It’s looking like Bayley was the victim of «rat poison»:

‘Rat poison was found in the pet food suspected of causing kidney failure that killed at least 16 cats and dogs, but scientists still don’t know how it got there, state officials said Friday. The toxin was identified as aminopterin, which is used to kill rats in some countries, state Agriculture Commissioner Patrick Hooker said.
‘Aminopterin is not registered for killing rodents in the United States, according to the Environmental Protection Agency, though it is used as a cancer drug. State officials wouldn’t speculate on how the toxin got into Menu Foods’ now-recalled pet food but said no criminal investigations had been launched. Scientists at the New York State Animal Health Diagnostic Center at Cornell and at the New York State Food Laboratory tested three cat food samples provided by Menu Foods and found Aminopterin in two of them. Hooker said they would test individual components of the pet food, as well. The early test results were released to give veterinarians a better idea of how to treat sick animals.
‘“Any amount of this product is too much in food,” Hooker said.’
—Associated Press

I think I’ll go be sick now.