The aim of the present study was to evaluate the effect of drying temperature on in vitro digestibility of organic maner (DOM), metabolizable energy (ME) and net energy for lactation (NEL) values, and drying efficiency of wheat dried distillers grains (WDDG), applied a tower heat-dryer system, using mixed rumen micro-biota obtained from Holstein steers. The technology was developed to dry WDDG when it was flewconstantlythrough a tower (10 m length) against a current of pressure of heated air at 185 .C (LAT) or 246 .C (HAT) with a pressure suction cooling. Dried samples were obtained from the lowest and the highest applied temperature, then ground to pass through a I-mm screen and subjected to a gas production technique. Rumen content was collected from four ruminally /istulated steers (420*13 kg, body weight) and straioed through 4 layers of cheesecloth. The laboratory handling of rumen fluid was carried out under a continuous flow of C02. In vitro incubation of the samples was done using a manual pressure transducer technique. Approximately 200 mg of each sample was weighed into a 120 ml serum bottle (n= 8). The bonles were pre-warmed at 38.6 .C before the injectionono ml rumen fluid-buffer mixture (10 ml rumen fluidand 20 ml buffer solution) into each bottle followed by incubation in a water bath at 38.6 .C. Gas pressure was recordedafter 2, 4,8, 12 and 24 h of incubation and converted to gas volume using experimentally deteomined calibrated curve. Metabolizable energy, NEL and DOM values of the samples were calculated using following equations: ME (MJlkg DM)= 1.56 +0.1390 GP +0.0074 XP +0.0178 XL; NEL(MJlkg DM)= 0.1010 GP +0.0051 XP +0.011 XL; DOM (glkg DM)= 14.88 +0.8893 GP +0.0448 XP +O.065IXA. WhereGPis netgasproducedafter 24 h of incubation(mVO.2 g OM), and XP, XL and XA are crude protein, crud fat and ash contentof the feed (glkg DM), respectively. Data were analysed using the GLM procedure of SAS. Results indicated that air temperature of the new drying technique had a significant (P< 0.05) effect on ME (MJlkg DM), NEL (MJlkg DM) and DOM (LAT= 9.7, 5.7 and 610, HAT= 10.0, 5.8 and 640, respectively) of the WDDG samples evaluated. Results indicated that the drying process of the samples dried at the air temperature of 185 .C was less efficient than the highest applied temperature, as observed in 9.8% of more consumed drying time with similar moisture output compared with the HAT samples. Therefore, the highest air temperature used in present study was more the efficient and safe for drying and enhancing the nutritive values of the WDDG samples evaluated.

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