Histologic and ultrastructural observations on the thyroid gland of the White Fulani (Zebu) cattle in Northern Nigeria

Abstract

The histology and ultrastructure of thyroid gland of White Fulani (Zebu) cattle were examined during the postnatal developmental period to show if variations in morphology exist with age and in relation to tropical climate. Eight prepubertal and ten pubertal cattle of abattoir origin were used to carry out this study. Histologically, the thyroid consisted of well-developed capsule, interlobular connective tissue, follicular and parafollicular cells from prepubertal to pubertal age of 5 to 7 years. The follicular cells were cuboidal in prepubertal period with some variations, became predominantly columnar in pubertal age of 2 to 4 years and highly flattened cells were common in the older pubertal animals of  5 to 7 years. The colloid was observed in the lumen at all age and was PAS-positive with abundant peripheral vacuoles in the pubertal age of 2 to 4 years. Significant variations (p˂0.05) in structure of the thyroids were observed at all age and the follicular size and number of follicles increased as the cattle matured. Follicular height was reduced significantly in the older pubertal cattle of 5 to 7 years. Ultrastructurally, the follicular cells showed highly dilated cisternae of rough endoplasmic reticulum which decreased with age. Flattened follicular cells seen in the older pubertal cattle contained few cytoplasmic organelles and microvilli. Apically placed pseudopods and blebs were commonly observed in the pubertal age of 2 to 4 years. Lysosomal bodies increased with age of development. The parafollicular cells were encountered frequently in the prepubertal age than in the older cattle. They consisted of numerous dense secretory granules which increased in number with age. The present results suggest an optimum thyroid function during the pubertal. Our findings would be useful in interpreting changes in thyroid morphology during experimental and pathological conditions.

Key words:  Cattle, postnatal thyroid, histology, ultrastructure.