Two Methods of Near Infrared Reflectance Spectroscopy for Determining the Digestibility and Energy Value of Feeds

Abstract

Abstract Two groups of rations with known in vivo digestibility and energy values were used in this study. These rations were composed of Italian ryegrass only (lRO. n = 45), and combination of Italian ryegrass and concentrates (lRC, n = 58). The IRC ration was obtained from two batches, namely IRC-l and IRC-2 consisting of 42 and 16 samples, respectively. Two methods of near infrared reflectance spectroscopy (NIRS ; direct and indirect method) were carried out for comparison with the in vivo value. Samples (30 each) of IRO and IRC-l group rations were randomly chosen to develop the NIRS calibration equations for estimating digestibility and energy value. These equations were used to determine the digestibility and energy value of the remaining 15 samples of IRO and 12 samples of IRC-I (direct method). Also, digestibility of those remaining samples were calculated based on the lignin indicator method using feeds and fecal components determined by NIRS (indirect method). Comparison of the value determined by direct and indirect methods with the in vivo of those remaining samples called validation test. Same comparison was conducted to IRC-2 ration samples for application test. The direct method of NIRS showed reliability only for ration at the same batch with that used in developing the calibration. However. the indirect method showed the potential and reproducibility for determination of digestibility and energy values of ration either originated from the same or different batch with that used in developing calibration. Anim. Sci. Technol. (Jpn.) 68 (4) : 351-359, 1997 Key words: NIRS, Digestibility. Energy value, Dairy cattle