Published online by Cambridge University Press: 27 March 2009
1. The results are reported of three experiments in which metabolism trials were carried out with milking cows given artificial diets low in magnesium with or without supplementary magnesium.
2. In Exps. 1 and 2, the basal diets provided cither about 13 or about 9 g. of magnesium/day, that is an intake of magnesium similar to that found previously with cut-grass diets (Rook & Balch, 1958) which produced hypomagnesaemia. The ‘availability’ of the magnesium of the artificial diets was, however, of the order of 25–35 % and higher than that of cut-grass diets, and for all cows the artificial diets provided magnesium in excess of requirements, as indicated by the excretion of measurable amounts of magnesium in the urine and the maintenance of normal concentrations of magnesium in the blood serum.