Concept:Thin-shelled eggs in layers usually indicate a calcium deficiency in the diet.
Solution:Calcium is essential for the formation of strong eggshells.
If the feed lacks enough calcium, the hen produces eggs with weak or thin shells.
Adding a calcium-rich ingredient helps correct this defect.
Among the given options, oyster shell meal is a rich source of calcium.
Maize, soya bean meal, and cowpea are not primary calcium supplements.
Answer:Option D (Oyster shell meal)