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Toxicology Michelle > Feed and Water Related Toxicants > Flashcards

Feed and Water Related Toxicants Flashcards

1
Q

Sources of NPN/Urea

A
  • Urea > common
  • Excess in feed as additive
  • Inadequate [ ]’s
  • Cotam of feed by urea fertilizer
  • NH4+ salts & NH3 tx’d feed
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2
Q

Phys and Chemical properties of NPNs/Urea

A
  • Liberation of NH3
  • One part urea -> ~3 parts protein
  • Urea by urease (rumen microflora) changes to NH3 & CO2
  • NH3 aminates ketoacids (from soluble CHOs) to AAs
  • AAs form bacterial protein
  • Bacterial protein converted to animal protein
  • Alkaline pH enhances hydrolysis of urea by urease (Urea is basic)
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3
Q

Toxicokinetics of NPN/Urea

A

NH3 produced rumen @ normal pH (5.0-6.5) is in the ionized form (NH4+) & not absorbed

  • Too much urea & NH3 -> elevation of the rumen pH (8.0-9.0) & ↑NH3
  • NH3 absorbed & converted by L to urea & excreted in U+
  • More than the capacity of the L, will produce hyperNH3
  • NH3 crosses cell membranes, BBB & placenta
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4
Q

Toxicity of NPN

A

Ruminants most susceptible

  • Eq susceptible
  • Urea is the most toxic NPN compounds

-3-6 weeks old tolerant

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5
Q

Feeding managment of Urea

A
  • Usual [urea] is 3% of grain ration & 1% total ration
  • Animals preconditioned or adapted to NPN are > tolerant
  • Toxic dose in Bv not preconditioned or adapted is ~ 0.45 g/kg; lethal dose in adapted animals is 1-1.5 g/kg
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6
Q

What increases toxicity of urea?

A

• Fasting, dehydration or ↓H2O intake, feeds rich in urease (soybeans), L insufficiency, & diet low in E & protein but Hi in fiber ↑ tox

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7
Q

MOA of Urea

A
  • NH3 inhibits citric acid cycle -> lack of E &↓cellular resp & tissue damage
  • ↑B+ NH3, anaerobic glycolysis, lactate & systemic acidosis, BG, BUN, K+&P+
  • ↑ transaminases & PCV
  • COD may be ♥ or resp failure
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8
Q

CS/Lesions associated w/ Urea

A

Rapid OoA (0.5-3 hr)
-CS: restlessness, aggression, muscle tremors, Slv+, teeth
grinding, colic, sternal recumbency while standing on the hind limbs (play bow), bloat, rumen stasis, usually no diarrhea, lots of urination C+ & death w/in 1-2h
-Nothing characteristic
-Main lesions d/t vascular damage
-Congestion & degeneration in L&K
-NH3 odor
-Dead usually very bloated

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9
Q

Analysis and Dx of Urea

A

-Analysis of feed & NH3 in whole B+, rumen fluid & vitreous fluid
-Freeze specimens (not B+) immediately
-↑rumen pH (7.5 or >)
Dx: B+ chem, Hx of exposure, CS, NH3 odor

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10
Q

Tx/Prognosis of urea

A
  • Tx bloat 1st
  • Acetic acid 5% or vinegar to Bv (2-6 L) or Ov & Cp (0.5-1.0 L) then large vol cold H2O
  • Repeat tx every 4-5h for 48h
  • Normal saline for dehydration
  • NaHCO3 IV for acidosis
  • Rumenotomy
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11
Q

Ddx of Urea poisoning

A

DDx: Agents which -> colic i.e., caustics, inorganic arsenic: Generally they cause diarrhea (often B+y) & no CNS signs

  • Pb, metaldehyde, & CCH pesticides: No abnormal posturing, jumping over objects & maniacal behavior as in CCH poisoning
  • OP: Parasympathomimetic signs, respond to atropine tx
  • Grain engorgement, nitrate poisoning, enterotoxemia & cyanide poisoning: DDx by necropsy & lab tests
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12
Q

Uses of Ionophores

A
  • Anti-coccidial
    -Growth promoter feed additive
    -↓ bloat & rumen acidosis
    -Prevent tryptophan-induced atypical Bv pulmonary
    Emphysema
    -Eq sensitive
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13
Q

