Chickens refusing to eat the maize they had been fed has led to the discovery that their feed had been genetically modified to include a well-known weed and insect killer.

Strilli Oppenheimer’s indigenous African chickens were refusing to eat the mealies in the chicken feed bought from a large supplier. Concerned that the birds may be ingesting genetically modified maize, she had the maize tested.

The results confirmed Oppenheimer's initial suspicion -- the maize had been genetically engineered to produce proteins that are toxic to certain insects and weeds.

About her chickens' refusal to eat their maize, Oppenheimer said: "They're smart."