The effects of maize cobs and supplemental rumen-protected conjugated linoleic acid (CLA) on production efficiency and meat quality characteristics of South African mutton merinos

Rousseau, Francois Jacques (2006-04)

Thesis (MScAgric) -- University of Stellenbosch, 2006.

Thesis

ENGLISH ABSTRACT: The objective of this investigation was to determine the effect of incremental inclusion of maize cobs, as well as supplemental rumen-protected conjugated linoleic acid (CLA) on the production efficiency and meat quality characteristics of South African Mutton Merino lambs. Prior to this trial, an in situ rumen degradability trial was conducted to determine the dry matter, protein and fibre degradability of maize cobs. Five ruminally cannulated Dohne Merino wethers were used to compare ruminal degradability of luceme and oat hay with that of maize cobs, using the in situ nylon bag technique. The samples were incubated in the rumen for varying time intervals. Both postincubated and original samples were analysed for dry matter (DM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent fibre (ADF). The percentage disappearance at each incubation time was calculated from the proportion remaining after rumen incubation. Results obtained clearly established that, on average, the degradability of maize cobs is comparable with that of oat hay. Twenty four South African Mutton Merino (SAMM) lambs were used in a feedlot finishing study to evaluate the effect of maize cobs at incremental inclusion levels (4, 8 and 12%) on individual feed intake, average daily gain (ADG) and feed conversion efficiency (FCE). The apparent digestibilities of the three diets were also determined. The three pelleted diets were formulated, on an isonitrogenous and isoenergetic basis. The lambs were slaughtered after the trial had finished and the longissimus dorsi and biceps femoris muscles were removed from each carcass for the determination of proximate chemical composition and physical quality characteristics. Neither ADG nor FCE of the lambs was influenced by dietary treatment. Lambs fed the diet containing 4% maize cobs had the higher nitrogen retention, while diet did not affect energy retention. The proximate chemical composition of both muscles was not significantly affected by diet. Diet only had a significant effect on the cooking loss and the colour measurements of the M. longissimus dorsi. Sixteen South African Mutton Merino (SAMM) lambs were used in a second feedlot finishing study to evaluate the effect of feeding a diet containing supplemental rumen-protected CLA. The procedure followed was the same as in the first feedlot finishing study, except for an additional sensory and fatty acid analysis. No significant differences occurred in the ADG, FCE and dressing percentage of the lambs. Both energy and nitrogen retention of the lambs were not affected by dietary treatment. The proximate chemical composition of both muscles was similar, but diet had a significant effect on the cooking loss and the colour measurements of the M. longissimus dorsi. Diet had no significant effect on any of the five sensory attributes measured. Fatty acid composition was significantly affected by dietary CLA. Palmitic (Cl6:0), stearic (C18:0) and oleic (18:ln-9) acid were the major fatty acids in both muscles, as well as in the three adipose tissue types. The rumen-protected CLA increased the CLA (Cl 8:2n-6) contents of both muscles, although the increase was only significant for the M. longissimus dorsi and not for the biceps femoris muscle.

AFRIKAANSE OPSOMMING: Die doe! van die ondersoek was om die invloed van toenemende insluitingsvlakke van mieliestronke, asook aanvullende rumen-beskermde gekonjugeerde linole"iensuur (CLA), op die produksie doeltreffendheid en vleis kwaliteitseienskappe van Suid-Afrikaanse Vleismerino (SAVM) lammers, te bepaal. Voorafgaande die proef, is 'n in situ degradeerbaarheidstudie uitgevoer om die droe materiaal-, protelen- en vesel degradeerbaarheid van mieliestronke te bepaal. Vyf Dohne Merino hamels met rumenkannulas is gebruik om, met behulp van die in situ nylon sakkie tegniek, die degradeerbaarheid van lusem en hawerhooi met die van mieliestronke te vergelyk. Sakkies met die monsters is by verskillende tydsintervalle in die rumen gelnkubeer. Monsters is voor en na inkubering ontleed vir droe materiaal (DM), ruprotelen (RP), neutraal bestande vesel (NBV), asook suur bestande vesel (SBV). Die persentasie verdwyning is by elke inkubasie tydperk bereken vanaf die oorblywende proporsie van die monster na inkubering in die rumen. Dit is bevind dat die gemiddelde degradeerbaarheid van mieliestronke vergelykbaar is met die degradeerbaarheid van hawerhooi. Vier en twintig Suid-Afrikaanse Vleismerino (SA VM) lammers is vir 'n voerkraalafrondings studie gebruik. Die effek van toenemende insluitingsvlakke (4, 8 en 12%) van mieliestronke op individuele voerinname, gemiddelde daaglikse toename (GDT) en voeromsettingsdoeltreffendheid (VOD) is gemonitor. Die skynbare verteerbaarheid van die rantsoene is ook bepaal. Die drie diete was geformuleer op 'n gelyke stikstof en energie basis. Na afloop van die proef is die lammers geslag en die longissimus dorsi, asook biceps femoris spiere van elke karkas is verwyder vir die bepaling van chemiese samestelling en fisiese kwaliteits eienskappe. Dieet het geen betekenisvolle effek op GDT of VOD van die lammers gehad nie. Die dieet met 'n mieliestronk insluitingsvlak van 4% het aanleiding gegee tot lammers met die hoogste stikstofretensie, terwyl energieretensie nie deur dieet belnvloed is nie. Die chemiese samestelling van beide spiere is nie betekenisvol deur die dieet belnvloed, maar wel slegs die kookverlies en kleur van die M. longissimus dorsi. Sestien Suid-Afrikaanse Vleismerino (SA VM) lammers is vir 'n tweede voerkraalafrondings studie gebruik om die effek van 'n dieet wat aangevul is met 'n rumen-beskermde CLA, te evalueer. Dieselfde proefprosedure as tydens die eerste afrondingsproef is gevolg, behalwe vir die addisionele/bykomende sensoriese, sowel as vetsuur analises. Geen betekenisvolle verskille het voorgekom vir GDT, VOD en uitslag persentasie van die lammers nie. Beide energie en stikstofretensies is ook nie deur die dieet be1nvloed nie. Cherniese samestelling van beide spiere was soortgelyk, maar dieet het wel 'n betekenisvolle effek op kookverlies en kleur van die M. longissimus dorsi gehad. Dieet het geen betekenisvolle effek op enige van die vyf sensoriese eienskappe van die vleis teweeg gebring nie. Vetsuursamestelling van die vleis was betekenisvol be"invloed as gevolg van die CLA aanvulling in die dieet. Palmitiensuur (C16:0), steariensuur (Cl8:0) en ole"iensuur (18:1n-9) het die grootste proporsie van die vetsure in beide spiere uitgemaak, asook in al drie die vetdepots. Die rumenbeskermde CLA het die CLA (Cl8:2n-6) inhoud van beide die spier tipes verhoog, alhoewel die verhoging slegs betekenisvol vir die M. longissimus dorsi was.

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