Effect Of Conditioning Temperature On Pelleting Characteristics And Nutrient Digestibility Of Broken Rice-Based Diets For Pigs

With the development of social economy,the limitations of corn-soybean meal diet have become increasingly prominent.The key to the development of the industry is to make full use of the by-products of food processing to replace corn and build a diversified feed formula.It is an important subject in the field of pig production and feed processing to optimize and adjust the processing parameters of conditioning processing by using the research method of animal nutrition,so as to realize the efficient processing of diet and improve the processing efficiency and product quality of diet.Therefore,the purpose of this study was to investigate the effects of conditioning temperature on the processing characteristics and nutrient digestibility of broken-rice based diet.In experiment 1,the optimum substitution ratio of broken rice in pig diet was obtained by the effects of different substitution ratios of broken rice on feed processing characteristics and growth performance of growing-finishing pigs.In experiment 2,different conditioning temperatures were set to modify the broken-rice based diet,and the effects of conditioning temperature on the processing characteristics,nutrient digestibility,pig growth performance and intestinal microflora of broken-rice based diet were investigated.The aim was to optimize and adjust the process parameters of conditioning temperature,so as to realize the efficient processing of broken-rice based diet and diversified diet formula technology.The main results are as follows:Study I.Effects of substitution of corn with broken rice on pelleting characteristics and nutrient digestibility of growing-finishing pigsThe pigs were processed with 20%,40% and 60% broken rice replacing corn,respectively,and samples were taken to test the pelleting characteristics of the diets.Then,120 growing pigs at 80 days of age(average weight 31.64±2.81 kg)were selected as test animals for a total of 60 days(30 days for the growing stage and 30 days for the fattening stage).The results are as follows:(1)Processing characteristics: shape rate and pellet durability index of the diets increased with the increase of the percentage of broken rice substitution,and the difference among the groups was significant(P<0.05);The pellet hardness and starch gelation degree of the diets of the 60% broken rice replacement group and the 40% broken rice replacement group were significantly higher than those of the corn-soybean meal group(P<0.05).(2)Growth performance and nutrient digestibility: the average daily weight gain of the 40% broken rice replacement group was significantly higher than that of other groups during growing phase(P<0.05);there was no significant difference in growth performance among groups during finishing phase(P>0.05).The average daily weight gain of the 40%broken rice replacement group tended to be higher than that of other groups during growing-finishing phase(P<0.1);the apparent digestibility of crude protein in the 40%rice replacement group was significantly higher than that of other groups during growing phase(P<0.05).During finishing phase,the apparent digestibility of dry matter in the 40%rice replacement group was significantly higher than that in other groups(P<0.05);the apparent digestibility of crude protein in the 40% rice replacement group and 60% rice replacement group was significantly higher than that in the control group(P<0.05).(3)Blood Profiles: During growing phase,the aspartate aminotransferase in the 40 %broken rice replacement group was significantly higher than that in the control group(P<0.05);During finishing phase,with the increase of the proportion of broken rice replacement,the levels of blood urea nitrogen,alanine aminotransferase and aspartate aminotransferase increased significantly(P<0.05).(4)Antioxidant and immune ability: During growing phase,with the increase of the proportion of broken rice replacement,the content of glutathione peroxidase increased significantly,and the content of malondialdehyde decreased significantly(P<0.05).The total antioxidant capacity of 40 % broken rice replacement group and 60 % broken rice replacement group was significantly higher than that of control group(P<0.05).During finishing phase,with the increase of the proportion of broken rice replacement,the malondialdehyde content decreased significantly(P < 0.05);the contents of total antioxidant energy,superoxide dismutase and glutathione peroxidase were significantly increased(P<0.05).There was no significant difference in the contents of Ig M,Ig A and Ig G among the treatment groups(P>0.05).Study II Effect of conditioning temperature on pelleting quality,nutrient digestibility and gut microbiota of broken rice-based diets for growing pigsFive conditioning temperatures of 70,75,80,85 and 90 °C were set up to process the diet of 40 % broken rice replacement group,and the processing characteristics of the diet were sampled and detected.Five pigs(average weight 21.40 ± 1.39 kg)with better recovery after T-type fistula at the end of ileum were selected for the experiment.The experiment was divided into five cycles(7 days per cycle).Fecal and terminal ileal digesta samples were collected to determine nutrient digestibility.A total of 300 growing-finishing pigs were selected and the growth performance and intestinal microbes were measured for 35 days.The results show that:(1)Processing characteristics: With the increase of conditioning temperature,the starch gelatinization degree,pellet durability index and shape rate of the diet increased linearly(P<0.05),and at 90 °C,the starch gelatinization degree,pellet durability index and shape rate were the highest.The content of resistant starch showed a significant quadratic curve change with the increase of conditioning temperature(P<0.05).When the conditioning temperature was 85 °C,the content of resistant starch was the lowest.(2)Nutrient digestibility: The apparent digestibility of dry matter,apparent ileal digestibility of energy and apparent ileal digestibility of starch showed a significant quadratic curve change with the increase of conditioning temperature(P<0.05).When the conditioning temperature was 85 °C,the apparent digestibility of dry matter,apparent ileal digestibility of energy and apparent ileal digestibility of starch were the highest.(3)Growth performance: The average daily feed intake and average daily gain of pigs showed a significant quadratic curve change with the increase of conditioning temperature(P<0.05).However,the conditioning temperature had no significant effect on the ratio of feed to meat(P>0.05).(4)Intestinal microorganisms: With the increase of conditioning temperature,the copy number of Lactobacillus sp.in jejunum increased linearly(P<0.05).For Escherichia coli,in the jejunum and ileum,the copy number of Escherichia coli decreased linearly with the increase of conditioning temperature(P<0.05).In summary,when the replacement ratio of broken rice was 40 %,higher average daily gain could be achieved in the feeding experiment;when the conditioning temperature was85 °C,the nutrient digestibility and feeding effect of broken-rice based diet were the best.Therefore,it is recommended to use 40 % broken rice replacing corn in production practice,and the optimal conditioning temperature of broken-rice based diet is 85 °C.