[Improvement of the feed value of straw by pelleting and sodium hydroxide addition. 1. Changes in the digestibility of rye and wheat straw].

Four series of pelleting experiments were conducted using straw from winter rye and winter wheat crops. Pelleting was done with and without grain addition. In each of the experimental series, 7 NaOH dosage levels were tested Further, 2 to 5% urea were added to the mixture to be pelleted. The 28 different pellet batsches and untreated straw were fed to sheep to study digestibility. Evaluation by difference trial revealed that straw pelleting without NaOH addition reduces the digestibility of organic matter by 4.7 units, on the average, whilst NaOH addition was found to increase digestibility depending on the dose applied. The following relationship was found between digestibility of straw dry matter (y) and NaOH dose in g/kg straw dry matter (x): y = 43.4 + 0.358x -0.00116x2. The grain proportion proved largely inert as far as the NaOH action is concerned. In one experimental series in which wheat straw without grain addition had been compacted at high pressing temperatures, an additional disintegration effect was observed irrespective of the NaOH dose applied. It increased digestibility by 8.0 units and is very likely to originate from the specific action of urea.