The effects of dietary lipids and antioxidants on growth performance, meat quality and moisture loss of the South African abalone, Haliotis Midae

Thesis (MScAgric)--Stellenbosch University, 2014.

ENGLISH ABSTRACT: Abalone has become a high valued commodity globally, with South Africa being one of the largest producers. Haliotis midae is the most important aquaculture species produced in South Africa, and is exported to the Eastern markets in a variety of forms, with live export and canned abalone being the two most important products. To meet the high international demand, abalone farmers need to remain competitive by optimizing growth rate, increase water absorption, and minimising the stress and moisture loss experienced by abalone during the live export period. Stress and moisture loss experienced during export can potentially contribute to a decrease in live weight and meat quality, which in turn will result in lower income generated, which will impact negatively on the cost-efficient production of abalone. No literature is available on reducing moisture loss in live abalone during export. Other factors such as diet composition (which can affect the growth rate of abalone), animal health condition (assessed by weight of the abalone per unit shell length), and meat composition and quality, can also affect the cost-efficient production of abalone. The aim of this study was therefore to determine the amount of moisture loss experienced by adult live abalone that have reached an export size, and to formulate a complete balanced diet that will minimize the moisture loss during export. Aspects that were investigated included a) the effect of diet on the growth rate of abalone, b) the effect of diet composition on moisture loss during live export of abalone, c) the effect of diet on the extent of post mortem and post cooking moisture loss, and d) the effect of diet composition on proximate and chemical composition of abalone meat. This study evaluated the effect of ten diets that differed in terms of their Vitamin E, polyunsaturated fatty acid (PUFA), chromium, and green rooibos content, The diets consisted of Control 1 (Abfeed®), Control 2 (NutroScience), LN (low PUFA with no additives), LM (low PUFA with vitamin E (mixed tocopherols)), LR (low PUFA with green rooibos) and LCr (low PUFA with chromium), HN (high PUFA with no additives), HM (high PUFA with vitamin E (mixed tocopherols)), HR (high PUFA with green rooibos), and HCr (high PUFA with chromium). Sunflower oil was used to formulate the high PUFA treatments, whilst rendered beef fat (tallow) was used to formulate the low PUFA treatments. Animals (n=25) from each treatment was sampled monthly to determine the effect of the different treatments on the growth performance (measured as weight and length gain, average daily gain and specific growth rate in terms of weight and length, feed conversion ratio, and condition factor). Proximate and chemical analyses were performed on the abalone meat post mortem to determine the effect of diet composition on moisture loss, water retention, and drip loss. Varying results were obtained for the high and low PUFA diets with added antioxidants, and it was suggested that PUFA levels and antioxidants did not play a significant role in improving the overall growth rate and meat composition of abalone. However, there was a trend for improved growth performance when the control NutroScience diet was fed, indicating that the diet can potentially be considered as a cheaper alternative feed for abalone growth performance. Further research, however, is required in this regard before it can be propagated as such. On completion of the feeding trial, a standard 40 hour export journey for live abalone was simulated under laboratory conditions to determine moisture loss during live export. The results from this experiment indicated that, even though not significant, PUFA and antioxidants tend to play an important role in ensuring the retention of body water, consequently reducing moisture loss. Overall, abalone fed the AquaNutro diet lost the least weight during the live export simulation, which differed significantly when compared to the weight loss experienced by abalone fed the Abfeed® diet. Abalone that gained the most moisture during the purging period (i.e. period where animals are starved to clean out their intestines) tended to lose the least total moisture after transport and cooking, respectively. These findings indicated a potential correlation between the absorption rate of water during purging, and moisture retention during handling, transport and cooking of abalone. Further studies are required to better understand the water loss and retention dynamics in live abalone during transport, and how this affects abalone meat quality, water absorption during purging and moisture retention during handling, transport and cooking.

