I had not heard of it so looked it up, to me it seems very expensive at over £17 per 15kg bag when the recommended rate of feeding is 1kg per 100 kg body weight, that works out at 1 bag every 3 days fed at the maximum daily rate which you may need for weight gain, or 1 bag every 6 fed at the lower end, for the average 500 kg small horse/ larger pony, you may be able to feed less but if the purpose is to put weight on there are probably better and cheaper ways to do so.
I would prefer to feed straights as a base and add a balancer or supplement to give the vits and mins.
It's a 20 kg bag but I'd still be going through 1 a week. I've started to look into straights yet the high starch values are putting me off. They do a cereal version of the mix above which is cheaper but the starch content is 24%
Straights don't have to be cereals or high in starch - look at things like unmollassed beet pulp, grass products, micronised linseed and other oil-based straights.
I've always feed her alfa a with oil, linseed, sugarbeet and equalibra balancer. She looks good on it but costs me a fortune. I think the alfa makes her sharper too. Its all manageable, Just considering if there are better alternatives.
There is alfafa in it so if you want to avoid that try soaked grassnuts, cheap and cheerful, plus a grass chop and linseed with a supplement to top up the vits, we have two on Equimins which is high spec and probably cheaper than the equilibra.
I'd stop the equalibra and feed Equimins Advance Complete instead. Its a much better spec and works out cheaper.
Then I'd stick with the sugar beet if you like it, but same as BP I'd go for grass nuts and linseed. You dont need alfa a oil and linseed so either option you can drop that. If you need more condition I'd drop the linseed and add rice bran oil pellet. Its a lot more concentrated and you need to feed a lot less of it if you need weight gain.