In the case of pet foods...8 billion male 1 day old baby chicks are suffocated to death in the egg industry to be used for huge profit as pet food. A 70 billion USD dollar per year industry that is ...the pet food industry.
They are devising new ways to slaughter animals such as controlled atmosphere killing, which slowly removes the oxygen from the animals' environment and replaces it with a non-poisonous gas that puts them to sleep before they die from lack of oxygen.
Here is a hypothetical scenaro: if they adapted the technology described above for use in veterinary hospitals as a method of euthanasia (which would have the effect of producing carcasses that are not contaminated with barbiturates), and if all pets came from breeders and there were no rescue pet animals in existence, and if some entrepreneur started a cat food company that utilized the bodies of euthanized pet rabbits and dogs, obtained from veterinary clinics, would you then say the animals were bred and killed to be pet food?
These hypothetical dogs and rabbits would have been bred for the retail pet industry, not the pet food industry. And they would be euthanized to end their suffering or for the owners' convenience if they didn't want to take care of them anymore or could not afford some treatment their pet needed - not to produce meat for use in pet food. But regardless of the reasons they were bred and killed, now that there is a carcass, it is used for pet food.
In the case of those 8 billion male 1 day old baby chicks, they were bred to procure female egg laying hen chicks, and killed to get rid of them because the egg industry has no use for them. If the bodies of those chicks do not go into pet food, they will go into a landfill.
There is a difference between day old chicks who are essentially waste products of egg industry activities and day old chicks that are bred and killed to be pet food. I would not buy pet food made from the latter, or trade a life for a life. If there were no "waste product animal carcass" pet food available, I would begin raising crickets and mealworms (beetle larvae) to feed to my cats, and hope these insects cannot suffer. I would not buy cat food made from animals specifically bred to be cat food.
In your rhetoric, you usually frame everything as "you are trading a life for a life, it makes no sense, you are illogical, the lives of chickens and turkeys are just as valuable as dogs and cats, you're being specialist, etc."
If there were currently a cat food made exclusively from euthanized dogs and rabbits I would start using it just to prove to you that this has nothing to do with speciesism, because while I don't have a dog, I do have some pet rabbits. And I wonder if you would think that buying this food represents some injustice being committed against the dogs and rabbits., the way you do with chickens and turkeys.
As it is and as Vegepets states, the cat food I currently feed my cats is made, partially, from euthanized dogs and cats, with barbiturates and flea collars included, so you have to admit you are at least partially wrong in what you say, to the extent that dog and cat meat is in cat food, because these dogs and cats were clearly not bred and killed to be cat food, as you claim livestock birds are.
Finally, one thing I hear on this forum a lot (but I have never heard you say this yourself) is that it is okay to use medicine made from animals if there are no vegan alternatives. One of my cats eats prescription cat food. What vegan cat food are cats who need prescription food supposed to eat? If humans can take medicine they need made from animals, and this is considered to be vegan, then why isn't it vegan when a cat is on prescription food made from animals?