Nutrient composition, digestion and rumen fermentation in sheep of wheat straw treated with calcium oxide, sodium hydroxide and alkaline hydrogen peroxide

This study tested the effect of calcium oxide (CaO), sodium hydroxide (NaOH) and NaOH plus hydrogen peroxide (H2O2; AHP) on cell wall composition, digestion and fermentation of wheat straw (straw) in sheep. Treated straws were prepared by mixing straw either with water followed by dusting with CaO at 160 g kg(-1) DM or with a NaOH solution alone at 31 kg(-1) DM to supply 80 g NaOH kg(-1) DM (Na) or pre-soaked with Na exactly as in the previous treatment for 27 h followed by mixing with 130 g H2O2 kg(-1) DM (AHP) for 6 h. After 14 days of storage, the treated straws and an untreated straw (U) were fed automatically every 2h to four individually housed sheep together with a supplement in a 4x4 latin square experiment. Each kilogram supplement DM contained 422 g CP and 10.8 MJ ME. NDF (p<0.001) and hemicellulose (p<0.01) contents were significantly reduced whereas cellulose was increased (p<0.001) in treated compared to untreated straw. ADL was reduced in Ca (p<0.05) but increased (p<0.05) in Na and AHP compared with U. The rumen and total tract digestibility were significantly (p<0.001) greater in sheep fed treated compared with untreated straw. Significant differences (p<0.05) between treatments for pH, NH3 and VFA were also observed. All treatments improved the nutritive value of straws compared with untreated through modification of cell wall with a subsequent increase in digestibility by sheep. Although the digestibility for Ca was lower than that for Na despite reduction in cell wall, its use to treat straws may be more safe and cost effective than Na. AHP was the most effective and could also improve the energy value of other low quality forages for ruminants. However, the need of AHP for a large amount of NaOH to achieve highly alkaline pH limits its farm scale application. Therefore, further studies should either consider reducing the amount of NaOH or finding alternative alkalis that are cost effective and user-friendly. (C) 1998 Elsevier Science B.V.