Which contamination triggered the massive 2007 pet food recall that severely impacted wildlife rehabilitation centers' food supplies for recovering predators?

In the world of animal and wildlife products, safety recalls can have significant impacts on both consumers and wildlife conservation efforts. This trivia question focuses on one of the largest pet food recalls in history that affected wildlife rehabilitation centers and zoos across North America. Test your knowledge about how product recalls in the animal industry can create ripple effects throughout the wildlife care ecosystem.

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Melamine and cyanuric acid from Chinese wheat gluten
Pentobarbital from euthanized livestock
Aflatoxin from moldy corn ingredients
Thiamine deficiency from processing errors