Digestibility of Wheat and Alfalfa Silage With and Without Wheat Straw

Wheat and alfalfa forages were harvested and ensiled in 208 liter silos for 19 and 17 mo, respectively. The forage was ensiled as direct cut forage (DC) or allowed to wilt (W) before ensiling. Wheat straw was added (DCS) to wheat forage at 21.3% of the dry matter (DM) or to alfalfa forage at 21.8% of the DM before ensiling to achieve a mixture that was similar to the wilted forage in DM content. Storage DM losses were greater (P<.05) for the DCS treatments than for the DC treatments for both wheat and alfalfa forages. Wilting either forage before ensiling decreased (P<.05) the amount of DM lost during storage as compared with the DCS treatment. Apparent digestibility of the silage was determined using steer calves that were limit fed each of the six experimental silages at 1% of body weight plus a concentrate supplement at .6% of body weight. Both DC and W alfalfa silages were more digestible than DC and W wheat silages. Adding wheat straw to either wheat or alfalfa forage increased (P<.05) the structural carbohydrate content and lowered (P< .01) the digestibility of the silage portion of the diet.