Stable Isotope Composition in Moroccan Milk: Feed and Water Relationships

This study investigated the use of stable isotope ratio analysis to trace the geographical origins of Moroccan dairy products, as well as possible applications to other Moroccan agricultural products. Ten agro-ecological zones with different climates were selected, including the Garb, Middle Atlas, Meknes, Lukos, Agadir, Taroudant, Settat and Casablanca regions. Milk samples were collected directly from cows on modern andtraditional farms, as well as the water they consumed.

Analytical methods such as isotope ratio mass spectrometry (IRMS) and the Piccaro system were used to determine stable isotope ratios in milk andwater samples. Chemometric methods including principal component analysis (PCA) and hierarchical cluster analysis (HCA) showed that stable isotope ratios (H, C, N, O) in milk were highly correlated with environmental factors specific to the region. Three distinct groups emerged, especially for oxygen isotopes, depending on altitude and distance from the ocean. The δ¹⁸O composition was particularly distinct, indicating regional differences: northern, low-altitude coastal areas and high- altitude inl andareas.

The study also showed that the isotopic composition of milk is influenced by the isotopic composition of drinking water. Nitrogen isotopes, especially δ¹⁵N, distinguished two groups of milk: one from an area with fertilizer use (low δ¹⁵N values, intensive agriculture) and another from an area with moderate agricultural practices (higher δ¹⁵N values). These results highlight the potential of stable isotope analysis as a tool to verify the geographical origin of dairy products in Morocco.