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Grazing cows could produce milk with a higher proportion of polyunsaturated fatty acids, which is beneficial to human health, compared with non-grazing cows, though grazing alone could compromise milk production. Under oceanic climate conditions, a study involving 15 dairy cows, fed total mixed ration (TMR) ad libitum in combination with different grazing times of 12 h (TMR12), 6 h (TMR06) and zero grazing time (TMR00) with the aim to evaluate different strategies on the fatty acids profile of milk and milk production. No differences were seen between the treatments with respect to milk yield (34.4+/-6.3 kg/d) or milk protein content (30.4+/-1.8 g/kg). The milk produced by the TMR12 cows had less total fat (36.2 vs. 38.2 g/kg) and saturated fatty acid (FA, 69.39 vs. 71.44 g/100 g FA) than that produced by the TMR00 cows. The concentration of vaccenic acid in the TMR06 and TMR12 milk was twice that of the TMR00 milk (4.22, 4.09 and 2.26 g/100 g FA respectively). Linear increases in conjugated linoleic (CLA) and linolenic acids were observed with increasing grazing time. Pasture was an important source of FA especially C18:3 for TMR06 and TMR12 cows. Under oceanic climatic conditions, the grazing of dairy cows as a complement to feeding with TMR can improve the FA profile of milk and increase its CLA content.

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Fast protein liquid chromatography (FPLC) was used with electrothermal atomic absorption spectrometric (ETAAS) detection for quantitative studies of aluminium binding species in unspiked human uremic serum. A rapid and reproducible separation of human serum proteins and other aluminium binders (citrate and desferroxiamine) was achieved on a Mono Q (HR 5/5) anion-exchange column using a sodium chloride gradient (0-0.25 mol l-1) at the physiological human serum pH of 7.4 (0.05 mol l-1 buffer TRIS-HCl). The aluminium distribution in the column fractions was determined by ETAAS. Aluminium contamination was avoided by using an inert chromatographic system equipped with an on-line aluminium-chelating scavenger column (Kelex 100-impregnated silica C18). The sensitivity of the proposed method (detection limit for Al in serum = 5 micrograms l-1) allowed aluminium speciation studies at clinically relevant concentrations (unspiked serum from dialysis patients). The results obtained confirmed that transferrin is the only serum protein binding aluminium and it contains about 90% of total serum aluminium (post-elution aluminium recovery = 105 +/- 5%). It was also confirmed that in the presence of the chelating drug desferrioxamine (DFO) most of the serum aluminium (80%) is bound to DFO.

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The coupling of fast protein liquid chromatography (FPLC) with inductively couples plasma mass spectrometry (ICP-MS) was evaluated as a technique for studying aluminium bound to proteins present in human serum. Separation of human serum proteins was achieved on a MonQ (HR5/5) anion-exchange column using an ammonium acetate gradient (0-0.25 mol I-1) at the physiological pH of 7.4 (0.05 mol l-1 TRIS-HC1 buffer). Aluminium contamination was avoided with an on-line Al-chelating scavenger column. Proteins were detected spectrophotometrically at 295 nm and the Al detection was carried out on-line using both quadrupole ICP-MS and double-focusing ICP-MS systems. At metal basal levels in serum the latter detector proved to be adequate for this detection. Results obtained with the procedure developed confirmed clearly that transferrin is the only significant A1-binding proteins in unspiked uraemic serum. In addition, a high-resolution ICP-MS instrument was applied successfully as an A1-specific detector allowing for the first time A1 speciation studies in unspiked normal serum. The technique can also be used for studying the protein binding of elements other than A1.

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