Rumen disappearance kinetics and chemical characterization of by-products from cellulosic ethanol production

Cellulose-rich biomasses can be used as an alternative to starch-rich corn grain as a source of sugars for ethanol (EtOH) production. However, converting cellulosic biomass to ethanol produces large quantities of co-products which need to be disposed of, preferably in a value-added process, possibly as animal feed. In order to estimate the feeding value of these co-products for ruminants, the chemical composition and ruminal in sacco disappearance of five mature forages (i.e., reed canary grass hay, timothy hay, alfalfa hay, corn stover, barley straw) were determined following no treatment (control), or treatment with ammonia fiber explosion (AFEX) or AFEX plus enzymatic hydrolysis of cellulose and hemicellulose (AFEX + ENZ). AFEX treatment alone doubled the N content of forages compared with controls. AFEX + ENZ-treated forages contained a similar level of N as the AFEX-treated forages. Acid-detergent insoluble N (ADIN) was twice as high in AFEX + ENZ-treated as in the AFEX-treated forages. The AFEX + ENZ-treated forages had 32% less neutral detergent fiber (NDF) and 18% less ADF than the controls. Effective ruminal disappearance of dry matter (DM), NDF, and N were higher (P<0.05) for AFEX + ENZ-treated forages than for untreated forages (719 g/kg versus 322 g/kg, 501 g/kg versus 200 g/kg, and 839 g/kg versus 437 g/kg, respectively). AFEX + ENZ treatment increased the N content and disappearance of plant constituents, but reduced the content of the major structural carbohydrates (ADF and NDF). The AFEX + ENZ-treated forages could therefore be considered for use as a non-protein N supplement in combination with high energy diets low in ruminally degradable protein.