Secondary or relay toxicity occurs when an animal indirectly ingests a toxic substance by consuming another animal that has been poisoned. In the case of rat poison, a dog could eat a rodent that has consumed the bait, leading to the dog absorbing the poison through the rodent's tissues. While the likelihood of secondary toxicity is generally lower than direct ingestion, it remains a significant risk, particularly with poisons containing anticoagulants or bromethalin, which can persist in a rodent's body. Veterinary intervention is critical if exposure is suspected.