Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Genetic (co)variances for body weight, clean fleece weight and fibre diameter were estimated for the South African Dohne Merino using data transformed as proportions of contemporary group means. The data analysed included body weight, clean fleece weight and fibre diameter records for 282 513 animals, evaluated between 1992 and 2011. There were 5 698 sires, 105 886 dams and 6 291 contemporary groups in the data. A three-trait animal model was fitted, where the random variables were the direct additive genetic effects, as well as the sire-flock-season (SFS) interaction, while the fixed effects included contemporary groups (FYSSM) (6 291 classes), birth status (single, twins or triplets), age of dam (1 to 3 years), which was plotted as a linear regression as well as age at performance measurement, which was fitted as a polynomial. The direct heritability estimates (SE) for body weight, clean fleece weight and fibre diameter were 0.265 (0.005), 0.210 (0.004) and 0.437 (0.005), respectively. Genetic correlations for body weight with clean fleece weight and fibre diameter were 0.035 (0.015) and 0.139 (0.011), respectively, while the genetic correlation between clean fleece weight and fibre diameter was 0.169 (0.012). Body weight had phenotypic correlations of 0.327 (0.002) and 0.150 (0.002), respectively, with clean fleece weight and fibre diameter, which had a phenotypic correlation of 0.190 (0.002) with clean fleece weight. The moderate to high heritability estimates suggests that there is substantial genetic variation, which may result in genetic improvement if selection is applied on these traits. Genetic correlations were generally low, suggesting that progress in all these traits was possible in a scientific selection program. Genetic trends derived during the study supported the contention that genetic progress in all traits was attainable in a well-constructed breeding programme. Transformation of the data to percentages of contemporary groups resulted in adjustments to breeding values. The breeding values for sires originating from flocks maintained in limiting environments (Low group; 180 sires) were adjusted upwards, while those of sires originating from a non-limiting production environment (High group; 146 sires) were adjusted downwards. These effects were markedly obvious for the quantitative traits (body weight and clean fleece weight), but to a much lesser extent for fibre diameter. This transformation resulted in the genetic trends for the Low groups being adjusted to be comparable to those in the High group for body weight and Fibre diameter. It was concluded that sire breeding values derived from transformed data would be more robust across the typical diverse environments supporting local Dohne Merino production. The genetic value of animals entering the recorded population from a commercial base (F4 animals) was below the fully recorded part of the population. The inclusion of phantom parent groups in the genetic analysis rendered genetic trends in F4 animals comparable to that of the pedigreed portion of animals in the analyses. It was concluded that animals from a commercial base (which are alleged to have advantages in terms of fitness and robustness) were more likely to perform satisfactorily for selection with the inclusion of phantom groups than without it. It was recommended that data in the national Dohne Merino analysis be transformed proportion of contemporary group means to account for heterogeneous contemporary group variances. Phantom parent groups should also be applied to the analysis to increase the probability of those animals entering the breeding flock from a commercial base being selected. / AFRIKAANSE OPSOMMING: Genetiese kovariansies vir liggaamgewig, skoonvaggewig en veseldikte is vir die SA Dohne Merino bevolking in Suid-Afrika beraam nadat data getransformeer as ‘n proporsie van die kontemporêre groep gemiddelddes uitgedruk is. Die data het rekords in van liggaamsgewig, skoonvaggewig en veseldikte van 282 513 diere oor die tydperk van 1992 tot 2011 ingesluit. Die data sluit rekords van 5 698 vaars, 105 886 moers en 6 291 kontemporêre groepe in. 