I have a hen that is 9 years old. She has been laying fine, but when I switched mates this time her 1st egg was the size of a marble?

A lot of work has been done on improving bone density in foals in horse racing. Has there ever been research done in racing pigeons?

A lot of hens only laid one egg?

Mijn duivinnen pikken mest. Wat is hier de oorzaak van?