I agree with both of the above replies. If you are going to load cattle, good sturdy pens are a must! I am in the process right now of building a new 64' by 64' pen. I have a blue heeler with no formal training, and she is good for moving cattle in some instances, but will get you hurt in others.
Recently we were trying to load a 500lb Longghorn steer so we could move it to another place and feed it out. We just threw together a small pen of T-posts and cattle panel against a pasture fence. The cattle came in the pen easily with a little feed, and we culled most of them out, leaving the steer and a few others. We then got a trailer and tried to load him (no chute). He would not go into the trailer and ended up going air born and smashing the cattle panel down. After 2 times, I told the owner we need a real pen if we're going to be loading cattle out of this pasture.
My experience with the dog has been that she is good for getting cattle into a pen from a wide open pasture, but when you are trying to cull cattle in the pen, she gets them to stirred up. In a confined space the cattle seem to turn on the dog, who usually runs back to me! :shock: So then I have a mad cow (no pun intended), coming at me and a scared dog.