The potential of quercetin to improve growth performance and meat quality in rabbits

North, Megan Kim (2019-04)

Thesis (MScAgric)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Flavonoids are naturally-occurring bioactive compounds that may improve livestock production and product quality. Unfortunately, while their antioxidant, antimicrobial and other activities have been demonstrated, there has been limited research on their practical use as a livestock dietary supplement. This study investigated the effects of quercetin dihydrate (0 or 2 g/kg feed) on the growth performance and meat quality of growing New Zealand White rabbits. Sixty-six rabbits (31 males, 35 females) were fed control (Ctrl, 34 rabbits) or quercetin-supplemented (Qrc, 32 rabbits) feeds from weaning (5 weeks) until slaughter. The growth, feed intake and feed conversion ratio (FCR) were measured, and serum hormone levels were determined at 11 weeks old. Sixteen males and 16 females were slaughtered at 12 weeks old; carcass and meat quality traits were measured and the fatty acid composition of the caecotrophes, dissectible fat, loin meat and hindleg meat were determined using GC-FID. Fifteen males and 19 females were slaughtered at 13 weeks old; caecal contents were collected from 12 rabbits for the 16STM metagenome sequencing of the microbiome, and the loins were minced and stored for 1, 3 or 5 days at 3.2 C under oxygen-permeable wrapping to test the shelf-life. Quercetin-supplementation did not improve live performance, with Qrc rabbits only tending (P ≤ 0.10) to have higher overall FCRs, smaller sex-differences in growth and FCR, and higher free triiodothyronine levels. Quercetin-supplemented rabbits also only had higher proportions of some Firmicutes families and Anaerofustis and lower proportions of Roseburia, Oscillibacter and Ruminococcus albus in the caecal microbiome. This limited effect may have been due to the aglycone being absorbed prior to the caecum. Strong correlations between the composition of the microbiome and live performance traits were found, supporting further research on this topic. Quercetin-supplemented rabbits had higher hindleg meat:bone ratios due to lighter bones, which could increase meat yields but could also cause bone-breakage problems. This was contrary to previous findings that flavonoids decrease bone demineralisation, but may have been due to its effects on the connective tissue, which could have also caused the higher skin weight found. The largest effect of supplementation was on the loin fatty acid (FA) composition, increasing C18:3n-6, C20:3n-6, C20:3n-3 and C20:4n-6, and decreasing C20:2n-6, among others, thereby decreasing the n-6:n-3 ratio and improving the nutritional quality of the meat. This suggested an interaction between quercetin and endogenous lipid metabolism, which may have been influenced by the FA composition of the diet. The caecotrophes, dissectible fat and hindleg FAs were unchanged by quercetin. Quercetin-supplemented rabbits’ meat samples had lower day one concentrations of hexanal (an oxidation indicator), but no difference in oxidation (TBARS and FRAP) or microbial status during the shelf-life study. Dietary quercetin therefore did not improve the shelf-life of rabbit meat. Further research on the effects of quercetin on lipid metabolism should be done, particularly testing different inclusion levels and dietary FA compositions. The effects on bone-integrity, whole-carcass meat:bone ratio and pelt/skin quality should also be looked into. While some sex differences were found in these studies, they did not meaningfully affect production or product quality.

