Cyanogenic glycosides
Cyanogenic glycosides are present in a number of food plants and seeds. Hydrogen cyanide is released from the cyanogenic glycosides when fresh plant material is macerated as in chewing, which allows enzymes and cyanogenic glycosides to come together, releasing hydrogen cyanide. This is called cyanogenesis. Cyanogenesis is the process by which plants produce hydrogen cyanide gas (HCN) to defend themselves against herbivores. HCN is poisonous not only to animals that eat plants, but to the plants themselves. To prevent poisoning themselves, the plants store cyanogenic glycosides1 in a vacuole of the cell and an enzyme that acts to produce HCN in a separate compartment. When the cell is damaged, the compartment walls are breached, allowing the reaction to take place. In this way, HCN is produced only when needed. Cyanogenic aren't all parts of plant. For example, common vetch store glycosides in seeds, lima bean in seeds and roots, sorghum in green parts, but fully-grown seeds not.
Biologic effects
The most important biologic effect is cytochromoxidase inhibiton as enzyme necessary for tissular breathing. Others enzymes and biochemical processes are influenced too - directly or indirectly. The most affected is system central nervous and heart. Primary symptoms are more intensive breathing, peripheral anaesthesia, next is totter, breathing difficulties, tetany convulsions, paralysis and death.
Monogastric animals particulary fission cyanogenic glycosides. Hydrogen cyanide is evolutioned by microflora in large intestine (optimal pH for enzymes is 4.0 - 6.2) There is wide difference between animal races and individuals too. Very resistant are e.g. rats. Chronical intoxication was detected in pigs fed by untreated cassada, which contented 500 mg/kg of hydrogen cyanide. There is a little datas about poultry, performance probably degrease with content of HCN higher than 100 mg/kg.
Many rumen bacteria can hydrolyse cyanogenic glycosides in Ruminants, whereas effectivity level depends on kond of glycoside - risk is mainly Prunasin - and feed ration character. Therefore ruminants are more sensitive to cyanogenic glycosides than other animals. It depends on race, category and size of animal, kind of feed intaken along with toxic forage and animal detoxication ability
In in vitro experiments were found, that condensed and hydrolysed tanstuffs inhibit cyanogenic glycosides hydrolyse. Influence of cyanogenic glycosides is low, when level of tanstuff in feed ratio is sufficient.
Human oral letal dose os 0.7 - 3.5 mg/kg body weight, sheep 2.0 - 2.4 mg/kg live weight. Cattle with body condition score 3 or more are more resistant to HNC than slimmer animals. The first ones can have intake of HCN on level of 50 mg/kg live weight without poisoning symptomes, the second ones have poisoning symptomes in much lower intake.