An average Mare can be expected to produce up to 4% of her bodyweight in milk every day for the first eight weeks of her foal's life, and during this time, secrete up to 500 gms of Protein in her milk. 

When the Foal start to show more of an interest in solid food after those first 2 months, her milk will gradually decrease in quantity and quality, so much so that at around 5 mths she will be only producing roughly 1/2 what she produced initially (around 2% of her body weight)

Remember that the Mare will need heaps of nutritional support until it's time to wean.

Gradually introduce solid foods to the foal in  a creep feeder environment to give him access to some of the minerals that the Mare will not pass on through her milk, such as Copper, Zinc or Iron and Magnesium etc in any significant amounts

To help wean the Foal it is a good idea to start cutting back on the mare's daily grain ration to roughly 50% of what was fed her in those first 8 weeks

Monitor this page as there will be an exciting announcement over the next few months