As a fundamental experiment to control the thyroidal function in swine, the methods for
in vivo measurement of the thyroidal function in swine using radioiodine were studied.
Sixteen Middle Yorkshires, whose age varied from 2 to 3.5 months, weighing 12-20kg were used. Each swine was injected intramuscularily with 64.3μc carrier-free Na
131I.
The radioactivity of swine placed in the immobilization apparatus was measured with a single channel spectrometer connected with the special scintillation detecter for swine.
The thyroidal function was measured with the uptake of
131I by the thyroid and the release of
131I from the gland, and the comparison of the two measurements was studied.
1. For the
in vivo measurement of the thyroidal function in swine, it was needed to use the immobilization apparatus which had been made to fit the size of swine.
2. The results of the examination for the scintillation spectra from intact swine from removed thyroid glands and from the
131I-standard in glass tube, showed the presence of greater numbers of scattering rays from intact swine than the others, and that the scattering rays were main source of errors.
3. Use of collimator drastically diminished scattering rays, and decresed the error for measurements to less than 4%.
4. As the rate of
131I uptake is influenced by scattering rays more than the rate of
131I release and it is difficult to determine the time of the peak uptake, the rate of release is a better criterion than the of uptake for the measurement of the thyroidal function of swine.
Thyroid glands of 393 swine slaughtered at 90kg weight were weighed to find the relation between the thyroid weight and the growth of swine. The swine used in this study were the 127 swine fattened by the farmers in Chiba Prefecture together with 20 swine used in the meat production test at the Chiba Experiment Station of Animal Industry and 246 at the Ibaraki Branch, Omiya Livestock Breeding Station. The results were as follows:
1. There was a large variation in the thyroid weight. The heavier the thyroid, the more rapid was the growth of the body and the thinner the back-fat.
2. From the result at the Ibaraki Branch, Omiya Livestock Breeding Station it was found that in the thyroid weight of the swine which passed the meat production test, significant correlation was seen between the season and the breed.
3. Between the body weight and the thyroid weight the phenotypic correlation coefficient was -0.31.
4. The mean and standard deviation of thyroid glands were 10.08±1.56g in weight of 13 gilts and 10.26±2.06g of 7 hogs in Chiba Exp. Sta. of Anim. Indust. and 8.31±3.33g of 127 swine at slaughterhouse in Chiba City.
5. The thyroids of swine which passed the meat production test were 11.20g in average weight, ranging from 8.34±2.17 to 16.05±3.74g, 4.51cm in longer diameter, 2.58cm in shorter diameter and 1.22cm in width of 256 swine.
6. The ratio of the thyroid to body weight was 1.33 in average, ranging from 0.96 to 1.72 in 256 swine.
Upon 220 cases from the Ibaraki Branch of Omiya National Livestock Breeding Station and 20 cases from the test of meat production at the Chiba Prefectural Experiment Station of Animal Industry, the microhisto metric assay was carried out all the specimens used in this part of the experiment. The thyroid glands were fixed in 10% neutral formalin and embedded in paraffin. Sections cut serially at 3μ were stained with Heidenhain's Azan, Hematoxylin Eosin, Kull's staining and PAS reacton. Epithelial cell heights of two cells from each of 100 follicles were measured on five sections cut through the middle portion of the thyroid of each individual. The rate of thyroid function were classified into 4 states, i. e., extreme hyperfunction, hyperfuncton, medium function and hypofunction.
The results were summerized as fol
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