Livestock eat grass and farm by-products that cannot be digested by people and convert them into milk, meat, and eggs. Dairy products in particular are a very effective way of restoring malnourished people to health, fast. Furthermore, animal manure is an excellent natural way to enrich the soil, so farmers can grow much higher yields of crops and vegetables. By keeping animals as well as growing crops, farmers spread their risks. They use their animals as a type of 'savings bank', selling a calf when a need such as a medical bill arises.