Forage Nutritive Value of Grazed Irrigated Pasture Mixtures for the Intermountain West.

Pasture paddocks comprised of birdsfoot trefoil or white clover in mixtures with meadow brome, orchardgrass, perennial ryegrass or tall fescue were rotationally stocked during three successive grazing seasons. Paddocks were 15 x 22 m and at each grazing, paddocks were stocked with a sufficient number of dairy heifers to graze for one day. Grazing interval was based on the regrowth height of each mixture, and mixtures were grazed from three to six times per season. Herbage dry matter production and utilization were determined using calibrated rising plate meter readings. Forage nutritive value was determined using calibrated near-infrared reflectance spectroscopy. Seasonal trends in nutritive value parameters were strongly influenced by year, and were influenced more by the grass component of mixtures than by the legume component. Data for crude protein, in vitro true dry matter digestibility, neutral detergent fiber (NDF) and NDF digestibility will be presented and discussed.