So basically this thread has reduced itself to the PETA arguments?
It seems this is going to go one of two ways:
Option 1: Humans (currently) run this planet, humans have domesticated dogs and other species, and humans engage in animal husbandry. This includes population controls and health choices for animals under their care.
Option 2: Animals of the world exist and manage themselves for their own reasons, and it is not ethical to interact with them in any way beyond observation. Care for the animals can be done, but only so far as it does not harm other animals or remove them from their natural habitats.
While I can understand the thinking behind option 2, I've seen enough of the world to know that life means death. Only plants and a few microscopic creatures can live without destroying other life. But when it comes to macroscopic animals, all animals live of the death of other organisms. Herbivores kill plants to live. Carnivores kill animals to live. Omnivores kill both.
If we do not kill, we will die.
We are omnivores, and many animals we use and raise are carnivores. If we want to care for those carnivores, we must kill to keep them fed.
That means no matter how much Option 2 appeals emotionally, it is not open to us.
We kill for ourselves, and we kill on behalf of our companions.
That means Option 1.
As I child I learned the lesson well, we had rabbits and chickens. When you know the drumsticks, wings, and chicken breasts on your grill were the same ones you had fed for months, the chickens were running around a few days before and that you were involved with herding them to be killed, watching them die, and plucking them, it gives a deeper respect for the food.
We have the capacity to choose and decide how we interact with the animals in a thoughtful way. We can be ethical about it, keeping useless deaths to a minimum, giving the animals a high quality of life and ending their lives quickly with as little pain as possible, and using as much of the animal as possible. We can also be unethical about it, giving the animals a terrible life up until they are slaughtered in pain and terror. Most prefer the ethical options.
I recall a group of PETA activists some years back breaking into a mink farm near my home. They vandalized the place leaving marks about how it was unfair to have the animals in cages and being destined to die. In a bitter irony, the news came out that many of the mink had been hit and killed on the highway next to the farm before the vandals even left the facility. Those that survived were going to suffer starvation because the site was on the desert border with no food or water for them and they were not taught to hunt.
The activists were thinking only about the short-term captivity of the animals, rather than the longer term issues of life quality and sustainability. The animals were released from captivity, true, but in captivity they had an easy life with all their physical needs cared for and a steady flow of entertainment, and only at the end getting a quick painless death; being released meant either a painful death on the highway or a painful death through starvation and dehydration.
While I sympathize and agree that animals should have the best life they can, often a "release to the wild" is not a better life, but a slow, painful death.
Similarly, castrating our pets who will not be reproducing means less of their life will be driven by their reproductive hormones. I've watched animals come to self-harm and harm others because of their uncontrollable drives. The animals in our care do have a better quality of life within the bounds we set because of their sterilization.