 ## Calculating Sulfur Intake Excess by Hand

• Estimate sulfur contributed by water (%SH2O):

• Determine the concentration of sulfate in the water by laboratory analysis. Sulfate concentration is usually expressed as parts per million (ppm). Milligrams per liter = ppm.

• Since sulfate is 1/3 sulfur, mg SO4/L is divided by 3 = mg S/L of water.

• Daily water intake in liters for beef cattle = 8%, 10%, 18% of body weight for ambient temperatures of 40°, 70°, and 90° F respectively. Daily water intake in liters for lactating cows = 10%, 15%, 15% of body weight for ambient temperatures of 40°, 70°, and 90° F respectively. Liters of water intake is multiplied by mg S/L = intake of sulfur in mg. Divide by 1000 for intake of sulfur in grams.

• Daily dry matter intake = 2-3% body weight in kg.

• %SH2O on DMI basis = total intake of S from water in grams divided by kg DMI divided by 10.

• Estimate sulfur provided by feed or forage as % DMI (%SFF):

• Determine the concentration of sulfur in the total mixed ration or individual diet ingredients. These are usually reported % sulfur as DM. If the data is given as % sulfate, divide the value(s) by 3.

• If a total mixed ration is analyzed, this is the value to be used as %SFF.

• If individual feed ingredients or forage components are analyzed, multiply the %S as DM for each ingredient by the proportion of the diet it represents. Then add the proportionally adjusted sulfur concentrations for all the components. This sum is the %SFF.

• To calculate the estimated total sulfur concentration us the following:
TSC = %SH2O + %SFF

Fort Collins Veterinary Diagnostic Laboratory
Fort Collins, CO 80526

Phone:
(970) 297-1281

Fax:
(970) 297-0320