Effects of Supplemental Iodine and Season on Thyroid Activity of White-Tailed Deer

Publisher Website
Google Scholar
Abstract
Blood samples were taken at 6-8 wk intervals from 18 captive, female white-tailed deer (O. v. borealis) over a 2-yr period to examine circannual changes in serum thyroid hormones and the effects of 3 levels of dietary I (+0, +0.2, +0.7 ppm) added to a basal diet generally containing 0.26-0.29 ppm I. I supplementation of the diet did not significantly affect T4 [thyroxine], FT4 [free thyroxine], body weight, reproductive performance, milk I concentration, serum T3 [triiodothyronine] and T4 levels of offspring, or dry weight and I content of the thyroid gland. Total T4 levels were higher (P < 0.05) in early winter and spring than in late winter, summer and fall, and showed a close relationship with cyclic changes in feed intake and body weight. FT4 levels were highly correlated (r = 0.74, P < 0.001) with T4. Total T3 did not follow a clear seasonal pattern. Serum T3 and T4 levels were higher (P < 0.05) in fawns than in adult does and in nonlactating does than in lactating does. Apparently, 0.26 ppm I in a diet consumed ad lib was sufficient to meet requirements for growth and reproduction in white-tailed deer.