摘要:Understanding the relative ability of forages to meet the needs of prime-age females, the productive component of elk (Cervus elaphus) populations, is necessary to decipher reasons for declines and potential for population growth. Information on forage nutrient dynamics for elk on Great Basin summer–fall ranges is lacking. Our primary objectives were to estimate nutrient levels in common elk forage species in northeastern Nevada at 3 time periods and evaluate whether nutrient levels met good requirements for lactating cow elk at time periods across summers. We compared crude protein, digestible energy, and macromineral levels in 2 forbs, 6 grasses, and 4 woody browse forage species to requirements for lactating cow elk in early summer, midsummer, and early fall 1999 and 2000. Spurred lupine (Lupinus caudatus) and snowbrush ceanothus (Ceanothus velutinus) were the most proteinaceous plants, exceeding requirements across all seasons. By midsummer, protein levels in all grasses were below elk requirements (12%). Digestible energy was the most limiting nutrient with woody browse meeting lactating cow elk requirements only in early fall (2750 kcal · kg−1). Sodium levels never exceeded about 10% of the required 600 µg · g−1. The potential for maintaining a relatively high density of elk at forage-quality levels that fulfill requirements declines as summers progress on Great Basin summer ranges. Maintaining highly productive elk herds in the Great Basin requires that managers maintain plant communities with a diversity of forbs, grasses, and browse to provide for nutritional needs of lactating cows and their growing calves.