David feeds his cattle with root vegetables such as turnips. which type of feed includes root vegetables such as turnips?

concentrates
dry roughage
green roughage
silage
dry matter

To be honest, I should know this answer because I am an animal science major, but its been a while since we learned about this stuff. So, from the brief 30 min google search I did: 

I can tell you it is almost certainly not "concentrates". Concentrates are usually made of high-energy, low-fiber cereal grains, like oats, corn, soybeans, etc.

Dry Roughage might be the answer just because according to http://modernfarmer.com/2014/12/turnips/, turnips are a diarrhetic for cows. So, they should be mixed with high-fiber feeds in order for the cow to more effectively use of the nutrients in turnips. However, the question asked specifically which feed INCLUDES root vegetables. So, I don't think that dry roughage can possibly be the answer. Dry roughage are high in fiber, low in energy, and usually around 10-15% moisture. Dry Roughages include things like hay, husks, and straw.  

Green Roughages is comprised usually contain high moisture content ranging from around 50-90%. I looked it up, turnips are slightly above that range; their moisture content resting at about 91-92%.  However other root vegetables did lie in range. Carrots having 88% moistuire, potatos 79%,  beet roots 87%, etc. So, I think you could make a case base on the moisture content of root vegetables that they would be found in green roughage. 

I do not think it would be Silage because that looks to be a mixture fodder(hay/corn) that has been anaerobically fermented in a silo into a succulent feed. 

I think dry matter can't be the answer because I believe it is just a measurement of how much dry matter is contained in a particular feed such as, silages, concentrates, and roughages. For example, this feed mixture is 885 dry matter feed.
In conclusion, my best guess would be the answer is GREEN ROUGHAGES just based on the moisture content. Does that make sense to you too? I hope I am correct. I am sorry that I have to guess and that I couldn't tell you a definite answer. I hope this info helped you anyway!