MVSc

A random survey study conducted employing serum T4 as a marker, in Cannanore, Trichur, Ernakulam and Idukki districts of Kerala indicated that hypothyroidism was one of the major aetiological factors responsible for non – infectious reproductive disorders in cattle. The mean value of T4 observed in clinically healthy cattle was 4.8727 + 0.1209 µg/dl. In conditions like infantile genitalia, the mean T4 value was 3.5617 + 0.1089 µg/dl and in anoestrum cases, the mean T4 level was 3.6913 + 0.1136 µg/dl. These observations emphasized the need to estimate the serum thyroxine level of cattle, in non – infectious reproductive disorders to exclude hypothyroidism as a causative factor.
The goitrogenic effect of cassava was assessed employing broiler rabbit as the experimental model. The experimental design included three groups of twelve rabbits each. One group (T2) was fed cassava flour at the rate of 25% in the diet for six months. Another group (T3) was administered propyl thiouracil at the rate of 1 mg/day/animal for a period of six months. A group (T1) of twelve rabbits was kept as control.
Body weight of rabbits at fortnightly interval was recorded. Four rabbits in each group were sacrificed at the second, fourth and sixth month. At the time of slaughter, fur weight, serum T3, T4 levels, serum cholesterol, blood sugar, haemoglobin, ESR, total leucocyte count, differential leucocyte count, erythrocyte count, were estimated. Also relative weight of the thyroid, adrenal, testes and ovaries were recorded. Detailed autopsy was performed after the slaughter of the rabbits. Appropriate samples of tissues from liver, kidney, spleen, testis, ovary, heart, thyroid and adrenal were collected for histopathological examination.
Rabbits fed cassava showed changes only after a period of four months. They registered an increase in the body weight and reduction in fur weight, by the end of six months. Normocytic hypochromic anaemia, hyperchloesteraemia, low T3, T4, increase in the relative weight of the thyroid gland were also observed by the end of six months. Histologically the thyroid gland showed hyperplasia and hypertrophy of the follicular epithelial cells and depletion of colloid at the end of six months. Rabbits fed cassava did not show any changes in the testis and ovary. However, the changes in the rabbits fed cassava were minimal when compared to the propyl thiouracil fed rabbits.
In the propyl thiouracil fed rabbits, there was progressive reduction in body weight and fur weight from the second month onwards. Bilateral alopecia on the ventral side of the belly, base of the ear and around the eyes were observed in them. Microcytic hypochromic anaemia, hypercholesteraemia, low T4, T3 levels, and low blood sugar were very much significant in propyl thiouracil fed rabbits. The thyroid glands were very much enlarged and conspicuous. Histologically, the thyroid follicular epithelial cells exhibited predominant hyperplastic changes and varying degrees of degeneration along with significant depletion of colloid. Microscopic picture of the testes in propyl thiouracil fed rabbits showed degenerative changes, with no evidence of spermeogenesis. Also the ovaries showed degenerative changes in the propyl thiouracil fed rabbits.
From the study it was concluded that cassava flour, although, a mild goitrogen can be advantageously fed to broiler rabbits at the level of 25% in the ration without causing undesirable effects.