'n Meer-eienskapdieremodel met 'n additiewe diere-effekte sowel as 'n vaar-kudde-seisoen (SFS) interaksie is as ewekansige effekte gemodelleer, bykomstig tot die vaste effekte van kontemporêre groep (FYSSM) (6 291 klasse), geboortestatus (enkelling, tweeling of drieling), ouderdom van moer (1 tot 3 jaar) gepas as 'n lineêre regressive, sowel as ouderdom by prestasie meting as ‘n polinoom gepas. Die beraamde direkte oorerflikheid (SF) van liggaamgewig, skoonvaggewig en veseldikte van die meereienskap dieremodel was onderskeidelik 0,265 (0,005), 0,210 (0,004) en 0,437 (0,005). Die genetiese korrelasies van liggaamsgewig met skoonvaggewig en veseldikte was 0,035 (0.015) en 0,139 (0.011) onderskeidelik, terwyl die genetiese korrelasie tussen skoonvaggewig en veseldikte 0,169 (0.012) beloop het. Liggaamsgewig het onderskeie fenotipiese korrelasies van 0,327 (0.002) en 0.150 (0.002) met skoonvaggewig en veseldikte gehad, terwyl skoonvaggewig ‘n fenotipiese korrelasie van 0.190 (0.002) met veseldikte gehad het. Die medium tot hoë oorerflikheidhede dui daarop dat daar aansienlike genetiese variasie voorkom, wat kan aanleiding gee tot genetiese vordering as seleksie op die eienskappe toegepas word. Genetiese korrelasies was oor die algemeen laag wat daarop dui dat vordering in al die eienskappe deur ‘n wetenskaplike seleksie program moontlik is. Die aanspraak is deur genetiese tendense in die studie bevestig. Die transformasie van data na proporsies van kontemporêre groep gemiddeldes het daartoe gelei dat teelwaardes aangepas word. Die teelwaardes van vaars uit kuddes met ‘n omgewing wat beperk word (Lae groep:180 vaars), is opwaarts aangepas. Daarenteen is vaars uit 'n nie-beperkende produksie omgewing (Hoë groep:146 vaars) se teelwaardes afwaarts aangepas. Hierdie effekte was veral ooglopend vir die kwantitatiewe eienskappe, liggaamgewig en skoonvaggewig, maar tot 'n mindere mate vir veseldikte. Die transformasie het daartoe gelei dat die genetiese tendense for die Lae groep aangepas word om vergelykbaar te wees met die Hoë groep vir liggaamsgewig en skoonvaggewig. Die gevolgtrekking was gemaak dat meer toepaslike vaar teelwaardes, bereken vanaf getransformeerde data, verkry word vir regoor die diverse omgewings wat produksie van plaaslike Dohne Merinos ondersteun. Die genetiese waarde van diere wat die aangetekende populasie uit ‘n kommersiële agtergrond (F4 diere) binnekom was laer as die volledig aangetekende gedeelte van die populasie. Die insluiting van skimgroepe in die genetiese ontleding het tot genetiese tendense gelei wat die F4 diere vergelykbaar gemaak het met diere in die ontleding wat wel stamboekinligting het. Die gevolgtrekking is gemaak dat diere van ‘n kommersiële agtergrond (wat aanvaar word om voordele in te hou in terme van fiksheid en robuustheid) meer geredelik geselekteer sal word vir die stoet met die insluiting van skimgroepe as daarsonder. Dit word aanbeveel dat die data in die Nasionale Dohne Merino na proporsies van die kontemporêre groepgemiddeldes getrensformeer word om vir heterogene kontemporêre groep variansies voorsiening te maak. Skimgroepe moet ook gepas word in die ontleding om die waarskynlikheid te verhoog dat diere vanuit 'n kommersiële basis, ook geselekteer sal word.

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aim of this study was to investigate the impact of an extensive (free-range) and intensive (feedlot) production system on the consumer’s intrinsic preference cues (physical attributes, chemical composition, fatty acid profile, aroma, flavour, initial juiciness, sustained juiciness, first bite, residue, instrumental tenderness) for three muscles (Biceps femoris, Longissimus dorsi, Semimembranosus) of Dohne Merino lambs (8 months). Secondly to investigate the effect of natural exercise (grazing, extensive production systems) or restrictive movement (intensive production systems), on the muscle fiber type composition of the same lamb muscles and the subsequent effect on the meat quality characteristics. Intensively raised lambs produced