Yes, those guidelines are the ones in question.
Also, I know it is completely not true that they have 3 to 6 months of storage. Maybe SOME horses...but others run out very fast. I think the more challenging the environment they need to keep healthy in, the faster they run out also. I think that is a very high estimate personally.
Hay looses beta carotene/A making stuff at about 10% a month after is is cut (E even faster 70% after a WEEK as a note which is also very important) If your hay is cut in the spring, by the time you feed it, it has lost a great deal of skin helping nutrients. Somewhere, the deficit needs to be made up. Horses on hay year round certainly need much more A and E.
Considering horses can utilize beta carotene out of good pasture at whatever rate they need, it stands to reason those rates vary per horse In the winter when on the same exact hard ration they recieve in the summer plus deficient hay, many become deficient. I notice it the most right around December-January here.
Someone needs to do a study on this. Its SO important and so many people don't supplement clearly low horses because they are afraid of overdosing. You should bump horses up in the winter during hay season to make up for the lack of grass. I find cheris suggestion of 5 CCs of cattle injectable over feed once a month to be perfect. No ODing. No rain rot. No guessing how many carrots I need to feed. Plus its cheaper. JME. Does Your Horse Need Extra Vitamins? Maybe... - Kentucky Performance Products