Chemical Treatment of Ryegrass Straw: In vitro Dry Matter Digestibility and Compositional Changes

Abstract

SAMPLES of ryegrass straw were sprayed or soaked in sodium hydroxide (NaOH) and soaked in potassium hydroxide (KOH), ammonium hydroxide (NH4OH) and sodium formate (NaCHO2) solutions of varying concentrations. The average in vitro dry matter digestibility (DDM) for untreated straw was 33.3%. Spraying a 2% NaOH (15 ml per g straw) solution on straw did not significantly improve DDM, while soaking at the same level produced a significant (P<.01) increase. There were no significant differences among particle sizes or treatment times. Two, four, six or eight percent levels of either NaOH or KOH solutions significantly (P<.01) enhanced DDM. However, there was no difference between NaOH and KOH. No significant improvement was rioted above the eight percent level. NaCHO2 significantly (P<.01) increased DDM above native straw, but higher treatment levels were necessary to achieve equal benefit to NaOH. NH4OH treatment produced variable results on DDM but the crude protein (CP) content of treated straw was consistently increased. This was in contrast to NaOH soaking, which significantly (P<.01) lowered CP, acid detergent fiber (ADF) and acid detergent lignin (ADL) with each added level of NaOH. Cell wall constituents (CWC) was also significantly (P<.01) lower for treated straw than for native straw.