1. Range Science, North Dakota State University, Fargo, ND 58108, USA
2. Livestock and Range Research Laboratory, US Department of Agriculture, Agricultural Research Service, Miles City, MT 59301, USA
3. Central Grasslands Research Extension Center, North Dakota State University, Streeter, ND 58483, USA
4. Department of Animal Sciences, North Dakota State University, Fargo, ND 58108, USA