Calf Manna "active ingrediant" as far as protein goe is soybean meal.
The protein content in CM is (off the top of my head) around 25%, which
is alot of protein. Sarah Ralston and I both posted some comments on
protein a few weeks ago that you might want to go look up in the
archives. The bottom line of those discussions was that endurance
horses that are done growing only need somewhere between 9-11% protein,
which is going to be provided if you're feeding a good quality hay like
bermuda or even a small amount of alfalfa. Protein might be slightly
lacking if you're feeding a poor quality hay. Protein quality is also
going to be improved in most cases by providing the ration from several
different feed sources---this means hay plus a mixed grain, not more
supplements. If you feel you need to supplement the protein, Calf Manna
or just soybean meal pellets are a good source, as the "protein quality"
(balance of essential amino acids) is very good. However, protein is
one of those things where too much can be as bad as not enough, so feed
with a light hand---Dr. Ralston suggested maybe a half pound, and I
agree with that as well. If your hay source is even halfway decent,
less or none at all is probably sufficient.
Keep in mind that too high a protein seems to be increasingly documented
as contributing to metabolic failure in performance horses (that means
that beyond a certain point, protein takes away from rather than adds to
the performance) and is also being attributed to as a factor in bone
problems in growing horses. Other problems, such as skin and
temperament problems can also be affected in some horses being fed high
levels of protein.
The other thing to keep in mind is that most horses that are overfed
protein and underfed energy. If your horse isn't performing up to the
levels you're expecting, you might try supplementing energy in the form
of grain or fats before you go supplementing protein content in the
Hope this answers your question