Concept:Waste products from livestock processing can be recycled into useful feed ingredients for poultry.
Explanation:Blood and bones are common slaughterhouse by-products.
They are dried and ground into blood meal and bone meal.
Blood meal provides a high amount of protein for poultry growth.
Bone meal supplies calcium and phosphorus needed for strong eggshells and bones.
Therefore, blood and bones are widely used in poultry rations.
Other options like hides, hoofs, fur, and skin are not suitable feed ingredients.
Answer:B. blood and bones