I see that dawg also recommends alternating valbazen with Zimectrin Gold or another wormer with the praziquantel in it. I may pick up some ZG this weekend. I feel mildly concerned about dosing the birds with so much, but better chemicals than tapeworms feeding off of them. Pumpkin seeds aint' gunna cut it! I'm somewhat amused/horrified that folks seem to think DE, fermented feed (which I do) and apple cider vinegar (I also use) act as wormer or preventative for their chickens. Nope, doesn't work that way.
People who "worm" that way probably don't have chickens with infestations, or visible infestations. So they think it works. How would you know, unless you have the bird tested for parasites before and after?