Lecture 2 Flashcards
(26 cards)
What are the 3 most important toxins
- Nitrate-nitrite
- Cyanogenic glycosdeis
- Soluble oxalates
List some plants that cause nitrate-nitrite toxicity
- Sorghum
- Rye grass
- Button grass
- Oats
Where are nitrates concentrated
- Stem and stalks
- Toxic amounts can also persist in hay
Describe the mechanism of action of nirtates
Nitrates are converted to nitrites by rumen bacteria. High levels of nitrites in the digestive tract will be absorbed into the blood stream. In the blood stream, nitrite oxidises haemoglobin to methamoglobin which means cells are unable to transport oxygen
What % of KNO3 is toxic
Greater than 1.5%
Explain how nitrates are toxic to monogastrics
They are unable to convert nitrate to nitrite in their digestive tract, however they are suseptible after microbial conversion of nitrate to nitrite in swill or wet hay
10 factors affecting the risk of nitrate-nitrite poisoning
- decreased sunlight
- Termperature
- Increased herbicides
- Increased insect damamge
- Increaed virus infection
- Previous exposure
- Carbohydrate supply increased
- Decresed Mo
- Decreased Fe
- Decreased Ionophores
5 Clincial Signs of nitrate-nitrie poisoning
- Salivation
- Abdominal pain
- Diarrhoea and vomiting
- Cyanosis
- Bloat
- Termors
- Staggers
What is the pathology of nitrate-nitirte poisoning
Chocolate-brown blood
Nitrate-nitrite is also a vasodialator: what is the problem with this
Reduced peripheral perfusion and circulation to the uterus
How to diagnose nitrate-nitrite poisoning
Phenylamine test is applied to plants or the aqueous humour of the eye
Merck test and urine analysis test are also avaliable for live animals
How to treat nitrate-nitrite toxicity
IV injection of methyl blue - converts methaemoglobin back to haemoglobin
How to prevent nitrate-nitrite poisoning
- Analysing feed
- Not grazing stock on dangerous pastures
- Frequent observation if on risky feed
- Not over stocking on risky pastures
- Disallowing grazing on high nitrate pastures
What is another name for a source of cyanide
Prussic acid
Plant species involved in cyanogenic glycoside poisoning
- Sorghum
- Native couch
- Reed sweet grass
- Cyodon
Why are runimants more suseptible to cyanogenic glycoside poisoning than monogastrics
- Ruminal microbial beta-glucoside releases HCN rapidly
- Low stomach pH of monogastrics inhibits beta glucosidase
Mechanism of action of cyanide poisoning
Plants store cyanide as cyanogenic glycosides in vacules and the activating agent in the cytosol. When animals chew the plant they mix producing HCN (prussic acid). HCN is rapidly absorbed into the animals blood and spreads into its cells
HCN blocks mitochondria cytochrome oxidase > no ATP is made > body goes into energy starvation
What is the HCN potential of plants influenced by
- Age
- Genotype
- Nutrition
- Stress
The poisoning occurance is influenced by (HCN)
- Feed intake
- Time since last feed
- Rumen pH
- Sulphur nutrition status
- Exposure history
Clinical signs of acute cyanide poisoning in cattle
- Rapid deep breaths
- Mucous membranes appear bright pink
- Irregular weak pulse
- Birgnt red blood
- Muscle spasms
- Coma
Rapid field test that can be used to test for free HCN in plants, rumen contents, liver and skeletal muscles
Prcric acid spot test
A compound that treats cyanide poisoning
Sodium thiosulphate IV and PO
How to prevent and control HCN poisoning
- Avoid feeding hungry ruminants stressed or exposed plants
- Reduce intake by feeding hay before hand
- Provide sulfur supplements
- Avoid sorghum crops under 45cm tall or those with regrowth
- Avoid hay made from cyanogenic plants
Soluble oxalates affect homeostasis of which ion in the body
Calcium
