NIRS analysis of forages

Significance of the Topic

High-quality forages such as alfalfa provide essential nutrients for livestock growth, maintenance, and productivity. Traditional laboratory assays for moisture, protein, fiber, ash and starch are time-consuming and laborious. Near-infrared spectroscopy (NIRS) offers a rapid, non-destructive alternative to assess multiple quality parameters in seconds without sample preparation.

Study Objectives and Overview

This application note evaluates the performance of a Metrohm NIR Analyzer to quantify fat, moisture, crude protein, neutral detergent fiber (NDF), acid detergent fiber (ADF), ash and starch in various alfalfa sample forms (pellets, cubes, fresh). Calibration models were built and validated against reference values determined by ISO standard methods.

Methodology and Instrumentation

Samples of alfalfa pellets, cubes and fresh material were measured in reflectance mode using a large cup accessory. Each sample was rotated to capture spectra from multiple spots and the resulting spectra were averaged. Calibration and validation models were developed in Metrohm software. Reference determinations followed ISO protocols:

• ISO 5983-1 for crude protein (Kjeldahl)
• ISO 5984 for crude ash
• ISO 6865 for crude fiber
• ISO 6496 for moisture
• ISO 6492 for fat
• ISO 6493 for starch

Key Results and Discussion

Calibration models exhibited strong correlations between NIR predictions and reference values. Representative performance for alfalfa pellets:

• Crude protein: R2 0.92, SEP 0.52%
• Moisture: R2 0.89, SEP 0.60%
• ADF: R2 0.91, SEP 1.22%
• NDF: R2 0.94, SEP 2.16%

Similar model quality was achieved for cubes and fresh samples. Figures of merit across all sample types confirm NIRS precision and reliability for routine forage analysis.

Benefits and Practical Applications

• Rapid multi-parameter analysis (<10 seconds per sample).
• No chemical reagents or extensive sample prep required.
• Cost-effective and suitable for high-throughput laboratories.
• Enables timely feed quality control for livestock nutrition management.

Future Trends and Opportunities

• Integration of portable and handheld NIR devices for field testing.
• Advanced chemometric algorithms and machine learning for enhanced calibration robustness.
• Expansion to other feed types and by-products.
• Real-time monitoring in feed processing environments.

Conclusion

The study demonstrates that NIRS using the Metrohm NIR Analyzer can accurately and rapidly quantify key quality parameters in alfalfa forages. This approach offers a reliable, efficient alternative to conventional laboratory methods, enabling enhanced feed quality monitoring and decision-making in agricultural practice.

Instrumentation Used

• Metrohm NIR Analyzer in reflection mode with large sample cup.
• Rotational sample handling to reduce inhomogeneity.
• Metrohm software for data acquisition and calibration model development.

References

• ISO 5983-1:2005 Animal feeding stuffs — Determination of nitrogen content and calculation of crude protein content — Part 1: Kjeldahl method.
• ISO 5984:2022 Animal feeding stuffs — Determination of crude ash.
• ISO 6865:2000 Animal feeding stuffs — Determination of crude fibre content — Method with intermediate filtration.
• ISO 6496:1999 Animal feeding stuffs — Determination of moisture and other volatile matter content.
• ISO 6492:1999 Animal feeding stuffs — Determination of fat content.
• ISO 6493:2000 Animal feeding stuffs — Determination of starch content — Polarimetric method.
• Saracen Horse Feeds. The Importance of Forage. (accessed 2025-07-09).
• Douliere Hay France. Alfalfa Hay for beef and dairy cow (accessed 2025-07-09).