Conrad - I've read those are a great breed of dog. Not sure how, with their heavy thick fur, would handle the summer heat (high 90's - low 100's) and thorn bushes everywhere. Jan does keep a couple of small terrier type mixed breed dogs that live in the goat coral. Not so much for protection of the sheep but more of an alarm system. Their barking can discourage a cat from trying to get in, but won't stop a seriously hungry one.
Like you can see from the picture above, leopard and cheetah are like the best domestic "mouser" cat...just on steroids. Put a cat in a room with a dozen mice and it will kill them all in short order. Same with leopard and cheetah. They get into a corral (Kaarl in Afrikaans) and the panic of the animals in the confined space just make the cats go into a killing frenzy. He says lion will do the same thing but he hasn't experienced that on his place....yet. The other two he has.
