Thesis (M. Ag.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 20-21). Also available on the World Wide Web.

Mycoplasmas are prokaryotic micro-organisms belonging to the class Mollicutes, which lacks rigid cell walls. Their genomic size ranges from 500-1500 bp. It causes a wide variety of different diseases in small ruminants and in particular ulcerative balanitis and vulvitis that affects Dorper Sheep in South Africa. The disease causes high economic losses to the Dorper sheep breeders in South Africa. The presence of the disease has been known in South Africa since 1979. Earlier publications have identified the causative agent of this disease as Mycoplasma mycoides mycoides LC (MmmLC). However, several Mycoplasma organisms isolated from cases of ulcerative balanitis have been shown not to be MmmLC. There is a need to characterize the organisms isolated from sheep suffering from this disease using conventional and genetic molecular methods. In this study, 16SrRNA gene-based PCR assays and gene sequencing was used for the detection and characterization of Mycoplasma species from cases of ulcerative vulvovaginitis and balanoposthitis in Dorper sheep in South Africa. This investigation was conducted on 34 stored field isolates of mycoplasmas collected between 2003-2009 from 15 different farms in the Northern and Western Cape provinces of South Africa. The isolates were screened and characterized by means of microbiological culture and biochemical methods and confirmed by PCR and sequencing. Evidence of involvement of these Mcoplasma idolates in ulcerative vulvovaginitis and balanoposthitis was obtained from the submission histories. All 34 isolates were analysed by means of PCR, cloning and sequencing of a 1 078 bp fragment length of 16S a rRNA gene and identified as Mycoplasma species. BLAST searches for sequence similarity from Genbank data revealed 18 isolates out of 34 four are 99 % similar to M. arginini, six out of 34 are 99 % similar to M. bovigenitalium, and two out of 34 were found to be 99 % similar to M. sp. ovine/caprine serogroup II. Two isolates out of 34 are 99 % similar to A. Laidlawii, and BLAST searches of two isolates gave 99 % similarity to M. sp. USP120. Two isolates were found to be 99 % similar to synthetic M. mycoides mycoides Jvc1. A last isolate gave 99 % similarity to M. canadense. Phylogenetic trees were drawn using the neighbour joining method and maximum parsimony analysis to compare the South African isolates with other GenBank reference strains to determine relationships between South African isolates with isolates in other parts of the world. This thesis is composed of five chapters. The first chapter deals with the historical background of ulcerative vulvovaginitis and balanoposthitis in Dorper sheep in South Africa and comparisons with findings from previous research. The chapter ends with the aims and objective of this research project. Chapter two contains a literature review that deals with ulcerative vulvovaginitis and balanoposthitis in various parts of the world and controversy about the views of researchers about the aetiology of ulcerative vulvovaginitis and balanoposthitis in sheep. Chapter three presents the first research on molecular characterization of mycoplasmas species isolated from cases of ulcerative vulvovaginitis and balanoposthitis in Dorper sheep in South Africa by means of PCR and gene sequencing. Chapter four provides the findings of the analyses of the various Mycoplasma species that were involved in ulcerative vulvovaginitis and balanoposthitis in Dorper sheep in South Africa. The chapter also gives the results of phylogenetic analysis of the various Mycoplasma species with their relationship to sequences from all over the world deposited by researchers in Genbank. Chapter five summarizes the research findings and provides conclusions. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Veterinary Tropical Diseases / unrestricted

