Changes during aerobic exposure of wheat silages

Aerobic stability is an important characteristic of silages because they are exposed to air during storage and feedout. The objective of the current study was to investigate changes that occur in wheat silages during aerobic exposure. Silages of whole crop wheat harvested at the flowering, milk and dough stages of maturity were prepared in 1.5 L anaerobic glass jars. Three months after ensiling, silages were subjected to a 7-day aerobic stability test. The silages of wheat harvested at the flowering stage were the most stable upon aerobic exposure, but had the largest fermentation losses. Silages of milk-stage wheat were unstable upon aerobic exposure, and had large amounts of CO2 and heating, large yeast populations, decreased amounts of fermentation products and decreased dry matter (DM) and neutral detergent fiber (NDF) digestibility (from 667 to 572 g/kg DM and from 597 to 558 g/kg DM, following 7-day aerobic exposure, respectively). Silages of dough-stage wheat had relatively low fermentation losses and were quite stable for at least 4 days of aerobic exposure. Silage samples from the center of commercial bunker silos, and from areas adjacent to the walls of the silos, were judged to be of good quality. Samples from the shoulders of bunker silos were spoiled with higher pH (P<0.05), higher ash content and lower DM and NDF digestibility compared with samples from the center of the silos and areas near the walls (6.8 vs. 4.0, 19.0 vs. 7.8, 477 g/kg DM vs. 634 g/kg DM and 230 g/kg DM vs. 487 g/kg DM, respectively).