carcasses with a significantly higher dressing percentage, thicker subcutaneous fat layer (13th rib and 3rd/4th lumbar vertebra) and a greater fat ratio (carcass composition). Meat of intensively raised lambs had a higher (p < 0.050) Homo-glinolenic (C20:3n6), Eicosapentaenoic (C20:5n3), Docosapentaenoic acid (C22:5n3) content and n3:n6 ratio. Extensively reared lambs had a higher (p < 0.050) slaughter weight, cold carcass weight and the meat of these lambs had a higher myoglobin content. Results of this study indicate that intensively reared lambs produced meat with more favourable sensory characteristics compared to the extensive production system as well as a significant increase in sensory tenderness for Biceps femoris muscle. Overall the Biceps femoris muscle was the muscle that was primarily affected by the treatment (production systems). The Biceps femoris from intensively raised lambs contained significantly more intramuscular fat and type IIB muscle fibers whereas the Bicpes femoris of the lambs from the extensive production system contained more (p < 0.050) insoluble collagen and type I muscle fibers. During texture profile analysis (instrumental tenderness test) the Longissimus dorsi and Semimembranosus of extensively raised lambs required a higher (p < 0.050) compression force during the first cycle of compression, indicating that these muscles are tougher. The results of this study provided valuable insight into the impact of production systems on lamb meat quality and that the application of intensive production systems will increase the sensory characteristics of the selected muscles from Dohne Merino lambs, especially the tenderness of the Biceps femoris, which has a high retail value. On the other hand health conscious consumers will prefer extensively produced meat due to the favourable n3:n6 ratio, intramuscular fat content and the presences of less visible fat (subcutaneous). / AFRIKAANSE OPSOMMING: Hierdie studie was tweedoelig en is uitgevoer op die Biceps femoris, Longissimus dorsi en Semimembranosus spiere van Dohne Merino lammers (8 maande oud). Die eerste doel van die studie was om te bepaal wat die effek van ‘n ekstensiewe (weiding) en intensiewe produksie sisteem sal wees op vleis verbruikers se algemene kwaliteit voorkeure (fisiese eienskappe, chemiese samestelling, vetsuur profile, aroma, smaak, sappigheid, taaiheid,). Tweedens om te bepaal tot watse mate natuurlike oefening, verkry deur weiding asook beperkte beweging as gevolg van voerkraal omstandighede, die spier vesel tipe samestelling sal verander en die direkte impak van die samestelling op kwaliteit eienskappe van vleis. Lammers van die intensiewe produksie sisteem het ‘n betekenisvolle verhoging in uitslagpersentasie, onderhuidse vet dikte (13de rib en 3de/4de lende werwel) en vet ratio (karkas samestelling) getoon. Die vleis van die lammers het meer (p < 0.050) C20:3n6, C20:5n3 en C22:5n3 vetsure bevat asook ‘n hoër n3:n6 ratio gehad. Lammers van die ekstensiewe produksie sisteem het ‘n betekenisvolle hoër slag en koue karkas gewig gehad. Die vleis van die lammers het meer (p < 0.050) mioglobien bevat as intensiewe lammers. Resultate van die studie dui aan dat die vleis van lammer van die intensiewe produksie sisteem meer gunstige sensories karakteristiek produseer in vergelyking met lammers van die ekstensiewe produksie sisteem, asook ‘n betekenisvolle verhoging in sensoriese sagtheid van die Biceps femoris spier. Die Biceps femoris was die spier in die studie wat die meeste geaffekteer was deur die behandeling (produksie sisteme). Die Biceps femoris spier van intensiewe lammers het meer intramuskulêre vet en tipe IIB spier vesels bevat teenoor die Biceps femoris van ekstensiewe lammers wat meer onoplosbare kollageen en tipe I spier vesels bevat het. Gedurende die tekstuur profiel analise (instrumentele sagtheid toets) het die Longissimus dorsi en Semimembranosus van ekstensiewe lammers a hoër kompressie krag vereis, wat aandui dat die spiere taaier is as die ooreenstemmende spiere van intensiewe lammers. Die resultate van die studie voorsien ons met waardevolle insig in die inpak van verskeie produksie sisteme op die kwaliteit van lams vleis. Die afleiding kan gemaak word dat die implementering van intensiewe produksie sisteem die sensoriese kwaliteit van die spiere van Dohne Merino lammers verbeter, veral die sagtheid van die Biceps femoris spier, wat ‘n hoë kommersiële waarde het. Laastens, gesondheidsbewus verbruikers sal verkies om vleis te koop van ekstensiewe lammers weens die gunstige n3:n6 ratio, spier vetinhoud en die minder sigbare vet (onderhuidse vet) op die vleis.