What sort of diet should my mare have??

I own a 7 year old QH x arab mare who Is going to be used as a pony club horse as well as pole bender and barrel racer. She can't eat certain hay or chaff because she scours.
Would this be an okay diet:
- grass 24/7
- a biscuit of paddock hay in the morning
- and two scoops of chaff with a supplement in it at night.
It sort of sounds a little to much but she's a little under wait and it's winter here so, Is that to much or just right and what supplements would she need.

Hi,

Firstly, not knowing what your grazing's like or the hay, can't comment on whether it's not enough or too much, but if she's been on this diet for some time & still underweight, I definitely wouldn't say it's too much. Horses need a minimum of 1.5-2% bwt daily of forage. For weight gain, 2.5-3% or more. You can also feed ingredients such as beet pulp or such, which is a high energy, high fibre but low starch alternative/additive to the chaff.

Regarding her scouring, sounds possibly due to hind gut acidosis, so likely sugary/starchy feeds at fault. 'Good quality' improved grass hay such as rye for eg can be a problem there. Fresh grass will be the same - depends what it is, etc as to whether it could be problematic. Too much alfalfa, clover or such can also be a prob. Oaten chaff/hay can be quite high NSC & can also include oats, so be aware of that. You can always soak the hay/chaff for a few hours & drain it to leach out some excess sugar.

Re her weight, has she been wormed effectively, teeth done, checked/treated for ulcers, particularly after the scouring? Probiotics may be a good move too, especially after gut upsets such as that or drugs. Re supplements, you need to find a good quality supp that fits your horse's specific diet. One good way of doing this is to get onto feedxl.com

Thank you for posting. She is slightly under weight but I have only just got her home so she should put on some weight. Thank you