Seasonal Dry Matter Yield and Digestibility of Seven Grass Species, Alfalfa, and Cicer Milkvetch in Eastern Montana1

Abstract

AbstractIn the past, seed and total dry matter (DM) yield have been two of the main criteria for forage plant selection and improvement. However, we have little information on seasonal digestibility, one of the most important criteria, of major forage species in the northern Great Plains. Our objective was to determine differences in seasonal digestibility and DM yield of seven grass species, three (‘Rambler’, ‘Drylander’, and ‘Orenberg’) alfalfas (Medicago sativa L. subsp. × varia (Martyn) Arcangeli), and ‘Lutana’ cicer milkvetch (Astragalus cicer L.) the first and second year after establishment. Forage species were seeded in 1974 in 50‐cm rows on a Williams loam soil (fine‐loamy mixed, Typic Argiborolls) near Sidney, Montana, which has an average annual precipitation of 35 cm. Dry matter yield and in vitro digestibility converted to in vivo digestibility were determined seven times hi 1975 and 11 times in 1976 at progressive growth stages. ‘Mayak’ Russian wildrye (Elymus junceus Fisch.) and ‘Prairieland’ Altai wildrye (Elymus angustus Trin.) produced the lowest peak DM the first year after seeding; however, they were among the species that produced the most DM the second year. The three alfalfas and ‘Luna’ pubescent wheatgrass [Agropyron trichophorum (Link) Richt.] produced the most peak DM the first year after seeding; however, by the second year, they were among those species that produced the least. Digestibility at a given stage of development also differed greatly among species. The second year, forage of Prairieland Altai wildrye and Lutana cicer milkvetch during the fall and early winter were 8 to 10 percentage units more digestible than ‘Nordan’ crested wheatgrass [Agropyron desertorum (Fisch.) Schult.]. ‘Regar’ meadow bromegrass (Bromus biebersteinii Roem. and Schult.), a selection of reed canarygrass (Phalaris arundinacea L.), and ‘Lodorm’ green needlegrass (Stipa viridula Trin.) were also studied. Evaluating DM yield of a forage species at a given stage of plant development, such as anthesis, does not adequately reflect its potential. Species are best evaluated for DM production at some given level of digestibility, based on animal requirements.