Too much concentrate in ruminant and other fermenter diets can be harmful or fatal. Fiber exists in many forms, some more digestible than others. Carnivores and omnivores cannot derive significant E from fiber. Fore- and hindgut fermenting herbivores can derive much of their energy from these compounds. Produces a bulkier feed which may reduce intake of other nutrients.
Fats can be important E source in some omnivores and many carnivores.
Fats are easily digested by most animals, although high concentrations can be problematic for some herbivores. In some species, feeding extra fat in late gestation and during lactation may increase survivability of neonates due to increased fat levels in milk and increased fat cover in the young animal Many animals, will eat to meet their energy needs. When E needs are met, appetite is suppressed. High levels of fat in a diet can increase E to a point where intake is reduced. This may affect the amount of other nutrients taken in.