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This study was conducted to investigate the effects of Trichoderma harzianum isolate T.447 (T.447) on the chemical composition and in vitro ruminal digestibility of treated maize, wheat, rapeseed and soybean straws. Preparation of each straw was divided into two equal parts and was treated with a suspension of T.447 spore or an equal volume of distilled water (control). Treated straws were placed in closed plastic bags and were incubated in a growth chamber at 25±1°C for 45 days. In vitro ruminal digestibility was determined after incubating the samples in buffered rumen fluid for 48 h using ANKOM DaisyII Incubator. For all data, a completely randomized design with a 4 × 2 factorial arrangement was used. The experimental factors were straw type at 4 levels (maize, wheat, rapeseed and soybean) and fungus application at 2 levels (T.447 and control). These findings show that crude protein, ether extract, ash, organic matter and cellulose, statistically, differed (P < 0.05) from straw type and fungus application. In vitro ruminal dry matter digestibility (IVRDMD), in vitro ruminal organic matter digestibility (IVROMD) and in vitro ruminal digestible organic matter in dry matter (IVRDOMD) differed significantly from straw type (P < 0.001) and fungus application (P < 0.05). The crude protein and ash concentrations increased (P < 0.05) in fungal-treated straws. The ether extract, organic matter, cellulose and in vitro ruminal digestibility values decreased (P < 0.05) in fungal-treated samples. These results obtained showed that the fungus has been active on the straws and had some desirable effects, such as enhancement of crude protein and undesirable effects, such as decrement of ether extract, organic matter and in vitro ruminal digestibility.
Key words: Trichoderma harzianum, chemical composition, in vitro ruminal digestibility, straw.