Grass tetany in grazing milking cows.

Statistical investigation showed that correlation existed between the incidence of grass tetany and the mean 24-hr, temperature, particulary in spring and autumn. There was also a significant positive correlation between the K/(Ca and Mg) ratio in the grass and the incidence of tetany. During the spring and autumn, when the average temperatures were below 14 degrees C., an increase in K uptake by the herbage being grazed was associated with a rise in temperature, and was followed, after a 5-day time-lag, by an increase in the number of cases of tetany, if the critical value of K/(Ca + Mg) (2.2) was exceeded. A fall in temperature was followed by a fall in the ratio value and in tetany incidence. High summer temperatures were associated with a lower value for the ratio and only a few cases of tetany occurred. The results favour the theory that the relationship between temperature and the incidence of tetany is correlated with the cationic composition of the herbage grazed. See Abs. 1013.-From authors'summary. (Abstract retrieved from CAB Abstracts by CABI’s permission)