I’m all for being concise, but this sign takes it to the next level. Signs should be short and to the point, but people should be able to understand them. Also, a comma never hurt anybody as far as we know, and it sure wouldn’t hurt this sign! Otherwise, some people might take this sign personally.
The way this sign is currently written, there are two ways to understand it: either someone was lazy and didn’t finish this sign (or failed to add a very necessary comma), or, as this sign suggests, cows in Texas are extremely intelligent, which doesn’t seem like a plausible explanation, although Texans take pride in their farm animals.