| Summary: | Thesis (MSc)--Stellenbosch University, 2015. === ENGLISH ABSTRACT: Aquaculture is one of the fastest growing food producing sectors in the world. Over the past few years, aquaculture research has focused on improving rearing protocols and standards for the culture of aquatic organisms. Probiotics are gaining increasing interest as an alternative to antibiotics to improve animal health and welfare. The effects of probiotics on the physiological and biochemical development of the digestive tract of commercially raised Argyrosomus japonicus (dusky kob) larvae were investigated. Two probiotic treatments were compared to a control where the standard rearing protocol was applied. The growth of the larvae and histological development of the digestive tract was studied. The specific enzyme activity of key digestive enzymes was determined. Amylase, trypsin, pepsin, alkaline phosphatase, aminopeptidase N and leucine-alanine peptidase were assayed. The mean growth of the control group of larvae differs from the CSIR and BactoSafe treatment groups (P = <0.001). There were no differences in the histological development between the control and two treatments. The histology did indicate a slight delay in development of the digestive tract when compared to previous studies on dusky kob. No significant differences were observed between the control and treatment groups for any of the enzyme assays. The effect of probiotics on the development of the digestive system of dusky kob larvae could not be definitively described as it was not determined to what extent the probiotics had established in the gut. What the study did conclude was that the enzyme assays need to be refined in order to determine the optimal reaction conditions required for the determination of specific enzyme activity in commercially raised dusky kob. === AFRIKAANSE OPSOMMING: Akwakultuur is een van die vinnigste groeiende voedsel produserende sektore in die wêreld. Oor die laaste aantal jare het akwakultuur navorsing gefokus op die verbetering van grootmaak protokolle en standaarde vir die cultuur van akwatise organismes So het die belangstelling in pro-biotika, as alternatief tot antibiotika ten einde die gesondheid en welsyn van diere te verhoog, vermeerder. Die effekte van pro-biotika op die fisiologies en biochemiese ontwikkeling van die spysverteringskanaal van kommersieel geproduseer Argyrosomus japonicus larwes was ondersoek. Twee probiotiese behandelings is vergelyk met ʼn kontrole (standaard grootmaak protokol). Die groei van die larwes en die histologiese ontwikkeling van die spysverteringskanaal is ondersoek. Die spesifieke ensiem aktiwiteite van die sleutel verteringsensieme was ook bepaal. Amilase, tripsien, pepsien, alkaliese fosfatase, aminopeptidase N en leusien-alanien peptidase was ondersoek. Die gemiddelde groei van die kontrole groep was effe hoër as die van die ander twee behandelings. Daar was geen verskil in histologie van die groepe nie maar die tempo van ontwikkeling vir alle behandelinge blyk stadiger te wees as die wat in vorige studies vir A. japonicus rapporteer is. Geen betekenisvolle verskille is opgemerk tussen die kontrole en die behandelingsgroepe vir enige van die ensiem analises nie. Die invloed van die probiotika op die ontwikkeling van die spysverteringskanaal van die larwes kon nie onomwonde beskryf word nie aangesien die vestiging van die pro-biotika in die spysverteringkanaal nie omskryf is nie. Wat wel gevind was, is dat die analitiese tegnieke rakende die ensieme verfyn moet word ten einde die optimale reaksie omgewings te bepaal wat dit sal moontlik maak om spesifieke ensiemaktiwiteite in die kommersieel geproduseerde A. japonicus te bepaal.
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