Bovine Nitrate Poisoning Flashcards
1
Q
What systems regulate nitrate uptake?
A
- Constitutive, low affinity transport system (LATS)
- Inducible, high affinity transport system (HATS)
- energy (ATP) dependent
2
Q
What results in Nitrate accumulation?
A
- unbalanced nitrate uptake and processing
- NO3 build-up in soil
- NO3 uptake by plant roots (mostly by HATS)
- NO3 to NO2 reduction in plant tissues (by NR)
3
Q
What are the risk factors for nitrate accumulation?
A
- Plant species
- Crop grasses, weed grasses, broadleaved annual weeds
- Time of year
- higher risk during growing season
- high soil nitrogen
- Fertilized fields
- Enclosures that previously had high animal densities
- Environmental conditions that reduce/stop plant growth
- Sumer drought
- Persistent cloudiness or plants growing in shade
- Unseasonal hot or cold weather
- Herbicides
4
Q
What weeds are able to accumulate nitrate?
A
- Ambrosia spp - Ragweed
- Amaranthus spp - Pigweed, Carelessweed
- Carduus nutans - Musk thistle
- Chenopodium spp - Lambsquarters
- Cisium arvense - Canada thistle
- Gnaphalium spp - Cudweeds
- Helianthus annuus - Annual sunglower
- Kochia scoparia - Kochia, Fireweed
- Lygodesmia spp - Skeleton plants
- Malva parviflora - Cheeseweed
- Melilotus officinalis - Sweetclover
- Polygonum spp - Smartweeds
- Rumex spp - Docks
- Salsola pestifer - Russian thistle
- Silybum marianum - Milk thistle
- Solanum spp - Nightshades
- Sorghum halepense - Johnsongrass
- Viguiera spp. - Golden-eyes
5
Q
What crops are capable to accumulating nitrate?
A
- Oat
- Beet
- Rape, Turnip
- Soybean
- Barely
- Flax
- Alfalfa
- Pearl millet
- Rye
- Sorghum sudan grass
- Wheat
- Corn
6
Q
What happens to nitrates in Ruminants?
A
- Nitrate is reduced to nitrite by rumen microbes - rapid, high capacity process
- Further reduced to ammonia and released into the air by eructation - less efficient
- If production rates are high ⇢ accumulates and gets absorbed
7
Q
What are the toxic effects of Nitrate
A
- Nitrite oxidizes hemoglobin (Fe2+) to methemoglobin (Fe3+)
- when MetHb reductase capacity is overwhelmed concentrations rise
- ⇡MetHb reduces O2 carrying capacity of blood
- 30-40% MetHb - mild signs
- >70% MetHb - severe signs and death
- Low but persistent nitrate exposure:
- Impaired Vit A function
- Endocrine abnormalities
8
Q
What does Acute nitrate poisoning look like?
A
- Signs of hypoxia
- weakness
- exercise intolerance
- tachypnea
- collapse
- convulsions
- death
9
Q
What does subacute/chronic nitrate poisoning look like?
A
- Abortions 3-7 dpi
- Weak calves
- decreased milk production
- decreased feed conversion rates
- increased susceptibility to infectios
10
Q
What are the postmortem findings of nitrate poisoning?
A
- Brown discoloration of blood and tissues
- may take 2-10 minutes to develop on opened carcass surfaces
- Can see on mm
- disappears after a few hours
- Non-specific signs of GIT inflammation
- Rumens often contain recognizable nitrate-accumulating plants
- placental necrosis
11
Q
How is nitrate poisoning diagnosed?
A
- Clinical signs
- Brown discoloration of blood and tissues
- Nitrate Analyses:
- Serum:
- antemortem
- normal values are about 35% higher than aqueous humor, but decline rapidly after death
- Eyeball/Aqueous humor:
- Postmortem
- Nitrates stable for 24 hours (room temp) 1week (refrigerated)
- Adults >10 ppm suspect; >20ppm diagnostic
- Neonates/fetuses 25-50 ppm suspect >50 ppm diagnostic
- Serum:
12
Q
What other samples should be taken when dealing with possible nitrate poisoning?
A
- Forage - 1% NO3 on dry matter basis is potentially lethal
- Water
- Suspect material
13
Q
What is the treatment for nitrate poisoning?
A
- Acute:
- remove suspected source
- Methylene blue (5 - 15 mg/kg IV 1% solution)
- 6 months WDT
- Subacute
- Injectable or oral vit A, D, E
- Iodized salts or organic iodine
- Feed high quality protein and abundant carbohydrates
