Generally yes, the problem is marketing and what a company calls their product LOL I consider a general v/m supplement to be fairly useless, as almost none of the nutrients are there in any meaningful amounts
A few forage balancers are more “complete” than most. The MadBarn products, something like High Point Grass and Arizona Copper Complete (maybe Lonestar Trace? not as familiar with that one) from Horsetech, are 4 that come to mind. Some may call them a v/m supplement, others call them a forage balancer
Most - California Trace, Vermont Blend, KIS Trace, and more, are very bare-bones for what’s almost universally low - copper, zinc, some have amino acids and magnesium some don’t, some have added manganese for the areas that are usually low (AZ Copper Complete for example), that sort of thing. Oh, they usually have iodine as well.
I wouldn’t start reducing fat for a PSSM1 horse.
Most PSSM/MIM horses don’t start showing issues until 5-6-7, after the high energy needs of growth are behind them
That’s a bit more than 1/2lb (1.08lb/qt) so insignificant calories. If he gained weight, it was likely due to more or better quality hay at your place
As long as you’re feeding ample Vit E (often needed in higher amounts for these guys), his Se level is good (bloodwork), then the diet sounds totally appropriate, especially with the addition of the AlCar for the MIM/PSSM2 issues. At this point it sounds like the bases are covered (see the above about fat)
The only exception is that with PSSM2/MIM he may start needing more, and higher quality protein . This could be more alfalfa, adding BCAAs, adding whey isolate protein (isolate’s important, that’s the removal of almost all lactose), to support his muscles.
