Table 1.

Results of serum magnesium levels in cows from a cow/calf operation in Ontario that experienced mortality due to hypomagnesemia. Tests performed by the Animal Health Laboratory, Guelph, Ontario, on whole blood collected from the tail vein of cows, stored in EDTA tubes, and refrigerated until processing (RR = 0.82 to 1.30 mmol/L)

Cow	Sample 1 (day 11 after case presentation) mmol/L	Sample 2 (day 25, 12 d after commencement of supplementation) mmol/L
Black and White	0.40	0.80
Mousy	0.70	0.80
Blonde	0.60	—
Red and White	—	0.80