There are 273 known species of harmful and poisonous plants. They are found on pastures, in hay, silage, haylage, straw. The most common poisonous plants are where acidic soils are present, in wet and swampy meadows and pastures, forest areas, among shrubs, in abandoned parks and gardens. Animals on pastures usually leave the poisonous plants untouched. However, where there are few edible and many poisonous plants, animals can eat (often hungry) both. In the spring, poisoning is observed with plants from the family of buttercup, umbrella, orchid and autumn plants, and in the summer, during a drought, milkweed, swallow, kutrov, etc.
The toxicity of plants is caused by the content of certain substances in them.
Alkoloids are nitrogen-containing organic compounds of mainly plant origin, consisting of atoms of hydrocarbon, hydrogen, nitrogen and oxygen. The content of alkaloids in different parts of the plant may be different, but in general it reaches 0.2-2 % of all toxic substances. Due to the strong physiological effect of alkaloids (for example, on the function of the nervous system) they are the most dangerous for animals.
Glycosides are nitrogen-free organic compounds of complex structure. Their molecules consist of a carbohydrate and a non-carbohydrate part, the so-called aglycone (genin). According to the chemical composition of aglycones, glycosides can be of the following types: phenylglycosides (when hydrolyzed, they form disinfectants, such as hydroquinone, and other compounds from bearberry leaves, in particular from arbutin); thioglycosides (contain sulfur, mustard essential oil is formed from mustard sinigrin); nitrile or cyanglicosides (from lianmarin, contained in linseed cake, cyanolic acid is formed).
In plants, flavonic glycosides, or flavones, yellow plant pigments can also be present, which eliminate the increased permeability and fragility of capillaries, have a hypotensive effect, protect ascorbic acid from oxidation, anthraglycosides (characterized by a laxative effect – hay, sabur, rhubarb); saponins (form strongly foaming colloidal solutions with water, are cellular poisons, cause blood hemolysis) , etc.
There are also glycosides-alkaloids – combinations of glycosides and alkaloids (for example, solanine in potatoes, etc.). Toxic in plants can be albumins – substances of a protein nature (for example, ricin in clover seeds), essential oils (the main part is terpenes and their oxygen – containing derivatives), organic acids and their anhydrides (oxalic acid, euphorbic acid anhydride), substances such as lactones (dicoumarin, santonin et al.).
The most sensitive to poisonous plants are donkeys, mules, horses, pigs, birds, the least – sheep, goats, rabbits. Poisoning can occur in acute (occur suddenly and have pronounced symptoms), subacute and chronic (develop gradually with longer use of food containing toxic substances) forms.
The central nervous system, gastrointestinal tract, cardiovascular system, etc. are affected. Cases of poisoning are characterized by the following signs: suddenness of the disease after a change of pasture or feed; mass disease of animals with the same clinical signs and pathoanatomical changes; new cases of the disease do not appear when the suspicious feed is withdrawn.
According to their physiological effect on the animal body and the clinical picture caused by them, poisonous plants include plants that mainly affect the central nervous system, respiratory organs, heart, gastrointestinal tract, kidneys, liver, causing symptoms: salt metabolism disorders, as well as anoxemic phenomena.
The content of toxic substances in plants during the entire growing season, as a rule, varies. Some plants are more poisonous during the flowering period, others-before and after flowering. In some, both the ground parts and the roots and rhizomes are dangerous, while in others, toxic substances can accumulate only in the seeds or vegetative parts of plants. Most of them contain alkaloids. When the plants are dried, the toxic properties are preserved. Some of them (hellebore, etc.) remain poisonous even during silage. The content of volatile toxic substances is significantly reduced during drying.
To prevent poisoning in the pasture and in the stable, appropriate measures are carried out both in summer and in winter.
They destroy poisonous plants in pastures and meadows by liming, plastering, plowing, reclamation, etc. Appropriate crop rotations with grass sowing are introduced. Mow and destroy plants that remain uneaten after grazing.
Explore the pasture area before driving the animals. When finding places with a large number of poisonous plants, shepherds are warned about the danger of grazing animals. In such cases, it is advisable to enclose these areas.
Do not drive the cattle out to pasture in the spring until the useful plants appear in sufficient quantity. Before driving the animals should be fed. When grazing on stubble, care must be taken, as there are poisonous plants (field horsetail, etc.).
Areas with poisonous plants are used for hay harvesting, taking into account their types, since many of them completely retain their poisonous properties even after drying.
Special attention is paid to animals recently brought to the farm, as well as young animals. With careful observation of them, you can always notice changes in the behavior and condition of the animals in a timely manner, quickly transfer them to another pasture and, thereby, prevent mass poisoning or provide immediate assistance to the sick.
For prevention purposes, destroy harmful weeds before their seeds ripen.
In the stable period, poisonous plants are less dangerous. However, even at that time, it is necessary to ensure that their content in the hay does not exceed 1 %, and in the bundle-no more than 0.2 kg. The same applies to straw.
Grain feed and products of their processing should not contain seeds and residues of poisonous plants. Especially carefully it is necessary to check grain waste, as they often contain a lot of poisonous seeds (intoxicating chaff, kukol, field mustard, etc.).
Harmful and toxic impurities in feed can not always be detected (in ground grain or mixed feed), so it is advisable to take samples of new feed entering the farm and examine them in the laboratory. Otherwise, you should resort to pre-feeding this feed to individual, less valuable animals and only in the absence of any harmful consequences, then use it for the entire livestock.
Some grain and mill waste, when used for animal feeding, serves as a source for spreading various plants, including many poisonous ones, in fields and meadows. It should be remembered that weed seeds, passing through the gastrointestinal tract, do not lose germination and fall with manure on fields and meadows. Therefore, grain waste should be fed to animals in a ground form, and it is best to pre-steam them well or boil them.
The grinding of grain waste must be fine in order to crush and destroy all viable weed seeds, including those that are small enough.
The existing standards in feed allow the presence of the following poisonous and harmful plants, seeds, mustard and vyazel in grain feeds (oats, barley, wheat, rye) should not exceed 0.1% of the total amount (together or separately), kukol – no more than 0.5%, heliotrope omitted – no more than 0.1%, trichodesma gray should not be at all.
In mixed feeds, the content of weed seeds is allowed, % of the total amount, not more than: kukol – 0.25; henbane, hemlock, dog parsley, cornflower, rattle, black nightshade (separately) – 0.01; intoxicating chaff – 1; coronilla, blackshark (separately) – 0.1; total number of seeds of henbane, hemlock, dog parsley, cornflower, rattle – 0.1; total number of seeds of coronilla, blackshark, nightshade, chaff – 1,1.
To reduce the toxicity of grain waste, they are washed, soaked, and boiled before feeding.
In order to prevent poisoning with poisonous and harmful plants, you should choose the right technology for harvesting, storage and mode of use.