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Effect of Phytogenic Feed Additives on Gonadal Development in Mozambique Tilapia (Oreochromis Mossambicus)

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Effect of Phytogenic Feed Additives on Gonadal Development in Mozambique Tilapia (Oreochromis Mossambicus) EFFECT OF PHYTOGENIC FEED ADDITIVES ON GONADAL DEVELOPMENT IN MOZAMBIQUE TILAPIA (OREOCHROMIS MOSSAMBICUS ) Akwasi Ampofo-Yeboah Dissertation presented in partial fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY (AGRICULTURE-AQUACULTURE), FACULTY OF AGRISCIENCE Stellenbosch University Promoter: Prof Danie Brink Co-Promoter: Dr Helet Lambrechts March 2013 Stellenbosch University http://scholar.sun.ac.za Declaration By submitting this dissertation electronically, I declare that the entirety of the work contained therein is my own original work, that I am the owner of the copy right thereof (unless to the extent explicitly otherwise stated) and that I have not previously in its entirety or in part, submitted it for obtaining any qualification. Signature: Date: February 12, 2013 Copyright © 2013 Stellenbosch University All rights reserved Stellenbosch University http://scholar.sun.ac.za Acknowledgements I want to give special thanks to the Almighty God and the Lord Jesus Christ for giving me life and so much blessing, strength to persevere against all odds to complete this study -a dream come true. I wish to acknowledge the following people and institutions for their support during this project: • The University for Development Studies (UDS), Ghana, particularly Prof S.K. Nokoe, and Ghana Education Trust Fund (GETFund), for the initial financial support that enabled me to enrol for the programme. • The Division of Aquaculture, together with the Postgraduate and International Office (Postgraduate Funding Section), Stellenbosch University (SU) for financial support during my studies. • My wife and daughters for their endless patience, support and prayers; my mother, siblings and uncle for their unflinching support and confidence in me. • My promoter Prof Danie Brink for his patience, support, guidance both academically and mentorship, and friendship; and co-promoter, Dr Helet Lambrechts for her understanding, patience, and guidance, and finally Mrs Annelene Sadie who assisted me in the Statistical Analysis. • Prof Krishen Rana for his contributions, particularly with regard tothe development of the methodology. • The administrative staff of Division of Aquaculture (Mrs Lorette de Villiers) and Department of Genetics (Ms Thanja Alison) for their assistance during my studies. • The staff at Histology Department, Faculty of Health Sciences, Tygerberg Campus (especially, Mr Reggie Williams), and the SU Central Analytical Facility (LC/MS Unit) for their assistance during my laboratory analysis (particularly, Mr Hiten Fletcher). • The technical staff at Division of Aquaculture, Welgevallen Experimental Farm, Stellenbosch University for the technical assistance (particularly, Mr Systel van Vyk and Mrs Sana van Vyk). Dedications This work is dedicated to: • The Almighty God and the Lord Jesus Christ, through whom “All Things Are Made Possible”. • My mother, Abena Akoma (a stalk illiterate whose efforts has produced 4 University Graduates - 3 PhD Holders), elder brother Dr Emmanuel Agyeman Gyawu and uncle, Kwasi Asamoah Owusu-Akyaw (the initiators of my education). • My wife, Afua Serwa (for sharing her life with me), and 3 lovely daughters (Akua Serwa, Akua Akoma and Akua Owusua - the birth of each signifies a landmark in my struggle against all odds). • The memory of my late sister, Faustina Ampofo and late niece, Awuraa Ama Serwa, who would have wanted to live to see this day (whose untimely deaths came as a shock). • My late father, Paul Kofi Appiah Ampofo (an educator who did not live long enough to see to the education of his children). ii Stellenbosch University http://scholar.sun.ac.za Summary This study investigated the “Effect of Phytogenic Feed Additives on Gonadal Development in Mozambique tilapia (Oreochromis mossambicus). Aquaculture remains the fastest growing animal food-producing sector and it is set to overtake capture fisheries as a source of food fish, and also to outpace population growth. This rapid growth can be attributed to the increasing demand for aquaculture products, and an urgent need for a sustainable food resource and the safe production of food. Globally, fish provides over 3.5 billion people with up to 15 percent of their average per capita intake of animal protein. The introduction of aquaculture to sub-Saharan African (SSA) took place during the 1940s and 1950s, and the main objectives were to improve nutrition in rural areas, allow for the diversification of activities to reduce the risk of crop failures, to generate additional income, and to create employment opportunities. Aquaculture was seen as a viable option for rural development in SSA, and