Study on selected minor trace elements in donkey milk: first results

Study on selected minor trace elements in donkey milk: first results F. Fantuz1, S. Ferraro2, L. Todini1, A. Fatica3 and E. Salimei3 1Università di Camerino, Scuola di Bioscienze e Medicina Veterinaria, via Gentile da Varano, 62032 Camerino, Italy, 2Università di Camerino, Scuola di Scienze e Tecnologie (sezione Chimica), via Gentile da Varano, 62032 Camerino, Italy, 3Università del Molise, Dip. Agricoltura, Ambiente, Alimenti, via De Sanctis, 86100 Campobasso, Italy; salimei@unimol.it Aiming to provide more in-depth data on the mineral content of donkey milk, the diurnal and nocturnal concentration of Lithium (Li), Boron (B), Titanium (Ti), Rubidium (Rb) and Strontium (Sr) and their distribution in different milk fractions have been studied. In experiment 1, four pluriparous jennies (Martina Franca derived population), 235 kg average body weight and in mid lactation (100-120 d), were machine milked during the day (at 10:00 and 18:00 h) and during the night (at 23:00 and 02:00 h) to provide individual milk samples. In experiment 2, individual milk samples from four donkeys were collected during the afternoon milking and aliquoted. One aliquot was ultracentrifuged to provide milk serum. Inductively Coupled Plasma-Mass Spectrometry was used for the analysis of the mentioned elements in whole milk and milk serum. Milk yield averaged 713.4 (±97.0, s.d.) ml/ milking. The individual daily intake (feedstuffs and water) accounted in average for 2.6 mg Li, 246.2 mg B, 48.3 mg Ti, 178.2 mg Rb, 250.2 mg Sr. Results from milk samples obtained at 10:00 and 18:00 h were grouped as day milk whereas samples obtained at 23:00 and 02:00 h were grouped as night milk. In experiment 1 data were processed by one way ANOVA. The average concentrations of the investigated trace elements did not differ significantly between milk obtained during the day and during the night (Li 6.54 vs 6.65 μg/l; B 308.88 vs 315.65 μg/l, Ti 130.66 vs 128.27 μg/l, Rb 909.69 vs 884.67 μg/l, Sr 485.53 vs 510.05 μg/l). First results on trace elements distribution indicated that all the milk Li (102%), B (99%) and Rb (98%) are associated with the serum fraction, whereas donkey milk serum contains only 44 and 28% of total Ti and Sr respectively, suggesting that the most of these latter elements are likely associated with the casein fraction.