Most of the chickens that have been killed were not sick. From Joel Salatin at rwmalonemd.substack.com:

Numbers change each day, but at the last count about 60 million chickens (mainly laying hens) and turkeys died in the last year. A bit more than a decade ago it was 50 million. Are these cycles inevitable? Are the experts funneling information to the public more trustworthy than those who controlled press releases during 2020’s covid outbreak?
If thinking people learned only one thing from the covid pandemic, it was that official government narratives are politically slanted and often untrue. In this latest HPAI outbreak, perhaps the most egregious departure from truth is the notion that the birds have died as a result of the disease and that euthanasia for survivors is the best and only option.
First, of the nearly 60 million claimed deaths, perhaps no more than a couple million have actually died from HPAI. The rest have been killed in a draconian sterilization protocol. Using the word euthanized rather than the more proper word exterminated clouds the actual story. Euthanizing refers to putting an animal out of its misery. In other words, it’s going to die and is in pain or an incurable condition.