My mare was on Equilibrium Low Energy, she is 14.2 and was on 3kg a day split between 2 feeds - 1 bag (15kg) lasted 5 days so worked out rather expensive, so put her on fibre plus by topspec, with topspec balancer, works out far more cost effective.
I retail Topspec, if you would like any recommendations, please email me rachael@byfleetsaddlery.co.uk
Rachael