Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/1998
Publication Date: N/A
Citation: Interpretive Summary: Forage grasses play a critical role in providing nutrients to dairy cows even though they are not fully digested. The fiber portion of grasses (structural carbohydrates) stored in cell walls is poorly digested by ruminants. Increasing the degradation of forage fiber would have a tremendous positive impact on dairy production by providing increased energy, improving protein utilization, and decreasing manure waste. Traditional breeding methods have led to the selection of bermudagrasses, such as Tifton 85, that have improved animal performance. This improvement is due to altering the composition of bermudagrass fiber making it much more digestible. The changes in bermudagrass fiber have not affected the total biomass production of the plant; in fact, it is higher. It is clear that minor changes in the chemical composition of grass walls result in increased digestion of structural carbohydrate and more energy to the animal without sacrificing total biomass production. This provides plant breeders with greater flexibility when selecting plants to maximize their utilization in farming systems.
Technical Abstract: Tifton 85 bermudagrass (T85) and Coastal bermudagrass (CBG) established on adjacent plots and managed similarly were harvested after 3 to 6 wk of regrowth and used to investigate the effects of fibrolytic enzymes or microbial inoculant treatment before ensiling on nutrient composition and digestion. Tifton 85 had higher concentrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF), similar concentrations of total lignin, and greater in vitro and in situ dry matter and NDF disappearances before and after ensiling when compared with CBG. Coastal bermudagrass had higher concentrations of acid insoluble lignin and ether linked ferulic acid (monomers and dimers), and lower concentrations of glucose than T85. Treatment of bermudagrass with microbial inoculant decreased concentrations of NDF, hemicellulose, butyrate, lactate, cell walls, and acid insoluble lignin, and increased concentrations of ammonia, total volatile fatty acids and acetate in silages. Treatment with fibrolytic enzymes had no effect on silage fiber concentration, cell carbohydrate fraction or concentration of p-coumaric and ferulic acids, but increased the concentration of butyrate. It is concluded that the greater cellulose content of cell walls 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 when compared with CBG at similar stages of maturity. Treatment of bermudagrass forage at ensiling with microbial inoculants may have more potential than extracts of fibrolytic enzymes in improving silage fiber digestion.