Effects of Steam Pelleting Conditions and Extrusion Cooking on a Swine Diet Containing Wheat Middlings

Abstract
One hundred and fourteen pigs were used to study a steam pelleted and extrusion cooked diet containing 15% wheat middlings. Pelleting variables were closely monitored during processing. Treatments included (1) mash, (2) dry pelleted mash, (3) steam pelleted mash and (4) corn and wheat middlings extruded before steam pelleting. Growth and digestibility trials were conducted with weanling (15.5 kg) and grower finisher (46 kg) pigs and a preference trial was conducted with 27.9-kg pigs. Steam conditioning before pelleting resulted in more durable pellets, less starch damage and reduced consumption of electrical energy compared with dry pelleting. More total energy was required to steam pellet than to dry pellet when energy required to generate steam was considered. Pellet production rate was increased by steam conditioning of the mash before pelleting. More than 70% of the energy required for steam pelleting was used to generate steam. The extrusion process resulted in extensive gelatinization of corn and wheat middling starch granules. All processing methods improved (P<.05) feed:gain ratios over that obtained with the mash diet in the weanling pig study. Average daily gain was not affected by treatment. Extruding the corn and wheat middlings before steam pelleting reduced (P<.05) feed intake. Steam pelleting and extrusion cooking increased dry matter and energy digestibilities. Results with grower finisher pigs showed that dry pelleting and extrusion cooking improved (P<.05) feed:gain ratio over that obtained with the mash and steam pellets. Daily gain was not affected (P>.05) by treatment. Dry matter and energy digestibilities were higher with the dry pelleted diets than with the mash and steam pelleted diets. Steam pelleting increased (P<.05) these digestibilities over those observed with the mash diet. Results indicated that pelleting process conditions may be correlated with animal performance. Copyright © 1983. American Society of Animal Science. Copyright 1983 by American Society of Animal Science.

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