Ionophore sources

A
  • Monensin > common
  • Eating feeds containing ↑ lvls in Ck, Bv & Pc
  • Eating feeds w/added ionophores, in Eq, Ov, & K9s
  • Malicious in Eq
  • Eq that ingest Bv levels not poisoned
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14
Q

Physical and chemical properties of Ionphores

A

-Also include lasalocid, salinomycin, narasin, semduramicin
sodium, & laidlomycin propionate K+
-Carboxylic acid derivatives antibiotics
-Slightly soluble in H2O & soluble in organic solvents & oils
-Form lipid-soluble complexes with polar cations (Na+, K+, Ca2+, Mg2+) that are transported across cellular membranes

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15
Q

Toxicokinetics of ionophores

A
  • PO
  • Ru absorb ~ 50%, Monos absorb most
  • WD
  • B+ & tissue lvls relatively ↓
  • P-450 rapid metab (except in Eq) excreted mainly in bile
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16
Q

Toxicity of Ionophores

A
  • All susceptible
  • Eq > sensitive followed by adult Tk
  • Concurrent admin of other Rx↑ toxicosis: ♥ glycosides, Tiamulin (DOC tx mycoplasma in LA, Fluro in SA) Chlor-amphenicol, Erythromycin, Sulfonamides (inhibit microsomal enzymes)
17
Q

MOA or Ionophores

A

-Disrupt transmembrane electrochem gradients
-Mitochondria of highly energetic tissues main target (myo♥, SKM, K, GI mucosa)
-Influx of the Na+-ionophore complex ↑ing intracellular Na+& Ca++
-Sequestering of Ca++ by mitochondria & inhibition of mitochondria & ↓ATP & E
-Cell death d/t disrupting homeostatic mechanisms
-Disruption of [ion] in excitable cells (neurons,
myo♥, SKM, SMM) alters their functions

18
Q

CS of equine ionophore toxicity

A

Anorexia, profuse sweating, colic, depression, incoordination, HrVent, tachy♥ tachyarrhythmias, prostration, & death
-Mainly ♥muscle lesions (pale ♥muscles, white streaks of necrosis in myo♥) & some SKM

19
Q

CS of bovine ionophore toxicity

A

Anorexia, diarrhea, ↓, labored breathing, ataxia, prostration, & death

20
Q

CS of poulty ionophore toxicity

A

Anorexia, diarrhea, ataxia, resting on the knees with wings & legs directed outward, & ↓egg production
-Both SKM & ♥muscle lesions in Bv & Av

21
Q

K9 CS of ionophore toxicity

A

Ataxia, muscle weakness of hind limbs, resp paralysis, dysuria, constipation, & ↓
-Mainly SKM lesions in Ov, PC & K9s (pale SKM)

22
Q

Lab Dx of ionophore toxicity

A 
Chem analysis for ionophores
• Methods detect ppb levels, FEED, GI contents, L, & feces
Clin Path
• ↑enzymes of muscle origin (CPK, AST)
• Others: ↑(LDH, ALP)
• ↑PCV
• ↓serum Ca2+ & K+ w/in 12h
23
Q

Dx of ionophore toxicity

A

-Hx of feed problem, CS, Lesions, Lab dx

24
Q

Tx/Prevent ionophore toxicity

A

-None specific
-Remove source
-↓ing absorption
• AC, Mineral oil, saline cathartics
-Symptomatic Tx
• IV fluid & electrolyte therapy (to correct HoVol & support
♥vascular & renal functions)
•K+ if

25
Q

ddx for ionphore tox in equines

A

Colic, Blister beetle (cantharidin toxicosis), Azoturia

26
Q

ddx for inophore tox in bovines

A

VitE/Se def, Poisonous plants:

  • -SKM–Coffee senna (Cassia occidentalis), Coyotillo (Karwinskia humboldtiana), White snakeroot
  • -♥toxic–Taxus spp., Vetch, Oleander, Milkweed
27
Q

ddx for ionophore tox in poultry

A

: Nutritional myopathy, Coffee senna toxicosis, Botulism, Na+-H2O deprivation toxicosis, Mycotoxicosis (moniliformis cyclopiazonic acid), Round-♥disease, Downer syndrome (viral arthritis)

Toxicology Michelle (5 decks)

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