Fermaid-O is an organic source of nitrogen and nutrients, vs Fermaid-K and DAP which are not. I used DAP in past batches, but the thought of urea-derived ammonium salts kind of grosses me out. Fermaid-O is, well, at least it’s derived from yeast.

from Scott Laboratories’ site:


Fermaid O is the latest nutrient developed by Lallemand’s winemaking nutrient research team headed by Dr.
Anne Ortiz-Julien. Fermaid O is a blend of inactivated yeast fractions rich in organic nitrogen. Fermaid O does
not contain added ammonia salts (DAP) or added micronutrients.
The importance of organic nitrogen from yeasts is well known as a highly efficient nutrient source for wine yeasts,
especially when compared to inorganic nitrogen from DAP. In addition, Fermaid O consistently produces lower levels of
negative sulfur compounds, compared with DAP. With its high content of organic nitrogen, Fermaid O can help
winemakers achieve steady fermentations, while limiting temperature peaks. When inorganic nitrogen (DAP) additions
are NOT desired, the use of Go-Ferm® or NATSTEP™ and Fermaid O is recommended. With this combination, Go-Ferm or
NATSTEP provides needed micronutrients during yeast rehydration, and Fermaid O supplies critical nutrients and
survival factors to help the yeast avoid stressed conditions. Note: In low nutrient situations, yeast available nitrogen
(YAN) may be insufficient to avoid fermentation problems.


400 ppm 40 g/hL 3.5 lb/1000 gal

From this we see that for 400ppm YAN we need 40 grams of Fermaid-O per hectoliter. A hectoliter (100 liters) is 26.4 gallons. If we divide the 40g by 26.4 we get 1.5, so we need 1.5 grams per gallon of must. For a staggered nutrient addition schedule, that’s .75 grams per gallon at lag phase and .75 grams per gallon at the 1/3 sugar break.