Are ecotypes of winterfat digested differently compared to alfalfa or western wheatgrass? Schellenberg, Michael^*,1, Jefferson, Paul¹, Cohen, Roger², ¹ Semiarid Agricultural Research Centre, Swift Current, Saskatchewan, Canada² Dept. of Animal and Poultry Science, Saskatoon, Saskatchewan, Saskatchewan

ABSTRACT- Winterfat (Krascheninnikovia lanata) has been recommended as a forage ideal for wildlife or livestock fall grazing. This shrub is noted for having a number of ecotypic differences for germination, growth and salinity tolerances. Digestion of two winterfat ecotypes (Sasaktchewan and New Mexico)have not been compared previously. This study examined digestion coefficient differences among ecotypes, alfalfa (Medicago sativa) and western wheatrgass (Pascopyrum smithii), when grown at Swift Curent and harvested in October, using the Orskov and MacDonald model (1979). The sampled plants had not been harvested during the previous growing season and represented "stock-piled" forage. Residual dry matter, crude protein and neutral detergent fibre from nylon bag procedure utilizing 3 rumen-fistulated steers were input to the model. Coefficients for residual dry matter effective digestibility (ED) and rumen undegradable (RU) were similar between Saskatchewan winterfat and western wheatgrass while New Mexico winterfat was similar to alfalfa (=0.05). Residual neutral detergent fibre was similar among New Mexico winterfat, western wheatgrass and alfalfa but greater than Saskatchewan winterfat(=0.05) for ED coefficient and lower for RU coefficient. Residual crude protein showed the same trend as residual sry matter. The winterfat ecotypes have different digestbility characteristics. This difference in digestibility for ecotypes requires more detailed examination with additional ecotypes and locations. The information in turn can be used to optimize livestock production and explain ecotypic grazing preferences.

KEY WORDS: ecotypes, Krascheninnikovia lanata, digestibility, fall grazing