Use of near-infrared reflectance spectroscopy for the rapid determination of the digestible energy and metabolizable energy content of corn fed to growing pigs

Background： The ability of near-infrared reflectance spectroscopy（NIRS） to determine the digestible energy（DE）and metabolizable energy（ME） content of corn fed to growing pigs was tested. One hundred and seventeen corn samples, comprising different planting regions and varieties were collected from all over China in a three-year period. The samples were randomly split into a calibration set（n = 88） and a validation set（n = 29）. The actual and calculated DE and ME content of the corn samples was determined by digestion-metabolism experiments and the prediction equations of Noblet and Perez（J Anim Sci. 71：3389–98,1993）. The samples were then subjected to NIRS scanning and calibrations were performed by the modified partial least square（MPLS） regression method based on77 different spectral pre-treatments. The NIRS equations based on the actually determined and calculated DE and ME were built separately and then validated using validation samples.Results： The NIRS equations obtained from actually determined DE, the coefficient of determination for calibration（RSQcal）, cross-validation（R^2CV）, and validation（RSQv） were 0.89, 0.87 and 0.86, and these values for determined ME were 0.87, 0.86 and 0.86. For the NIRS equations built from calculated DE, the RSQcal, R^2CV, and RSQvvalues were 0.88, 0.85 and 0.84, and these values for calculated ME were 0.86, 0.84 and 0.82. Except for the equation based on calculated ME（RPD_v= 2.38, 〈 2.50）, the other three equations built from actually determined energy and calculated DE produced good prediction performance（RPD_vranging from 2.53 to 2.69, 〉 2.50） when applied to validation samples.Conclusion： These results indicate that NIRS can be used as a quantitative method for the rapid determination of the available energy in corn fed to growing pigs, and the NIRS equations based on the actually determined energy produced better predictive performance than those built from calculated energy values.

Effect of variety and drying method on the nutritive value of corn for growing pigs

Background：This experiment was conducted to determine the nutritive value of corn from the north of China for growing pigs.The experiment examined corn variety（LS1,LS2,LS3 and LS4）grown in one location,drying method（sun dried and artificially dried）and different drying temperatures.Corn harvested at 20-25%moisture was dried to about 12%moisture by sun drying and artificially drying at 80,100,or 120℃ in a fluidized bed dryer.Ninety-six barrows（average BW of 33.4 ± 2.7 kg）were housed in individual metabolism crates to facilitate separate collection of feces and urine.A five-day collection period followed a seven-day diet acclimation period.Results：The results indicated that variety significantly influenced（P〈0.01）the 1,000 kernel weight of corn but not the bulk weight.Variety also influenced the available energy content（digestible energy of dry matter,P〈0.01;metabolisable energy of dry matter,P〈0.01）and digestibility of organic matter（P〈0.01）,as well as dry matter（P〈0.01）and gross energy（GE）content（P〈0.02）.The drying method of corn significantly influenced the 1,000 kernel weight（P〈0.01）,bulk weight（P〈0.01）and digestibility of ether extract（EE）（P〈0.01）.No effect of drying temperature on the digestibility of organic matter,dry matter（DM）,crude protein（CP）,neutral detergent fiber（NDF）,acid detergent fiber（ADF）and gross energy was observed,but gelatinization（P〈0.05）and test weight（P〈0.01）decreased with an increase in temperature.Conclusions：Variety has a significant impact on the nutritive value of corn for growing pigs,and greater attention needs to be paid to these influences in the assignment of the nutritive value of corn given to growing pigs.