Application of dietary bentonite clay as feed addictive on feed quality, water quality and production performance of African catfish (Clarias gariepinus)

Ayoola, Mathew Oluwaseyi (2016-03)

Thesis (PhD)--Stellenbosch University, 2016.

Thesis

ENGLISH ABSTRACT: Aquaculture remains the fastest growing animal food producing sector and is gradually overtaking capture fisheries as a source of food fish. The challenges of poor feed quality, feed utilisation and water quality are recurring issues that hinder the growth of aquaculture industry. This study investigated the effects of natural bentonite (NB) and its acid activated form (AB) as feed additives on aquafeeds with reference to the physical quality, growth performance, gut evacuation rate and water quality with African catfish (Clarias gariepinus) as the experimental species. Bentonite clay has found application as a feed additive in animal science and aquaculture. It is used as a mycotoxin binder to improve feed utilisation. Application of dietary activated bentonite form is yet to be fully elucidated to the best of our knowledge. Aquafeeds’ physical qualities, including water stability, feed durability, feed bulk density and nutrient leaching, were investigated. Dietary bentonite clay was added to commercial aquafeeds and each treatment were replicated four times. Water stability, feed durability, feed bulk density and nutrient leaching were all significantly affected (p<0.05) by treatments. Measured parameters (water stability, feed density and feed durability) increased (p<0.05) with the quantity of AB in the clay blend and at high inclusion level as compared to control. Values increased with an increased inclusion level of clay in feed, while nutrient leaching value decreased with quantity of AB and high inclusion. AB had higher values as compared to NB and the control. These results validated the potential utilisation of NB and AB as feed binders. Their ability to improve pellet physical qualities is expected to enhance feed utilisation, maintain good water quality and increase fish growth. Aquafeeds with bentonite clay blend, and each at different inclusion levels improved (p<0.05) growth performance, feed conversion ratio (FCR), specific growth rate (SGR), red blood cell (RBC), and haematocrits (HCT). Parameters improved with an increase in quantity of natural bentonite and at low inclusion level. Growth performance increased (p<0.05) as compared to control with bentonite inclusion up to 1500 mg/kg and decline at 3000 mg/kg. The contents of crude protein (CP), fat, moisture, ash and abdominal fat in the whole body composition were significantly affected (p<0.05) by the treatment diets. Abdominal fat and tissue fat content increased with bentonite inclusion. To evaluate the effect of NB and AB on gut evacuation rate of Clarias gariepinus, fish were randomly allocated to treatment diets and fed ad libitum. Four (4) fish were randomly selected per treatment to measure post feeding stomach content (SC) and intestinal filling (IC) content at (5, 30, 60 and 120 min). The control diet had higher values for SC at 5 min which differed significantly (p<0.05) as compared to clay diets. SC decreased (p<0.05) with time in all diets and clay diets had higher value (p<0.05) between (30 – 120 min) as compared to control. In clay diets, SC decreased faster over time with reduced quantity of AB and low inclusion level. The IC of control diets had higher values (p<0.05) over time as compared to clay diets. The water quality parameters (pH, N02-, NH3-N and TSS) were evaluated in a static aerated tank. Aquafeeds were fed to adult fish at 3% body ratio twice daily. Each treatment diet was replicated four (4) times, and 10 fish were randomly allotted to each tank. The water temperature was 25 ± 2°C and dissolved oxygen (DO) was 3-9 mg/L. Water samples were collected daily from each tank. In phase I, water quality was evaluated over seven (7) days, and in phase II over five (5) days. No mortality was recorded during the study. The values of pH, N02-, NH3-N and TSS increased significantly (p<0.05) in all treatment diets over time. In both phases, clay treated diets had lower values for measured parameters (p<0.05) compared to those of control. In clay diets, values increased (p<0.05) with quantity of AB and high inclusion level. Fish feed intake reduced as water quality deteriorated, and uneaten feeds contributed to increase in poor water quality. Thus, high water stability of clay treated diets attributed to maintenance of good water quality as compared to the control. The results showed that dietary clay enhanced feed binding, which affected digesta viscosity. This reduced the rate of feed evacuation in the gut, and, thus, enhanced proper breakdown and absorption of nutrients. Higher inclusion levels of bentonite clay and increased quantity of AB are not suitable for improved growth and feed utilisation, as increased in digesta viscosity led to fermentation in the gut. An optimum level of performance was recorded at 1500 mg/kg inclusion with natural bentonite (B1500) with a significantly (p<0.05) better performance as compared to control and acid activated bentonite. A clay combination blend up to 50% (A50B50) at low inclusion level (500 mg/kg) of acid activated bentonite is considered optimum.