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The objective of this study was to evaluate Dohne Merino sheep and Boer goats in terms of the degradable parameters of a high-fibre diet, a low-fibre diet and two vegetable protein sources commonly used in South Africa. Differences between species were evaluated following the potential differences within species. The feedstuffs used were those for the following diets: low-fibre diet (LF); high-fibre diet (HF); sunflower meal (SFM) oilcake; and soybean meal (SBM) oilcake. In the first trial, the digestible characteristics of the HF and LF diets were determined by means of a digestibility study. A 6 × 6 Latin square design was used to determine whether Dohne Merino sheep or Boer goat wethers differ regarding the digestibility characteristics of low- and high-fibre diets. The diets were fed once daily at 1.24 kg to all the wethers, which had ad libitum access to fresh water. Each period consisted of 10 days of adaptation and seven days of faecal and urinary sampling. The results indicated that the intake and digestibility characteristics of nutrients did not differ between sheep and goats. However, the different diets differed in terms of the nutrient intake and digestibility range of sheep and goats. The second trial was an in sacco degradability trial to determine the dry matter (DM) and crude protein (CP) degradability of the LF, HF, SBM and SFM diets. Six Dohne Merino and six Boer goat wethers were fitted with rumen cannulae so that they could be used in the trial. All wethers received the same basal diet. The samples were incubated in the rumen in polyester Dacron bags, with the bags being removed at intervals of 0h, 3h, 9h, 12h, 24h, 48h, 72h, and 96h for the LF and HF diets. All the oilcake was removed at intervals of 0h, 2h, 4h, 8h, 12h, 16h, 24h, 36h and 48h. The sheep and goats were found not to differ from one another in terms of effective degradability of any of the feedstuffs concerned. However, within species differences were observed. To establish a fully integrated outcome of degradability, the study described in the current thesis was structured in such a way that the in vitro trial ran parallel with the in sacco trial, being performed with the aid of a Daisy Incubator (ANKOM Technology Corp., Fairport, NY). Such a procedure was only adopted in relation to the SFM and SBM diets in order to evaluate their in vitro data in relation to the in sacco data. The same oilcake was tested in the case of both trials, with the composite sample of rumen liquid of four sheep or goats, which was used in the in sacco trial, also being used in the in vitro study. In the study, DM disappearance values were determined and fitted to a single-compartment model by means of an iterative least-square procedure in order to determine the DM and CP degradability parameters. The DM used in vitro or in sacco was compared, using the actual values obtained after 8h incubation, due to only a limited amount of residue being left after incubation. In the study, the in vitro method overestimated the digestibility of SBM by 37% to 39% and the digestibility of SFM by 17% to 20% compared with that found to occur in the in sacco method. In vitro DM disappearance values for all SBM samples were found to be higher than those that were detected in the SFM samples. The percentage of in vitro true digestibility parameters was also calculated. No significant differences were found between species for effective degradability, though differences were observed within species between the two substrates concerned. In conclusion, the sheep and goats used in the study were not found to differ in terms of digestion parameters when they were compared on different types of roughage or protein sources. However, within species differences were, indeed, found to occur. Sheep and goats digested the SBM better than they did the SFM. