gyp lacking heat cycle any ideas?

I was once told that feeding a dog alphalfa pellets would bring them in heat more often and quicker. I did not think that horse feed could do that until...my gyp, would go to every horse trough and eat from them and them when she was in her kennels, she would bark like crazy and i would put her a scoop of sweet feed and alphalfa pellets mix in her kennel for her. She came in heat at 8 months...and me not paying attention, she got bred. While weening her 1st litter, still giving her the horse feed mix, she got bred again!! Needles to say, I stopped the horse feed after being told this and she has not came into heat in 6 months!! Thank God!! She gave us a run of 16 pups in 2 litters, in 6 months timing!! All of which have turned out to be some pretty good hunting pups! Its funny cause both litters were unexpected and we have people calling back to see if she has had any more!! Good luck with your dog...its a cheap way to find out if it works for her...about $9 a bag for just plain ol alphafa pellets.