AFRIKAANSE OPSOMMING: Akwakultuur bly die vinnigste groeiende diereproduksiesektor en is geleidelik besig om visserye in te haal as 'n bron van vis vir voedsel. Die uitdaginge gekoppel aan swak kwaliteit voere, voerbenutting en waterkwaliteit is herhalende kwessies wat die groei van die akwakultuurbedryf verhinder. Hierdie studie het die effek van natuurlike bentoniet (NB) en sy suurgeaktiveerde vorm (SB) ondersoek as voertoevoeging op akwavoere met verwysing na die fisiese kwaliteit, groeiprestasie, spysverteringsontruimingstempo en waterkwaliteit met die Afrika baber (Clarias gariepinus) as die eksperimentele spesies. Bentonietklei het aanwending as 'n voertoevoeging in veekunde en akwakultuur gevind. Dit word gebruik as 'n mikotoksienbinder om voerbenutting te verbeter. Die aanwending van 'n dieetgeaktiveerde bentonietvorm is nog nie ten volle toegelig na die beste van ons kennis nie. Akwavoere se fisiese eienskappe, insluitend waterstabiliteit, voerduursaamheid, voermassadigtheid en die loging van voedingstowwe is ondersoek. Dieetbentonietklei is tot kommersiële akwavoere bygevoeg en elke behandeling was vier keer herhaal. Waterstabiliteit, voerduursaamheid, voermassadigtheid en voedingstofloging is almal beduidend beïnvloed (p <0.05) deur behandeling. Gemete parameters (waterstabiliteit, voerdigtheid en voerduursaamheid) het toegeneem (p <0.05) met die hoeveelheid SB in die kleimengsel en teen 'n hoë insluitingvlak in vergelyking met die kontrole. Waardes het toegeneem met 'n verhoogde insluitingsvlakke van klei in voer, terwyl voedingstofloging se waarde gedaal het met hoeveelhede SB en hoë insluiting. SB het hoër waardes in vergelyking met NB en die kontrole. Hierdie resultate bevestig die potensiële benutting van NB en SB as voerbinders. Hul vermoë om voerkorrels se fisiese eienskappe te verbeter, sal na verwagting voerbenutting verbeter, en tesame goeie waterkwaliteit handhaaf met verhoging in visgroei. Akwavoere met ‘n bentonietkleimengsel, en elk teen verskillende insluitingsvlakke het die groeiprestasie, voeromsettingsverhouding (VOV), spesifieke groeitempo (SGR), rooibloedselle (RBS), en haematokrit (HKT) verbeter (p <0.05). Parameters het verbeter met 'n toename in die hoeveelheid van natuurlike bentoniet en lae insluitingsvlakke. Groeiprestasie het toegeneem (p <0.05) in vergelyking met die kontrole tot en met ‘n bentoniet insluiting van 1500 mg/kg en ‘n afname het plaasgevind by 3000 mg/kg. Die inhoud van ru-proteïen (RP), vet, vog, as en abdominale vet in die hele liggaamsamestelling is beduidend beïnvloed (p <0.05) deur die behandelingsdiëte. Abdominale vet en weefselvetinhoud het toegeneem met bentoniet insluiting. Om die effek van NB en SB op spysverteringontruimingstempo van Clarias gariepinus te evalueer, is vis ewekansig toegewys aan behandelingsdiëte en ad libitum gevoer. Vier (4) vis is ewekansig gekies per behandeling om post-voeding maaginhoud (MI) en spysverteringsvullingsinhoud (SV) by (5, 30, 60 en 120 minute) te meet. Die kontrole dieet het hoër waardes vir MI by 5 min getoon wat beduidend verskil het (p <0.05) in vergelyking met kleidiëte. MI het afgeneem (p <0.05) met verloop van tyd in alle diëte en kleidiëte het hoër waardes (p <0.05) tussen (30-120 min) getoon in vergelyking met die kontrole. In die kleidiëte, het MI vinniger afgeneem met verloop van tyd met 'n verminderde hoeveelheid SB en lae insluitingsvlak. Die SV van die kontrole dieet het hoër waardes (p <0.05) met verloop van tyd getoon in vergelyking met kleidiëte. Die waterkwaliteitsparameters (pH, N02-, NH3-N en TSS) is geëvalueer in 'n statiese belugte tenk. Akwavoere is gevoer vir die volwasse visse teen 3% liggaamsmassa-verhouding, twee keer per dag. Elke behandelingsdieet is vier (4) keer herhaal, en 10 visse is ewekansig toegewys aan elke tenk. Die watertemperatuur was 25 ± 2°C en opgeloste suurstof (OS) was 3-9 mg/L. Watermonsters is daagliks versamel uit elke tenk. In in fase I, is waterkwaliteit geëvalueer oor sewe (7) dae en in fase II oor vyf (5) dae. Geen mortalitiete is aangeteken tydens die studie. Die waardes van pH, N02-, NH3-N en TSS het aansienlik toegeneem (p <0.05) in alle behandelingsdiëte met verloop van tyd. In beide fases, het kleibehandelde diëte laer waardes vir gemete parameters (p <0.05) in vergelyking met die kontrole getoon. In kleidiëte het waardes toegeneem (p <0.05) met die hoeveelheid van SB en hoë insluitingsvlak. Visvoerinname het verminder soos die waterkwaliteit verswak het, en ongevrete voere het verhoog in hierdie swak waterkwaliteitsomgewing. Dus, 'n hoë waterstabiliteit van kleibehandelde diëte kan bydrae tot die handhawing van goeie waterkwaliteit in vergelyking met die kontrole. Die resultate het getoon dat dieetkleie verbeter voerbindinge, wat die verteringsmengsel se viskositeit beïnvloed. Dit het die tempo van voerontruiming in die spysvertering verbeter. Hoër insluitingsvlakke van bentonietklei en die verhoogde hoeveelheid van SB is nie geskik vir 'n beter groei en voerbenutting nie, want ‘n toename in verteringsmengsel se viskositeit het gelei tot fermentasie in die spysvertering. 'n Optimale vlak van prestasie is aangeteken by 1500 mg/kg insluiting met natuurlike bentoniet (B1500), met 'n beduidende (p <0.05) beter prestasie in vergelyking met die kontrole en suurgeaktiveerde bentoniet. 'n Klei kombinasie mengsel tot en met 50% (A50B50) teen 'n lae vlak insluiting (500 mg/kg) van suurgeaktiveer bentoniet, word as optimaal beskryf vir aanwending.

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