Milk and blood serum concentration of selected trace elements in lactating donkeys

Donkey milk can be considered a functional food for sensitive consumers such as infants and elderly people but the concentration of minor and potentially toxic trace elements is not well documented. The aim of this study was to measure the concentrations of Ti, V, As, Mo, Cd, Cs, and Pb in donkey milk and blood serum. Sixteen clinically healthy lactating donkeys (Martina Franca derived population) were used to provide individual milk and blood samples (n = 112) during a 3months period. Milk and blood samples were collected every 2 weeks. Milk and blood serum samples were analysed for Ti, V, As, Mo, Cd, Cs, and Pb by Inductively Coupled PlasmaMass Spectrometry. Data were processed by analysis of variance for repeated measures. More than 80% of samples were below the limit of detection for V, As, and Cd in milk and for Cd, and Pb in blood serum. The average milk concentrations (± SD) of Ti, Mo, Cs, and Pb were 77.3 (± 7.7), 4.5 (± 1.6), 0.49 (± 0.09), and 3.2 (± 2.7) μg/L, respectively. The blood serum concentrations of Ti, V, As, Mo, and Cs averaged 12.4 (± 3.7), 1.0 (± 0.38), 0.49 (± 0.12), 28.5 (± 13.8), and 0.17 (± 0.05) μg/L, respectively. The effect of the stage of lactation was significant for all the measured elements in milk and blood serum but only small changes or inconsistent trends were observed. The average milk concentrations of Ti and Cs was higher than those of blood serum whereas that of Mo was lower. Current results suggest that the mammary gland play a role in determining the milk concentrations of Ti, Mo, and Cs.