I think egg production by chickens is actually more efficient than that. If I'm reading Figure 1 in the following link correctly, it looks like modern farms are about 17% efficient for calories of food fed to the chickens to calories of eggs produced: http://iopscience.iop.org/article/10.1088/1748-9326/11/10/10...

For comparison (from the same figure) pork is 9%, chickens raised for meat are 13%, cow production of milk is 17%, and cows raised for beef are 3% efficient.