>So I'm aware that, most notably, humans and cows suffer quite a debilitating condition if they partake in cannibalism, as Kuru and mad cow disease from prion infection.

I think it's important to understand exactly how Kuru happened.

Specifically, it happened in a group of people who engaged in ritual cannibalism of members of their own group who had died. Someone in that group had a spontaneous case of CVJD. They died, presumably of the disease, and were eaten by group members...specifically by women and children. Men occasionally at meat, but never organ and brain tissue. And nearly all cases of Kuru were in women or children. People who ate infected tissue and became infected themselves died, were eaten, and passed the disease along.

So it wasn't just cannibalism that allowed kuru to spread, it was the specific circumstances of cannibalism. First of all, a rare case of CJVD had occurred in the population to kick the whole tragedy off. The people who were eaten had died of natural causes, so people who had advanced stages of kuru were themselves eaten and able to infect others. The people being consumed were group members, so the disease could form a continuous chain.

In other circumstances, Kuru would not have been as likely to propagate. For example, if this was cannibalism where enemies killed or captured in battle were eaten, there'd be less chance for the disease to spread. A person killed in combat would be less likely to be suffering from the disease in the first place. If the disease did spread from the first individual to those eating them, it would be less likely to get a second chance to spread (Because those warriors would have to themselves be taken by enemies that also practiced cannibalism and eaten). And if the tissue being eaten was flesh and not brain and nerve tissue, spread would also be less likely.

This plays in to the spread of the disease in other mammals as well. It's exactly what happened in cows, for example. Older animals that had the disease were ground up and their organ meat was fed to many other cattle, who were themselves ground up and refed when they died. That made for a continuous chain of transmission. In contrast, using your example of cannibalism in the wild of young animals, they are less likely to have a spontaneous prion disease in the first place. And even if it does, the chain of infection would not persist because the adult that ate the offspring would be unlikely to themselves be cannibalized, especially by more than one individual (which is required for the disease to actually spread).

TLDR

To actually spread prion diseases by cannibalism, it's not enough for cannibalism to occur. The individuals which contract the disease by cannibalism must themselves be cannibalized, and by multiple individuals, and so on in a chain of transmission.

That said, cannibalism does also expose you to other, more ordinary diseases. It's also often risky, since adults of the same species are usually dangerous prey. And you also run the risk of harming your fitness by eating a relative.