Fibrolytic Enzymes Increase Fermentation Losses and Reduce Fiber Content of Sorghum Silage

Fiber digestibility is a key-point of forage usage in ruminant production systems. The present study aimed to evaluate the effect of fibrolytic enzyme blend on whole-plant sorghum silage fermentation profile, fermentative losses, chemical composition, in vitro degradation, and aerobic stability. It used fifty experimental silos (plastic bucket, 28 cm i.d. and 25 cm in height) in a blocked randomized design to evaluate the following fibrolytic enzyme levels: 0, 150, 300, 450, and 600 mL per ton of dry matter (DM). Enzymes had 300 U/mL of xylanase and 300 U/mL of cellulase. Enzymes linearly increased acetic acid, branched-chain organic acids, and ethanol concentration of silage. Although there was no treatment effect on silage DM recovery over the ensiling process, enzyme levels linearly increased gas, effluent, and total losses. Intermediary levels of enzymes (from 312 to 342 mL/ton DM) decreased fiber content (NDF and ADF), whereas improved NFC silage content. Besides, enzymes did not affect DM and NDF degradation and tended to linearly reduce acid detergent fiber in vitro degradation. The enzymes addition linearly decreased silage temperature after aerobic exposure. However, there was no treatment effect on silage pH after aerobic exposure also during the time that silage remained with a temperature lower than 2°C above environmental temperature. Thus, fibrolytic enzymes reduce fiber content, promote a heterolactic fermentation, and reduce silage temperature after aerobic exposure. However, this increases fermentative losses and has no positive effect on in vitro degradation and the time of aerobic stability.