For example, linseed oil meal isn't a high-quality protein. So, avoid it in late-pregnancy. The mare may not be able to eat as much in late pregnancy due to the size of the fetus plus the fluids and tissues of pregnancy. Data show that some mares don't gain any weight or may even lose weight in late pregnancy. Feeds should be easily digested.
Yeast cultures increase the digestibility of fiber, phosphorus, and protein.
So, consider adding yeast culture to the rations of mares in late pregnancy. They also need a supply of clean, fresh water. Give late-pregnant mares access to a trace mineralized salt. Use a mineral mix if minerals in the ration need to be balanced. Increases in calcium and phosphorus in late pregnancy are large, about 75-100 percent above maintenance.