The lambs have been on the turnips and kale for a week and are getting the hang of it as a feed source. We measured the yields today and I was pleasantly surprised. The turnips yielded 9,900 lbs of dry matter per acre (not counting bulbs!), and the kale yielded 5,700 lbs.
There seems to be more waste with the turnips. I haven't measured residue yet, so the net yield isn't known, but it appears that the turnips will have a major advantage over the kale.