| The purposes of this study were to measure the influence of normal variety, location, drying method and particle size on the nutritive value of corn. An additional objective was to establish prediction equation for available nutrients of corn. Five experiments were included in this study.(1) The objective of this experiment was to evaluate the affection of variety and loacation on the nutritive value of corn in finishing pigs of com. Four corn varieties were collected in one loacation, and one of these four varieties were collected in Shandong province, Jilin province, Anhui province, Inner Mongolia, and Hebei province. Total nine com samples were carried in this metabolism experiment. In Exp.1,54crossbred barrows with an initial body weight of33.5±5.4kg were used to determine the digestible energy (DE) and metabolisable energy (ME). Pigs were allotted to one of nine diets according to a completely randomized design, and each diet was measured with six pigs. The results indicated that variety significantly influenced available energy content (P<0.01) of com. The difference between DE in four varieties was0.52MJ/kg. Variety also influenced the digestibility of nutrients except ether extract. The difference between max and min on DE in five provinces was about0.33MJ/kg, and the statistics was also significant.(2) The objective of Exp.2was to evaluate drying methods on the nutritive value of corn in growing pigs. Four normal corn varieties were collected and grain samples from each variety were divided into four subplots of each. One of the subplots was placed on an airfield and allowed to dry. The remaining three were dried in a fluidized bed dryer at80,100or120℃. Ninety-six barrows (initial BW of33.4±2.7kg) were used in this experiment. The pigs were Duroc×Landrace×Yorkshire crossbreeds. Pigs were allotted to one of sixteen diets according to a completely randomized blockdesign, and each diet was measured with six pigs. A five-day collection period followed a seven-day diet acclimation period. The drying method significantly influenced the1,000kernel weight (P<0.01), bulk weight (P<0.01) and dry matter (DM)(P<0.01). No effect of drying method and drying temperature on the digestible energy and nutrient digestibility except ether extract.(3) The objective of Exp.3was to evaluate the affection of particle size on the nutritive value of corn in finishing pigs. Thirty barrows (initial BW of53.1±3.9kg) were used in this experiment. The pigs were Duroc×Landrace×Yorkshire crossbreeds. Pigs were allotted to one of five diets according to a completely randomized design, and each diet was measured with six pigs. The particle size of corn were441,543,618,659, and768μm when the corn were ground through screen size of1.0,1.5,2.0,2.5, and4.0mm, respectively. The DE and nutrient digestibility increased as the particle size decrease except the crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF).(4) The objective of Exp.4was to evaluate the DE and metabolizable energy ME of100corn samples which obtained from China com main plant areas. The total experiment consisted of five digestibility trials. A total of six hundred crossbred barrows (Duroc×Landrace×Yorkshire)(initial BW,35.3±1.9kg) were used according to a completely randomized block design, and each diet was tested with six pigs. A five-day collection period followed a seven-day diet acclimation period. Corn was assumed to be the only source of energy in the diet. The result indicated that the difference of the DE content of corn was significantly among five provinces (P<0-01). In the100com samples, the mean of DE and ME contents were4053kcal/kg and3923kcal/kg. Sixty com samples were used to build the prediction equations; the remaining forty samples were used to test the suitability of these equation. The best fit equations were as follows: DE, kcal/kg of DM=1062.68+(49.72×ether extract)+(0.54×gross energy)+(9.11×starch), with R2=0.62, residual standard deviation (RSD)=48kcal/kg, and P<0.01; ME, kcal/kg of DM=671.54+(0.89×DE)-(5.57×NDF)-(191.39×ash), with R2=0.87, RSD=18kcal/kg, and P<0.01. To test the suitability of these models to predict the DE content of a normal com sample, the DE content of40samples of com was measured by both the in vivo method and prediction models. Our results showed that the difference between observed group and prediction group was only13.32kcal/kg. Therefore, the prediction models in this article can be used to predict the DE content of com for pigs with acceptable accuracy. Exp.5was conducted to determine the apparent (AID) and standardized (SID) ileal digestibility for crude protein and amino acids in the10com samples using chromic oxide as an inert marker. Twelve barrows (average initial body weight=35.3±2.0kg) fitted with a simple T-cannula were assigned to one of two6×6Latin square designs with six periods and six diets comprising one nitrogen-free diet and five corn test diets in each Latin square. Each period lasted7d,5d for adaptation,2d for collection. The results showed that there were no significant differences in the AID and SID for crude protein and all amino acids except for arginine, histidine, phenylalanine, alanine, cystine, proline, and tyrosine among different double-low rapeseed meals. The best prediction equations for SID of lysine and methionine of corn were SID Lys (%)=85.41-6.11×EE (R2=0.29), SID Met (%)=101.00-3.39×NDF+98.15×Met (R2=0.93). To summarize, the variety, location, drying method and particle size all call effect the value energy or physical and chemical characteristics of com. The chemical composition of corn can be used to predict energy value and amino acids digestibility for growing pigs. The data of study enrich China feed data base, and provide a basis for accurate, real-time and dynamic formulated diets. |
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