How much is too much (vitamins & minerals)

[julie.rockley]

How do I know if my horse is getting the right amount of vits and mins?
ATM he is fed on Balanced horse feeds Showmix, ultimate balancer, and Alfa beet.
He is slightly underweight for my liking he is thoroughbred 15.3 and 24.
I have been recommended to try the Cush care instead of Alfa beet but then swap the show mix for 'just grass'
Any ideas

 

[Chinchilla]

Following

 

[Theocat]

You can't know if you don't know what your grass and forage contains.

Short of getting analysis, you just need to look at the horse in front if you, and gauge how they look.

 

[wkiwi]

Each mineral or vitamin has different recommended amounts (based on a best guess from research i.e. doesn't mean that it will be ideal for your horse). If some are given in excess then it doesn't matter, but others can be toxic e.g. a double dose of selenium is toxic, excess vitamin C also has side effects. Some will interfere with the absorption etc. of another i.e. if you feed mineral X then it might stop mineral Y from working and the horse ends up with a deficiency of mineral Y even though it is getting enough in its feed.
For this reason, never feed more than one supplement source of vitamins/supplements and make sure it is from a very reputable company (not someone mixing a formula together on the kitchen table).
A research project was done some decades ago that found a lot of event horses had problems because they were OVER supplemented.
Not sure why you are giving a mix plus a balancer, unless it is the amounts involved?(haven't looked at ingredients of the show mix but most mixes already have vits/mnls added and balancers are usually for those not getting them from elsewhere e.g. fattys who can't have normal feed).

As theocat says, knowing what is in grass and forage is important. If your paddocks are deficient in something then it is best to treat the paddock (fertiliser) rather than the horse and it is always important to know what fertiliser has been used (e.g. don't add selenium to the fertiliser AND give a supplement with selenium in).
If you suspect the horse has a deficiency then testing is best. Normal supplements stay within 'safe' ranges and so won't provide the extra for a deficiency.
Nutrition is a massive subject and far too big to cover in a forum. Being too thin can be caused by many many things, from over rugging to not enough calories (i know of one person that fed a TB a CUP of mix a day !!!!!) so best to get a vet to look at your actual horse, have blood tests done, talk to them about what you are feeding and the amounts etc, then discuss the best plan for that individual horse.
PS presume you have had teeth checked, worming etc,

 

[Shay]

You are already doubling up. The balanced show mix says quite clearly that when fed to recommended amounts no further supplementation is needed. Yet you are also feeding a balancer designed to supplement a forage only diet.

Its really hard to give good nutritional advice without seeing the horse but your feed solution right now seems unbalanced. I would opt for either unlimited high quality forage, the balancer and possibly a sugar beet based top up. Or compound feed to reccommended amounts and a chaff.