The only real "change" that could be attributed to this is that the birds have a ready source of protein in the bug bodies -- if your feed program was on the low side of protein to begin with (ie layer ration which is generally on hte low end plus any sort of low protein treats like scratch, veggies, etc) then the increased protein could certainly cause an increase in production as it would better support the hens' bodies in a way to make more regular production possible.
Whether there is a cause/effect situation here would depend on how long there was between the zapper's arrival and the increase in production, the age of the birds (ie if they are young you may have had more birds come into production at about the same time as you go the zapper, giving the appearance of a cause/effect), etc.
