Hypomagnesaemia in milking cows: the response of serum magnesium to alterations in herbage composition resulting from potash and nitrogen dressing on pasture.

Detailed results presented in this paper were obtained during an experiment reported previously (D.S.A. 21 [872]) and concern relationships between fertilizer treatment of pasture, chemical composition of the herbage and serum Mg levels. A heavy potash dressing caused increases in herbage K and decreases of 15-20% in the Mg level, while a heavy N application increased crude protein and Mg levels in the herbage. There was a significant correlation between serum Mg levels and Mg contents of the herbage in the week preceding blood sampling; in 822 cows no low serum Mg levels were found when the Mg content of the herbage was >0.20%. Negative correlations between serum Mg levels and crude protein or K content were significant. There was no relationship between daily milk yield and serum Mg levels. M.P.H. (Abstract retrieved from CAB Abstracts by CABI’s permission)