[chicken george25]

one of my pekings has been mating with a cockerel she layed her first egg yesterday but i dont know if its fertile? How can you tell if it is?

[joyfull]

are you hoping to hatch her eggs? If not then when you crack open the egg if it is fertile you can see the germinal disc on the yolk.
If you look at this web page it will help:-

http://4hembryology.psu.edu/fertile.html