Chicken forum gurus commonly set out to recommend regular worming. Some are so determined to push this practice, they never mention the almost-certainty that regular worming will produce resistant worms more successfully than it will rid the flock, or their ground, of parasites. Put simply, worming can only rescue susceptible birds from a worm overload; it can't eliminate worms.
More interestingly, a recent study of people suffering from irritable bowel (IBS) and similar problems found that a high percentage of those who chose to be infected with hookworms had their IBS symptoms appear to resolve! Now that's amazing. It appears the worm activity caused a strengthening of the weakened gut wall. (My reference for this, with apologies, is an article in Australia's Sydney Morning Herald of a few days ago... I know I ought to dig it out, and will try! Promise.) At any rate, it seems the idea that intestinal worms are inevitably bad is perhaps overstated in modern medicine.
The question of whether small worm burdens may be helpful aside, it's also true that different zones have different worm problems, and these problems are to a large extent related to things like humidity, rainfall patterns (e.g. summer rain can cause worm explosions) and, gasp, shock, horror, minerals in the soil. Yet you don't hear forum wormer-pushers mentioning that minerals and paddock rotation matter when it comes to worms.
Coastal soils in areas with high summer rainfall are almost inevitably depleted in copper, cobalt and other minerals. Sheep raised coastally in these areas often succumb to barber's pole worm, which causes anaemia. However I know from keeping sheep in an area notorious for worm problems (Coffs Harbour, NSW) that frequent worming isn't necessarily the answer. In fact, one lamb that had succumbed to what appeared to be a high worm burden failed to respond to worming treatments at all. The vet decided the worms were possibly resistant, and kept applying different worming products. The poor lamb just got worse. His wool had stopped growing, he had dermatitis, was bone-thin and pot-bellied, and had bottle jaw (a swelling around the jaw caused by anaemia).
I finally gave up on worming the poor fellow, and gave him injections of vitamin B-12 (effectively, cobalt) as well as drenches high in copper (mainly in the form of seaweed meal). Immediately — as in a matter of hours — I could see that his wool had begun to grow. He certainly had worms, but they weren't his main problem. He was susceptible to worms and had eroded gut lining because of copper-cobalt anaemia caused by poor soils, an insufficient mineral lick, and insufficient dietary protein.
After that terrible experience I began to keep my sheep entirely without worming, which is to say using a combination of paddock rotation, a copper-enriched mineral block, and a small amount of supplementary feed (barley, lucerne and lupins). This was only a short experiment (under 6 years) but it seemed to prove that, at the very least, an emphasis on minerals and protein could reduce the need for worming with harsh chemicals, and eliminate it in otherwise-healthy and well fed sheep.
Now to chickens, which are, of course, quite different to sheep. However it also seems possible that a creature that evolved in rainforest may have slightly stronger constitutions than they're given credit for. At the very least, I decided after my sheep experience to cut back on worming.
I now only worm when I see definite signs of a need. So far, my growers are entirely without mucky bottoms or other signs of worms. I'll have a check of their intestinal tracts when each of the four eaters are processed for the table, and speak up if I see anything troubling. I recently moved five adult pullets to the breeding pen, and was somewhat astonished to find that the ISA browns in particular — not exactly notorious for carcass weight — were chunky, weighty birds, as were the australorp cross leghorns.
Like everything I do, this blog relates a process of learning as well as reading, thinking, making mistakes and fixing them... But I'll let you in on a secret. Those ISA browns I found surprisingly heavy are about ten months of age, and neither has ever been wormed. They've been kept in a pen where I've raised several batches of layers, and the pen has had its share in the past of visiting birds. They've also spent time free ranging and digging the soil. Now, ten months isn't long to go without commercial worming. But if I'd listened to some of those forums, I'd have wormed them three times already! So whether or not I have to worm them in future (and I will if they appear to need it) I honestly think their present condition says it's possible to do things differently.
And sometimes I find myself wondering... Do modern chemical wormers make intestines more susceptible to future worm burdens? It sounds unbelievable, but on the other hand, it would be a good way for a chemical company to stay in profit... But of course I can't believe anyone, even a scientist, could be that hard-nosed.
Meanwhile I'll continue to wait for worm signs before worming... And I'll keep up the protein and fresh feeds, as well as mineral supplements like seaweed meal (judicious amounts only, of course: seaweed meal is high in iodine) just in case.