I've tried many things, but here's something cheap and readily available if you live near a pine forest.
I've been cursing our property's pine trees ever since we moved in. Their needles kill everything else, and there are often beads of sap that stick incorrigibly to everything they touch. Then the trees themselves are overgrown and tall, providing a habitat for goshawks to then swoop down on unprotected birds. Lastly they overshadow our block, making it hard for us to develop an understorey.
But now I've found a cost-reducing use for them:
What a fabulous pen floor they make! They're non slip, a pretty colour, and the droppings tend to drain through when it rains instead of piling on top.
They're slower to break down than many other litters like straw, and I feel there may be some antiparasitical properties as well.
They're also quite soft underfoot, so a heavy bird like the hybrid above can walk comfortably. In fact I've even put pine needles in the night-shed for a comfy floor and nesting material.
Our area has a reasonably high rainfall, and there's nothing worse than a slushy pen. However pine needles seem very good at keeping the mud away from the surface, and are quite fine to walk on even in the squelchiest weather.
Last but not least... In my 'neck of the woods' they're free. Having spent $14 for a bag of sugar cane mulch earlier in the year, this is a big saving. And I would say they're a much better choice.
So instead of cursing the trees for their various drawbacks, I'm feeling lucky they're here.
By the way, I'm sure many other trees can be used in this way — last year I was gung ho about eucalyptus leaves and she-oak (two native Australian trees that also like to kill everything that tries to grow nearby). Both also have antimicrobial properties, though eucalyptus leaves aren't particularly nice to walk on. The springy, spongy feeling of pine needles underfoot is certainly a pleasant change.
And after all 'the natural chicken' isn't just about the birds themselves, but about raising and growing as much as possible at home, including the mulch.