Urea
Acute Oral Toxicity
A
web search for urea and wildlife reinforced the procedural guidance of cleaning
loading sites. Most of the information about urea and animal toxicity deals
with cattle and other domestic ruminants because urea is regularly used as a
nitrogen supplement in cattle feed.
Urea
toxicity is highly dependent on the rate at which urea degrades to ammonia. Humans
and monogastric animals do not rapidly convert urea to ammonia and urea is
practically nontoxic following ingestion by these species. However, ruminant
animals very rapidly convert urea to ammonia following oral ingestion and are
much more susceptible to toxicity following ingestion of urea. Accidental
ingestion of granules of urea should be considered nontoxic unless a large amount
was ingested.1
Quick
Facts…
-Urea
can be fed to ruminants as an economical replacement for a part of the protein
in a ration.
-The
amount of urea a ruminant animal can use depends on the digestible energy or
total digestible nutrients (TDN) content of the ration.
-No
more than 45 to 113 grams of urea per head per day should be fed to feedlot
cattle.
-Toxicity
should not be a problem if urea is fed according to recommendations.
Many
years ago, researchers recognized that nonprotein nitrogen (NPN) compounds are
used by bacteria in the rumen of cattle and sheep. Since that time, studies
show that these compounds are broken down to ammonia during the normal
fermentation process in the rumen. Animals with simple stomachs (pigs and
chickens) cannot make use of large concentrations of NPN compounds because of a
lack of enzymes and bacteria to break down the NPN to ammonia and synthesize it
into protein. 2
Table
of urea oral toxicity
|
LD50
|
Rat
3
|
14,300
mg/kg
|
|
LD50
|
Mouse
3
|
11,500
mg/kg
|
|
LD50
|
Cattle
3
|
510
mg/kg
|
|
LDLO
|
Dog
4
|
3,000 mg/kg
|
|
LDLO
|
Goat/sheep
4
|
511
mg/kg
|
|
LDLO
|
Pigeon
4
|
14,800
mg/kg
|
|
LDLO
|
Rabbit,
oral 4
|
10,000
mg/kg
|
LDLO – the lowest published lethal dose
of a substance determined by testing on animals.
A 1000-pound cow needs to consume 150
grams of urea in 30 minutes for toxicity to occur. 5
Deer and moose are ruminants. No
toxicity data specific to them was found. Given that they are ruminants, it
seems reasonable to conclude that urea toxicity is similar to other ruminants,
therefore in the vicinity of 500mg/kg of body weight. Cleaning of loading sites
and spills should provide adequate protection from excessive exposure to urea,
and the normal application rate of urea pellets on the forest floor should not
pose a toxicity risk to ruminants.
Other references:
http://www.goatworld.com/articles/urea_toxicity.shtml
http://www.luresext.edu/goats/training/nutrition.html
2.) http://www.ext.colostate.edu/Pubs/livestk/01608.html (Colorado State U)
3.)
Agrium MSDS
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