This Yeast Nutrient is a blend of vital minerals/nutrients that aid in yeast activity during fermentation. (Zinc, Phosphorous, Potassium and Manganese) The recommended dosage is 40ppm (5g:25L). It should be slurried in a few liters of liquid and added to the kettle about 15 minutes before the end of the boil.
This is highly recommended when making yeast starters with DME. DME does not contain vital nutrients for yeast health, like zinc. It is beneficial to add yeast nutrient to your yeast starters.