Feed & water related toxicants: NPN Dr. Shokry

Question 1

Most common NPN toxicosis

Answer 1

NPN = non protein nitrogen (source)

Urea

Question 2

mechanism of urea metabolisis by ruminants

Answer 2

ingesteed Urea →broken down by rumen microflora + H2O⇒ ammonia & CO2

the ammonia + CHO ⇒ AAs ⇒ microbial proteins → digested by ruminant to form animal proteins

Question 3

toxicokinetics of NPN toxicity

Answer 3

ammonia produced at norm rumen pH (5.0-6.5) is ionized form (NH4) & not absorbed

too much urea & ammonia elevates rumen pH (8.0-9.0) & ammonia produced is non ionized (NH3) and absorbed

non ionized ammonia is absorbed → converted by liver to urea & excreted (not a problem)

Too much ammonia overwhelms capacity of liver ⇒ hyperammonemia

non ionized ammonia crossed cell membranes, BBB & placenta!

Question 4

factors contributing to NPN toxicity

Answer 4

alkaline pH

incr temp (for urease enzyme to work)

Question 5

NPN toxicosis is only an chronic toxicity T or F

Answer 5

False!

The urease reaction takes 30 min - 2hrs so toxicosis in ONLY ACUTE!

no sub acute or chronic.

Question 6

What are ammonia & urea as far as ph scale & how will that help in tx

Answer 6

Ammonia & urea are weak bases

Acidification of urine will incr elimination!

Question 7

What age of cattle are more sensitive to NPN toxicosis

Answer 7

calves <1 year

non ruminating calves are tolerant (3-6 weeks of age)

Question 8

What is MoA of NPN toxicosis

Answer 8

inhibits energy cycle (krebs/citric acid), decr cellular resp!

Question 9

CoD in NPN toxicosis

Answer 9

respiratory failure or cardiac arrest beforehand

Question 10

lesions seen in NPN toxicosis

Answer 10

none generally

can have ammonia smell to rumen contents

pH >7.5 of rumen

dead animals can have extreme bloat

Question 11

tx of NPN toxicosis

px

Answer 11

Acetic acid 5% or vinegar (2-6L) followed by cold water

sodium bicarb to tx acidosis

normal saline for dehydration

rumenotomy

guarded to poor