Nonprotein Nitrogen (NPN) Flashcards Preview

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Flashcards in Nonprotein Nitrogen (NPN) Deck (28)
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1
Q

What is the most commonly used NPN ?

A

Urea

others: ammonium nitrate, ammonium carbonate, ammonium chloride, and ammonia birate

2
Q

Which NPN is the most toxic?

A

UREA

it is the most efficient therefore the most economical but also the most toxic

3
Q

T/F: Urea is toxic

A

FALSE

Urea itself is not toxic

***lethal synthesis of ammonia is the problem

4
Q

What is the MOA of urea toxicosis?

A

Lethal synthesis of ammonia + lack of energy due to inhibition of the TCA cycle + decreased cellular respiration/tissue damage

5
Q

What is the normal rumen pH? What is the state of ammonia in that pH?

A

Normal rumen pH = 6.5

ammonia (weak base) will be mostly ionized at that pH - so it is trapped and inactive

When the pH increases (greater than 7)- ammonia will become non ionized and get absorbed –> Toxicosis

6
Q

1 urea molecule will produce ___ equivalents of animal protein

A

3

(300% protein profit) super efficient

7
Q

What does urea require in the rumen to be transformed into Ammonia + Carbon Dioxide?

A

Urease from the rumen microflora and water

The ammonia will then be broken down into amino acids to form microbial proteins –> animal proteins

8
Q

What pH will enhance hydrolysis of urea by urease?

A

Alkaline pH

Urea is basic

9
Q

T/F: Horses are susceptible to NPN toxicosis

A

TRUE

although cattle are considered the most susceptible since NPN is often used in their feed

10
Q

What is the usual concentration of Urea in cattle feed?

What is the toxic dose?

A

Usual: 3% of the grain ration and 1% of total ration

**Animals adapted to NPN are more tolerant

Toxic: 0.45 g/kg (in non adapted animals)
Lethal dose in adapted animals = 1-1.5 g/kg

Moderately toxic in non adapted animals
Slightly toxic in adapted animals

11
Q

What animals are more sensitive to NPN toxicosis?

A

Animals less than one year, greater than 3 months

*very young animals (3-6 weeks) are tolerant since they do not have a developed rumen at that time

12
Q

T/F: Fasting will increase urea toxicity

A

TRUE

so will dehydration or low water intake

13
Q

Will feeds rich in urease increase or decrease the toxicity of Urea?

A

INCREASE

ex: soybeans

14
Q

Will hepatic insufficiency increase or decrease the toxicity of Urea? Why?

A

Increase

If the liver is not fully functional - it will not metabolize ammonia appropriately leading to an accumulation

*the liver SHOULD convert ammonia to urea, which is then excreted in the urine

15
Q

A diet low in energy and protein but high in fiber will ____ urea toxicity

A

Increase

16
Q

Too much urea and ammonia result in elevation of the rumen pH (up to ______), then ammonia is in the _____ form

A

pH up to 8-9

ammonia will be in the non ionized form allowing it to be absorbed and have a toxic effect

17
Q

Does non ionized ammonia cross the BBB and placental barrier?

A

YES

as well as other cell membranes

Too much non ionized ammonia = hyperammonemia

18
Q

What acid-base condition will hyperammonemia cause?

A

Metabolic acidosis

Increase in anaerobic glycolysis, increase in lactate

Also increased: BG, BUN, K, Phos, PCV

19
Q

what is the usual cause of death associated with Urea toxicosis?

A

Cardiac failure (hyperkalemia) and respiratory failure (seizures)

20
Q

What clinical signs are associated with Urea toxicosis?

A

Rapid onset ( 30min - 3 hr)

Restlessness, colic, muscle fasciulations, ataxia, convulsions, teeth grinding/salivation, bloat, rumenal tympany

**no dhr

Death within 1-2 hours

21
Q

T/F: Characteristic lesions of urea toxicosis aid in diagnosis

A

FALSE

there are no characteristic lesions - death occurs too rapidly

22
Q

What are the main lesions noted with urea toxicosis?

A

lesions due to vascular damage
Congestion and degeneration of the liver and kidney
Ammonia odor (subjective - not reliable)
Usually dead animals are severely bloated

23
Q

What specimen sample is the most stable PM in a patient that died from urea toxicosis?

A

Ocular fluids - from the vitreous body

  • can also perform urea and ammonia analysis on whole blood, rumen content, and analyze feed
  • all specimens besides blood should be frozen immediately
24
Q

What may be DDX for urea toxicosis?

A

agents which cause colic such as caustics or inorganic arsenic

but these generally cause DHR and no neuro signs (which is the opposite of Urea tox)

other: lead, metaldehyde, chlorinated hydrocarbon pesticides, organophosphates, nitrate, cyanide

25
Q

What treatment can be used for a patient with urea toxicosis?

A

Bloat should be relieved first
Acetic acid or vinegar + cold water into the rumen to decrease pH and slow down the urea to ammonia rxn - this needs to be repeated q4-6 hrs

supportive care: IVF, sodium bicarb for acidosis, rumenotomy

26
Q

What is the prognosis for cattle with urea poisoning?

A

POOR

27
Q

When the liver converts ammonia to urea - what happens to it?

A

Some will get recycled in the saliva and most will be excreted in the urine

28
Q

Should animals less than 300 lbs have urea added to their food rations?

A

NO

and animals less than 500 lbs do not tolerate urea well