Afterward I saw that a clarification had come in:
Sorry for the length; in short, the question is whether the fact that a food contains poison makes it unfit for a dog’s consumption, or whether these are two separate categories—meaning that the ground wheat is leaven and therefore included in the prohibition, and the presence of the poison is irrelevant. I should note that I tend toward the latter possibility, and I’ll add one more fact: dogs tend to eat these baits.

My response:
In the Shulchan Arukh, Orach Chayim 442:1-2, it says that moldy bread is unfit for consumption and therefore there is no prohibition of owning leaven regarding it. So you see that something that was leaven and became spoiled, and is no longer fit for consumption, is not subject to the prohibition of owning leaven. True, one might distinguish and say that with moldy bread, the bread itself spoiled, whereas here something else was added to it—but logically there is no reason to distinguish. Moreover, many halakhic decisors wrote that pouring bleach on bread counts as destruction of the leaven (for according to Jewish law we do not require burning, unlike the view of Rabbi Yehuda). And that is really just like our case.
However, if it is fit to leaven other doughs, then its law is like sourdough even though it is not fit for eating, as the Mishnah Berurah writes there, section 10.

As for the fact that dogs eat these baits: since it is unfit for human consumption, the whole discussion is only about a rabbinic prohibition, if it is fit for a dog’s consumption. If it is truly dog food in the full sense, and not that the dog merely puts it in its mouth, then perhaps there is a rabbinic prohibition here. But simply speaking, there is no rabbinic prohibition of owning leaven. And from the case of moldy bread it seems that even when it is fit for a dog’s consumption but not for a person’s, there is no prohibition of owning leaven unless it is fit to leaven other doughs.

And one should further add, logically, that since this was made for use as poison, it does not have the status of food even if someone/something does eat it.

Hello, honorable Rabbi,
It is well known that one may not use syrups—for example, Acamol—that contain sweeteners derived from leaven, or any other leaven.
And I ask, based on the Rabbi’s view: since the medicine itself is a poison (taking Acamol in high doses is certain death), then what does it help that we added sugar to it and now have sweet poison?
True, in small doses it is a medicine, but a medicine cannot be treated as food—seemingly a definition that is needed in order for there to be a prohibition of leaven.

You’ve gone overboard. Medicine is not poison. Chocolate too is harmful in high doses.

In any case, if the sweetener gives taste, it is not nullified in the medicine. So perhaps it is enough that the sweetener is food. But as I said, there is no need for that here.