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COWS TOXICOLOGY NOTES

INFORMATION BY:

  • Iliahi Neizmen, DVM

  • S Fleming, DVM

CLASSES OF TOXINS

  • Inorganics and Farm Chemicals

    • Heavy metals

    • Insecticides

    • Other farm chemicals (fertilizer, etc.)

  • Plants

  • Animal and Insect Bites

HEAVY METALS

  • Lead

    • Most common heavy metal poisoning.

  • Arsenic

    • Cattle are attracted to the taste; commonly encountered in fruit tree sprays.

  • Copper

    • Significantly problematic in sheep; it is advised to avoid feeding cattle feed and minerals to sheep, especially salt.

LEAD POISONING - #1

  • Sources:

    • Most reported cases from lead-based paints (before 1950)

    • Putty, linoleum, old car batteries, lead fishing weights

    • Improperly glazed ceramic bowls

    • Lead bullets become toxic only when present in the gastrointestinal (GI) tract or synovial fluid.

    • Golf balls

  • Acute Significance:

    • Sudden onset of severe diarrhea

    • Nervous signs: collapse and death

  • Chronic Significance:

    • Mild anemia due to RBC destruction

    • Slow onset of brain swelling and nervous damage; signs include circling, blindness, and head pressing

INSECTICIDES/PESTICIDES

  • Classes of Insecticides:

    • Organophosphates and Carbamates

    • Clinical Signs: Salivation, Lacrimation, Urination, Defecation (SLUD), constricted pupils

  • Chlorinated Hydrocarbons (Organochlorides):

    • Signs of excitation, muscle tremors, convulsions, and death

PLANT TOXINS

CYANIDE POISONING (PRUSSIC ACID POISONING)

  • Mode of Action:

    • Inhibits cytochrome oxidase

    • Causes cellular hypoxia

    • Present in plants as cyanogenic glycosides, which can be converted to free HCN

  • Predisposing Factors:

    • Heavy nitrate fertilization, especially in phosphorus-deficient soils

    • Grazing on stunted plants during drought is a common cause of poisoning.

    • Often follows wilting of plants

    • Frozen plants can contain high levels for several days

CYANIDE CONTINUED…

Affected Plants

  • Species:

    • Sorghum species (Johnson grass, Sudan grass, Common Sorghum)

    • “Fruits”:

    • Apricot, Peach, Wild Black Cherry, Elderberry

  • Other Plants:

    • Flax, Corn

CYANIDE CONTINUED…

Clinical Signs

  • Symptoms:

    • Sudden death

    • Bright red mucus membranes

    • Cherry red blood

    • Smell of bitter almonds

    • Excessive salivation

    • Dyspnea

    • Staggering

    • Convulsions

CYANIDE CONTINUED…

Treatment

  • Immediate Actions:

    • Sodium Nitrite IV: Breaks the cyanide-cytochrome complex

    • Sodium Thiosulfate IV: Binds cyanide

    • Sodium Thiosulfate PO: Binds cyanide in the rumen

  • Prevention Measures:

    • Do not graze pasture grasses until 15-18 inches tall.

    • Young plants contain the highest levels of cyanide

    • Avoid feeding frozen forages for 5 days post-frost

    • Monitor grazing during periods of stress

NITRATE POISONING

  • Mode of Action:

    • Nitrates are converted by the rumen to nitrites

    • Nitrites oxidize hemoglobin to methemoglobin, leading to tissue anoxia

  • Etiology:

    • Highest levels found in stems (lower third of stalk)

    • Accumulation occurs during drought

    • 14 days required to return to low levels

    • Low and high temperatures increase levels

    • Nitrogen fertilizers increase levels

    • Acid soils favor accumulation

    • Ensiling can decrease levels by 40-60%

NITRATE CONTINUED…

Affected Plants

  • Crops:

    • Forage sorghum, Grain sorghum, Sudan grass, Pearl millet

    • Corn, Wheat, Soybeans

  • Weeds:

    • Lambsquarters, Sunflowers, Pigweed, Jimson weed, Canada thistle

NITRATE CONTINUED…

Clinical Signs

  • Significance in Animals:

    • Cattle are more affected than horses, which are more affected than sheep and swine

    • Symptoms include:

    • Signs associated with cyanosis (dark, chocolate-colored blood)

    • Muscle tremors

    • Direct irritant causes salivation, diarrhea, abdominal pain

    • Abortion and stillbirths

NITRATE CONTINUED…

Treatment

  • Actions:

    • 1% Methylene Blue IV (4-22 mg/kg)

  • Control/Prevention Measures:

    • Gradual adaptation to high nitrate feeds

    • Dilute with other feeds

    • Supplement grain

    • Do not feed to stressed animals

    • Consider ensiling forages instead of hay

OXALATE POISONING

  • Mode of Action:

    • Calcium combines with oxalate to form insoluble calcium oxalate

    • Results in functional hypocalcemia, potential for vascular crystallization leading to necrosis and hemorrhage

  • Etiology:

    • Highest oxalate levels in leaves, then seeds

    • Metabolization occurs in the rumen

  • Cattle may detoxify large quantities in the rumen, decreasing chances for toxicity

OXALATE CONTINUED…

Affected Plants

  • Notable Species:

    • Pigweed

    • Lamb's Quarters

    • Halogeton

    • Rhubarb

    • Greasewood

OXALATE CONTINUED…

Clinical Signs

  • Primarily affects cattle and sheep

  • Symptoms include:

