Effect of chemical and biological preservatives and ensiling stage on the dry matter loss, nutritional value, microbial counts, and ruminal in vitro gas production kinetics of wet brewer's grain silage

Wet brewer's grain for cattle feeding is highly susceptible to loss of quality and nutritive value during storage and feeding. Thus, this study seeks to evaluate the effectiveness of an array of preservatives to extend shelf life and improve digestibility at different stages of storage. Lay Summary Wet brewer's grain (WBG) is the most abundant byproduct in the manufacture of beer and its rich nutritional composition makes it a valuable feed for cattle. However, WBG is highly susceptible to spoilage so the application of cost-effective preservatives may be a viable approach to prevent nutrient losses during ensiling and feed out. The present study evaluated the effects of chemical and biological preservatives on the nutritional composition and in vitro fermentation and gas production of WBG across three silage production stages: fresh, ensiled, and aerobically exposed silage (AES). Preservatives tested were propionic acid, a bacterial inoculant, and sodium lignosulfonate (NaL) applied at 1% and 2%. Propionic acid successfully reduced the loss of nutrients and preserved more sugars and starch than all other treatments during ensiling, which resulted in higher digestibility in vitro. However, due to its greater concentration of digestible nutrients, ensiled WBG treated with propionic acid also suffered extensive spoilage in the AES. All other treatments failed to improve the preservation of ensiled or AES WBG, but NaL at 2% prevented the decrease of digestibility for AES. This study evaluated the effects of chemical and biological preservatives and ensiling stage on spoilage, ruminal in vitro fermentation, and methane production of wet brewer's grain (WBG) silage. Treatments (TRT) were sodium lignosulfonate at 10 g/kg fresh WBG (NaL1) and 20 g/kg (NaL2), propionic acid at 5 g/kg fresh WBG (PRP, 99%), a combination inoculant (INO; Lactococcus lactis and Lactobacillus buchneri each at 4.9 log cfu per fresh WBG g), and untreated WBG (CON). Fresh WBG was treated and then ensiled for 60 d, after which mini silos were opened and aerobically exposed (AES) for 10 d. Data were analyzed as an RCBD (five blocks) with a 5 TRT x 3 stages (STG; fresh, ensiled, and AES) factorial arrangement. Results showed that ensiled PRP-treated WBG markedly preserved more water-soluble carbohydrates and starch than all other ensiled TRT (P < 0.001). Dry matter losses of ensiled PRP-treated WBG were 48% lower than all other ensiled TRT (P = 0.009) but were not different than CON in AES (P = 0.350). Due to its greater concentration of digestible nutrients, PRP-treated AES was less aerobically stable than CON (P = 0.03). Preservation was not improved by INO, NaL1, or NaL2 but the latter prevented the increase of neutral detergent fiber across STG (P = 0.392). Apparent in vitro DM digestibility (IVDMD) decreased only in ensiled CON, INO, and NaL1 relative to fresh WBG and AES NaL2 had greater IVDMD than all other AES TRT (P <= 0.032). In vitro ruminal fermentation of fresh WBG resulted in a greater methane concentration and yield than the other STG (P < 0.033). In conclusion, PRP was the most effective at preserving WBG during ensiling but failed to improve aerobic stability under the conditions tested.