The objective of this experiment was to determine
whether feeding 250,000 IU or 500,000 IU of vitamin D3
per day to pigs would effectively raise plasma calcium
concentrations. On the basis of data in Figure 1, we
observed that feeding 500,000 IU per day raised plasma
calcium to approximately a maximum of 15.0 mg/100
mL plasma by 5 d of feeding the vitamin D3, which is
a 39% increase, whereas the 250,000 IU per day resulted
in only 11.0 mg/100 mL by d 5 of the trial. Cessation
of feeding supplemental vitamin D3 to pigs previously
fed 250,000 IU/d and to those previously fed
500,000 IU/d resulted in decreases in plasma calcium