In a few past issues of the Dairy Pipeline, I reported the initial stages of a Conservation Innovation Grant (CIG) project of the Department of Dairy Science, and funded by Natural Resources Conservation Services, in which we were comparing the nutritional quality of different winter crops for silage. For this project we planted 15 different winter crops in three locations within the Commonwealth of Virginia. These crops included the grasses barley, rye, ryegrass, triticale and wheat in monoculture, and the same grasses planted with either crimson clover or hairy vetch. These crops were harvested and ensiled in the laboratory. After 60 days of fermentation, we determined the nutritional composition and the digestibility of the silages in the Dairy Nutrition Laboratory at Virginia Tech. Following are some results and conclusions.
Nutritional Composition. Adding legumes increased protein concentration of the silages. Protein concentrations were 14.2% for grasses in monoculture, 16.6% for mixtures including crimson clover, and 18.3% for mixtures including hairy vetch. Similarly, adding legumes reduced fiber concentration of the silages. Neutral detergent fiber concentrations were 53.2% for grass silages and 50.0% for silages including legumes with grasses. These results suggest that adding legumes to grasses improves the nutritional composition of the silages.
Digestibility. In vitro dry matter digestibility (IVDMD) was lowest for barley silage (81.9%) and greatest for rye grass silage (89.8%). The in vitro digestibility of the fiber (IVNDFD) was also lowest for the barley silage (70.1%) and greatest for the ryegrass silage (77.3%). The addition of legumes as a mixture decreased in vitro fiber digestibility (68.4 and 72.4% for barley and ryegrass silages, respectively). Based on this decrease in fiber digestibility, one might wonder if adding legumes can be counterproductive to obtain best quality silage. The answer to this question is no. Keep in mind that the fiber digestibility of legumes is typically lower than the fiber digestibility of grasses, but fiber concentration is typically lower in legumes than in grasses. In this study, even though the digestibility of the fiber was reduced, adding legumes increased the concentration of highly digestible non-fibrous components (i.e., cell contents) in barley, rye, triticale and wheat silages. As non-fibrous components are completely and uniformly digestible, for these silages the nutritional composition was actually enhanced.
Conclusions. Deciding which species to plant can be difficult when speaking about winter crops for silage. From a nutritional perspective, including legumes can improve the nutritional composition of the silage, especially in mixtures with barley, rye and triticale. For high quality forages, such as ryegrass, the improvements are marginal.
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
September 29, 2016