Method of propionic acid-based preservative addition and its effects on nutritive value and fermentation characteristics of wet brewers grains ensiled in the summertime

This research evaluated nutritional value and DM loss of wet brewers grains (WBG) mixed or top-dressed with a propionic acid-based preservative. On d 0, treatments were randomly assigned to 19-L plastic buckets (6 buckets per treatment) and consisted of WBG without preservative (control), or WBG mixed or top-dressed with a commercial propionic acid-based preservative (Myco Curb; Kemin Industries) at a rate of 1 g/kg of WBG (wet weight). Buckets were individually sealed and stored at ambient temperature with exposure to sunlight and precipitation for 14 or 28 d (3 buckets per treatment for each storage day). On d 14, total DM loss was least for control, greatest for top-dressed, and intermediate for WBG mixed with propionic acid (P ≤ 0.02). On d 28, total DM loss was similar between methods of propionic acid addition (P = 0.64), but both methods were less than the control (P < 0.0001). The TDN and NEm concentrations did not differ (P ≥ 0.32) between control and WBG mixed with propionic acid, but both were less (P ≤ 0.05) than WBG top-dressed with propionic acid. Mean lactic:acetic ratio was similar between control and top-dressed WBG (P = 0.58), but both were greater than WBG mixed with propionic acid (P ≤ 0.03). Overall, top-dressing and mixing the propionic-based preservative had similar reduction on total DM loss after 28 d of storage compared with WBG without preservative. However, top-dressing had minimal effects on nutritional value and is less laborious than mixing with WBG.