I can't give you any concrete guidance on this but you could work it out by either using relative body mass (human weighing 14 stones drinks 20ml of 10ppm a day so cow weighing 24 would need to drink X ml of 10ppm) or by amount of water drunk per day (human drinks 6l day & 30ml CS, cow drinks 2l day so 10ml CS). At the end of the day though you'll probably need to change whatever you give them just through trial & error, see if its having any effect, if not increase it.
How much drinking water does your stocktank hold? also I'm presuming it is metal - this wouldn't be the best container for cs as it'd lose its potency.
Incidentally I did hear some time ago of farmers using CS soaked mats or trays containing cs & walking their cattle through it to get rid of infections on their ?feet/hooves?.