It really depends on the actual individual goat. I kept my nigerians years ago, I dont have any more. Just Boers now. And I never had them at the same time so I didn't keep them together. I DID however keep a boer meat project wether in with a couple 7-8 year old nigerian x wethers. The Boer boy was about a year or two old and maybe 120 # when he was in there with them and those guys were 7-8 years old and maybe 100#. They were old guys, polled, and my wether was horned and young. They got along fine. If they got near him during feeding, he would maybe give them a small shove, or if they were standing on his tire he would knock them off. But nothing too extreme. Just normal goat pecking order. But, it definitely depends on the personality of the goat and especially the size. Since these were nigerian crosses they were a bit bigger, probably 100#. I have seen 20# nigerians before and they would most definitely be not a good choice in with boers.