LD2668 .T4 1941 F71 / Master of Science

Call number: LD2668 .T4 1963 L54 / Master of Science

LD2668 .T4 1962 P55

Call number: LD2668 .T4 1966 M137 / Master of Science

Call number: LD2668 .T4 1951 N6 / Master of Science

Call number: LD2668 .T4 1957 L33 / Master of Science

The present investigation was conducted to determine the effect of an infection with Eimeria acervulina on vitamin A deficient birds. One hundred day-old chicks were divided into 2 equal groups, and one group was raised on 440 I.U. vitamin A per kilogram of feed, while the second group received the normally recommended 4400 I.U. per kilogram. At 5 weeks of age, half the birds from each group were given an immunizing infection with 3 million oocysts of E. acervulina. The clinical symptoms were more acute, and the oocyst production, mortality, and weight losses significantly higher, in the birds on the low vitamin A diet. When the birds were 9 weeks old, half were subjected to a second infection and the other half held until they were 19 weeks old. The 9-week-old birds were given an oral inoculation of 10 million oocysts to evaluate the effect of a low vitamin A diet on: the strength of the immune response; a primary infection with E. acervulina in 9-week-old birds; and the early tissue stages of the parasite in immune and non-immune birds. The results from this experiment showed that the degree of immunity is not affected by a low vitamin A ration, but primarily determined by the severity of the initial infection; and that the primary infection in 9-week-old chicks is clinically very similar to that in younger birds. The histological examinations demonstrated that the low vitamin A level used in this study did not affect the integrity of the intestinal epithelium, nor the development of the endogenous forms of the parasite. It was also shown that the sporozoite invasion was the same in immune and non-immune birds, but the schizont development was severely inhibited in the immune birds regardless of the vitamin A level. The non-immune birds on the low vitamin A ration did not show as distinct a heterophil response to infection as did the other groups. The remaining birds, half which were immunized, were maintained on their respective diets until 19 weeks of age, and during this period there was no clinical evidence of a vitamin A deficiency, and the growth rate was not significantly affected by the level of vitamin A in the diet. When 19 weeks old, the birds were inoculated with 25 million oocysts of E. acervulina to assess the effect of an extremely heavy primary infection in older birds, and to evaluate the degree of immunity still retained 14 weeks after an initial infection. The mortality was very high, and the weight losses significantly greater, in birds on the low vitamin A dietary level. Immunity, although decreased from the earlier experiment, was still present in birds on both levels of vitamin A. / Land and Food Systems, Faculty of / Graduate

The study of thyroid metabolism usually involves the employment of antithyroid compounds and exogenous thyroid hormones in order to elucidate the thyroid function through the understanding of the effects of these compounds. In this study, the effects of die thiouracil and rapeseed meal goitrogens were examined in chicks. The goitrogenic effects of the thiouracil were manifested rapidly by increased thyroid weight, thyroid epithelium and uptake of radioiodine. The goitrogenic effects of rapeseed meal were similar to the effect of thiouracil except that at the level of meal fed, the effects were less pronounced and evident only after prolonged feeding. When an iodine deficient diet was fed to growing chicks, the goitrogenic effect was less than when thiouracil or rapeseed meal was fed. Histological studies of the thyroid glands of adult birds fed an iodine deficient diet showed slight hyperplasia without thyroidal enlargement and with persistence of colloid,whereas growing chicks fed an iodine deficient diet displayed severe hyperplasia and loss of colloid. By contrast, the effects of thiouracil were independent of the age of chicks. A combination of thiouracil and rapeseed meal produced goitrogenic effects greater than those occurring when thiouracil or rapeseed meal was fed singly. Thiouracil fed in an iodine deficient diet, on the other hand, showed no goitrogenicity for chicks. High doses (4.0 μg) of thyroxine administered daily to thiouraci1-treated chicks alleviated the antithyroid effects of thiouracil as indicated by the decrease in thyroid weight, thyroid epithelium and radioiodine uptake. Low doses (1.0 ug or less) of thyroxine administration, however, produced the opposite effects. Nevertheless, high doses of thyroxine did not relieve the growth depressing effects of thiouracil completely. Autoradiographic studies on thyroids of thiouraci1-treated or rapeseed meal-fed chicks showed a uniform distribution of radioiodine in the colloid within five hours of administration of tracer. Differences in activity were observed among the individual follicles in each gland. The smaller follicles concentrated more iodine than the larger ones. Furthermore, very little iodine was observed in the epithelial cells. These findings, together with previous reports that inorganic iodine was present in the thyroid after its administration, suggested that iodination did not occur in the apical membrane of the follicular cells bordering the colloid. Different rapeseed cultivars contain different amounts of glucosinolates which are responsible for the goitrogenic effect of the rapeseed meal. Goitrogenicity of three different kinds of rapeseed meals was compared in growing chicks and the results indicated that Candle meal had the least goitrogenic activity than the Tower and Span meal. / Land and Food Systems, Faculty of / Graduate

Call number: LD2668 .T4 1952 P9 / Master of Science

Call number: LD2668 .T4 1956 B36 / Master of Science