No easy answer to that one. I would keep in mind that it always pays to try and get along with neighbors.
I would say the rules are a little different depending on whether you are running stock or not. If you are and he has a bull that keeps getting in, and his bull is better than yours (assuming you run a bull), it's not as big of a deal unless you're feeding in the winter. If his cows are getting in with yours then you should remember that both of you have responsibility to keep the fences up. Of course it's no fun having a lazy neighbor, but it usually does pay to get along.
I agree that the sheriff should be in the loop on any action taken. If you give up on the neighbor and plan to load him and take him to the sale it would not hurt to contact the Texas and Southwestern Cattle Raisers Association and seek some guidance.
<A HREF="http://www.texascattleraisers.org/index2.htm" TARGET="_blank">http://www.texascattleraisers.org/index2.htm</A>