What is the is the conversion of Nitrate to Nitrite and where does it take place?
Nitrate (NO3) is absorbed from the soil by the plant and converted to Nitrite (NO2)
This can also happen in the blood and in the rumen
What converts Nitrate to Nitrite?
Nitrate reductase
What leads to accumulation of the nitrate in the plant?
the rate of Nitrate to Nitrite is reduced with the continuation of Nitrate uptake from the soil
What factors favor plant nitrate accumulation?
High Nitrate or ammonia in the soil
Soil conditions: Rain, Moisture, acid soil, low soil molybdenum, etc
Decreased light reduces activity of nitrate reductase
Use of phenoxy acetic acid herbicides
Stage of plant growth
What parts of the plant contain the highest concentration of Nitrate?
The stalks
What plant species accumulate nitrate?
Sweet clover alfalfa wheat corn Pigweed Oats Beets Johnson grass Sudan grass Milo Lamb's quarters Sunflower
what is the use of Nitrates?
Fertilizer
Sodium Nitrite IV as a vasodilator
What animals are susceptible to nitrate poisoning from Sodium NitrIte IV?
Horses
What is the source of Nitrate or Nitrite poisoning?
Rapid ingestion of forages or hays containing high amount of nitrate
Accidental ingestion of feeds or water contaminated with nitrate
Overdose with Nitrite IV
Properties of Nitrates?
Water Soluble
Salty - Palatable
What form of Nitrate or Nitrite is more toxic?
Nitrite is 10 times more toxic than nitrate
What age of animals are more susceptible to Nitrate poisoning?
greater than 3 months of age
2-3 years old
What diseases cause an increase in toxicity of Nitrates?
Anemia and Methemoglobinemia
What is the half life of Nitrite?
Less than 1 hour
What is the half life of Nitrates?
4-48 hours
What is the Acute mechanism of action for Nitrate Poisoning?
One molecule of Nitrite interacts with two molecules of hemoglobin resulting in oxidation off ferrous iron to ferric and conversion of hemoglobin to methemoglobin
What is the chronic mechanism of action for Nitrate poisoning?
Abortion due to decreased progesterone
weak
weight loss
wasting
What are the clinical signs of Nitrate Poisoning?
Sudden death rapid breathing restlessness apprehension dyspnea weakness sternal recumbency cyanosis terminal convulsion due to not enough O2 Abortion due to fetal anoxia
What are the lesions associated with Nitrate Poisoning?
Congestion of organs
Brown-chocolate color of blood
What is the specimen of choice for nitrate poisoning in dead animals?
Ocular Fluid
What are the specimens for nitrate poisining in live animals?
Serum
Plasma
urine
rumen contents
What is the test for nitrate in forages, rumen contents, and water?
Diphenylamine test
What is the color of the positive result for the Diphenylamine test for Nitrate poisoning?
Dark blue color
What is the differential diagnosis for Nitrate Poisoning?
Acetominophen in cats
What is the treatment for Nitrate Poisoning?
Methylene blue 1% IV for ruminanats and monograstics
Activated charcoal, ruminal lavage with cold water, oral antibiotics inhibit rumen microflora and nitrate reductase
What is the prognosis for Nitrate Poisoning?
Die before treatment because death is rapid
What is the source of Cyanide Poisoning in Large animals?
Ingestion of cyanogenic plants
What is the source of Cyanide Poisoning in small animals?
Hydrogen cyanide and cyanide salts
Hydrogen cyanide as a fumigant rodenticide
Sodium nitroprusside used as a hypotensive
Combustion of plastic compounds
What are the cyanogenic plants?
Wild Cherry Sudan grass Johnson grass Sorghums Apples plums lima beans cassava roots
What are the properties of Cyanide Poisoning?
Volatile gas
characteristic bitter almond odor
CN radicals form complexes with ferric ion, cupric, and molybdenum
What is the effect of Thiocyanate SCN?
antithyroid effect
What type of toxin is Cyanide?
Highly Toxic
What causes the release of Cyanide from cyanogenic plants?
Hydrolysis by the rumen microflora
What cause the plant to release cyanide?
Stress
Plant damage
How is cyanide released from the plant during stress?
Beta-glucosidase causes hydrolysis of cyanogenic glycosides and release of cyanide
Where do cyanogenic glycosides accumulate the most?
The seeds
What soil condition causes an increase in glycosides?
High Nitrogen
Low Phosphorus
Where is cyanide rapidly absorbed from?
GI tract
Skin
inhalation
What is the mechanism of action of cyanide poisoning?
CN in the blood and tissues binds with ferric iron and cupric copper of the mitochondrial cytochrome oxidase blocking the electron transport and inhibits the cells to utilize the available oxygen resulting in histotoxic anoxia
What are the clinical signs of acute poisoning?
rapid onset Die without manifesting clinical signs Tachypnea severe panting gasping salivation lacrimation urination defecation severe colic vomiting bright red mucous membranes
What are the chronic clinical signs of Cyanide Poisoning?
Posterior paralysis
urinary incontinence
cystitis
constipation
What are the lesions associated with Cyanide Poisoning?
Mucous membranes are bright red and blood is cherry red
Congestion and petechial hemorrhages of the GI tract and lungs
What is the danger of cyanide poisoning?
could be poisoned during necropsy from opening the rumen
What is the test for Cyanide Poisoning?
Sodium picrate paper test
What is the differential diagnosis for Cyanide Poisoning?
Carbon Monoxide
What is the treatment for Cyanide Poisoning?
Sodium Nitrite IV Sodium thiosulfate IV Sodium Thiosulfate Oral Oxygen therapy Vinegar in cold water orally to slow microbial hydrolysis
What are the plants containing Soluble oxalates?
Pigweed Beet Lamb's quarters Halogeton Sorrel Soursop Greasewood
What species are most susceptible to soluble oxalate poisoning?
Sheep
Cattle
Where does soluble oxalates accumulate in plants?
leaves
What decreased toxicity of soluble oxalate poisoning?
Calcium or calcium rich diet
What increases toxicity of soluble oxalate poisoning?
oxalate-producing fungi
What are the toxicokinetics of soluble oxalate poisoning?
Soluble oxalates can be metabolized to a certain extent in the rumen to carbonates and bicarbonates
Calcium rich diet inhibit absorption by forming insoluble calcium oxalates which are excreted in feces
What is the mechanism of action for soluble oxalate poisoning?
soluble oxalates combine with calcium ion to form insoluble calcium oxalate leading to hypocalcemia
Precipitation of calcium oxalates crystals in the kidney tubules causing kidney damage and necrosis
What are the clinical signs of soluble oxalate poisoning?
depression
muscle twitching
muscle weakness
head and neck pulled to one side in sheep ( like milk fever in cattle)
Blood tinged froth around the mouth
Convulsions if the calcium is deposited in the brain
Calcium oxalate precipitation in renal tubules lead to fatal renal tubular toxicosis
What are the lesions associated with soluble oxalate poisoning?
The mouth and esophagus filled with blood tinged froth
Kidneys show dark red cortex and medulla separated by a gray line from accumulation of oxalate crystals in the renal tubules
What are the laboratory findings associated with soluble oxalate poisoning?
Presence of Calcium oxalate crystals in the kidneys
What is a differential diagnosis for soluble oxalate poisoning?
Milk Fever
What is the treatment for soluble oxalate poisoning?
Calcium gluconate IV
Saline-glucose to treat alkalosis
Supplementation of calcium salts
Supportive therapy