| Winterfat, Krascheninnikovia lanata (Pursh) A. D. J. Meeuse & Smit, a native shrub that exhibits ecotypic variation, has been recommended for extending the grazing season into the fall, when protein levels are low in other plants of the northern Great Plains. A series of studies was established in 2001 and 2002 at Swift Current, SK to examine developmental and nutritional differences between a northern seed source (Ducks Unlimited Canada ecovar(TM), DU) and a southern seed source (New Mexico, NM). Additionally, winterfat's nutritional contribution to mixtures containing alfalfa and western wheatgrass was examined. For the first experiment, plants were clipped once, at 50% of plant height, between June and snow fall. New Mexico winterfat was 8.7% taller in 2002 than DU, but DU plants were more productive (P < 0.05) on a g m-2 basis (15% in 2002, 110% in 2003) than NM with more primary branches (40% in 2002, 20% in (2003), higher fibre (4% in 2003) and decreased digestibility (7% for 3 year old plants) than NM. NM and DU plants had different (P < 0.05) crude protein, Ca, P, K, Na, Mn, Zn, Fe, Co, and Cd concentrations in 2002 and 2003. Supplementation of Ca, Cu, Co and Se for both seed sources and Zn for older NM plants would be required, to meet nutritional requirements of a medium framed British breed replacement heifer in its first trimester. Sulfur, Mg and Fe were in excess of animal requirements and may decrease Cu availability. In a study examining seed production of both seed sources as affected by fertilization and irrigation, DU plants produced seed in potentially commercial potential quantities while NM plants remained vegetative. Fertilizer and water had no effect on seed production (P > 0.05). The third study examining seeding mixtures of winterfat with alfalfa and western wheatgrass indicated that the mixtures provided adequate crude protein for a medium framed British breed heifer. Two in sacco experiments modelled (a) digestion of the two winterfat types compared to alfalfa and western wheatgrass; and (b) digestion of the same species as poly- or mono-cultures. Alfalfa and NM winterfat, were similar, and had greater (P < 0.05) effective degradability than DU winterfat or western wheatgrass. The poly-culture feed mixture degradability of crude protein was greater (P < 0.05) than DU winterfat or Western wheatgrass. A positive synergy was observed for effective degradability of CP in mixtures. The studies overall demonstrate (1) northern and southern winterfat ecotypes have different growth and nutritional characteristics and (2) inclusion of alfalfa in mixtures with winterfat could provide adequate crude protein with a proportion (390 g kg-1 CP) being in the form of rumen undigestible crude protein. |
