I have the same problem with a mare that was chased into my yard.
In Texas if you know the county you can find out who owns the brand.
However, in Texas there are 254 counties.
You may want to call the3 Texas and Southwester Cattlemens Ass.
Theya re responsible for checking brands at auctions and locqating stolen livestock.
The Dept of Agriculture will do you no good here. Shalom