(13)C discrimination between diet, faeces, milk and milk components

Area of Science:

• Agricultural Science
• Analytical Chemistry
• Food Science

Background:

• Stable isotope analysis is crucial for food authenticity and origin tracing.
• Understanding isotope discrimination in livestock products is essential for accurate analysis.
• Previous studies show variability in carbon isotope discrimination data.

Purpose of the Study:

• To quantify carbon-13 (¹³C) discrimination between diet and milk components (fat, casein, lactose) and feces in dairy cows.
• To assess the impact of feeding environment (pasture vs. stall) on ¹³C discrimination.
• To provide a comprehensive dataset for improving stable isotope analysis in food authenticity and origin testing.

Main Methods:

• Eight lactating dairy cows were studied over 8 weeks, fed pasture herbage and supplemented with maize.
• Diet, feces, whole milk, milk fat, casein, and lactose were sampled regularly.
• Carbon isotope composition (δ¹³C) was analyzed using mass spectrometry.

Main Results:

• Whole milk showed slight ¹³C depletion (Δ = 0.4‰) relative to the diet.
• Milk fat was significantly depleted in ¹³C (Δ = 2.2‰), while casein (Δ = -1.1‰) and lactose (Δ = -0.7‰) were enriched.
• Feces were depleted in ¹³C (Δ = 1.7‰), and feeding environment had a minor effect (<0.4‰).

Conclusions:

• This study provides the first comprehensive analysis of ¹³C discrimination across all major milk components and feces.
• The detailed data improve the reliability of stable isotope analysis for food authenticity and origin verification.
• Results confirm the utility of stable isotope analysis in livestock product traceability.