The aim of the present study was to evaluate the effect of the air temperature on in vitro digestibility of organic matter (DOM), metabolizable energy (ME) and net energy for lactation (NEL) values, and drying efficiency of brewer s grains (BG) using a new technology of a tower heat-dryer system. The technology was developed to dry BG when it was flew constantly through a tower (10 m length) against a current of pressure of heated air at 180 ºC (LAT) or 240 ºC (HAT) with a pressure suction cooling. Dried samples were obtained from the lowest and the highest applied temperature, then ground to pass through a 2-mm screen and subjected to a gas production technique. Rumen content was collected from three ruminally fistulated sheep (42±2.5 kg, body weight) and strained through 4 layers of cheesecloth. The laboratory handling of rumen fluid was carried out under a continuous flow of CO2. 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 bottles were pre-warmed at 38.6 °C before the injection of 30 ml rumen fluid- buffer mixture (10 ml rumen fluid and 20 ml buffer solution) into each bottle followed by incubation in a water bath at 38.6 °C. Gas pressure was recorded after 2, 4, 8, 12 and 24 h of incubation and converted to gas volume using experimentally determined calibrated curve. Metabolizable energy, NEL and DOM values of the samples were calculated using following equations: ME (MJ/kg DM)= 1.56 +0.1390 GP +0.0074 XP +0.0178 XL; NEL (MJ/kg DM)= 0.1010 GP +0.0051 XP +0.011 XL; DOM (g/kg DM)= 14.88 +0.8893 GP +0.0448 XP +0.0651XA. Where GP is net gas produced after 24 h of incubation (ml/0.2 g DM), and XP, XL and XA are crude protein, crud fat and ash content of the feed (g/kg 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 (MJ/kg DM), NEL (MJ/kg DM) and DOM (LAT= 9.71, 5.64 and 620, HAT= 9.98, 5.79 and 640, respectively) of the BG samples evaluated. Results indicated that the drying process of the samples dried at the air temperature of 180 ºC was less efficient than the highest applied temperature, as observed in 9% of more consumed drying time with similar moisture output compared with the HAT samples. Therefore, the highest air temperature used in the present study was more efficient and safe for drying and enhancing the nutritive values of the BG samples evaluated.

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