Yields, Nutrient Quality, and Palatability to Sheep of Fourteen Grass Accessions for Potential Use on Sagebrush-Grass Range in Southeastern Idaho

Abstract

Fourteen grass accessions were evaluated in terms of yields, nutrient quality, and palatability to sheep at the U.S. Sheep Experiment Station in southeastern Idaho. The interspecific hybrid (Agropyron cristatum × A. desertorum) produced the greatest amount of total biomass (which includes leaves, stems, and heads), but Russian wildryes (Psathrostachys juncea), tall fescue (Festuca arundinacea), and the RS- hybrid (Elytrigia repens × E. spicata) produced a greater proportion of leaf material. Crude protein contents declined with advance in plant maturity in all accessions, except Russian wildryes (Bozoisky-Select and RWR-V13) in which crude protein contents declined only slightly between June 30 and September 15. All accessions contained adequate Ca, Mg, and Mn levels in the forage throughout the spring, summer and fall. Phosphorus and Zn levels were inadequate for sheep during late summer and fall. Sulfur content was below recommended levels for sheep. Potassium levels dropped below recommended rates in some accessions on September 15, and certain accessions indicated a proneness towards inducing grass tetany in early spring based on K: (Ca + Mg) ratios. Copper levels were adequate for sheep on June 30, but 10 of 14 accessions were below recommended levels on September 15. When preference is considered without interference from seedstalks, all accessions were preferred similarly by sheep. However, preference decreased as numbers of seedstalks increased. Burning in mid-March removed dead standing seedstalks and litter providing more accessible forage, but tended to aggravate the problem by increasing the number of new seedstalks. Heavy use in the spring may reduce flowering, and produce a greater proportion of vegetative stems. An index based on leaf yields, crude protein content, and sheep preference was used to rank species. This index ranked the Russian wildrye (Bozoisky-Select) first followed by RWR-V13 second.