The goal is to prevent pregnancy diseases (milk fever, pregnancy toxemia) in the ewe, in order to do so producers need to provide all the nutrients the ewes need to maintain a healthy pregnancy. Not only does the ewe need the right nutrients to maintain herself, but she also needs to maintain the growing lambs in utero, udder development, and the development of colostrum.  The best indicator you did your job correctly with feeding the ewe is the color of the colostrum, once she lambs. If the color is a bright yellow color and very thick, the ewe has been fed correctly, a pale yellow and thin  consistency would indicate the ewe was lacking requirements in her diet prior to giving birth.

 
The last 4-6 weeks prior to lambing is a very critical phase in the flock, for both the ewe and the lamb(s). The ewe will require more energy and protein than she has required previously and it will double or triple if she is carrying more than 1 lamb. "Energy is especially important during late gestation as it affects lamb size and vigor at birth. Lack of energy results in small, weak lambs that are more prone to create problems for the shepherd and many of these are at increased risk for mortality."         
(Mike Neary-Purdue Sheep Specialist)

Another issue sheep farmers have to deal with is the lambs are growing quite a lot in the last 4-6 weeks and are taking up more and more space in the ewe. This occurring will cause the ewe to eat 25-35% less than her original diet. That is why it is very important to slowly increase the nutrient density of the ewe's diet to go along with the fetal growth.

A Bred ewe that is roughly 160 pounds should be on a 14% protein diet, along with free choice minerals and vitamins throughout her gestation. This will allow is the ewe to maintain a healthy pregnancy and weight, a good supply of minerals will also ensure healthy and vigorous lambs at birth. 

Body Condition Scoring is another critical issue sheep producers need watch. This will help determine what feed requirements are needed for the ewes. The ideal BCS at lambing should be between 3-3.5, below a 3 producers tend to see pregnancy diseases in the thin females and above a 3.5 we see the same for being too heavy. 

All of the pregnancy diseases can be prevented from proper nutrient and management. If you are looking for help with these requirements your veterinarian can work closely with your nutritionists to set up a plan for your operation.