My first answer will be, it depends on the weather in late winter and early spring. Feeding the suckling mare well means ensuring good growth of the foal without harming the breeding capacity of the mother. Nutritional requirements during pregnancy are increasing very gradually and late. Lactation is the physiological state that demands the most nutritional intake: the needs of the mare at the beginning of lactation represent twice its maintenance needs. There are two cases, the first is if the milling is offset in relation to the growth of the grass (before January-March, or after n June-July). The quantity (<5 cm height of grass) and / or the quality of the grass offered (grass mounted on the ear) is insufficient: It is necessary to supplement with good quality forage (wrapped / hay harvested young), and Complementary food to meet its needs for quality protein.
The second case is when foaling is synchronous with the growth of grass (spring). The quantity (between 5 and 15 cm height of grass) and the quality of the grass (leaf stage) offered are sufficient:
Supplements (energy and protein) are not necessary. Check regularly (every 2 days) that the quality and quantity of grass are sufficient.