Is there a reliable test to check the titer of immunity before we revaccinate each year for flu, rhino, etc.? Why is a tetanus shot good for five or more years in humans and only one year or less in the equine?

I purchased a 3-year-old Thoroughbred gelding with a fractured knee. My veterinarian put him on lay-up for an additional four months of stall rest. I am concerned about nutrition during both the period of stall rest and the subsequent turnout.

I have a 2-year-old Quarter Horse gelding who has been in training for three months. When should I start giving him a joint supplement? Also, when should I begin giving him a vitamin supplement?