21 Feed-associated toxicity

what is non-protein nitrogen converted to in the ruminant gut

protein

what are some sources of non-protein nitrogen

urea, buret, ammonium sulfate, mono ammonium phosphate

what type of rumen pH promotes NH4 absorption

increased, basic

how long does it normally take to convert non-protein nitrogen to protein

2-3 days

what type of toxicity has a mechanism of depletion of the krebs cycle, resulting in an increase in lactate and and decrease in ATP

Ammonia toxicosis

what is the mechanism of toxicity of urea

Ammonia forms corrosive solution with water which promotes ammonium absorption

what is the target organ of ammonia toxicosis

CNS

is ammonia toxicity chronic or acute presentation

acute

why might feed be exposed to ammonia

increase digestibility, increase crude protein, increase palatability

What must be present in hay being exposed to ammonium gas to produce toxic pyrazines and imidazoles

high amounts of sugars

why is it not recommended to expose good quality hay to ammonium gas

high amounts of sugars reacts with amino acids to produce toxic pyrazines and imidazoles

what is the moa of toxic pyrazines and imidazoles

intermittent abnormal nerve function and convusions

what is the clinical presentation of an animal that has eaten good quality hay exposed to ammonium gas

intermittent, spontaneous periods of neurologic abnormalities

T/F nursing animals can’t be affected by toxic pyrazines

F

what two systems control nitrate uptake

low affinity transport system, high affinity transport system

which system of nitrate uptake is ATP dependent

HATS

which system of nitrate is ATP independent

LATS

what enzyme reduces nitrate to ammonium in plants

nitrate reductase

What is the normal method of nitrate excretion in ruminants

nitrate to nitrate by rumen microbes → nitrate reduced to ammonia → ammonia eructated

T/F reduction of nitrate to nitrite by rumen microbes is a highly inefficient process

F

T/F nitrate reduction to ammonia is an inefficient process

T

what type of animal is most susceptible to nitrate poisoning and why

ruminants because nitrate reduction is inefficient

by what ways can ruminants be exposed to high levels of nitrates

consumption of plants grown in a recent drought, consumption of plants recently exposed to a nitrate-based fertilizer

is nitrate or nitrite more likely to be absorbed into the ruminant bloodstream when high levels are present and the cause of toxicosis

nitrite

what are the clinical signs of nitrate poisoning

GI irritation, weakness, ataxia, depression, tremors, diarrhea

at what levels do methemoglobin need to be for clinical intoxication to occur

30-40%

what variant of hemoglobin is formed with nitrate poisoning

methemoglobin

Compounds of what element is commonly included in feed to prevent urinary calculi but in high doses can cause cerebral necrosis

sulfur

what are the possible MOAs of sulfide

blocking of neuronal energy metabolism, interferes with cerebrum blood flow, generates reactive oxygen species

what toxin commonly included as a feed additive to prevent urinary caliculi formation can cause polioencephalomalacia

sulfur

what are some clinical signs of sulfur toxicity

weight loss, diarrhea, dehydration, head pressing, ataxia, convulsions

sulfur poisoning has very similar clinical signs to what other toxicity

lead

what blood changes are you likely to see on chemistry with sulfur toxicity

metabolic acidosis, hpyokalemia, hypochloremia

what is the purpose of ionophores

growth enhancer, feed conversion, increased milk production efficiency

what is the MOA of toxicity for ionophores

Transmembrane shift of sodium hydrogen, potassium, calcium

in ruminants with ionophore toxicity, which fatty acid is primarily produced

proprionic acid

which direction does calcium shift in ionophore toxicity

intracellular

how does increased intracellular calcium affect mitochondria (ATP production)

decreases it

how many times the recommended label does must be fed to ruminants to be lethal

10x

what species is most sensitive to ionophore toxicity

horses

what are some clinical signs of ionophore toxicity

diarrhea, ataxia, knicukling, weakness, CHF, dyspnea