Steam Treatment of Crop Residues for Increased Ruminant Digestibility. II. Lamb Feeding Studies

Steam pressure-treated rice straws with and without added chemicals were fed to lambs in digestibility and performance trials. A diet containing 65% rice straw treated with steam only at 28 kg/cm2 for 20 sec had lower digestibility of organic matter (−6.3%), cellulose (−9.7%), nitrogen (−26.4%) and energy (−8.1%) than did an identical untreated straw control diet, although overall animal performance (weight or energy gain and feed intake) was similar. A diet containing 65% rice straw treated at 28 kg/cm2 for 90 sec was inferior in all respects to the untreated control. A diet containing 65% rice straw treated with 4% NaOH by weight and then steam treated at 28 kg/cm2 had higher organic matter (4.0%) and cellulose digestibility (17.6%), poorer nitrogen digestibility (30.5%) and essentially the same energy digestibility as the untreated control. Animal growth was significantly improved with the NaOH diet than with the untreated control. Comparison of diets containing 72% rice straw treated with NaOH (3%) or NH3 (2.6%) prior to steam treatment at 21 kg/cm2 indicated that the NaOH-treated diet produced significantly better gains than did the diet treated with NH3 or the untreated control. Lambs fed the NaOH-treated straw diet approached the performance characteristics of those fed a positive control diet containing alfalfa hay (82%). Digestion coefficients for all components except nitrogen were higher for the NaOH-treated straw than for the NH3-treated sample or the untreated control.