| A series of 3 experiments were conducted to optimize the extrusion process parameters of corn and broken rice and to investigate its effects on the growth performance of weanling pigs. Weaning is stressful to the piglets and always damage the structure and function of the digestive tract, cause gastrointestinal disturbances, increase diarrhea incidence and growth retardation. In general, Improving feed digestibility and adding functional additives in feeds were used to promote weaned nutritional intake and digestive physiology recovery. After extrusion, the gelatinization of cereal starch were increased, and the digestibility and palatability of cereal grain were improved. And the extruded cereal grains were perfect energy source for young animals. Over, selecting the suitable process parameters to extrusion corn and broken rice, increasing the palatability and digestibility of cereals, and applying the extruded cereals in diets, was a good strategy to ensure the nutrient intake and digestive recovery of weanling pigs. This study contains 3 experiments as follow:Experiment 1. Optimization the extrusion process parameters of corn and broken riceThe starch gelatinization was used as quality indicator, and extrusion process parameters of corn and broken rice were optimized, respectively. A 3 parameters and 3 levels orthogonal experimental design was conducted (1. Corn:moisture content,14%,16%,18%; temperature of extrusion barrel,100℃,120℃,140 ℃; feeding ratio,18.71 kg/h,23.85kg/h, 28.94kg/h.2. Broken rice:moisture,16%,18%,20%; temperature of extrusion barrel, 105℃,115℃,125℃; feeding ratio,13.66kg/h,20.21kg/h,25.90kg/h). The results showed that, (1) Extruding corn under the experimental situation, the moisture content of corn and barrel temperature were significant affect (P<0.05) the starch gelatinization of extruded corn, and the order from the great to minor could be as follows:moisture content> barrel temperature> feeding ratio; the best technological parameters combination of extruding corn could be optimized as:the moisture content of corn was 14%, the barrel temperature was 140℃, the feeding ratio was 28.94kg/min. (2) Extruding broken rice under the experimental situation, the moisture content of broken rice was significant affect (P<0.05) the starch gelatinization of extruded broken rice, and the order from the great to minor could be as follows:the moisture content of broken rice> feeding ratio> barrel temperature; the best technological parameters combination of extruding broken rice could be optimized as:the moisture content of broken rice was 16%, the barrel temperature was 125℃, the feeding ratio was 20.21kg/min.Experiment 2. Effect of extrusion process on nutritional value and ATTD of nutrient in corn and broken rice.Extruding corn and broken rice used the technological parameters optimized in experiment 1, then sample the corn, extruded corn, broken rice and extruded broken rice. The chemical composition, amino acid (AA) composition and scanning electron microscopy (SEM) of the samples were analyzed. And 28 barrows were chosen to randomly allocate to 4 groups to determine the DE, ME and ATTD of other nutrients. Pigs were fed the semi-single diets formulated by corn, extruded corn, broken rice and extruded broken rice, respectively. The results showed that, (1) Extrusion process changed the chemical composition of corn and broken rice. After extruded, the dry mater (DM), crude protein (CP), nitrogen-free extract (NFE), ash, calcium (Ca), phosphorus (P), total starch and gross energy (GE) of corn and broken rice were increased, but the ether extract (EE) content was decreased. The amylose and amylopectin in extruded corn were slightly greater than un-extruded corn, but in the extruded broken rice the content of amylose was decreased while the content of amylopectin was increased. (2) There was no strong effete on the AA composition in corn and broken rice by extrusion processing. (3) Extrusion process changed the micro morphology of corn and broken rice remarkably, and destroyed the starch granules. (4) Extrusion process increased the ATTD of DM and GE in corn and broken rice (P<0.01). The DE and ME content in extruded corn were significant greater than raw corn, but there was no significant difference of DE and ME content between extruded broken rice and raw broken rice. Extrusion process increased the ATTD of N in corn, but not for broken rice.Experiment 3. Effect of broken rice and extruded broken rice on growth performance of weanling pigsA total of 120 weaned pigs (21 day of age and 5.76±0.07 kg BW) were chosen and allotted randomly to 6 groups by sex, and weight. From 0 to 35 day of the trail, pigs were randomly allocated to 1 of the 6 dietary treatments. Each treatment was fed to 5 pens with 4 pigs (2 barrows and 2 gilts) per pen. The dietary treatments were as follows:1) control (CON), a basis diet which main energy source was contributed by corn (50%) and extruded corn (50%); 2) treatment 1, which main energy source was contributed by corn (40%), extruded corn (40%), broken rice (10%) and extruded broken rice(10%); 3) treatment 2, which main energy source was contributed by corn (30%), extruded corn (30%), broken rice (20%) and extruded broken rice (20%); 4) treatment 3, which main energy source was contributed by corn (20%), extruded corn (20%), broken rice (30%) and extruded broken rice (30%); 5) treatment 4, which main energy source was contributed by corn (10%), extruded corn (10%), broken rice (40%) and extruded broken rice (40%); 6)treatment 5, which main energy source was contributed by broken rice (50%) and extruded broken rice (50%). In 36 days of trail, pigs form 4 treatments which showed better performance were chosen and allotted into 4 new treatments by weight, and feed the followed diets:1) control (CON), a basis diet which main energy source was contributed by corn (100%); 2) treatment 1, which main energy source was contributed by corn (50%) and extruded corn (50%); 3) treatment 2, which main energy source was contributed by corn (50%) and broken rice (50%); 4) treatment 3, which main energy source was contributed by corn (50%) and extruded broken rice (50%). The results showed that, (1) During the first week, the pigs fed the diet of treatment 5 had the greatest ADFI and ADG. And the pigs in treatment 5, treatment 4 and treatment 1 showed greater (P<0.05) ADFI and ADG and lower FCR (P<0.05) than other treatments. (2) From the day 36 to 49 of the trial, no differences in ADFI and ADG were observed among pigs fed the CON diet and other treatments diets, but the FCR in treatment 2 was significant lower than CON (P<0.05).(3) In the overall experiment, pigs fed the diets substitute corn by broken rice had greater growth performance, but did not reach the significant levels. (4) As the substitution of broken rice increased in the diet, the pig showed lower incidence of diarrhea, but did not reach the significant levels. (5) There was no significant differences in the concentration of glucose, plasma urea nitrogen, total protein, phosphorus, and total cholesterol among treatments. However, the pigs fed the diet substitute corn with broken rice showed lower (,P>0.05) concentration of calcium and triglyceride than CON. As the substituted ratio of broken rice increased, the plasma concentration of Ca (14d, P<0.001; 28d, P<0.05) and TG (14d, P<0.001; 28d, P<0.05) were decreasing linearly. At day 14, the plasma urea nitrogen content in treatment 4 and treatments 5 were tended to be lower than other treatments (P<0.05).In conclusion, the present results demonstrate that extrusion process changed the chemical composition and micro morphology of corn and broken rice, and increased the digestibility and palatability of corn and broken rice. In the early of postweaning, including broken rice and extruded broken rice in the diet would increase the growth performance of weanling pigs, and reduce the incidence of diarrhea. Therefore, feeding the weanling pigs with broken rice based diet last 1 week and then changed to corn based diet is more appropriate. |
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