substantial resources were invested to support its development. Poor results were however, recorded in terms of production and sustainability. Tilapia is the most widely cultured of all fish species farmed, and the second most important group of freshwater and brackish water fish after carps. Tilapia has all the necessary traits that makes it an excellent species to culture, but cost- efficient production is hampered by the animals attaining sexual maturity at a an early age, which then result in precocious breeding in aquaculture systems. The production of single-sex populations (i.e. all male) is a potential means to address the problem of precocious breeding, but the technologies used to establish single-sex populations are not readily available to resource-poor communities that farm with tilapia for food purposes. Phytochemicals, also known as phytoestrogens, are plant-derived compounds that structurally or functionally mimic mammalian estrogens that affect the sexual differentiation of fish. Phytochemicals occur in plants like Pawpaw (Carica papaya) and Moringa (Moringa oleifera). The study thus had a threefold objective. Firstly, the study investigated the potential of Pawpaw seed meal (P) and Moringa seed meal (M), as part of a commercial tilapia diet, to be used as endocrine disrupting compounds (EDC’s) to control the reproduction of sexually mature Mozambique tilapia (20-45g). Secondly, assess the potential of P and M to inhibit the attainment of sexual maturity in immature tilapia (2-8g). Finally, P and M to determine its influence on sexual differentiation of tilapia fry (9-12 days posthatch) to produce all-male populations. The study indicated that both P and M seeds contain bio-active chemicals that are capable of disrupting the gonad function, differentiation and sexual maturation of Mozambique tilapia. Sperm production was affected, evident in the degeneration of the testicular tissue samples. Egg production, ovulation and spawning were all affected, as evident in the difference in colour of the degrading eggs, as well as the absence of spawning. Ovo-testes were observed in cases where diets containing 10.0g P and 10.0g M /kg basal diet were fed. Eggs were observed in the ovaries of sexually immature fish, but spawning did not occur. The study also presents the first report on the isolation of Oleanolic acid in Moringa seeds. The evident of antifertility properties of both Pawpaw and Moringa seeds can be exploited to control or prevent reproduction of Mozambique tilapia in SSA aquaculture systems. This could be of particular importance to aquaculture development in rural areas of Sub-Saharan African countries, given the abundant year round availability of these compounds. Further studies are required to optimise the preparation of the experimental compounds; as well as determining the optimal inclusion level of the phytogenic compounds, as well as how their efficacy to manipulate the reproductive potential and ability of Mozambique tilapia are influenced by environmental factors such as water temperature. iii Stellenbosch University http://scholar.sun.ac.za Opsomming Akwakultuur is die vinnigste groeiende dierlike voedsel-sektor. Daar word verwag dat dit visserye sal oortref as ʼn bron van voedsel en dat groei in dié bedryf selfs die bevolkingsgroei sal verbysteek. Die vinnige groei in die sektor kan toegeskryf word aan die toenemende vraag na akwakultuur produkte en 'n dringende behoefte vir 'n volhoubare voedsel hulpbron, wat ook die veilige produksie van voedsel sal verseker. Wêreldwyd voed vis meer as 3.5 miljard mense en dra tot 15% van die gemiddelde hoeveelheid dierlike proteïen per kapita ingeneem, by. Die bekendstelling van akwakultuur in sub-Sahara Afrika (SSA) het gedurende die 1940's en 1950's plaasgevind, met die belangrikste doelwitte om voeding in landelike gebiede te verbeter, geleenthede vir diversifisering te skep wat die risiko van misoeste verminder, om bykomende inkomste te genereer en werksgeleenthede te skep. Akwakultuur is gesien as 'n lewensvatbare opsie vir die ontwikkeling van die landelike gebiede in SSA en aansienlike hulpbronne is belê om die ontwikkeling daarvan te ondersteun. Swak resultate is egter in terme van produksie en volhoubaarheid behaal. Tilapia is die mees algemene spesies wat gekweek word en is die tweede mees belangrike groep van varswater en brak water vis soesies, na Karp. Tilapia beskik oor al die nodige eienskappe wat dit ʼn uitstekende spesie vir voedselproduksie maak, maar koste-doeltreffende produksie daarvan word gekortwiek deur die feit dat die spesie seksuele volwassenheid op 'n vroeë ouderdom bereik, wat dan lei tot vroeg-rype teling en die gevolglike oorbevolking en swak groei van tilapia in ʼn akwakultuur sisteem. Die produksie van enkel-geslag bevolkings (d.i. slegs manlike vis) is ʼn potensiële oplossing vir dié probleme, maar die tegnologie wat gebruik word om
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