There are two methods that are used to balance a diet. The algebraic and Pearson's square are widely used but with the use of computers has led to innovative approaches to balancing rations. Most nutrition consultants and feed stores are now using computer programs to balance their diets. The only time range ewe's need to be fed is if they are either experiencing inclement weather or if they are confined for shed lambing. In these instances you can feed them the same way that you would if they were farm flock ewe's.
Gestation occurs during the winter when forage nutrient contents are lowest.
During this time alfalfa hay is usually supplemented of choice. Energy, protein, phosphorus, and vitamin A are the nutrients that are limiting for range ewes. Energy is usually the most limiting in winter because of limited forage available. Usually during this time grain is used as a supplement to the ewes diet. Body condition scores are the best indicator of the nutritional status of range ewes and are an initial indicator of nutritional adequacy of available range forage.