Russian Wildrye Nutritional Adequacy and Chemical Composition1

Abstract

AbstractApparent metabolic problems were observed in yearling steers grazing Russian wildrye (Elymus junceus Fisch.) in spring or early summer. This study was initiated to determine what factors were involved in these metabolic problems. Forage samples were obtained from small plots established in an existing 10‐year‐old stand of Russian wildrye, growing on Temvik silt loam (flne‐silty, mixed Typic Haploborolls) soils. The objective of the experiment was to examine the effect of sampling dates and N, P, and K fertilization on the chemical composition and subsequent nutritional adequacy of this forage for grazing cattle. Levels of N, P, K, and in vitro digestible organic matter (IVDOM) in Russian wildrye declined consistently between weekly sampling dates both years. Forage Ca and Mg levels increased (P < 0.05) between initial and final sample dates, but weekly changes were not consistent between years. The tetany hazard to cattle grazing Russian wildrye appeared greater when evaluated by the ratio of forage K/(Ca + Mg) than when evaluated by estimated blood serum Mg data. Regrowth forage, although morphologically similar to early cut forage, appeared quite different chemically. Nitrogen fertilization increased (P < 0.05) forage N and K and consequently the K/(Ca + Mg) ratio. Nitrogen fertilization decreased (P < 0.05) forage P, but the decrease was not progressive with higher N levels. Fertilization with P increased (P < 0.05) forage P, but effects on other parameters were inconsistent. Potassium fertilizer had little effect on any parameters measured. The data indicated substantial differences in forage chemical composition as affected by year, season, and fertility, but the results did not suggest a cause of the severe scours, excessive urination and depressed weight gains which had been exhibited by yearling steers.