Re: mum weanin 8 wk old foal already ???????
Some mares get fed up with babies after a few months, she obviously is one of them going on her previous foal.
Most feed companys do mares milk replacers that can be fed up to 3 months
http://www.baileyshorsefeeds.co.uk/studareahome/studproducts/maresmilk.htm
We orphaned a foal that had been 'weaned' from mum at a market at 3 months and fed him a replacer for a while, he was soon into feed and hay. The owner of the mare doesn't sound very helpful!
Don't worry too much if he looks a bit ribby, most foals do, better a bit ribby than overweight for babies, going on the pictures he looks in good condition. I'd try him on the replacer for a month and go from there.