Concept:Iron is essential for making haemoglobin, which is needed for proper blood formation in animals.
Explanation:Iron is an important mineral in the diet of livestock.
It forms a key part of haemoglobin, the protein inside red blood cells.
Haemoglobin carries oxygen from the lungs to all body tissues.
Without enough iron, livestock cannot produce sufficient red blood cells.
This can lead to anaemia and weakness in the animals.
Therefore, iron is mainly used for blood production rather than for teeth, feathers, or hair formation.
Answer:D. Blood production