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om te bepaal of Dohne Merino skape verskil van Boerbokke in terme van degradeerbaarheidsparameters van ‘n hoë vesel-, ‘n lae veseldieët en twee plantaardige proteïenbronne wat algemeen in Suid-Afrika gebruik word. Die verskille tussen spesies is ge-evalueer en daarna die potensiële verskille binne spesies. Die volgende grondstowwe is geëvalueer: ‘n laevesel-dieët (LF), ‘n hoëvesel-dieët (HF), sonneblom-oliekoekmeel (SFM) en sojaboon-oliekoekmeel (SBM). In die eerste proef is die degradeerbaarheidsparameters van die HF dieët en die LF dieët met behulp van ‘n verteerbaarheidstudie bepaal. Dohne Merino hamels of Boerbok kapaters was gebruik om te bepaal of skape en bokke verskil in terme van inname en degradeerbaarheid van voedingstowwe wanneer hul hoë- en lae vesel voere gevoer word. Al die hamels en kapaters het ad libitum toegang tot vars water gehad en hul was een keer per dag (1.24 kg) gevoer. Elke periode het bestaan uit ‘n 10 dag aanpassingsperiode en ‘n toegelate 7 dae vir mis- en urienmonster versameling. Die resultate het aangedui dat die inname- en degradeerbaarheidsparameters van nutriënte beinvloed word deur verskillende diëte binne spesies. Geen verskille is gevind tussen spesies wanneer daar hoë- en lae kwaliteit voere gevoer is nie. Die tweede proef was ‘n in sacco-degradeerbaarheidsstudie om te bepaal wat die droë materiaal (DM) en ruproteïen (RP) verteerbaarheidsparameters van die HF dieët, die LF dieët, die SBM en die SFM is. Ses Dohne Merino’s en ses Boer bokke met rumen kanullas is in die studie gebruik en al die diere het dieselfde basale dieët ontvang. Die monsters is in die rumen geïnkubeer in poliester dakronsakkies en die sakkies is verwyder na onderskeidelik 0 uur, 3 uur, 9 uur, 12 uur, 24 uur, 48 uur, 72 uur en 96 uur intervalle. Laasgenoemde intervalle was geldig vir die lae vesel- en hoëveseldieët. Die oliekoeke se intervalle het verskil en is verwyder na 0 uur, 2 uur, 4 uur, 8 uur, 12 uur, 16 uur, 24 uur, 36 uur en 48 uur. Daar was geen verskille tussen spesies in effektiewe degradeerbaarheid nie, alhoewel verskille voorgekom het binne spesies. Skape verteer veselagtige grondstowwe meer effektief terwyl bokke weer hoë proteïn bevattende grondstowwe beter verteer. Om ‘n volkome geïntegreede uitkoms van degradeerbaarheid te bewerkstellig is die in vitro proef en die in sacco proef gelyktydig gedoen. Die in vitro-degradeerbareheidstudie is met behulp van ‘n ANKOM Daisy Inkubeerder uitgevoer (ANKOM Tegnologie Korp., Fairport, NY) vir net die oliekoek behandelings. Gedurende die studie is dieselfde oliekoeke gebruik. ‘n Saamgestelde monster van die rumenvloeistof van vier van die skape of bokke wat vir die in sacco-studie gebruik was, is gebruik vir die in vitro-inkubasie van die monsters. DM verdwyningparameters is bereken en dan met ‘n interaktiewe kleinste kwadraat prosedure op ‘n een-kompartement model gepas om die in sacco DMdegradeerbaarheidsparameters te bepaal. Die DM verdwyning, na 8h inkubasie, was gebruik om die in vitro en die in sacco metodes met mekaar te vergelyk, weens ‘n beperkte residu na die afloop van die elke inkubasiestudie. Tydens die studie het die in vitro metode degradering oorskat in vergelyking met die in sacco metode. DM verdwyningswaardes vir al die SBM monsters was hoër in vitro as die SFM monsters. In die studie is die persentasie in vitro ware degradeerbaarheidswaardes bereken. Geen verskille is opgemerk tussen spesies vir effektiewe degradeerbaarheid nie. Daar was wel verskille binne spesies. Om af te sluit het dit voorgekom dat skape en bokke nie verskil aan degradeerbaarheidswaardes wanneer daar ‘n vergelyking was tussen verskillende vesels- en proteϊenbronne nie, alhoewel verskille voorgekom het binne spesies. Skape en bokke het SBM effektief beter verteer as SFM.