Alice Dee on Facebook already has a thread going about this topic however it’s worth making my own post about because it’s important. I have no pets nor ever plan to have a dog or cat. I would in theory if I was in the financial position where I owned land out in the country. However I do have strong feelings about this topic because I agree with the majority of vegans and even some non-vegans who care about avoiding the suffering and death of many dogs and cats by preventing them from breeding.
The majority of what I have read shows that the benefits of sterilizing animals always outweighs the risks of allowing them to breed. The only alternative to sterilization is to literally watch them 24/7 to make sure they do not have sex with animals of the opposite sex or keep them in a cage while you are gone at work all day. Because of this, I believe it is the less cruel option just to sterilize them if you can afford it and it may even benefit their health because most of what I read shows the fixed animals live longer than the intact ones on average.
People do not consider the various causes of death that reproduction involves. Especially for females, they will live shorter lives if their body spends energy procreating. Additionally fixing them removes the possibility of cancers or anything else that might be a cause of death that involves diseases of the ovaries and testicles.
I have some links here which are worth a look.