Thesis (PhD (Animal Sciences))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The Dorper sheep breeders developed their own linear type scoring system based on a 5-point scale which assesses Conformation, Size, Type, Fat distribution and Colour. For many decades Dorper sheep breeders have been so consistent with adherence to these breed standards without paying much attention to performance testing of their stud animals. However, there is a paucity of information pertaining to the genetic relationships between visually assessed traits and objectively measured growth, reproduction and fitness traits in the breed. Slow genetic gains in Dorper production traits are assumed to be caused by over-accentuation of type traits but those assumptions needed to be scientifically validated. It was therefore vital to derive these relationships as they could have a negative impact on genetic progress in the event that some antagonisms existed. Against this background, the major objectives of this study were to estimate genetic parameters and trends for production, reproduction, fitness and subjective traits using data extracted from National Small Stock Improvement Scheme (NSIS). Furthermore, the study correlated performance data with subjectively assessed traits to derive genetic relationships between them to establish the effect of selecting Dorper sheep on breed standards has on objective traits of economic importance. Genetic parameters and relationships were estimated for subjectively assessed and objectively measured traits using linear and threshold methods. Linear methods were applied via the implementation of Residual Maximum Likelihood (REML) procedures and Bayesian methods were implemented through Gibbs sampling. It was established through the implementation of single-trait and multi-trait analyses that live weight and growth traits were moderately to highly heritable. Maternal effects were also significant for such traits. Subjectively assessed traits were demonstrated to be lowly to moderately heritable using both linear and threshold methods. There were positive genetic and environmental correlations between live weight, growth and subjectively assessed traits with the exception of Colour. There was favourable selection response to live weight and growth traits in a Dorper flock, with the exception of average daily gain during the post weaning phase where there was a slight negative trend. Subjectively assessed traits with the exception of Size responded favourably to selection. It was concluded that breeders should consider removing Colour from their breeding objectives, and focus more on selecting animals based on BLUP breeding values of objectively measured traits. The across flock genetic evaluation of all Dorper records demonstrated through the implementation of both linear and threshold methods that reproduction and fitness traits were lowly to moderately heritable and exhibited favourable genetic correlations amongst themselves. It was further established that ewe rearing ability, ewe stayability and ewe productive life are lowly heritable and have some favourable correlations with component traits of reproduction. There was little genetic change in reproduction and fitness traits, but traits generally deteriorated where significant trends were found. It was concluded that breeders should select their animals on objectively measured production and reproduction traits and not put as much emphasis on breeding standards. / AFRIKAANSE OPSOMMING: Die Dorper skaaptelers het hul eie liniêre puntestelsel ontwikkel wat op ‘n 5-punt skaal bouvorm, grootte, tipe, vetverspreiding en kleur beoordeel. Dorper skaaptelers se fokus was vir baie dekades om hierdie rasstandaarde na te kom, sonder om aandag te gee aan die prestasietoetsing van hul stoetdiere. Rasverbetering in die Dorperskaapras is gebaseer op subjektiewe beoordeling van eienskappe soos dit in die skouring bepaal word. Daar is egter ‘n gebrek aan inligting aangaande genetiese verwantskappe tussen visueel beoordeelde eienskappe en objektiewe eienskappe soos groei, reproduksie en fiksheid. Dit word aangeneem dat stadige genetiese vordering in produksie-eienskappe van Dorpers deur ‘n oorbeklemtoning van tipe eienskappe veroorsaak word, maar hierdie aannames moet wetenskaplik bewys word. Daarom is dit uiters belangrik om die verwantskappe tussen subjektiewe en objektiewe eienskappe te bepaal, aangesien hulle ‘n moontlike negatiewe effek op genetiese vordering mag uitoefen as daar wel antagonismes bestaan. Teen hierdie agtergrond is die hoofdoelwitte van hierdie studie om prestasiedata vanuit die Nasionale Kleinveeverbeteringskema (NSIS) te onttrek en die beraming van genetiese parameters en tendense vir produksie, reproduksie, fiksheid en subjektiewe eienskappe. Verder het hierdie studie prestasiedata met subjektiewe beoordeelde eienskappe gekorreleer om genetiese verwantskappe