Page 9 - UNAM Virtual Graduation e-Book (April2021)

FACULTY OF AGRICULTURE &
NATURAL RESOURCES

DOCTOR OF PHILOSOPHY
(FISHERIES AND AQUATIC SCIENCES)
CANDIDATE: GABRIEL Ndakalimwe N

CURRICULUM VITAE

Ndakalimwe Naftal Gabriel was born in Kwanza-Sul, Angola. He matriculated
from Nuuyoma Secondary School in the Omusati region. His qualifications include
Bachelor of Science in Environmental Biology, Molecular and Physiological
Biology (University of Namibia); Master’s in Agriculture (Aquaculture) (Nanjing
Agricultural University, China). His professional career includes working as an intern at the Namibia Institute of
Pathology (NIP), as fisheries research technician at the Ministry of Fisheries and Marine Resources (MFMR), as junior
lecturer and currently as a senior Lecturer at UNAM, Department of Fisheries and Aquatic Sciences, Sam Nujoma
Campus. His research interest focus is based on aquaculture nutrition, phytogenic feed additives in aquaculture,
climate smart aquaculture technologies, fish health, and fish welfare preservation in aquaculture production
systems.

CANDIDATE’S DISSERTATION

DIETARY ALOE AND GARLIC CRUDE POLYSACCHARIDES: EFFECTS ON GROWTH PERFORMANCE, HAEMATOLOGICAL,
AND BODY COMPOSITION PARAMETERS OF CLARIAS GARIEPINUS

The doctoral study was undertaken and completed under the supervision of Dr. Margit R. Wilhelm (University of
Namibia) as Main-Supervisor, Prof. Percy M. Chimwamurombe (Namibia University of Science and Technology),
and Dr. Habte-Michael Habte-Tsion (Kentucky State University, USA) as Co-Supervisors.

This study aimed to develop and introduce phytogenic diets made up of Aloe vera, and Allium sativum (garlic)
crude polysaccharide extracts (separately and in mixture), which would promote growth, feed utilisation, health,
and increase resistance against stress in African catfish (Clarias gariepinus) in aquaculture. Fish were divided into
five triplicate groups before being fed feeds supplemented with control 0%, 0.5%, 1.0%, 2.0% and 4.0% A. vera
for 60 d. Fish fed a 1.0% A. vera supplemented diet showed a significant increase in some growth and feed
utilisation parameters compared to the control (P < 0.05). Fish fed diets supplemented with 1.0%, and 2.0% A.
vera showed higher survival probability throughout the low water pH challenge period compared to the control
and those fed the 4.0 % A. vera supplemented diet. Furthermore, fish fed A. sativum supplemented diets showed
a significant improvement in some growth parameters and feed utilisation indices compared to the control (P <
0.05). A significant increase was only observed in the red blood cells (RBC) for those fed the 0.5%, 1.0%, and 2.0%
A. sativum supplemented diet and in mean corpuscular haemoglobin concentration for those fed 0.5%, and
1.0% A. sativum supplemented diets compared to all other groups (P < 0.05). Fish fed a 1.0% and 0.5% A. vera-A.
sativum mixture (1:1 ratio) supplemented diet presented a significant increase in all growth parameters compared
to all others (P < 0.05). Similarly, some feed utilisation indices significantly improved in fish fed diet supplemented
with the 1.0% A. vera-A. sativum mixture when compared to unsupplemented ones, and those fed the 2.0% and
4.0% A. vera-A. sativum mixture (P < 0.05). A. vera-A. sativum mixture extracts improved some haematological
indices when compared to unsupplemented fish, with a significant increase observed in RBC of fish fed 1.0% and
in platelets of fish fed 2.0% A. vera-A. sativum mixture supplemented diet when compared to unsupplemented
ones (P < 0.05). Fish fed the 1.0% A. vera-A. sativum mixture showed the highest survival probability throughout the
low pH challenge period among groups. Fish fed dietary A. vera-A. sativum mixture of 2.0%, followed by those
fed the 4.0% and 1.0% mixture demonstrated a significantly lower lipid content compared to those fed a control
diet (P < 0.05). This study demonstrated that A. vera, and A. sativum crude polysaccharides extracts could be
recommended as feed supplements in C. gariepinus culture, and now C. gariepinus farmers have a choice
to use cost effective natural dietary remedies. However, before these extracts could be fully implemented in
aquaculture, the study recommends future studies to include the effects of different factors (i.e., temperature, fish
species, fish sizes, extracts combination ratios) on herbal extracts performance in fish for better optimisation

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