A mature horse doing light work will consume about 1 oz. of salt daily. However, salt intake is quite variable between horses. As long as a horse has plenty of water available, salt toxicity should never be a problem. Salt can be provided in block or loose form. The block form is handy to use and decreases waste, but it takes longer for a horse to lick off what it needs.
Loose salt is easier to eat, but is often wasted.
In general, if a horse needs to consume a lot of salt, such as an endurance horse, loose salt is recommended. Most idle horses and pleasure horses will easily meet their needs with block salt. It is recommended when feeding salt to always use trace mineralized salt. An exception to this may be the horse that is eating large amounts of salt as it might produce a trace mineral toxicity. Trace Minerals Ohio is deficient in the trace minerals iodine and selenium, and sometimes deficient in copper and zinc.