Animals will eat substances containing harmful heavy metals when pecking. These heavy metals are mainly stored in brain tissue. The older they are, the more they are stored and the stronger their toxicity is.
While enjoying delicious food, consumers also ingest heavy metal poisons. If they eat too much, they may cause toxic reactions. Therefore, the head of a chicken, the head of a duck and the head of a goose should not be eaten more.
Parts that other animals can't eat:
Thyroid gland, adrenal gland and pathological lymph gland on pigs, cattle, sheep and other animals. Eating thyroid by mistake can cause hyperthyroidism, with symptoms such as dizziness, headache, excitement, mania, convulsion, fatigue, palpitation, rapid pulse, poor appetite, nausea, excessive sweating, fever, etc. Studies have shown that people will be poisoned if they ingest1.8-3 mg. People who eat adrenal glands and diseased lymph glands by mistake will also suffer from many diseases.
Reference to the above content: People's Daily Online-Can chicken and duck fish heads be eaten or not? Under what circumstances should soy milk not be drunk?