Submitted to: Grassland International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 6, 1996
Publication Date: N/A
Interpretive Summary: Both annual and perennial bunch grasses on sagebrush-bunchgrass rangelands are important to grazing animals. Nitrogen (crude protein), energy, P, and Zn decline with increasing maturity of herbage and thus limit productivity of calves and lactating cows. Benefits have been shown when supplementing available forage with N, P, An, and energy. Documenting changes in herbage quality is useful in livestock management. Perennial species would provide a more stable yield, have a longer green-feed period, and produce more usable forage. An improved overall management strategy might be to move growing calves to more productive irrigated pasture by midsummer while continuing to graze maturing rangeland grasses with dry, mature cows.
Technical Abstract: Annual and perennial grasses growing in the semiarid, west-central North American continent mature by early to midsummer. Forage mineral concentrations in these C-3 grasses decrease curvilinearly as the season advances from day of year (DOY) 75 to 300. Total digestible dry matter (TDDM) and digestible cell wall (DCW) decrease linearly with DOY while neutral detergent fiber (NDF) increases curvilinearly. By midsummer; energy, N, P, and Zn usually become deficient for ruminant nutrition.