Yes, MOLD is VERY toxic! It can make your pet very sick...
The link above mentions Mycotoxins from Pet Poison Hotline (dot) com. I'll link it here:
My Dog Ate Moldy Food - Mycotoxin Poisoning in Dogs, Cats Moldy Food (Mycotoxins) Poisonous to: Cats, Dogs
Level of toxicity: Generally moderate to severe
Common signs to watch for:
Vomiting
Agitation
Walking drunk
Tremors
Seizures
Severe secondary hyperthermia
Ingestion of moldy food from the garbage or a compost pile puts dogs, cats, and even wildlife at risk for toxicity due to tremorgenic mycotoxins. These toxins may be found in moldy bread, pasta, cheese, nuts, or other decaying matter like compost. Clinical signs include vomiting, agitation, walking drunk, tremors, seizures, and severe secondary hyperthermia. Signs may persist from hours to days, but typically resolve within 24-48 hours with aggressive veterinary treatment.
Poison type: Foods
Alternate names: aflatoxin, Aspergillus, moldy food, mold, penitrem, roquefortine, tremorgenic, compost, tremors, seizures, Penicillium