Influence of fertilizer treatment of grassland on the incidence of hypomagnesaemia and hypomagnesaemia tetany (grass tetany) in milking cows.

Abstract

In grazing experiments with 16 milking cows during 1956 and 1957 heavy K dressings lowered Mg levels of the blood serum, particularly in spring and autumn. Heavy N dressings had similar but less marked effects. The greatest differences were between light and heavy NK dressings. The mean differences were 0.82 mg per 100 ml serum over the whole growing season and >1.20 mg in spring and autumn. Heavy P dressings in autumn were accompanied by a slight drop in serum Mg. In 1957 grass tetany occurred in 6 cows on the heavy-K plots; the Mg level of these animals was 0.2-0.7 mg/100 ml serum. In an experiment on 23 farms the serum-Mg level of 90 milking cows decreased when they were released on pastures occupied the previous day by cows showing tetany; 60 % of them had an Mg level of <1.1 mg/100 ml serum. Evidently hypomagnesaemia is prevalent in milking cows in Holland during the spring and autumn. (Abstract retrieved from CAB Abstracts by CABI’s permission)