    • Colic, depression, muscular weakness

    • Prostration resembling milk fever

    • Rapid, labored breathing

    • Blood-tinged froth and fluid around the mouth

OXALATE CONTINUED…

Pathologic Lesions

  • Significant Findings:

    • Ascites and hydrothorax

    • Mouth and esophagus filled with blood-tinged froth

    • Kidneys appear pale, edematous, swollen; yellow striated appearance in renal cortex

OAK OR ACORN POISONING (QUERCUS POISONING)

  • Mode of Action:

    • Toxic principle: gallotannins

    • Causes gastrointestinal and renal dysfunction

  • Plants:

    • Young oak leaves

    • Green acorns

OAK CONTINUED…

Clinical Signs

  • High mortality rates are common

  • Notable effects include malformed calves and abortions in the 2nd trimester

  • Symptoms include:

    • Anorexia, depression, emaciation, rumen stasis

    • Smell of ammonia on breath

    • Signs of renal insufficiency

OAK CONTINUED…

Pathologic Lesions

  • Key Findings:

    • Pale swollen kidneys

    • Perirenal edema

    • Ascites and hydrothorax

    • Esophageal and abomasal ulceration

OAK CONTINUED…

Treatment

  • Interventions:

    • Calcium hydroxide

    • Purgatives

    • Magnesium sulfate

    • Mineral oil

    • Fluid therapy if needed

GOSSYPOL POISONING

  • Mode of Action:

    • Affects cardiac, hepatic, renal, and reproductive systems

    • Cardiotoxic due to conduction failure

    • Hepatotoxic due to damage to hepatocytes

    • Reproductive effects in males due to inhibition of steroid synthesis in testicular Leydig cells

  • Etiology:

    • Readily absorbed from the GI tract; toxic effects usually follow long-term exposure

  • Plants:

    • Cottonseed and cottonseed products

GOSSYPOL CONTINUED…

Affected Animals

  • Sensitivity Levels:

    • Monogastric & immature ruminants & poultry most affected

    • Pigs and rabbits are sensitive

    • Dogs and cats have intermediate sensitivity

    • Horses are usually unaffected

GOSSYPOL CONTINUED…

Clinical Signs

  • Symptoms:

    • Acute heart failure or congestive heart failure

    • Anemia

    • Reduces sexual libido and affects cycling and pregnancy

    • Green discoloration in chicken egg yolks

    • Violent “thumping” in pigs

GOSSYPOL CONTINUED…

Pathologic Lesions

  • Findings:

    • May be absent

    • Copious amounts of tan to red-tinged fluid with fibrin clumps in abdominal, thoracic, and pericardial cavities

    • Enlarged, flabby, pale heart

    • Pale skeletal muscles

GOSSYPOL CONTINUED…

Treatment

  • Management:

    • None specific for gossypol poisoning

  • Prevention:

    • Removal of all cottonseed products

    • High intake of protein, calcium hydroxide, or iron salts

    • Consideration of tissue residues in meat products for human consumption as a public health concern

BRACKEN FERN POISONING

  • Mode of Action:

    • Poisoning in non-ruminants due to thiamine deficiency

    • Bone marrow toxin in cattle

    • May act as a carcinogen

  • Etiology:

    • Toxic effects are cumulative

    • Acute cases often seen during drought; cattle are less susceptible to thiaminase form of toxicity

BRACKEN FERN CONTINUED…

Clinical Signs

  • Cattle Symptoms:

    • Acute hemorrhagic syndrome or sudden death

    • Pyrexia (106-110°F)

    • Blood will often fail to clot

    • Chronic enzoonotic hematuria

    • Intermittent hematuria

    • Death from anemia, bladder may contain tumors or hemorrhages

  • Sheep Symptoms:

    • Bright blindness

    • Progressive retinal atrophy

    • Hyperreflectivity of tapetum leading to permanent blindness

  • Pig Symptoms:

    • May resemble heart failure

BRACKEN FERN CONTINUED…

Treatment

  • Management Options:

    • Treatment usually fatal in cattle

    • Thiamine administration

    • Antimicrobial treatment

    • Blood or platelet transfusions

SWEET CLOVER POISONING

  • Mode of Action:

    • Harmless natural coumarins in sweet clover are converted to dicoumarol

    • Dicoumarol combines with the proenzyme required for prothrombin synthesis

    • Results in hypoprothrombinemia

    • Dicoumarol can cross the placenta

  • Etiology:

    • Weather affects toxicity

    • Large round bales often involved; any storage that allows molding promotes dicoumarol formation

SWEET CLOVER CONTINUED…

Clinical Signs

  • Affected Species:

    • All species susceptible but mainly cattle

  • Symptoms:

    • Signs due to hemorrhages from faulty coagulation including:

    • Sudden death

    • Lameness and stiffness due to bleeding into muscles and joints

    • Hematomata, epistaxis, GI bleeding

SWEET CLOVER CONTINUED…

Treatment

  • Management Strategies:

    • Whole blood transfusion

    • Subcutaneous or intramuscular Vitamin K1 (1 mg/kg BID or TID for 2 days)

AFLATOXINS

  • Effects:

    • Toxic to the liver due to mold presence

  • Zearalonone:

    • Considered estrogen-like

SUMMARY

  • History of the incident is critical for diagnosis

  • Rapid identification of the cause through necropsy

  • Immediate removal of animals from source

  • General treatment options include:

    • Non-specific treatments with laxatives

    • Use of toxin binders (e.g., activated charcoal)

  • Consideration that humans may also be susceptible

QUESTIONS?

  • Humorous Note:

    • Where do cows usually go on a Saturday night?

    • To the moovies!