In Vitro Digestibility, Crude Protein, and Phosphorus Content of Straw of Winter Wheat, Spring Wheat, Barley, and Oat Cultivars in Eastern Montana

Straw from small grains could be an important source of feed for maintenance of ruminants if its nutritive quality could be improved. This study was conducted to determine any differences in straw digestibility among and between cultivars of winter and spring wheats (Triticum aestivum L. var. aestivum, and T. turgidum L. var. durum), barley (Hordeum vulgare L.), and oats (Avena sativa L.) grown in eastern Montana. In vitro dry matter digestibility, crude protein, and P content of straw were measured on 8 to 25 cultivars of each crop for 2 years. Heading date, plant height, lodging severity, and grain yield were also determined to detect whether selecting for higher straw digestibility would adversely affect these important traits for grain production. The average in vitro digestibility of straw of winter wheat, spring wheat, barley, and oats was 36, 36, 40, and 45% the first year, and 40, 42, 47, and 45%,, respectively, the second year. Differences in straw digestibility were greater among cultivars within a crop than between crops. Straw digestibility of winter wheat, spring wheat, and barley cultivars differed by 9 and 14 percentage units, depending on crop and year. Straw of oat cultivars differed by 8 percentage units the first year but only 4 percentage units the second year. Differences in straw digestibility among crop cultivars was as great as some researchers have achieved by chemically treating the straw to improve its digestibility. Cultivars with higher straw digestibility did not have higher lodging or lower grain yield. Neither was straw digestibility consistently associated with heading date, plant height, crude protein, or P content. The first year, the average crude protein of winter wheat, spring wheat, barley, and oat straw was 2.5, 2.7, 4.4, and 3.3%, respectively; the second year, it was 2.5, 4.0, 5.9, and 5.8%, respectively. The first year, the average P content of winter wheat, spring wheat, barley, and oat straw was 0.02, 0.06, 0.15, and 0.07%, respectively; the second year, it was 0.05, 0.05, 0.09, and 0.06%, respectively.