Effect of enzyme or microbial treatment of bermudagrass forages before ensiling on cell wall composition, end products of silage fermentation and in situ digestion kinetics

Tifton 85 bermudagrass (T85) and Coastal bermudagrass (CBG) established on adjacent plots and managed similarly were harvested after 3 or 6 weeks of r egrowth and used to investigate the effects of fibrolytic enzymes or microb ial inoculant treatment before ensiling on nutrient composition and recover y, cell wall chemistry and digestion. Prior to ensiling T85 had higher conc entrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF), similar concentrations of total lignin, and greater (p < 0.05) in vitro an d in situ dry matter (DM) and NDF disappearances when compared with CBG. Co astal bermudgrass had higher ( p < 0.05) concentrations of acid-insoluble l ignin and ether-linked ferulic acid (monomers and dimers), and lower concen trations of glucose and mannose than T85. Treatment of bermudagrass forages with microbial inoculant decreased (p < 0.05) concentrations of NDF, hemic ellulose, butyrate, lactate, cell walls and acid-insoluble lignin, and incr eased (p < 0.05) concentrations of ammonia, total volatile fatty acids (VFA ) and acetate in silages. Treatment of bermudagrass forages with fibrolytic enzymes had no effect on silage fiber concentration, cell wall carbohydrat e fraction or concentration of p-coumaric and ferulic acids, but increased the concentration of butyrate. Among silages, T85 had higher (p < 0.05) in vitro and in situ dry matter DM and NDF disappearance and higher (p < 0.05) potentially digestible fractions and smaller (p < 0.05) indigestible fract ions of DM and NDF than CBG. Treatment of bermudagrass forages with fibroly tic enzymes had no effect on in vitro or in situ DM or NDF disappearance of silages. Treatment of bermudagrass forages with microbial inoculant increa sed in situ DM disappearance at 72 h of incubation (p < 0.10) and the poten tially digestible fraction of DM (p < 0.05) of silages. Although treatment of bermudagrass forages with microbial inoculant had no effect on silage in vitro or in situ NDF disappearance at 48 h of incubation, it increased in situ NDF disappearance at 72 h (p < 0.05) and the potentially digestible fr action of NDF. It is concluded that the greater cellulose content of cell w alls with the same or less lignin in T85, and the greater concentration of ether-linked ferulic acid in CBG explain the greater digestibility of T85 w hen compared with CBG at similar stages of maturity. Treatment of bermudagr ass forage at ensiling with microbial inoculants may have more potential th an extracts of fibrolytic enzymes in improving silage fiber digestion. (C) 1999 Elsevier Science B.V. All rights reserved.