Effect of drying temperature on in vitro gas production and energy content of wheat dried distillers grains using mixed rumen micro-biota obtained from Holstein steers

Abstract

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