Final answer:
Secondary foods like vitamins and minerals supplement an animal's diet when primary sources don't suffice. They are essential for metabolism, health, and reproduction, and must be included in a balanced diet.
Step-by-step explanation:
Secondary foods, such as vitamins and minerals, are essential in small quantities and act as additional nutrient sources when the primary food source is not adequate or abundant.
They serve various functions, including acting as cofactors and coenzymes for metabolic processes.
While the animal body can synthesize many molecules from organic precursors, it requires these essential nutrients from food because it cannot produce them on its own.
These are crucial for processes like biosynthesis and ATP production, and for maintaining good health and reproductive capability.
Therefore, a balanced diet that includes these essential nutrients is necessary for animals.