Evaluation of the South African small stock genetic resources for production and meat quality traits

Cloete, Jasper Johannes Erasmus (2007-03)

Thesis (PhD (Agric)) -- University of Stellenbosch, 2007.

Thesis

ENGLISH ABSTRACT: The study includes separate papers, which are all linked by their emphasis on the evaluation of South African small stock genetic resources for production and meat quality. This abstract is intended to provide readers with a broad overview of the outcomes of the study. Part 1: Comparison of breeds Chapter 2 dealt with the slaughter and meat quality traits of wool (Merino), dual-purpose (Dohne Merino and South African Mutton Merino (SAMM)) and meat type (Dormer) sheep. The more expensive retail cut weights were higher in the meat type sheep but the latter breeds also had a thicker fat cover. Dormer and SAMM sheep had heavier but fatter carcasses than Merinos and Dohne Merinos, with no marked differences in meat quality among breeds. Chapter 3 provides production parameters obtained from Merino, Dohne Merino and SAMM stud flocks. An economic simulation indicated differences in gross income per small stock unit between the breeds. Merinos generally outperformed the other two breeds in terms of income per small stock unit. In Chapter 4, Dorper, Merino and Boer Goat breeds were compared on reproduction potential. Reproduction and growth of the three breeds were comparable with figures found in the literature. An economical analysis indicates that Merino ewes outperformed the other two breeds in terms of income per small stock unit. Part 2: Assessment of Merino and Merino type ewe breeds as terminal dam lines Chapter 5 details the production performance of ewes that originated from a terminal crossbreeding experiment that involved five Merino type dam lines and two terminal crossbreeding sire lines (Dormer and Suffolk). In Chapter 6 slaughter data and meat quality of the crossbred progeny were compared and discussed. Differences between progeny in slaughter age, marketing weight, dressing percentage and carcass weight could largely be attributed to the comparison of purebred Merino lines with dual-purpose lines. In Chapter 7 an economic simulation indicated large differences in gross income per small stock unit between ewe lines. Chapter 8 provides details of slaughter traits of lambs born from a terminal crossbreeding experiment that involved Merino ewes crossed with Dormer, Ile de France, Merino Landsheep, Suffolk and Dorper rams, purebred Merinos were used as control. No conclusive advantages in favour of any of the terminal sire breeds were obtained. Part 3: Importance of carcass quality using leaner sire breeds on early maturing Dorpers In Chapter 9 Dorper ewes were crossed with Ile de France, Merino Landsheep and SAMM rams to produce lean carcasses without sacrificing growth performance. Terminal crossbred lambs were equal to or superior to purebred Dorpers with regard to quantitative and qualitative carcass parameters evaluated (Chapter 10). SM2000 economic simulation model was used to assess the economic output of the respective breed combinations and discussed in Chapter 11. No real differences were found for income per small stock unit between the different crossbred combinations and purebred Dorper lambs. Terminal crossbreeding could thus be implemented in commercial Dorper flocks, without compromising productivity and/or product quality. Implications The study revealed marked differences in the performance of the breeds contributing to the South African small stock genetic resource. As with other experiments with finite monetary and animal resources, animal numbers (and especially those of sires sampled to represent a breed) were relatively low. Further studies on the evaluation of the South African small stock genetic resource is indicated. Studies on the integration of sheep breeds in structured crossbreeding systems should have a high priority, since it appears to be a sustainable way to ensure economic viability of commercial small stock production.

