Abstract
Three experiments, each of 7 days' duration, were conducted with intact growing male mice (ddS strain) to determine the effect of changes in thyroid function on protein retention, feed efficiency and liver protein content at different ages. Ages examined were 23, 33 and 60-day-old. In each experiment hyperthyroid (T4) group was daily injected L-thyroxine sodium salt (10 μg/100 g b. w.) intraperitoneally and hypothyroid (TU) group was orally administered 2-thiouracil (0.05% in the diet). During experimental period mice were pairfed the purified diet containing 20% casein.
The effects of changes in thyroid function differed as the ages of animals were different. In T4 group of 33-day-old and TU group of 60-day-old protein retention increased by 146 and 126% respectively. Feed efficiency tended to increase and liver protein content increased significantly in abovementioned groups. On the other hand, in TU group of 33-day-old and T4 group of 60-day-old theeffect seemed to be antagonistic to each T4 and TU group respectively. However, in the case of 23-day-old, there were little differences between groups.
