The prospective of using plants with antifertility effects in controlling the rodent pest, mastomys natalensis
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Date
2022
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Sokoine university of agriculture
Abstract
The prolific nature of some rodents has been a significant threat to the livelihood and
public health in sub-Saharan Africa escalating the use of rodenticides. Regrettably, rodent
pests are increasingly becoming resistant to rodenticides due to bait shyness or resisting
death. Also, the rodenticidal poison has been killing other untargeted species of animals.
Thus, alternative methods of rodent control including the use of birth control methods are
increasingly being explored. So, the current study investigated the antifertility potential of
Acacia nilotica pods and Albizzia lebbeck stem bark extracts in the Mastomys natalensis.
Specifically, the study was done to investigate the effect of the plant's extracts on the
fertility success rate of female and male M. natalensis, to evaluate the effect of the plant's
extracts on follicular and corpora lutea counts in the female rat’s ovaries, to explore the
effect of the plant’s extracts on the sperm cells parameters and histomorphology of the
testes in the male rats and to determine the phytochemical constituents of the two plants.
Pods of A. nilotica were collected from Kilwa and stem barks of A. lebbeck were
collected from Morogoro urban, in Tanzania. The M. natalensis were collected from
Sokoine University of Agriculture (SUA) owned farms. Experiments and Laboratory
works were done at the College of Veterinary Medicine and Biomedical Sciences
(CVBMS) at SUA. This thesis contains the research works done in the current study and
is divided into three sections. Section one comprises introduction and literature review,
problem statement, objectives, the rationale of the study, scope and limitations of the
study. Section two encompasses the three manuscripts describing the research work done.
The third section consists of the general conclusion and recommendation of the study. The first manuscript assesses the pathophysiological significance of A. nilotica pods
aqueous extract and A. lebbeck stem bark methanolic extract on the reproductive system
of female M. natalensis. A total of 60 sexually mature rats were randomized into a 2 x 3
factorial design for treatments (Control A. nilotica, and A. lebbeck) and treatment duration
(7 or 14 days). Control rats consumed basal feed, treated rats consumed feed with 2%
w/w of either of the plant extracts. At the end of treatment duration, treated female rats
were cohabited with males for 16 days and sacrificed 20 days after the first day of
cohabitation. Parameters assessed at necropsy included the pregnancy rates, number of
fetal implantations, possible resorption sites, and fetal litter size. Other evaluated
parameters included the ovarian weights, follicular and corpora lutea numbers, and
general histopathology of ovaries. Results showed that pregnancy percentages, the
number of fetal implantations, and fetal litter size were significantly reduced (p< 0.01) in
rats under the A. nilotica and A. lebbeck extract treatments relative to the control.
The ovarian weights of rats receiving the extracts did not differ significantly from the
control (p > 0.05). However, the number of corpora lutea of pregnancy was significantly
reduced (p < 0.001) in the ovaries of rats under extract treatments than in the control.
Instead, the ovaries of rats receiving the two extracts contained a larger number of atretic
follicles, signifying halted ovulatory and conception activities. In conclusion, the study
demonstrated that dietary inclusion of crude extracts from A. nilotica pods and A. lebbeck
stem bark can lead to decreased fertility success rates in M. natalensis female rats through
suppression of ovulatory activities and induction of follicular atresia.
The second manuscript evaluated the contraceptive potential of the methanolic extracts
from A. nilotica pods and A. lebbeck stem bark in male M. natalensis. A total of 90 rats
were randomized into a 3 x 3 factorial design for treatment (control, A. lebbeck and
A. nilotica) (n = 10) and treatment durations (15, 30, or 60 days). Control rats consumed plain feed. Treated rats consumed feed with 2% w/w of either of the plant extract.
Following treatment, male rats were mated to untreated females before sedation in ether
and sacrification. Assessments were done on fertility success rates (number of
impregnated females), weights of testes and reproductive glands, sperm cell parameters,
and testes histopathology. Results revealed that the fertility success rate was reduced to
0% in the A. nilotica treated rats at all the treatment durations and in the A. lebbeck
treated rats after 60 days of treatment. Moreover, the extract-treated rats revealed a
significant reduction in the testes, seminal vesicles, and epididymides weights.
Also, sperm cell density and the proportions of live and progressively motile spermatozoa
were significantly reduced and there were numerous seminiferous tubules with damaged
and thinned germinal epithelium and widened empty lumen in the extract-treated rats.
In conclusion, treatment with A. nilotica or A. lebbeck extract in male rats reduced their
fertility success rates through distortion of testicular structure and disruption of
spermatogenesis.
The third manuscript evaluated the phytochemical constituents of raw grounded materials
and methanolic extracts of A. nilotica pods and A. lebbeck stem bark extracts and the
potential effects the methanolic extracts may have on spermatozoa morphologies in the
male M. natalensis. A portion of the grounded materials from each plant was extracted in
70% methanol. Both the grounded materials and corresponding methanolic extracts were
assessed for the presence of phytochemicals with antifertility potentials. A total of 90
male rats were randomized into 9 groups based on treatment (control, A. lebbeck and
A. nilotica) (n = 10) and extract treatment durations (15, 30, or 60 days). Results indicated
that flavonoids, tannins, saponins, steroids, terpenoids and plant phenols were all present
in the powdered raw materials and their corresponding extracts of both plants.
However, saponin was shown to be more intensely present in the powdered and methanolic extracts of the A. lebbeck compared to those of A. nilotica while the reverse
was true for flavonoids and tannins. Spermatozoa with normal head-abnormal tail, normal
head-tailless, abnormal head-normal tail, both abnormal head and tail spermatozoa were
more revealed in extracts treated rats relative to the control. In conclusion, the studied
pods of A. nilotica and the Stem bark of A. lebbeck are rich in flavonoids, tannins,
saponins, steroids, terpenoids and plant phenols which possess some antifertility
properties explaining the adverse effects of the plant’s extracts on spermatozoa
morphologies. The research information contained in this thesis contributes significantly
to the limited available knowledge on the antifertility efficacies of medicinal herbal
extracts in the wild rodents, more particularly the M. natalensis.
Description
Thesis
Keywords
Rodent pest, Mastomys, Natalensis, Antifertility, Plants