tussen subjektiewe en objektiewe eienskappe te bepaal. Genetiese parameters en -verhoudings was beraam vir subjektief beoordeelde en objektiewe gemete eienskappe met die gebruik van lineêre- en drumpelwaardemetodes. Lineêre metodes is toegepas d.m.v die implementering van Residuele Maksimum Waarskynlikheid (REML) prosedures en die Bayesiaanse metodes deur Gibbs steekproefneming. Dit is bevestig dat dat liggaamsgewig en groei-eienskappe matig tot hoog oorerflik is. Maternale-effekte het ook ‘n beduidende invloed op hierdie eienskappe gehad. Subjektiewe eienskappe is laag tot matig oorerflik, volgens beide lineêre en drempelwaarde metodes. Daar was positiewe genetiese- en omgewingskorrelasies tussen liggaamsgewig, groei en subjektiewe eienskappe, met die uitsondering van kleur. Daar was ‘n gunstige seleksie respons vir liggaamsgewig en groei-eienskappe met die uitsondering van gemiddelde daaglikse toename gedurende die na-speense fase wat ‘n afname in die gemiddelde voorspelde teelwaardes getoon het. Subjektiewe eienskappe, met die uitsondering van grootte, het in die studietydperk geneties verbeter. Die gevolgtrekking is dat telers dit moet oorweeg om kleur (subjektiewe eienskap) van hul teeldoelwitte te verwyder en om diere op BLUP teelwaardes van objektiewe eienskappe moet selekteer. Die genetiese evaluasie van die nasionale kudde het getoon dat reproduksie- en fiksheidseienskappe laag tot matig oorerflik is en gunstige korrelasies onderlings toon. Dit is verder bevestig dat grootmaakvermoë, terughouvermoë en produktiewe leeftyd laag oorerflik is, en sekere gunstige korrelasies met die komponente van reproduksie toon. Daar was geen genetiese verandering in reproduksie en fiksheid eienskappe in die nasionale kudde nie, moontlik omdat geen seleksie toegepas is nie, a.g.v ‘n oorbeklemtoning van rasstandaarde. Die gevolgtrekking is dat telers diere moet selekteer gebaseer op produksie en reproduksie eienskappe, en minder klem lê op rasstandaarde.

The study aims to determine the contribution made by available ram growth- and breed standard parameters on the sale price of auctioned rams in Namibia. These findings serve as an indication of the importance ram buyers place on individual parameters in selecting rams for breeding purposes. It furthermore tries to establish whether scientific measurement for the estimation of ram breeding values takes precedence over subjective appraisal. The analysis of the 100 day and 270 day growth performance of the progeny of selected Veldram tested rams were used to evaluate the accuracy of the estimation of ram breeding values and may serve to validate the proper execution of these Veldram tests.

Thesis (M. Tech.) - Central University of Technology, Free State, 2010 / The objective of this research study was to quantify the differences in average daily gain (ADG), back fat thickness (BFT), eye muscle area (EMA), fat thickness (FT) on different body parts, the feed conversion ratio (FCR) and body dimensions (by means of body measurements) of Dorper lambs exposed to supplemented light. For this study 120 Dorper lambs (115 ± 10 days old) weighing (29.76 ± 5.01kg) were used. The lambs were randomly divided into three homogeneous groups (20 castrated and 20 intact males). The three groups were then exposed to different levels of supplemented light at 145 lux (16h, 24h and normal photoperiod). The animals were fed ad libitum with pellets containing 9.5 MJ ME/kg DM and 12% CP in open pens. The animals were weighed every 7 days while ultrasound scanning of the EMA and the BFT was done at the beginning and the end of the 35 day trial. The ADG, FCR and feed intake (FI) were calculated at the end of the trial. Linear body measurements including shoulder height, body length and heart girth were taken at day 1 and day 35 respectively. All the animals were slaughtered at the end of the trail. The carcasses were then weighed, graded and the FT was measured with a caliper. The final results of the study showed that no significant differences between the three treatment groups (consisting of wethers and rams) in terms of body measurements, ultrasound scanning ADG and FCR could be detected. However, a significant difference was found between the wethers and the rams in the whole trial for ADG. The ADG of the rams exposed to 16 hours of supplemented light was significantly better than the normal photoperiod and the 24 hour light supplementation group.