AFRIKAANSE OPSOMMING: Perlemoen is 'n hoë waarde kommoditeit wêreldwyd, met Suid-Afrika as een van die grootste produsente. Haliotis midae is die belangrikste akwakultuur spesie wat in Suid-Afrika geproduseer en na die Oosterse markte as veral ʼn lewende en geblikte produk uitgevoer word. Om te voldoen aan die groot internasionale aanvraag, moet perlemoen produsente so kompeterend as moontlik bly deur die groeitempo van die diere te optimaliseer, waterabsorpsie tydens vervoer, asook die stres en vogverlies wat lewende diere tydens uitvoer ondervind, te beperk. Laasgenoemde kan potensieel tot ‘n afname in lewende gewig en vleiskwaliteit bydra, wat die winsgewendheid van perlemoen produksiesisteme negatief kan beïnvloed. Geen literatuur is beskikbaar oor die beperking van vogverlies tydens uitvoer nie. Ander faktore soos dieet samestelling (wat die groeitempo van perlemoen kan beïnvloed), die gesondheid status (bepaal deur gewig van die perlemoen per eenheid dop lengte) en vleis samestelling en kwaliteit (waarvan vogverlies ʼn groot komponent is) kan almal ʼn invloed op die winsgewendheid van perlemoen produksie hê. Die doel van hierdie studie was dus om die mate van vogverlies ondervind deur volwasse perlemoen wat gereed is vir die lewende uitvoermark te bepaal, asook om ʼn volledig gebalanseerde dieet te formuleer wat vogverlies tydens uitvoer sal beperk. Aspekte wat ondersoek is, het ingesluit a) die effek van dieet samestelling op die groeitempo van perlemoen, b) die effek van dieet samestelling op die mate van vogverlies ondervind in lewende perlemoen tydens uitvoer, c) die effek van dieet op die hoeveelheid drupverlies in perlemoen vleis ondervind post-mortem en d) die potensiële invloed van dieet op die proksimale en chemiese samestelling van perlemoen vleis. Die studie het die effek van tien diëte, wat ten opsigte van Vitamien E-, poli-onversadigde vetsuur (PUFA)-, chroom- en groen rooibosteevlakke verskil het, op perlemoen groei, water retensie en vleiskwaliteit ondersoek. Die diëte het bestaan uit Kontrole dieet 1 (Abfeed ®), Kontrole dieet 2 (NutroScience), LN (lae PUFA met geen bymiddels), LM (lae PUFA met vitamien E (gemengde tokoferole)), LR (lae PUFA met groen rooibos) en LCr (lae PUFA met chroom), HN (hoë PUFA met geen bymiddels), HM (hoë PUFA met vitamien E (gemengde tokoferole)), HR (hoë PUFA met groen rooibostee) en HCr (hoë PUFA met chroom). Sonneblomolie is gebruik om die hoë PUFA behandelings te formuleer, terwyl gereduseerde gefiltreerde beesvet gebruik is vir die formulering van die lae PUFA diëte. Diere (n=25) van elke behandeling is maandeliks gemonster om die effek van die verskillende behandelings op die groeiprestasie (gemeet aan toename in gewig en lengte, gemiddelde daaglikse toename en spesifieke groeitempo in terme van gewig en lengte, voeromsetverhouding en liggaamskondisie faktor) te bepaal. Perlemoen vleismonsters is post-mortem met behulp van proksimale en chemiese analises ontleed om die invloed van die onderskeie diëte op vogverlies, water retensie en drupverlies te bepaal. Variërende resultate is verkry vir die onderskeie diëte. Resultate in dié studie het aangedui dat PUFA vlakke en antioksidante nie 'n beduidende rol in die groeitempo en samestelling van perlemoenvleis gespeel het nie. Daar was egter 'n neiging vir ʼn versnelde groeitempo ondervind in diere wat die NutroScience dieet ontvang het, wat dui op die potensiaal van die dieet om as 'n goedkoper alternatief vir kommersiële produksie van perlemoen gebruik te kan word. Verdere navorsing word egter benodig in dié verband voor dit so gepropageer kan word. Na afloop van die dieetkomponent van die studie, is 'n standaard 40 uur uitvoerperiode vir lewende perlemoen nageboots onder laboratorium toestande om die omvang van vogverlies tydens uitvoer te bepaal. Die resultate van hierdie eksperiment het aangedui dat PUFA en antioksidante neig om 'n belangrike rol te speel in die behoud van liggaamswater, wat bydra tot ʼn vermindering in vogverlies tydens uitvoer. Diere wat die AquaNutro dieet ontvang het, het die minste gewig gedurende die gesimuleerde uitvoer reis verloor, wanneer dit met die Abfeed® dieet vergelyk is. Diere wat die hoogste vogopname tydens die suiweringsproses (d.i. tydperk waar diere uitgehonger word om die spysverteringsisteem skoon te maak) getoon het, het geneig om die minste totale vog na die vervoer en kookproses te verloor. Hierdie bevindinge dui op ʼn potensiële korrelasie tussen die opname van water tydens die suiweringsproses en die mate van vogretensie tydens hantering, vervoer en kookprosesse. Verdere studies is nodig om die dinamika van vog verlies en –retensie tydens vervoer van lewende perlemoen, asook die invloed op vleiskwaliteit te verstaan.