PS13-12. Effect of Propionic Acid-Based Additives on the Aerobic Stability and Fermentation Profile of Wet Distillers Grains with Solubles.

Abstract Wet distillers grains with solubles (WDGS) are used in livestock diets. However, their limited shelf life, three to four days in summer and up to one week in winter under aerobic conditions, restrict their use. Additives have been proposed to enhance the aerobic stability of WDGS during storage. Therefore, the objective of this study was to evaluate aerobic storage of WDGS using different additives. Changes in quality during storage be assessed using indicators as organic matter (OM), volatile fatty acids (VFA), and in vitro gas production (GP) at 24 h. Trays (27 kg/tray) of WDGS were assigned to one of five additives (3 trays/additive): 1. untreated control (CON); 2. propionic acid at 0.2% (PA 0.2); 3. propionic acid at 0.4% (PA 0.4); 4. propionic acid and formic acid blend (60:40) at 0.2% (PFA 0.2); and 5. propionic acid at 0.3% combined with Lactobacillus plantarum at 106 CFU/mL (PA 0.3 + LP). Trays were stored for 14 d in a barn and the experiment was replicated over 3 summer months. After additive application (d 0) and after 7 and 14 d of storage, samples were collected from tray to determine OM content (%) and incubated on an in vitro batch culture to determine VFA concentration (mM) and GP at 24 h (mL/g incubated OM). Data were analyzed using a linear mixed model with repeated measures (InfoStat, interfaced with R). Significance was declared at P ≤ 0.05. Total VFA and acetate production were not affected (P > 0.05) by additive, time, or their interaction. In contrast, propionate and butyrate concentration as well as GP and OM content decreased (P < 0.05) over storage time. Propionate production was similar at d 0 (42.23 mM) and d 7 (42.37 mM), but declined (P = 0.001) at d 14 (40.61 mM). A similar pattern was observed for butyrate and GP, decreased (P < 0.05) from 7.18 mM and 52.81 mL at d 0 to 7.05 mM and 48.09 mL at d 14. The A:P was similar at d 0 (1.36) and d 7 (1.36), but increased (P = 0.006) at d 14 (1.39). OM decreased (P = 0.001) from 94.48% at d 0 to 94.34% and 94.33% at d 7 and d 14, with no difference between d 7 and d 14. Propionate concentration differed among additives (P = 0.045), with PFA 0.2 and PA 0.4 showing higher concentration than CON, whereas PA 0.3 + LP and PA 0.2 did not differ from CON or from PFA 0.2 and PA 0.4. These results suggest that WDGS can be aerobically stored for up to 7 d with minor OM losses, whereas extended storage to 14 d resulted in significant alterations in fermentable nutrients. Among additives, PFA 0.2 and PA 0.4 showed potential to mitigate changes.