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The objective of this study was to evaluate the nutritional effects of expander processing of dietary ingredients for weanling pigs. The grains used for this experiments were unprocessed(R) or thermally processed(T). The non-expanded meal(NEM) was manufactured by mixing simply unprocessed ingredients including corn, soybean meal, soy oil and milk replacer. For production of the raw material expanded meal(REM) and the raw material expanded pellet(REP), NEM was expanded and then ground(REM) or pelleted(REP). The thermally processed meal(TM) was prepared by mixing thermally processed grains(T) and other raw feed ingredients and the thermally processed pellet(TP) was by agglomeration TM through a pelleting system. A total of 225 pigs(15pigs/pen with an average initial BW of 5.8kg) were randomly allotted to the five experimental for a 14 d growth assay. REP was more durable(p$lt;0.05) in terms of pellet durability index(PDI) and stronger(p$lt;0.05) in terms of pellet hardness(p$lt;0.05) than TP. Both TM and TP, which contained thermally processed grains showed higher degrees of gelatinization(DG), REM and REP had relatively lower DG. During growth study, pigs fed TM and TP showed significantly improved ADG, ADFI and FIG over those fed REM and REP. Furthermore, pigs fed TP had higher ADG and ADFI than those fed the meal diets. This study found a relatively poor ADG and ADFI of weaned pigs when whole diet was expanded together but rather improved ADG and ADFI when only the grain portion in whole diet was thermally processed. This suggests that expander processing has damaged the high quality proteins and heat sensitive milk components included in the whole mixture. Apparent nutrient digestibilities of TP were significantly higher than those of REM and REP. Digestibility of each nutrient determined by piglets in the weight range of 5∼8㎏ was not affected by the expander treatments in this trial. Therefore, expanding whole diet compared to diet simply mixed with already heat processed ingredient did not exert any favourable effects for the weaned pigs. However, pellet diet was generally preferred to the mash diet. In conclusion, this results suggest no benefit by expanding whole raw material but some benefit by the inclusion of heat processed grain for the weaned pigs.
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