Silage

The Trouw laboratory results were compared with the NeoSpectra NIR device across 11 silage quality parameters and 17 samples.

Agreement between the two methods varied considerably by parameter:

• Strong (R ≥ 0.70): pH, ADF, lactic acid, dry matter, and NDF.
• Moderate (R = 0.47–0.60): crude protein, VFA, ash, and D-value.
• Poor (near-zero or negative R): oil and ammonia-N. Results for these parameters should be interpreted with caution.

Systematic bias was detected for ADF, NDF, crude protein, VFA, and D-value. A bias correction is recommended before NeoSpectra readings are used interchangeably with Trouw values for these parameters.

NeoSpectra vs Trouw
Silage Quality Measurements
Measurement	Correlation1	Agreement	Bias2	Bias Correction
pH	0.84	Strong	0.17	No
ADF (%)	0.81	Strong	3.98	Required
Lactic Acid (g/kg)	0.77	Strong	-3.24	No
Dry Matter (%)	0.70	Strong	0.30	No
NDF (%)	0.70	Strong	9.69	Required
Crude Protein (%)	0.60	Moderate	-0.94	Required
VFA (g/kg)	0.56	Moderate	11.85	Required
Ash (%)	0.56	Moderate	-0.25	No
D-Value (%)	0.47	Moderate	-2.81	Required
Oil (%)	-0.07	Poor	-0.30	No
Ammonia-N (%)	-0.67	Poor	-0.09	No
1 1.0 = perfect agreement, 0 = no relationship
2 Systematic difference between methods (Trouw – NeoSpectra)

pH

Recommendation: No correction needed

• Correlation: 0.84 → excellent agreement
  
• Bias: 0.166 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 0.241
    
  • Bias-corrected: 0.256 (-6.2% improvement)

¹ Diff = Trouw – NeoSpectra

ADF (%)

Recommendation: Apply bias correction

• Correlation: 0.815 → excellent agreement
  
• Bias: 3.979 → significant systematic bias (measurements consistently differ from reference)
  
• Standard Error of Prediction:
  
  • Uncorrected: 3.869
    
  • Bias-corrected: 1.037 (73.2% improvement)

¹ Diff = Trouw – NeoSpectra

Lactic Acid (g/kg)

Recommendation: No correction needed

• Correlation: 0.767 → good agreement
  
• Bias: -3.244 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 14.091
    
  • Bias-corrected: 15.289 (-8.5% improvement)

¹ Diff = Trouw – NeoSpectra    Shaded rows excluded as outliers.

Dry Matter (%)

Recommendation: No correction needed

• Correlation: 0.703 → good agreement
  
• Bias: 0.3 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 4.31
    
  • Bias-corrected: 4.413 (-2.4% improvement)

¹ Diff = Trouw – NeoSpectra

NDF (%)

Recommendation: Apply bias correction

• Correlation: 0.7 → good agreement
  
• Bias: 9.687 → significant systematic bias (measurements consistently differ from reference)
  
• Standard Error of Prediction:
  
  • Uncorrected: 10.484
    
  • Bias-corrected: 2.625 (75% improvement)

¹ Diff = Trouw – NeoSpectra

Crude Protein (%)

Recommendation: Apply bias correction

• Correlation: 0.596 → moderate agreement
  
• Bias: -0.942 → significant systematic bias (measurements consistently differ from reference)
  
• Standard Error of Prediction:
  
  • Uncorrected: 1.823
    
  • Bias-corrected: 1.411 (22.6% improvement)

¹ Diff = Trouw – NeoSpectra

VFA (g/kg)

Recommendation: Apply bias correction

• Correlation: 0.564 → moderate agreement
  
• Bias: 11.854 → significant systematic bias (measurements consistently differ from reference)
  
• Standard Error of Prediction:
  
  • Uncorrected: 15.738
    
  • Bias-corrected: 11.938 (24.1% improvement)

¹ Diff = Trouw – NeoSpectra

Ash (%)

Recommendation: No correction needed

• Correlation: 0.558 → moderate agreement
  
• Bias: -0.248 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 0.917
    
  • Bias-corrected: 0.927 (-1.1% improvement)

¹ Diff = Trouw – NeoSpectra

D-Value (%)

Recommendation: Apply bias correction

• Correlation: 0.466 → moderate agreement
  
• Bias: -2.813 → significant systematic bias (measurements consistently differ from reference)
  
• Standard Error of Prediction:
  
  • Uncorrected: 4.138
    
  • Bias-corrected: 3.551 (14.2% improvement)

¹ Diff = Trouw – NeoSpectra

Oil (%)

Recommendation: No correction needed

• Correlation: -0.071 → poor agreement
  
• Bias: -0.298 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 0.705
    
  • Bias-corrected: 0.703 (0.3% improvement)

¹ Diff = Trouw – NeoSpectra

Ammonia-N (%)

Recommendation: No correction needed

• Correlation: -0.667 → poor agreement
  
• Bias: -0.09 → no significant bias
  
• Standard Error of Prediction:
  
  • Uncorrected: 1.656
    
  • Bias-corrected: 1.723 (-4% improvement)

¹ Diff = Trouw – NeoSpectra