I need to convert my numerous comments into an answer...
The reality of evolution is that you really can't speed it up. The process of changing from something you aren't into something else (e.g., a chicken into a tool-using, vulgarity-spewing creature) requires about 100 million years.
There is plenty of evidence that behavioral adaptation can occur very quickly. Consider the Peppered Moth, where the black versions were better able to survive due to better camouflage during the Industrial Revolution. But that's not "evolution." The changes were merely superficial adaptations. The Black Peppered Moth is still a moth. Indeed, it's still a peppered moth.
Keep in mind that one of the complaints against evolution is the idea of a creature "becoming something else." It's easy to draw a line between apes and humans, but a lot harder to draw a line between "fish" (ocean-dwelling creatures) and apes. (I'm not arguing against evolution, just making a point).
**But here is where we need to discuss what it means to be a "threat to humanity."
Basic problem-solving skills can develop in any animal. Think of mice in a maze. Given enough experience over enough generations (and not too much time from an evolutionary standpoint), the mouse can develop (evolve) better problem-solving skills such that the maze can be analyzed and resolved more quickly. Is that intelligence? Sure. Does it threaten humanity?
You haven't explained what threat you're looking for. Cattle rising up in rebellion against their oppressive masters isn't going to happen. We kill aggressive animals. Indeed, we weed out anything that doesn't belong on a plate with an appropriate condiment. It's very hard to imagine a set of laws, industry regulations, or other conditions that would permit the development of that kind of intelligence.
It would be easier to consider what laws would need to change to permit the enslavement of humanity for the purpose of food. (C.F., Through Darkest America by Neil Barrett)
The problem is that intelligence, even primitive intelligence (insofar as we understand evolution) requires the ability to manipulate your surroundings first (hands, etc.). How must a cow change to do that? Shorter rear legs, lighter forward body, fingers rather than hooves... It's the hands/tentacles/fingers that are the problem. We need them to develop rational intelligence.
Condition #1: remove rather than kill
The scale of this problem makes it difficult to believe, but let's run with it. let's assume in a large enough national or international scale (America, the European Union, India... we need big) laws are passed to create no-kill farming from the perspective of defects can't simply be disposed of. Animals that change such that they're no longer ideal for the dinner plate must be put out to pasture rather than destroyed.
That preserves the tendency to evolve, but it also removes the evolutionary pressures that brought about whatever minor evolution set them free (a couple of digits on the end of a chicken's wing).
And I just shot down my own idea
I'm having trouble seeing where we can set evolution free while maintaining the evolutionary pressures and yet maintaining the corporate bottom line — and do it within a very short period of time (at worst, centuries rather than the millions of years normally needed). What I just proposed wouldn't do it. It's actually easier to justify turning humans into zombies via the meat industry than it is to justify a cow rebellion.
But what if the threat wasn't direct? The old idea that the world is just a handful of meals away from anarchy could be used. What if just enough intelligence is born to justify uncontrollability? The cost of keeping the "unhappy" animals under control gets so high that one of the dominant food sources (meat) is withheld from industrialized Man?
I can believe that.
And I can believe the chaos that would ensue in the world because of the massive shifts of price as other food sources become more expensive due to the rarity of the other.
Unfortunately, that's a long way away from what I think you were hoping to get.