Grassia is plentiful in various varieties of luscious grass, loved by cows, from Crispy Grass to Ghost Grass to Boi Grass. While the cows take delight in ravaging the viridian fields of Grassia, the Grassian people are not similarly ecstatic. The main problems here are that the Grassian economy is highly dependent on grass. And also some of the grass is sentient and suffers and pain.
This alone is not much of a problem, however. The sentient Grassians normally stay far outside the eating grounds. And new grass grows from the "head" of Grassia into the "tail" of Cowboland, creating a natural cyclic equilibrium.
The spheg is another highly sought-after commodity of Grassia. So sought after, in fact, that people tend to just come in and try to take it by force. I mean what are they gonna do to stop them? They're grass. So tens of thousands of people come in every year trampling the grass while they search around for the meme booty.
The real trouble occurs when these two elements are combined. It turns out that whenever a cow swallows a spheg, they can become a really strong, depending on the particular desires of that cow at that moment. The meme juice, once digested, will generally attempt to satisfy those desires, through its great meme power, and this can be particularly destructive due to the simplicity and crudeness of cows' desires.
Usually the desire of the cow is "eat grass". In this case it tends to end up spawning many many demonic minions, including many spooks. These consume all the grass in the vicinity, and relay the creamy taste of Grassia GrassTM to their cow overlord. Thus, the "head" of Cowboland expands unexpectedly much into Grassia. Usually one instance of the spheg is not enough to cause trouble, as the Grassians are wise and well prepared, but several sphegs being quickly consumed in under a few days can have terrible cataclysmic consequences.
Sometimes, the cow does something beneficial with the spheg's powers. One cow, for example was slightly thirsty, causing a light rain all throughout Grassia, thus replenishing the grass. Then, the spheg immediately got teleported into a cow who was annoyed by this rain, resulting in large chunks of Grassia being cast into a fiery blaze. Many cows got barbecued that day.
There was also a cow that swallowed the spheg, and then decided it wanted to eat a treat a Cowbo was holding. The meme juice figured the most efficient way of achieving this was to transform the cow into a seductive humanoid, and so the first Cowgirl was formed.