ARS | Publication request: Near Infrared Analysis of Forages: Challenges and Opportunities in the Application of the Dairy Nrc 2001

Submitted to: Journal of Dairy Science
Publication Type: Abstract
Publication Acceptance Date: February 1, 2005
Publication Date: August 1, 2005
Citation: Berzaghi, P., Martin, N.P., Undersander, D. 2005. Near infrared analysis of forages: challenges and opportunities in the application of the dairy NRC 2001 [abstract]. Journal of Dairy Science. 88(1):275.

Technical Abstract: The Dairy NRC 2001 has created a demand for new analytical assays, some relatively simple others like NDF digestibility requires sources of ruminal fluid and analytical skills not available in the vast majority of commercial labs. The NIRS Consortium has been providing calibration equations for forage prediction used in several laboratories, with performances (standard error of cross validation and r2) that in average across forages are 1.0%, 0.89 for Ash, 0.7%, 0.95 for CP, 0.2%, 0.86 for fat, 2.2%, 0.94 for NDF and 1.8%, 0.91 for ADF. Commercial laboratories using NIRS calibrations can return accurate predictions to farmers within one day. The need to determine in vitro digestible NDF (dNDF) - 48-hour used in the summative equation of the dairy NRC has been a challenge for labs using NIRS. The lack of standardized in vitro methods across commercial and research laboratories creates confusion. The development of calibrations for digestible NDF using a reference method coming from a single laboratory creates the opportunity to reduce differences in results coming from different labs. However, the development of such calibration has been a challenge. The NIRS Consortium calibrations performance for dNDF has on average a 2.4 % standard error of cross validation and R2=0.84 and. The performance of calibration on NDF digestibility (NDFD), however has been disappointing, standard error of cross validation around 5% and r2 below 0.4. Analysing data from 70 samples of corn silage with quadruplicates runs per samples has shown that standard deviation among replicates for NDFD was more than double than of dNDF (2.04 vs 0.94 %), partially explaining the lower NIRS performances on NDFD. Despite the lower accuracy compared to reference methods and in particular with in vitro techniques, NIRS can provide timely responses which combined to the possibility or frequent testing can help farmers and nutritionists manage the continuous changes in forage quality.