AFRIKAANSE OPSOMMING: Die tesis bestaan uit aparte artikels wat almal verband hou met die belangrikheid van die evaluasie van Suid -Afrikaanse kleinvee genetiese bronne vir produksie en vleiskwaliteit. 'n Opsomming van die artikels het dus ten doel om die Jeser 'n bree perspektief oor die uitkomste van die studie te voorsien. Deen 1: Vergelyking tussen rasse Hoofstuk 2 handel oor die slag- en vleiseienskappe van wol (Merino), dubbeldoel (Dohne Merino en .' Suid-Afrikaanse Vleis Merino (SA VM)) en vleistipe (Dormer) skape. Die duurder snitte was swaarder in die vleistipe rasse en die vleistipes het ook meer onderhuidse vet gehad. Daar is gevind dat Dormer en SA VM skape swaarder en vetter as Merino's en Dohne Merino's was, met geen duidelike verskille in vleiskwaliteit tussen die rasse nie. Hoofstuk 3 verskaf inligting oor produksie-eienskappe, afkomstig van Merino, Dohne Merino en SA VM stoetkuddes. 'n Ekonomiese ontleding het aangedui dat die inkomste per kleinvee-eenheid tussen die drie rasse verskil het. Merino's het in terme van inkomste per kleinvee-eenheid oor die algemeen 'n hoer inkomste as die ander twee rasse gelewer. Hoofstuk 4 handel oor 'n vergelyking tussen Dorper, Merino en Boerbokke in terme van reproduksiepotensiaal. Reproduksie- en groeiresultate van die drie rasse is in ooreenstemming met syfers in die literatuur. 'n Ekonomiese ontleding het aangedui dat inkomste per kleinvee-eenheid van Merino-ooie hoer was as die ander twee rasse. Deel 2: Ondersoek van Merino en Merino tipe ooie as 'n terminate moederlyn Hoofstuk 5 handel oor die produksievermoe van ooie en lammers afkomstig uit 'n terminale kruisteeltproef met vyf Merinotipe ooilyne en twee terminale kruisteelt ram rasse (Dormer en Suffolk). In Hoofstuk 6 word slagdata en vleiskwaliteit van die kruisteeltnageslag vergelyk. Die nageslag van suiwer Merino- en dubbeldoellyne het in terme van slagouderdom, bemarkingsgewig, uitslagpersentasie en karkasgewig verskil. In Hoofstuk 7 dui 'n ekonomiese ontleding aan dat daar groot verskille tussen ooilyne is, i.t.v. inkomste per kleinvee-eenheid. v Stellenbosch University https://scholar.sun.ac.za Hoofsuk 8 verskaf inligting oor slageienskappe van lammers van 'n kruistelingsproef waartydens Merino-ooie met Dormer-, lie de France-, Merino Landskaap- , Suffolk- en Dorperramme gekruis is. Suiwer Merinoramme is as kontrole gebruik. Geen duidelike voordele ten gunste van enige van die tenninale ramrasse is gevind nie. Deel 3: lBelangrikheid van karkaskwaliteit deur gebruik te maak van maerder ramrasse gekruis met vroegryp Dorperooie In Hoofstuk 9 word Dorperooie in 'n terminate kruisteeltstelsel gepaar met lie de France- , Merino Landskaap- en SA VM ramme om karkasse te produseer sonder om groei in te boet. Daar is gevind dat tenninale kruisteeltlammers dieselfde of beter as suiwer Dorperlammers gevaar het met verwysing na kwalitatiewe en kwantitatiewe karkaseienskappe (Hoofstuk 10). SM2000 ekonomiese simulasiemodel is gebruik om 'n ekonomiese uitkoms te verkry van die verskillende raskombinasies en word in Hoofstuk 11 bespreek. Geen betekenisvolle verskille is gevind vir inkomste per kleinvee-eenheid tussen die verskillende kruisteeltkombinasies en suiwer Dorperlammers nie. Tenninale kruisteling kan dus gebruik word in kommersiele Dorperkuddes sonder om produktiwiteit of produkkwaliteit te belnvloed. [mplikasies Die studie toon duidelike verskille in die produksie- en reproduksievermoe van verskillende rasse om bydrae tot die genetiese materiaal van die Suid Afrikaanse kleinveebedryf te maak. Soos met antler proewe met beperkte geld en natuurlike hulpbronne was die aantal diere, veral ten opsigte van die aantal ramme wat gebruik is om 'n ras te verteenwoordig, relatief laag. Verdere studies oor die evaluasie van die SuidAfrikaanse kleinvee genetiese hulpbronne is egter nodig. Studies oor die integrasie van verskillende skaaprasse in gestruktureerde kruistelingstelsels blyk 'n hoe prioriteit te wees, omdat dit voorkom of dit 'n manier is om volhoubaar en ekonomies met kleinvee te boer .

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