The nodules seen on the chicken feet are likely the region where bony projections called metatarsal spurs grow out from.
National University of Singapore bird researcher David Tan said chickens use these spurs for self-defence and aggression.
In roosters, this spur can grow to up to several inches, said Mr Tan.
Hens usually have shorter spurs, although they can grow to "impressive lengths" in some breeds.
"All chickens have them but, in different breeds, they will look slightly different," said Mr Tan.
Some farmers may trim or cut these off to ensure the chickens do not accidentally injure one another.