economical to raise for profit.
Some of the signs include:
(1) Laying fewer eggs than usual
(2) Their feathers starts dropping (Excess feathers pulling from their body)
(3) The cost of feed and inputs remains the same but their earning capacity is greatly reduced, etc.