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Nitrate poisoning occurs in
humans, cattle, goats, horses, dogs, birds, sheep
and swine to a lesser degree.
The nitrate ion itself is
relatively non toxic, it is when the nitrate is
broken down in the digestive system that the
trouble occurs. Nitrate becomes nitrite which
becomes ammonia, which
becomes a protein. It is the nitrite phase in the
stomach(s) where some of the nitrite can enter the
bloodstream where it changes into a chemical that
reduces the bloods ability to carry oxygen. Oxygen starvation of the tissues
occurs, along with a different process in which
Prussic acid causes death of the tissues. Nitrate
poisoning happens when animals eat grass, hay, or
drink water that contain large amounts of the
chemical. This can come from plants, or from
fertilizers used for farming.
Nitrates occur in most plants and
in water, but sometimes the levels get so high as
to become toxic. Grazing animals are usually
poisoned by forage and hay. Nitrate consumption of
as little as 0.05% of the animal's body weight may
be lethal. Problems occur most often during cool
temperatures, cloudy days or drought; also where
heavy use of nitrate fertilizers occur. Nitrate
formation increases when soil temperatures are 80
- 90 degrees.
Low light (cloudy days) and night
time causes nitrates to build up in plants, it is
dispersed when
sunlight hits the plants. The accumulation of
nitrates in plants is a natural process. The plant
gathers nitrogen through its root system and then
stores it as nitrate in the stems. This nitrogen
is later converted to protein in the leaves. Horses can tolerate up to 0.50%
nitrate in their total dry matter diet. A rule of
thumb is to select hay for horses that contains no
more than 0.65% nitrate ion on a dry matter basis.
Poisoning happens quickly, animals may be found
dead before symptoms are noticed.
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