Evaluation of The Morphology of The Female Reproductive System of The Grasscutter (Thryonomys swinderianus, Temminck 1827)

ABSTRACT 

Fifteen female grasscutters, obtained from David Mark Farms, Otukpo, Benue State, Nigeria, were used for the study. They were randomly assigned to 3 groups of 5 each according to their ages; 1-3 months, 4-6 months and 7-9 months. They were acclimatized for 14 days. The live weights of the grasscutters were obtained. They were then euthanized with gaseous chloroform in an air-tight container. The female reproductive system (ovaries, uterine tubes, uterine horns, uterus duplex, cervix and vagina) were carefully dissected out and observed for gross features. The morphometry was also obtained. Each segment was then fixed in 10% Bouin’s solution and 10% neutral-buffered formalin of equal volume for 24 hours and processed routinely for light microscopy. Photomicrographs of the sections were taken using Moticam MC 2001 digital camera. The data were subjected to one way analysis of variance. Variant means were separated using Duncan’s multiple range test. Significance was accepted at p < 0.05. Grossly, the ovaries were spindle-shaped at 1-3 months, oval at 4-6 months and round at 7-9 months. In all the age groups studied, the uterine horns had a firm consistency on palpation, the uterus presented the appearance of a double uterus, the cervix had a rubber-stopper consistency on palpation, and the vagina had a soft consistency on palpation. The weight and length of each segment of the female reproductive system of the grasscutter increased as the animal attained puberty. Thus, the organ sizes and lengths may not be pre-determined pre-natally, but increased proportionately as the animal attained puberty. There were significant (p < 0.05) variations between the means of the relative weight and length of the ovaries, uterine tubes, uterine horns, uterus duplex, cervix and vagina of all the age groups. Histomorphologically, the oocyte was peripherally located in the Graafian follicle as well as corpora haemorrhagica and lutea in the cortex at 7-9 months. An intensely eosinophilic vaginal plug that was absent in the lumen of the vagina at 1-3 and 4-6 months, was very conspicuous at 7-9 months. The female grasscutter could thus be said to attain puberty at 7 months of age. xvii C