Cholecalciferol, also known as vitamin D3 or colecalciferol, is a type of vitamin D that is produced by the skin when exposed to UVB light; it is found in certain foods and can be taken as a dietary supplement.
...Rodents are somewhat more susceptible to high doses than other species, and cholecalciferol has been used in poison bait for the control of these pests.
The mechanism of high dose cholecalciferol is that it can produce "hypercalcemia, which results in systemic calcification of soft tissue, leading to kidney failure, cardiac abnormalities, hypertension, CNS depression, and GI upset. Signs generally develop within 18–36 h of ingestion and can include depression, loss of appetite, polyuria, and polydipsia." High-dose cholecalciferol will tend to rapidly accumulate in adipose tissue yet release more slowly which will tend to delay time of death for several days from the time that high-dose bait is introduced.
In New Zealand, possums have become a significant pest animal. For possum control, cholecalciferol has been used as the active ingredient in lethal baits. The LD50 is 16.8 mg/kg, but only 9.8 mg/kg if calcium carbonate is added to the bait. Kidneys and heart are target organs. LD50 of 4.4 mg/kg has been reported in rabbits, with lethality to almost all rabbits ingesting doses greater than 15 mg/kg. Toxicity has been reported across a wide range of cholecalciferol dosages, with LD50 as high as 88 mg/kg or LDLo as low as 2 mg/kg reported for dogs.
Researchers have reported that the compound is less toxic to non-target species than earlier generations of anticoagulant rodenticides (Warfarin and congeners) or Bromethalin, ....Nevertheless, the same source reports that use of cholecalciferol in rodenticides may still pose a significant hazard to other animals, such as dogs and cats, when rodenticide bait or other forms of cholecalciferol are directly ingested.