Yeah, I do know. I would suggest you look up some of the threads about animal consent, it gets brought up FREQUENTLY. The way I look at it is like this. No, animals cannot give verbal consent (as we understand verbal consent), but they have NUMEROUS ways of expressing consent nonverbally using queues and body language. A female dog in heat will signal intent with tail flagging and humping, for example. A male dog will literally fuck anything that will hold still long enough.
And then think about it another way. Have you ever tried to bathe a cat who doesn't consent to being bathed? That cat is going to scratch the shit out of you. Now imagine trying to fuck a horse that doesn't consent to being fucked. It's going to kick the shit out of you and could possibly kill out. Those are all non-verbal expressions of non-consent. You just have to expand your concept of what consent really means.
There are more complicated issues such as power imbalance, but those exist in human relationships as well, and it is up to each person and their own morals not to exploit a power imbalance for their own sexual gratification. One could, for instance, withhold food from a dog until the dog allows you to have sex with it. This would be immoral and unethical, and no respectable zoo would do such a thing, just as no ethical person would do the same to another human. It's an issue that has been debated by legitimate philosophers and many of them can't come up with good reasoning why it is wrong or unethical:
When you really try to discuss the issue with an anti-zoophile, most of their arguments boil down simply to "ew gross I don't like it."
I'm happy to continue discussing the topic with you, but there are plenty of good resources already out there if you want to learn more