Effects Of Glucose Release Modes Of Extruded Grain Starches On Energy Utilization In Growing Pigs

Starch is the most cost-effective energy source in feed,and it has always been a hot spot in the field of animal nutrition research.Lots of researches have shown that the glucose release mode of starch can change the digestion of nutrients and energy metabolism in animals.In this research,extrusion modification technology was used to change the glucose release mode.The effects of glucose release mode on substance oxidation and energy deposition in growing pigs were studied by the combination of in vitro and in vivo research.It provides a theoretical basis for precise nutrition regulation and reasonable feed energy structure of growing pigs,which provides technical parameters for the development of extruded feed products for efficient use of animals.This research mainly includes the following content:Experiment 1: Effects of extrusion modification on physicochemical properties and in vitro digestibility of grain starchesFour kinds of raw cereal starches: degerminated corn,decorticated white sorghum,brown rice and husked barley were selected to explore the effects of extrusion on the physicochemical properties and in vitro digestion of grain starches.The results showed that:1.1 Extrusion modification has significant effects on the physical and chemical properties of cereal starch.The dry matter content of starch decreased significantly after extrusion(P < 0.05);Lipid-amylose complex could be formed;The content of total starch decreased significantly(P <0.05);The ratio of amylopectin to amylose decreased significantly(P < 0.05);The degree of gelatinization has been significantly improved(P < 0.05).It was observed that the extruded starch particles lose their original geometric structure,showing an irregular zigzag and flaky spatial structure by SEM.It was found that extrusion modification can lead to a significant decrease in the crystallinity of starch by FTIR(P < 0.05).1.2 Extrusion caused the starch to show a very fast glucose release mode.The content of RDS increased significantly(P < 0.05).SDS and RS decreased significantly(P < 0.05).The content of RDS was positively correlated with the degree of gelatinization and the ratio of A1022/A1047(r= 0.968,r = 0.982,P < 0.01).Experiment 2: Effects of extruded corn diet on blood Indexes,nutrient digestibility and energy utilization of growing pigsEight 33.9±2.85 kg castrated boars(Duroc × Landrace × Large White)were selected as the research objects,and each pig was separately placed in the open-circuit respiratory calorimetry equipment.The experiment was conducted in 2 rounds by 2×2 Latin square design.The prefeeding period for the first round was 5 days,followed by a formal trial for 5 days.In the second round,the feeds of the two groups were switched and the first round of experiment was repeated.After the second round,the fasting metabolism experiment lasted for 3 days.The pre-feeding period and the formal test period were free drinking water,the feeds were fed with be fed as mash and mixed with water just before feeding,and sufficient water is guaranteed during fasting metabolism.The effects of extruded corn on material and energy metabolism of growing pigs were explored through blood indexes,nutrient digestibility and energy supply and distribution.The results showed that:2.1 The glucose release mode of extruded corn significantly affected the blood biochemical indexes of growing pigs.The ability to rapidly release glucose from extruded corn could increase the levels of blood glucose and insulin in growing pigs(P < 0.05),and the significant increase of urea nitrogen in plasma represented the exuberant metabolism of amino acids(P < 0.05).2.2 The glucose release mode of extruded corn significantly affected the digestibility and energy metabolism of growing pigs.Compared with the raw group,extruded corn significantly increased the apparent digestibility of dry matter and crude protein of growing pigs(P < 0.05).It also significantly increased the digestible energy and metabolic energy of growing pigs(P < 0.05).However,the excessive glucose release rate of extruded corn increased the total heat production of growing pigs(P = 0.269),in which the heat increment also has an upward tendency(P = 0.563).As a result,the net energy of the two groups were basically equal.(P = 0.864).2.3 The proportion of energy provided by oxidation of the three nutrients observably affected by the glucose release mode.The rapid glucose release rate of extrusion starch significantly increased the oxidative energy supply of protein and fat in growing pigs(P < 0.05),and decreased the oxidative energy supply of carbohydrate(P = 0.003).As a result,the respiratory quotient(RQ)of growing pigs was reduced(P < 0.05).2.4 The rapid glucose release mode in extruded corn altered lipid and protein retained energy in growing pigs.The carbon deposition rate of growth pigs fed extruded corn was significantly increased(P < 0.05),and the nitrogen deposition rate was significantly reduced(P < 0.05).Excess glucose release rate resulted in an increasing trend of fat retained energy(P=0.517)and significantly decreased protein retained energy(P < 0.05).Finally,it indistinctively effected on the total retained energy(P = 0.803).In conclusion,extrusion modification changed the physical and chemical properties of starch,and improved the rate of glucose release and nutritional value of starch.Compared with the raw group,Nutrient digestibility and energy absorption efficiency of growing pigs could be improved by using full proportion of extruded corn diet.However,the excessively fast glucose release mode of extruded corn could lead to an upward tendency in the total heat production and heat increment,which reduced the energy conversion efficiency and the optimization of energy structure.As a result,the net energy of the two groups were basically equal.