Wow they look great.
Ziggy and Llwyncwn, can I ask what you fed them on to get them looking so good?
My sister is picking her new horse up this weekend and she needs to gain some weight/topline.
I fed him a basic fibre and oil diet with one magic ingredient. The diet was HiFi Light, D&H Country Cubes, Speedy Beet and veg oil. The ingredient which sorted his head and hind gut out was Coligone. Lots of turn out and plenty of Dr Green together with a regular routine, your sister will soon turn her new mare around.
I had problems feeding my mare as she can't tolerate any kind of cereal, she goes bonkers and the weight just falls off.
Last summer I did a feed trial for Winergy Equilibrium (a conditioning feed based on fibre and oil, no cereal and very low starch) which was a revelation. The third pic that I posted was my 'after' pic that I sent to Winergy after four weeks on the feed.
Sorry, thats a shameless plug, but I thought this feed was amazing, so much so that I've got sacks of it stacked up in my shed ATM ready for this winter. As Llwyncwn says you want to base whatever you feed on fibre and oil, and get them onto good grazing where possible too. Good luck