It is possible to grow veg and have chickens but you need to be able to keep them away when necessary, I let mine out during autumn and winter onto the veg patch, but as mentioned above in the spring when you have young plants it would be a disaster! They never pick over the bit that you want them to, always heading for your prize seedlings. Having said that, what about fruit bushes and canes or herbs, they dont go for onions or leeks but as both of those like quite dry ground the chickens are likely to dust bath there!