Dave Beede, dairy nutritionist at MichiganStateUniversity, offers this quick thumb-rule for producers to check the amount of phosphorus in their lactating cows’ diet. In a non-pregnant, mature milking cow, there is generally a 1-to-1 relationship between grams of phosphorus needed in the diet and pounds of milk production; that is, 1 gram of ration phosphorus for each pound of milk produced meets the cow’s dietary requirement.

So, a cow producing 80-pounds of milk per day will have a dietary requirement of about 80 grams of total ration phosphorus per day.  And a cow producing 60 pounds of milk per day will only need 60 grams of phosphorus per day.