Effects of replacement of all of corn contained in feed with brown rice and feeding brown rice together with sweet potato on growth performance and quality of pork of fattening pigs

The aim of this study was to clarify whether all of corn contained in diet for finishing pigs could be replaced by brown rice without hindering growth performance and quality of pork and to elucidate appropriate ratios of brown rice and sweet potato when both of them are contained in a diet for finishing pigs. In the experiment 1, we replaced all of corn contained in a diet, the ratio of corn was 75%, with brown rice. Live weight gains, feed intake, and feed efficiencies were not affected by the replacement. In the experiment 2, diets contained both brown rice and sweet potato were given to finishing pigs. There were four levels of ratios of brown rice, 0, 30, 52.5, and 75%, while those of sweet potato were 0, 22.5, 22.5, 0%, respectively. Live weight gains and feed intake were not affected by the diets. Feed efficiencies were tended to be affected (P<0.10) ; the average feed efficiencies of pigs given the diet contained 30% of brown rice and 22.5% of sweet potato were the lowest whereas feed efficiencies did not differ among the other three groups. In order to increase the amount of brown rice given to a pig, pigs were given diets contained 52.5% of brown rice from 30kg to 120kg in the experiment 3. When these pigs reached to the finisher period (70kg), they were also given sweet potato (22.5%) together with brown rice. Feed intake during the grower period and that of during the overall trial were higher in the pigs given both brown rice and sweet potato (P<0.05). Further, feed efficiencies during the overall trial were lower in those pigs (P<0.05). However, growth performances were not affected by the diets during the finisher period. Throughout the three experiments, feeding brown rice increased total ratios of saturated fatty acids and those of mono-unsaturated fatty acids of inner layer of subcutaneous fat while it decreased those of poly-unsaturated fatty acids. In particular, increases in ratios of oleic acid and decreases in ratios of linoleic acid were highly reproducible. Although melting points of inner layer of subcutaneous fat were higher in pigs given brown rice in the experiment 2, feeding brown rice did not affect them in the experiments 1 and 3. Feeding brown rice and feeding both brown rice and sweet potato did not affect drip losses and shear force values of longissimus dorsi muscle throughout the three experiments. In conclusion, there won't be any major problems of growth performances and qualities of pork even though all of corn contained in diet for finishing pigs is replaced by brown rice. We also conclude that appropriate ratios of brown rice and sweet potato when both of them are contained in a diet for finishing pigs were approximately 50% and 20 to 25%, respectively.