Extrusion of Grass Silage Increase Intake and Milk Yield in Dairy Cows

Abstract This research evaluated effects of grass silage extrusion on dairy cow performance. A grass dominated (70% timothy, 26% meadow fescue, 3% red clover and 1% undefined) first cut ley was harvested on June 13, 2019, and 10 days later near Uppsala, Sweden (58°83′ N, 17°82′ E). Crops were wilted (45% DM for early cut, 50% DM for late cut), round baled and wrapped into plastic film for ensiling. At feeding out, bales were chopped in a TMR feeder, and a portion was processed in an extruder, where screws shear the material under pressure, for further particle size reduction and cell wall break up. Eight Swedish Red cows in two blocks (4 ruminally fistulated, 143 ± 38 DIM and 4 intact, 68 ± 10 DIM) were used in a Latin square design experiment with 4 periods of three weeks each and 4 treatments. The 2x2 factorial arrangement of treatments included silage from early or late harvest that was chopped or extruded. Silage was fed separately ad libitum and supplemented (daily amounts on an as fed basis) with 2 kg of soybean meal, a compound feed (6 kg for fistulated and 8 kg for intact cows), and 120 g of a mineral mix. Extrusion increased silage DMI (1.8 kg/d, P < 0.001) with greater effect at late harvest (P = 0.021 for interaction between processing and harvest) and milk yield (1.8 kg ECM/d, P = 0.004) with a tendency to greater effect at late harvest (P = 0.055). Extrusion depressed total tract OM digestibility (2.3 percentage points, P < 0.001), eating time (0.5 h/d, P = 0.014), rumination time (2.0 h/d, P < 0.001) and rumen pH (0.1 units, P = 0.008). Extrusion improves intake and milk production in dairy cows, despite depressed digestibility.