Dry‐matter losses and changes in nutrient concentrations in grass and maize silages stored in bunker silos

To reduce losses and improve forage use efficiency in dairy farming systems, mass and nutrient flows during silage production have to be measured from the field to feed bunk. However, data on these losses at the farm scale are scarce. Thus, we examined dry‐matter (DM) losses and changes in nutrient concentrations (proximate constituents, nitrogen [N], phosphorus [P]) and energy values (net energy for lactation [NEL]) of silages on three experimental farms from ensiling to feed‐out. The investigated material included forages from permanent grassland and whole‐crop maize that were stored in 64 side‐walled bunker silos. To determine DM losses, the total‐in versus total‐out method was applied. Additionally, the changes in the nutrient concentrations were measured by comparing the concentrations before and after ensiling. Data analyses were carried out by using ANOVA, and the means across groups were compared via multiple contrast tests. On average, the farms had good silage production management. Average values showed a trend towards higher DM losses during the ensiling process with grass (9%) than maize (7%). The N and P concentrations of the silages remained mainly unchanged during the ensiling process, suggesting that the total losses of N and P were also low (<10%). Regarding the fibre fractions, ensiling resulted in a significant reduction in the concentration of amylase‐treated ash‐excluded neutral detergent fibre (aNDFom) for grass (11%) and maize (15%), while ash‐excluded acid detergent fibre (ADFom) was not affected by the ensiling process. These changes resulted in slightly improved energy values in the silages.