I've heard of people feeding calf manna to their horses for a various reasons, though I've never tried it myself. Would you recommend this?
(Anonymous, United States)
In general, no. Calf Manna is what is called an all-stock product, meaning that it is made to feed all species (sheep, cattle, horses, etc).
Because it has to be safe for all species, it is not nutritionally "correct" for any species -- it has too much of some nutrients, and not enough of others (this is mostly the case).
Though some horses appear to do well on it, there are many better choices for increasing protein, putting weight on, or feeding foals and broodmares...
Calf Manna also has high amounts of grain (especially corn) that make it have even more of a negative effect on the equine digestive system.
With all the advances in equine feeds in the past years, Calf Manna is not something that I would feed to any of my horses.
Thank you for a great horse nutrition question!