Calculations

Question 1

What is the most common method of expressing concentrations in veterinary toxicology (animal tissues, feed, water, solvents, etc.)?

Answer 1

Part per million (ppm) on weight/weight basis

Question 2

1 ppm =

Answer 2

1 mg/kg

1 microgram/gram

Question 3

1 ppb =

Answer 3

1 microgram/kg

Question 4

1 ppt =

Answer 4

1 ng/kg

Question 5

ppm to percentage: 1 ppm =

Answer 5

0.0001%

Question 6

How do you convert from ppm to percentage?

How do you convert from percentage to ppm?

Answer 6

Move the decimal point 4 places to the left

Move the decimal point 4 places to the right

Question 7

How to make a diluted solution from a concentrated stock solution

Answer 7

The mL needed from the stock = (% required dilution) x (volume required in mL) / (% of the stock)

Question 8

You want a pig feed to contain 300 ppm arsanilic acid as a growth promoter. How many grams are needed per ton?

Answer 8

100 g/ton = 110 ppm
300/110 = (X g/ton) / (100 g/ton)
X = 273 g/ton

Question 9

A feed additive for piglets was added at a concentration of 220 ppm. How much is needed for 8 tons?

Answer 9

100 g/ton = 110 ppm
(220/110) = (X g/ton) / (100 g/ton)
X = 200 g/ton
200 g/ton x 8ton = 1.6 kg

Question 10

Conversion from the level of drug in feed as ppm to toxicity (mg/kg)

Answer 10

Toxicity (mg/kg) = (ppm in feed) x (% of feed consumed daily)

Question 11

If the toxic level of drug in feed is 50 ppm for a 20 pound pig, what is the calculated toxicity in mg/kg if 20 pounds pig eats 8% of its body weight?

Answer 11

Toxicity (mg/kg) = (ppm in feed) x (% feed consumed)

Toxicity = 50 x 0.08 = 4

Question 12

Conversion from toxicity (mg/kg) to level in feed as ppm

Answer 12

Level in feed (ppm) = (toxicity in mg/kg) / (% feed consumed daily)

Question 13

What is the rule for estimating dosages when exposure is based on consumption of green forage that has been sprayed?
What 2 assumptions is this rule based on?

Answer 13

Every animal ingests green forage that has been sprayed by a chemical at the rate of 1 lb/acre, will be approximately exposed to 7 mg/kg body weight

1) Good quality pasture will produce approx. 45 g green forage per square foot
2) Grazing animals consume 3% of their body weight green forage