Russian wildrye nutritive quality as affected by accession and environment

Abstract

High-quality forage for spring and fall grazing is an important need of ranchers in the Northern Great Plains and Intermountain-West regions of the United States of America and in the prairie provinces of Canada. Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] has been used to meet this grazing need, especially in Canada. However, its use has probably been limited by its reputation for seedling establishment difficulties and scattered reports of grass tetany. The purpose of this research was to characterize the variation in nutritive quality of Russian wildrye accessions used in a multi-location grass tetany project, to access the effect of environment on quality components, and to determine the relationship between forage nutritive quality components and entities associated with grass tetany. Sixty-seven Russian wildrye accessions from the US National Plant Germplasm System were established in spaced-plant nurseries at Logan, UT, Mandan, ND, and Swift Current, SK, Canada. Plants were sampled at two stages of development over 2 yr. Location, year, and stage of development effects were significant (P < 0.01) for in vitro true dry matter digestibility (IVDMD), crude protein (CP), and neutral detergent fiber (NDF). At the early stages of development used in this study the range in nutritive quality traits among entries was rather narrow. Relatively high positive correlation coefficients between K and IVDMD, and K and CP suggest that breeding for higher nutritive quality may also produce a more tetany-prone forage, because high K concentration is usually associated with grass tetany. On the other hand, Mg concentrations were also highly correlated with IVDMD and CP, and higher Mg concentrations would be beneficial in preventing grass tetany. The K/(Mg + Ca) ratio, which has been suggested as an indicator of grass tetany, was only moderately related to IVDMD, CP, and NDF. Key words: Digestibility, crude protein, neutral detergent fiber, stage of plant development