Figure 2.

Effects of vitamin A supplementation on sera retinol concentrations in feedlot steers on days −91, −35, 0, 28, 56, 84, and 112 in relation to treatment initiation (n = 30). Treatments were 0IU, 2,200IU, and 11,000IU. The dotted lines indicate phase 1, a 91-d vitamin A depletion phase prior to treatment allocation or initiation, while the solid lines represent phase 2, where two of the treatments have entered vitamin A repletion. The average sera concentrations were 149.5, 159, and 113 ng/mL for days −91, 0, and 112, respectively.