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.
Environmental stress alters the energy requirements of all classes of sheep.
Protein Sheep have higher protein requirements per unit of weight than many other ruminants because of the extra protein needed for wool growth. Protein within the sheep's body is in a constant state of flux with degradation and synthetic activities occurring simultaneously. Usually, the quality of protein is less important in the diet of mature sheep than is the quantity. In turn, microbial protein is enzymatically digested in the lower GIT of sheep to yield amino acids for absorption. Requirements for protein, like energy, are affected by the stage and level of production.