Magnesium supplementation of lactating ewes and lamb growth

Ewes rearing twin lambs on a restricted ration of irrigated pasture were either supplemented daily with 12.5 mg magnesium chloride or not. Serum magnesium levels measured 24 hours after the previous day's dose did not differ between treatments. They averaged 0.74 mmol/l during the period of supplementation with 36% of values below 0.7 mmol/l, the lower limit of the "normal" range. Milk consumption by and liveweight gains of lambs were not increased by magnesium supplementation indicating that ewe magnesium levels below 0.7 mmol/l serum did not limit production in this instance.