The organization and daily routine of a wagon train depended on the danger expected from the Native American tribes into whose territory it had traveled, the terrain, and the size of the caravan. Mormon trains, in particular, had a semi military formation.
Side effects. Taken at normal doses, selenium does not usually have side effects. An overdose of selenium may cause bad breath, fever, and nausea, as well as liver, kidney and heart problems and other symptoms. At high enough levels, selenium could cause death.
The current recommended daily allowances for selenium are  70 micrograms (mcg) a day for men and 55 mcg a day for women. I recommend that you get at most 200 mcg a day as a supplement.