A Comparison Between Upper and Bottom Layers in Bunker Silos: Performance of Dairy Cows

Peripheral areas of horizontal silos are more susceptible to aerobic deterioration, which may affect silage quality. This two-trials study evaluated the performance of Holstein cows fed diets containing corn silage from the upper or bottom half of a well-managed bunker silo. In Trial 1, 20 cows were assigned to a 4 × 4 Latin Square design, with a 2 × 2 factorial arrangement, with 21-days periods. The dietary treatments were (dry matter basis): 50% corn silage from the Top; 60% corn silage from the Top; 50% corn silage from the Bottom; and 60% corn silage from the Bottom. In Trial 2, 24 cows were assigned to a cross-over design with two 21-days periods. The treatments were: 60% corn silage from the Top and 60% corn silage from the Bottom. Corn silage was the sole forage source in both trials. In Trial 1, no interaction was observed among treatments. Cows fed Top silage had greater dry matter intake and milk yield (p < 0.01), whereas feed efficiency (p < 0.01) was higher for cows fed diets with 60% corn silage. In Trial 2, milk urea nitrogen increased (p < 0.01) for cows fed Top compared with Bottom silage. Cows fed diets containing Bottom silage showed greater N retention (p < 0.01), indicated by a more positive N balance (p < 0.01). Collectively, this study suggests that under good silo management, the entire panel can be unloaded for feeding lactating dairy cows.