AFRIKAANSE OPSOMMING: Flavonoïde is natuurlike, bio-aktiewe komponente wat die produksie en die produkkwaliteit van vee mag verbeter. Die antioksidant en antimikrobiese aktiwiteit, asook ander voordelige eienskappe van flavonoïde, is reeds breedvoerig bewys in die literatuur, maar tog is daar baie min beskikbare inligting oor die praktiese implikasies van die insluiting daarvan in veevoeding. Daarom fokus hierdie studie daarop om die effek van kwersetien dehidraat (0 of 2 g/kg voeding) op die groei en vleiskwaliteit van Nieu-Seelandse Wit konyne te ondersoek. Ses en sestig konyne in totaal (31 manlik en 35 vroulik) is gebruik, waarvan 34 van die konyne die kontrole voer en 32 konyne die kwersetien-aangevulde voer ontvang het, vanaf speen ouderdom (5 weke) tot slag. Die groei en voer-inname is gemeet, en die voer omset verhouding (VOV) is bereken, tesame met die bepaling van die serum hormoon vlakke op 11 weke ouderdom. Daar is 16 van elk manlike en vroulike diere geslag op 12 weke ouderdom, waarna die karkas- en vleiskwaliteitseienskappe bepaal is. Die vetsuursamestelling van die cecotropes, dissekteerbare vet en die lende en agterbeen vleis is ook bepaal op ‘n GC-FID toestel. Op 13 weke ouderdom is 15 manlike en 19 vroulike konyne geslag en die inhoud van 12 van die konyne se sekums is ingesamel om sodoende die 16STM metagenoom volgorde van die mikrobioom te bepaal. Die lendevleis is gemaal en toe gestoor vir 1, 3 of 5 dae by 3.2 °C onder suurstof-deurlaatbare, plastiek verpakking om sodoende die rakleeftyd te toets. Die konyne wat die kwersetien aanvulling ontvang het, het nie ‘n verbeterde lewendige gewig getoon nie. Daar was slegs tendense (P ≤ 0.10) van hoër algehele VOV, kleiner geslags verskille in groei en die VOV, asook hoër vrye triiodothyronine vlakke. Die mikrobiome het ook slegs hoër proporsies van sommige van die Firmicutes families en Anaerofustis en laer proporsies van Roseburia, Oscillibacter en Ruminococcus albus gehad. Die beperkte effek van kwersetien mag wees as gevolg van die absorbsie van die aglycone voor die cecum. Sterk korrelasies is gevind tussen die samestelling van die mikrobioom en die lewendige gewigseienskappe, wat die noodsaaklikheid vir verdere navorsing in terme van hierdie onderwerp versterk. Die kwersetien aanvulling het gelei na ‘n hoër agterbeen vleis:been verhouding as gevolg van ‘n laer been gewig in die konyne wat dié voer ontvang het. Dit mag lei na ‘n verhoogte vleis opbrengs, maar kan ook die negatiwe gevolg hê van die breking van die agterbene wat makliker plaasvind. Hierdie bevinding is in teenstelling met vorige navorsing wat getoon het dat flavonoïde die de-miniraliserings proses verlaag. Dit mag wees dat die flavonoïde ‘n effek op die bindweefsel uitoefen wat ook kon gelei het na die hoër vel gewig van hierdie konyne. Die grootste effek van die aanvulling was egter op die samestelling van die rugstring spier se vetsuur inhoud. Die kwersetien in die voeding het gelei na toenemende vlakke van C18:3n-6, C20:3n-6, C20:3n-3 en C20:4n-6 vetsure, en ‘n laer C20:2n6 inhoud. Die n-6:n-3 verhouding is dus laer in die lende spier van hierdie konyne, wat ‘n positiewe effek op die voedingswaarde van die vleis het. Hierdie bevinding dui op ‘n interaksie tussen kwersetien en die endogene lipied metabolisme, en die feit dat dit moontlik beïnvloed is deur die vetsuursamestelling van die dieet. Die cecotropes, vet en vetsure van die agterbeen is onveranderd gelaat deur die kwersetien in die dieet. Die monsters van die konyne op die kwersetien aanvulling het laer vlakke van hexanal (‘n indikator van oksidasie) op dag een getoon, maar geen verskil is opgemerk in die oksidasie (TBARS en FRAP) of die mikrobiese stand tydens die rakleeftyd studie. Die teenwoordigheid van kwersetien in die dieet het dus nie die rakleeftyd van die konynvleis verbeter nie. Verdere navorsing op die invloed van kwersetien op lipied metabolisme is nodig om veral die effek van verskillende vetsure in die voer, asook verskillende insluitingskoerse, te ondersoek. Die invloed op been integriteit, heel karkas vleis:been verhouding, en vel kwaliteit is verdere faktore wat aangespreek moet word. Terwyl daar wel sommige geslagsverskille gevind is in die studie, het dit nie ‘n betekenisvolle invloed getoon op die produksie en produkkwaliteit nie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105576
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