Published Article / Birth stress is associated amongst other things with a small pelvic surface area in ewes. It is a factor which has far-reaching consequences for the producer. The use of pelvic area size as a selection criterion appears to be promising as pelvic area size is 50-60% heritable. The objective of this study was to develop an instrument that can measure the pelvic area of sheep and to be able to quantify the relationship between pelvic measurements and a number of easy-to-measure body measurements. A pelvis meter was developed and used to measure 322 Dorper ewes (± 12 months old, ± 48kg) and 272 Dorper rams rectally, and to take various body measurements on the same animals. No significant relationship was observed between pelvis measurements and linear body measurements in Dorper ewes or rams. The pelvis meter and measuring technique developed in the study are viewed as usable and accurate aid in measuring the pelvic area.

The aim of this study was to characterise and cryopreserve semen of the indigenous Namaqua Afrikaner breed, and to compare it to that of Dorper and Dohne Merino sheep, whose semen is commercially frozen on a large scale. The study was conducted between January and August 2015. September 2013-born Namaqua Afrikaner (12), Dohne Merino (12) and Dorper (9) rams were used in the study. The rams were kept under kraal conditions with adequate shade, and they received a high protein, high energy diet. Originally it was envisaged to collect semen samples using the artificial vagina (AV) method, which proved to be problematic with the Namaqua Afrikaner rams. Semen samples were subsequently collected twice a week by either AV (Dohne Merino and Dorper) or electro-ejaculation (EE; all three breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each semen sample was diluted with Triladyl® (1:3) and subsequently frozen in liquid nitrogen vapour in straws. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5 ml) from each thawed sample was assessed microscopically for post-thaw motility and percentage live sperm..

Thesis (MScAgric) -- Stellenbosch University, 1993. / ENGLISH ABSTRACT: A model of interdependents that makes provision for the particular needs of dorper sheep farming and is based on the relationship between the main groups of behaviour determined variables, was constructed. This model served as a basis for an interview schedule whereby personal interviews were held with 130 randomly drawn dorper farmers in the summer rainfall area of the Dorperland. Various independent and mediatory variables were examined and in certain cases it was quantified. Thus certain relationships between the needs, aspirations and endeavours of the respondents and their particular personal and environmental factors were determined. The determination of the independent and mediatory variables provide the extension officer with important background information whereby the application/non-application of certain practices as well as the efficiency of practice application are put into perspective. In this respect the findings of this survey serve as an important reference point by which specified extension actions could be evaluated in the future. The effectiveness of practice application is determined on the basis of 5- and 10-point scales as well as a description of what is actually done. In doing this the existence of certain definite differences between the perceptions of the respondent~ concerning the efficiency of praxis application and the assessment of the interviewers, baled on • description of what is actually done, was found. Practice accepta1Ce, • manifested in efficiency is measured on the basis of particular effectivity stMcWds. Thus relationships between the efficiency standards and certain personal, socioeconomical, socia-psychological and biological-technical variables wet"d determined. / AFRIKAANSE OPSOMMING: 'n Model van interafhanklikes wat voorsiening maak vir die eiesoortige behoeftes van dorperskaapboerdery en gebaseer is op die verwantskap tussen die hoofgroepe van gedragsbepalende veranderlikes, is gekonstrueer. Hierdie model het as basis gedien vir 'n onderhoudskedule aan die hand waarvan persoonlike onderhoude met 130 ewekansig gelote dorperboere in die somerreenvalgebied van Dorperland gevoer is. Verskeie onafhanklike en bemiddelende veranderlikes is ondersoek en in sekere gevalle is dit gekwantifiseer. Sodoende is verwantskappe tussen die behoeftes, aspirasies en strewes van die respondente en bepaaIde persoonlike- en omgewingsfaktore van sodanige respondente bepaal. Die bepaling van die onafhanklike- en bemiddelende veranderlikes bied die voorligter belangrike agtergrondinligting op grond waarvan die toepassing/nie-toepassing van bepaalde praktyke asook die doeltreffendheid van praktyktoepassing in perspektief geplaas word. Die mate waartoe sekere praktyke wat met dorperskaapboerdery verband hou toegepas word. is ook bepaal. In hierdie verband dien die bevindinge van hierdie ondersoek as belangrike verwysingspunte aan die hand waarvan bepaalde voorIigtingsaksies in die toekoms geevalueer kan word. Die doeltreffendheid van praktyktoepassing is aan die hand van 5- en 10puntskale. asook 'n omskrywing van wat werklik gedoen word, bepaaI. Sodoende is die bestaan van sekere duidelike verskille tussen die persepsies van die respondente wat betref die doeltreffendheid van praktyktoepassing en die aansIag van opnemers, gebaseer op 'n beskrywing van wat werklik gedoen word, bevind. Praktykaanvaarding, saos dit manifesteer in doeltreffendheid. is aan die hand van bepaalde doeltreffendheidsmaatstawwe gemeet. Sodoende is verwantskappe tussen die doeltreffendheidsmaatstawwe en sekere persoonlike, sosio-ekonomiese, sosio-psigologiese en biologies-tegniese bepaal.

