[Effect of the inoculation of the comestible fungus Pleurotus ostreatus on the chemical composition and digestibility of barley straw].

The purpose of the present study was to determine whether incubation of the edible mushroom Pleurotus ostreatus in barley straw for 45 or 60 days, proved to be a means of increasing the nutritive value and digestibility of the straw for ruminant animals. In this respect, the following determinations were performed in untreated barley straw (control), and in incubated barley straw with the mushroom strain mentioned previously, for 45 or 60 days: pH, moisture, crude protein, ash, hemicellulose, cellulose, lignin, gross energy and in vitro digestibility of the dry matter. Results showed that crude protein percentage remained constant (p less than or equal to 0.05) in all treatments (means 2.67%), increasing the ash content of the straw incubated for 60 days. The hemicellulose and cellulose percentages diminished significantly (p less than or equal to 0.05) in the straw incubated for 45 or 60 days (16.74, 32.24, 17.43, 32.41% respectively) than in the control straw (24.54, 40.15%). The lignin percentages increased, although not significantly in the straw incubated for 45 or 60 days with respect to the control straw (8.36; 9.10, 9.06%, respectively). Energy values were lower for the straw incubated 45 or 60 days (2.70; 2.74 Kcal/g) than for the control straw (2.80 Kcal/g), without difference in the in vitro dry matter digestibility by incubating the straw for 45 or 60 days with Pleurotus ostreatus and the control (56.04; 52.65; 53.06% respectively). It is concluded that the Pleurotus ostreatus strain used in this study was unable to delignify the straw, because of its lack of fenoloxidases, enzymes which are necessary for lignin biodegradation.(ABSTRACT TRUNCATED AT 250 WORDS)