Effect of treatment of selected mature forages with sodium hydroxide on in vitro dry matter degradability.

摘要

Maturity is one of the factors that reduce digestibility of forages species and can limit growth and production of ruminant animals. The objective of this experiment was to evaluate in vitro degradability of forages when treated with sodium hydroxide (NaOH). Mature forages were harvested in 2008, and dry matter (DM) yield was calculated from 12 field replicates. Subsamples were ground and analyzed in duplicate for DM, ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), crude protein (CP), fat, and gross energy. Fermentable sugar content of forages were also analyzed after hydrolysis.. Samples were pre-treated with 0, 2, 4, and 6% levels of NaOH for 24 h. In vitro organic matter disappearance (IVOMD) and in vitro dry matter disappearance (IVDMD) were determined in triplicate by using ruminal fluid from an Angus heifer that was fed alfalfa hay and a corn-based supplement. The experiment was a 7 X 4 X 7 factorial arrangement of forages, NaOH levels and in vitro incubation times for IVDMD and a 7 X 4 factorial arrangement of forages and levels of NaOH for IVOMD. Field DM of selected mature forages ranged from 45.5 to 28%. The concentrations of NDF ranged from 77.1 to 47.1%, ADF from 43 and 34% and CP from 13.5 to 4.8%. Eastern gamagrass (EGG), switchgrass (SG), bermudagrass (BG), johnsongrass (JG), crabgrass (CG), and tall fescue (TF) had greater NDF concentration than sweet sorghum (SS). The greater ADF content was observed in SG, JG, TF, EGG, CG, while BG and SS were lower in ADF. Forage CP was greatest in BG (13.5%), while SG had the least CP content (4.8%). The IVDMD differed (P 0.01) among forages according to forage composition itself, NaOH treatment levels and duration of incubation. The IVOMD was greater after pretreatment with 4 and 6% NaOH for all forage species compared to controls and 2% NaOH. Treatment with NaOH was more effective in forages with greater fiber concentration. The sugar analysis showed that SS, BG and SG had greater concentrations of glucose and xylose+mannose than other forages used in the experiment (39.8, 30.0, and 30.9% DM of initial sample weight, respectively). The NaOH treatment had a positive effect on IVDMD and IVOMD of different forages species and 4% NaOH appeared optimum.