Carbohydrates are the major source of energy. Quantitatively, energy is the most important item in the sheep's diet. Major sources of energy for sheep are grazed forages, hay, silage, and grains. Optimum energy intakes from these sources result in efficient reproduction, growth, lactation, reproduction, and wool production. However, excessive energy consumption can lead to decreased efficiency because of excessive fattening, which can reduce growth rate, lower milk production, increase reproductive failure, and decrease efficiency of wool growth.
Energy is the most common limiting nutrient encountered in sheep production, especially for ewes.
Inadequate energy intake causes slow growth, weight loss, reproductive failure, decreased milk production, lowered resistance to diseases and parasites, and increased mortality. Only that portion of the daily ration that is actually digested and absorbed from the gastrointestinal tract benefits the animal. But, if these feedstuffs are fed as the complete diet, excess water content sometimes causes an energy deficiency because sheep simply cannot consume enough dry matter for their productive functions. Energy requirements vary dramatically through the annual production cycle of ewes. Maximum energy intakes are required by ewes during late gestation and lactation.