PETA offers three different dispensers, because it is crucial to control the dispense rate of the treatment material for the health of the animals. With zinc especially, the toxic dose and the correct dose are so close together, that it is crucial to have the right dispenser. A one-size-fits-all dispenser is not safe. You must use the specific Zinc Dispenser for controlling facial eczema.
The Bloat Dispenser was made specifically for the liquid bloat material, and is available in two models: 12-hour units or the 24-hour unit. The 12-hour units specifically match the drinking rate of milking cows, while the 24-hour unit suits drystock.
The Multi-Purpose Dispensers have enhanced technology inside because they need to allow for solid material. They have been designed to meter magnesium sulphate, trace elements or salts into the water trough at the correct rate.
Also note, it is important not to mix bloat material with the salts in the same dispenser. If combined they will form a thick gel which will block the dispenser.
For more detail about how the dispensers work, including how the dispense rate matches the drinking pattern of animals, with How The Dispensers Work.