The effect of intramuscularly administered vitamin D3 on serum vitamin D metabolites and electrolytes in vitamin D3 deficient dairy cows.

The effect of intramuscular administration of vitamin D (1×10 IU D/100 kg bodyweight) to 3 different dairy breeds on the serum levels of vitamin D, 25-OH-D, 25-OH-D, Ca, inorganic P and Mg was studied. The vitamin metabolites and the electrolytes were analysed on 9 occasions during a 36-day period. Vitamin D was analysed on 6 occasions during the same period. No significant breed differences were observed except for 25-OH-D (P ≤ 0.05). The D level rose in 1 day from < 2 ng/ml to 906 ng/ml and decreased to below 50 % of the peak level after 6 days. At the end of the experiment (day 36) vitamin D was < 2 ng/ml. 25-OH-D rose from < 2 ng/ml to 106 ng/ml in 6 days and stayed at this level during the whole experiment. 25-OH-D decreased from 16 ng/ml to 5 ng/ml during the observation period.