In my opinion, we don't have any business providing a solution for predation. Our responsibility to animals is to leave them alone in the wild and not destroy their habitats. We have already messed this up by domesticating several wild animal species. Domesticating these animals has caused them to become completely dependent on us which has brought them immeasurable suffering and death and our responsibility to them now is to not let any of them reproduce, so that they eventually go extinct, leaving only wild animals extant. I am not saying we shouldn't have pets. I have three 'rescue' cats myself. What I am saying is that we should never intentionally allow a single domesticated animal to reproduce because to do so is to just bring more pitiful creatures into the world who are entirely dependent on human's for their well being.
Biologically, I don't think what you are suggesting could ever work. Maybe it could work in theory with some kind of futuristic or alien technology, I don't know. Many reptiles and and other animals, such as various kinds of fish will not eat anything that isn't moving, so that is one thing.
As for the statement, "so what, animals eat other animals, it's natural", here is how I would answer them:
First, the way that you obtain and process meat isn't natural, so if your argument is "what is natural is moral" then you are immoral by buying meat in a grocery store, or using a gun to hunt, etc. To be moral all of the meat you eat should be from animals that you kill with your bare hands and/or teeth and devour raw, or it should be carrion that you come upon, which should also be eaten raw.
By the same token, it is unnatural to consume the mammary secretions of another species. Human beings are the only animal to do this, and also the only animal that consumes milk past infancy, so nothing whatsoever is natural about dairy, making it completely immoral.
Second, animals rape each other all the time. Rape is totally natural. So does that make rape moral as well? [Edit: other things that occur in the animal kingdom: the killing of the offspring of rival males, infanticide, cannibalism, etc.]
Third, animals do not have the degree of self awareness that humans have evolved, which allows us to contemplate the ethics of meat eating in societies in which veganism is a viable alternative. When something isn't necessary it is a choice. Animals cannot even contemplate that choice, let alone make it, so it is absurd to compare them to us in this respect.
There are probably other ways to answer it but I can't think of any more.