Study On Available Energy And Amino Acid Digestibility Of Wheat Milling By-products For Growing Pigs

Six independent experiments were conducted to investigate the effects of different inclusion levels, physical forms, growth stages and digestion sites on the nutritional values of wheat milling by-products fed to growing pigs, and to develop prediction equations for digestible energy (DE), metabolizable energy (ME) content, and standardized ileal digestibility (SID) of amino acids (AA) based on their chemical composition of the wheat milling by-products. In Exp.1, six diets were fed to36barrows (Initial BW=55.1±5.6kg) according to a completely randomized design. The basal diet was a corn-soybean meal diet, while the other five diets contained five inclusion levels (9.6%,19.2%,28.4%,38.6%and48.0%) of wheat middlings added at the expense of corn and soybean meal. When the inclusion level was9.6%, DE was only8.9MJ/kg of dry matter (DM), which was significantly (P<0.01) lower than the values derived from the other four inclusion levels (11.3,11.9,10.7and11.8MJ/kg, respectively). The coefficient of variation among each replication was reduced (P<0.05) with the increased inclusion levels. In Exp.2, eight diets were fed to24castrated growing pigs (Initial BW=42±3.6kg) according to a2×4factorial design with2periods. The basal diet was based on a corn-soybean meal diet and three experimental diets (wheat middlings, wheat shorts and wheat red dog) processed to mash and pelleted forms were used to determine the DE, ME content as well as nutrient digestibilities. The results showed that there was an increase (P>0.05) in energy content for wheat milling by-products and diets in pelleting form, except for wheat middlings. The DE content in wheat milling by-products for mash and pelleted forms were listed below:DEpelleting=0.99×DEmash+0.5124, R2=0.99. In Exp.3, sixteen diets were fed to thirty-two growing pigs (Initial BW=35.8±.2kg) according to a completely randomized design during three successive periods. The basal diet was based on corn and soybean meal, while the other fifteen diets contained wheat shorts (n=7) or red dog (n=8), added at the expense of corn and soybean meal. The apparent total tract digestibility (ATTD) of energy in wheat shorts and red dog averaged75.1%and87.9%. The DE of wheat shorts and red dog averaged13.8MJ/kg (13.1～15.0MJ/kg) and15.1MJ/kg (13.3～16.6MJ/kg) of DM, respectively. From the stepwise regression analysis, the best fit equations for wheat shorts and red dog together were:DE=-0.13×NDF+16.92, R2=0.84; ME=-0.6×NDF-0.16×Xylans+0.26×CP-2.02×P+12.73, R2=0.88. In Exp.4, twelve growing pigs (Initial BW=35.1±2.2kg) were allotted to two6×6Latin Square Designs with six periods. Ten of the diets were formulated based on60%wheat shorts or red dog and the remaining two diets were nitrogen-free diets based on cornstarch and sucrose. The results of this study indicated differences (P<0.05) among the different sources of wheat shorts and red dog in AID and SID for CP and all the indispensable AA. The SID of lysine averaged87.78%(79.54%～90.36%) and the lysine content in CP unit was the best indicator for prediction:(SID Lys=6.41×Lys/CP+66.46, R2=0.51).In Exp.5, thirty samples of wheat milling by-products (wheat bran, wheat middlings, wheat shorts, wheat red dog and wheat feed flour) were fed to growing pigs (Initial BW=61.9±3.2kg) to determine DE and ME content and to establish equations for predicting their DE and ME content based on chemical analysis. The31diets were fed to96growing pigs according to a completely randomized design during two successive periods. The chemical composition of the30samples was variable, and starch and fiber content had a very strong negative correlation. The DE content of wheat feed flour, wheat red dog, wheat shorts, wheat middlings and wheat bran averaged17.43,16.88,15.15,12.45and12.04MJ/kg of DM, respectively. From the stepwise regression analysis, a series of DE and ME prediction equations were generated. The best fit equations for wheat milling by-products were:DE (MJ/kg DM)=19.2-0.016x NDF, R2=0.94, RSD=0.58; ME (MJ/kg DM)=16.9-0.0136×NDF, R2=0.94, RSD=0.50. In Exp.6, this study was to determine the effects of graded inclusions of wheat bran and two growth stages on energy and nutrient digestibility in different digestion sites in growing pigs. Six light pigs (initial BW=32.5±2.1kg) and six heavy pigs (initial BW=59.4±3.2kg) were surgically prepared with a T-cannula in the distal ileum. Each group of pigs was allotted to two6×3Youden Square Designs. The results showed that significant differences (P<0.05) were observed for hindgut DE fermentation in the two different growth body weight stages (3.68and4.41MJ/kg). And hindgut fermentation DE content were also very significant (P<0.01) affected by in different inclusion levels of wheat bran. Increasing high fiber ingredient levels in diets can positively affect the DE fermentation in the hindgut and may be underestimated after a period. In summary, the nutritional value of wheat milling by-products is variable. Therefore, we should get a deeper understanding of the effects of different factors on the nutritional value in wheat milling by-products and then can provide a basic parameters for more accurate and dynamic feed formulations.