Practically all authors on oxalates,vide supra, refer to tetany as a result of hypocalcaemia in ruminants. In addi-tion the serum Mg levels reported are also exceptionally variable between authors. refer to the production of tetany in cows infused with Ca-EDTA and regard this as a suit-able model for experimental production of hypocal-caemia. It must, however, be pointed out that EDTAcomplexes both Ca and Mg (although the latter lessstrongly) and, therefore, the tetany may have been produced by a combination of both hypocalcaemia andhypomagnesaemia.In contrast, Findlay (1998) describes uncomplicatedhypocalcaemia (“milk fever”) in the cow and ewe as a flaccid paralytic condition and that tetany (signs of “grassstaggers”) may be seen briefly only if concurrent hypomag-nesaemia is present. This is in stark contrast to non-rumi-nants where eclampsia in the bitch and the queen results inexcitement and tetanic muscular activity. In would indeed be interesting to know how often the magnesium status has been assessed in small animal “eclampsia”.In contrast to calcium, magnesium homeostasis is notregulated by a hormonal feedback system and is simplydependent on inflow and outflow across membranes(Martens and Schweigel, 2000). The analytical techniquesof determining serum magnesium levels are oftenreported to be unreliable with only the referenced atomicabsorption method atomic absorption and the enzymaticmethods giving consistently reliable results. However,this is cumbersome and difficult to set up and calibrate.Photometric or colorimetric techniques are unreliable asthey are influenced by a number of factors, including thecalcium level and bilirubin Reyers, Specialist Clinical Pathologist, Pretoria: personalcommunication, 2006).