Optimisation of nutrient input to integrated aquaponics systems through mineral supplementation by way of fish feed additives

Date
2020-12
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Aquaponics is an integrated production system with the primary goal of sustainable food production in the form of fish and vegetables. The main challenge in aquaponics is the imbalance of nutrients between the fish and plants grown in the system as each has different nutritional requirements. The requirements of fish are met through fish feed and those of plants by supplementing nutrients, especially trace elements, through nutrient solutions, which adds extra costs to the production system. Therefore, the aim of this study is to design a feed to fulfil a dual role: provide optimal nutrition to the fish and optimise plant production in integrated aquaponics systems. The aims were met by i) determining whether dietarysupplementation of minerals through different feed additives in a recirculating aquaculturesystem can benefit the production performance and haematological profile of the Africancatfish, ii) determining whether dietary supplementation of minerals through different feedadditives in a recirculating aquaculture system can enhance the excretion of iron in wastewater for ultimate use in aquaponics systems, and ultimately iii) evaluating theperformance of the feed additives using the African catfish in combination with lettuce in anintegrated aquaponics system. The inclusion of feed additives, potassium, and iron in the diet of the African catfish improvedits haematological profile and excreted wastewater with high concentrations of potassiumand iron in a recirculating aquaculture system. Fish production and non-specific immunitywere not affected by the inclusion of different additives. Further investigations into anintegrated aquaponics system revealed that the inclusion of these feed additives at the rightinclusion level in the diet of the African catfish improved lettuce growth. The highconcentrations of potassium and iron excreted from the supplemented feed were absorbedby the lettuce in the aquaponics system, resulting in improved growth when compared to thecontrol treatment. From these results, it can be concluded that the addition of minerals through fish feed additives can reduce or even eliminate the need to supplement plants with nutrients in the form of nutrient solutions. The improvement of plant growth through dietary feed additives of fish in aquaponics systems can improve the efficiency of integrated aquaponics production systems. These results contribute to the improvement of the overall performance of the aquaponics system and the production of the African catfish in recirculating systems.
AFRIKAANSE OPSOMMING: Akwaponika is ’n geïntegreerde produksiestelsel met die primêre doel van volhoubare voedselproduksie in die vorm van vis en groente. Die hoof uitdaging in akwaponika is die wanbalans van nutriënte tussen die visse en plante wat in die stelsel groei omdat elkeenverskillende voedingsvereistes het. Die vereistes van visse word bevredig deur visvoer en dié van die plante deur supplementêre nutriënte, veral spoorelemente, deur nutriëntoplossings wat ekstra kostes by die produksiestelsel bydra. Daarom is die doel van hierdie studie om ’n voer te ontwerp wat ’n dubbele doel dien: om optimale nutriënte aan die visse te verskaf en plantproduksie te optimeer in geïntegreerde akwaponikastelsels. Die doelwitte is bereik deur i) te bepaal of dieetkundige aanvulling van minerale deur verskillende voerbymiddels in ’n hersirkulerende akwakultuurstelsel die produksiedoeltreffendheid en hematologiese profiel van die Afrika-baber kan bevoordeel, ii) om te bepaal of dieetkundige aanvulling van minerale deur verskillende voerbymiddels in ’n hersirkulerende akwakultuurstelsel die ekskresie van yster in afvalwater, vir die uiteindelike gebruik in akwaponikastelsels, kan verbeter, en eindelik iii) die doeltreffendheid van die voerbymiddels te evalueer deur die Afrika-baber in kombinasie met blaarslaai te gebruik in ’n geïntegreerde akwaponikastelsel. Die insluiting van voerbymiddels, kalium en yster in die dieet van die Afrika-baber het sy hematologiese profiel en uitgeskeide afvalwater met hoë konsentrasies van kalium en yster in ’n hersirkulerende akwakultuurstelsel verbeter. Visproduksie en nie-spesifieke immuniteit is nie geaffekteer deur die insluiting van verskillende bymiddels nie. Verdere ondersoeke in ’n geïntegreerde akwaponikastelsel het gewys dat die insluiting van hierdie voerbymiddels by die regte insluitingsvlak in die dieet van die Afrika-baber die blaarslaai se groei verbeter het. Die hoë konsentrasies kalium en yster uitgeskei van die gesupplementeerde voer is geabsorbeer deur die blaarslaai in die akwaponikastelsel, wat verbeterde groei tot gevolg het as dit met die gekontroleerde behandeling vergelyk word.Uit hierdie resultate kan dit afgelei word dat die byvoeging van minerale deur visvoerbymiddels die benodigheid om plante met nutriënte te supplementeer in die vorm van nutriëntoplossings, te verminder of selfs te elimineer. Die verbetering van plantegroei deur dieetkundige voerbymiddels van visse in akwaponikastelsels kan die doeltreffendheid van geïntegreerde akwaponikaproduksiestelsels verbeter. Hierdie resultate dra by tot die iv verbetering van die algehele doeltreffendheid en die produksie van die Afrika-baber in hersirkulerende stelsels.
Description
Thesis (PhD)--Stellenbosch University, 2020.
Keywords
Potassium -- Supplement, Nutrition, UCTD, Iron -- Supplement, Nutrition, Aquaponics, Catfishes, Fish feeds -- Additives
Citation