So one thing I came up with was that there is a possibility that something like in-Vetro-meat becomes such an economically cheap product that we would use it to preserve carnivores without sacrificing the lives of others. in that case, from an intergenerational perspective, we may be justified to let animals continue eating meat (or even provide them with meats from animals that are not endangered) in order to keep them surviving till that day comes.
I do not have a stance on this justification yet, I just came up with it now. So it may be flawed. Please offer your criticism on where you find problematic.
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And one other point, I really am enjoying this discussion with you guys. @mrnormal5150 @unenlightened @Bitter Crank@Noble Dust

Can you explain and give an example? I'm not sure what you mean.

I think utiliterianism by its nature is a maximizing consequentialism.
So the first line of wikipedia on utilitarianism is:

Utilitarianism is an ethical theory that states that the best action is the one that maximizes utility. — wikipedia

also by Bentham:

The said truth is that it is the greatest happiness of the greatest number that is the measure of right and wrong.' — Jeremy bentham

But I can imagine a version of utilitarianism that may say: "Do what cause more pleasure than pain." But that kind of principle has the obvious problem of being useless in cases where you have to decide between a bad choice and a worse choice; something that is a deal breaker for most utilitarians I've met (not many, it turns out).
One of the most serious criticisms towards utilitarianism is that it is too much demanding. I myself found it useful in many situations, but it also takes a lot of time and energy to analyze consequences of my actions. (feeding my dog, being one).

In any case, even if I don't kill my puppy (honestly that's unimaginable to me.) I would really need to know if I should advocate for such actions.

I'm with you bud.

I hope I'm not insulting anyone by insisting on utilitarianism. I'm not insisting on utilitarianism because I have negative attitudes towards alternatives. I insist because of the hugely unintuitive implications that utilitarianism have in this situation.

There certainly are ways to justify any actions using different principles. And every principle has itsown unintuitive implications. But as the topic title indicates, I'm specifically looking into analysis of this exact problem, using this exact school of taught.

Guys, I really appreciate your inputs. But they are not really what I'm looking for.
@unenlightened I'm partially familiar with deep ecology. And it would solve some problems and give rise to some others. But that's not really what I'm looking to answer. Inherit or intrinsic rights are completely separate issues.
@Bitter Crank the thing is that though one can say that doing all those things are doing our best. But when analyzing in a theoretical sense "good enough" for utilitarianism is "the absolute best result possible". So just doing what is intuitively apealing is not neccacerally the right answer. Doing analysis based on a clear principle is not dehumanizing, as non other than humans have achieved such levels of abstraction. It's not dehumanizing, it's just using all faculties of human brain instead of just relying on implicit, intuitive thought.
@Noble Dust
Thanks for your input. But changing the delima is not cannot solve the problem. Cats also cause more death than they live. Still that's changing the delima. It's like trying to solve the trolley problem by saying: OK, i will not cross any train rails anymore.
Ownership is also not an intrinsically bad thing. Nor is it that easy to define and implicate around the edges. So that's whole other story altogether.

I really appreciate your time and efforts.

I would agree. However, by giving the intrinsic right of living to all animals, we still face some animals that quantitatively cause an early death to many other animals per year. We also have to justify that making such a "right" would cause more happiness to all that are capable of happiness and vice versa.

The problem here is that "ought implies can" is only with consideration to the choices one thinks one has, in other words, Maybe my dog cannot make that choice because that's not a choice for him. But I can kill my dog. I have the choice. I can. Therefore it should be considered as an alternative.