Thesis (MScAgric)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: AN ASSESSMENT OF PERFORMANCE EVALUATION PROCEDURES OF DORPER RAMS UNDER EXTENSIVE MANAGEMENT CONDITIONS. During 1988 to 2000, Dorper rams (n=2565) maintained on the Kalahari Experimental Farm during performance test periods of approximately 180 days, were subjected to evaluation according to specific body measurements and breed standards. The respective body measurements included live weight, shoulder height, body length, body width, scrotal circumference and average daily weight gain (ADG). The measurements were recorded at the beginning and end of each evaluation period. The rams were evaluated visually by breed inspectors and classified according to breed standards. Live weight recorded at the beginning of evaluation periods, was moderate to high, and positively correlated with most of the body measurements recorded in the study. The exception was ADG, which was negatively correlated (-0.25) with live weight. Live weight recorded at the end of evaluation periods was moderately and positively correlated with scrotal circumference (0.57), and highly correlated with body width (0.76). Average daily weight gain was high and positively correlated with live weight (0.63) recorded at the end of the evaluation periods. Large variations within test periods, that could be attributed to age differences and variation between the respective groups of rams, necessitated correction of the data for the effect of year/season. The rams were divided into above- and below average groups according to their weight at the beginning of the test period. Analysis of the growth patterns of rams during the study period, using the adjusted end data, indicated that 75% of the rams remained in their respective groups. This finding supports the above-mentioned positive correlation of 0.58 that was reported for live weight at the beginning and end of evaluation periods. Body measurements recorded at the beginning of the evaluation periods were in most cases moderately to high and positively correlated (P<0.0001) with measurements recorded at the end of the evaluation periods. The exception was ADG, which was low and negatively correlated with the respective body measurements that were recorded at the beginning of evaluation periods. After each body measurement was quantified by the sum of squares, it became evident that year/season had the greatest influence on the body measurements recorded at the end of an evaluation period. Year/season influenced live weight, body width, shoulder height, scrotal circumference and ADG, with the largest effect on live weight and the least influence on ADG (R2 = 31.62). After correction for year/season, the contribution of the respective measurements to live weight recorded at the end of evaluation periods were still in the same order. After a step-wise procedure for adjusted live weight at the end of evaluation periods was performed, it was found that body width contributed the most to live weight. Average daily gain made the third largest contribution, i.e. with respect to body width (largest) and body length (second largest), to corrected live weight recorded at the end of evaluation periods. The high correlations reported between the respective body measurements necessitated the analysis of the data for multi-colinearity to determine whether the partial contribution of the respective body measurements would differ from the initial values. The partial contribution of the respective body measurements, however, was not affected by the analysis. Regression analysis indicated that the respective body measurements and weights recorded at the beginning of evaluation periods decreased significantly (P<0.0001) over the entire period (1988-2000). The largest annual decreases were reported for ADG (- 2.5%) and body width (-1.1%), respectively. The decreases in ADG and body width are indications that Dorper sheep decreased in size during the period of this study. The value of visual appraisal methods therefore need to be seriously considered to determine whether this is a valuable management tool to assess the production performance of Dorper rams under extensive conditions. The influence of corrected body measurements and ADG, i.e. after selection by breed inspectors and according to breed standards, was plotted on scatter plots. The plots indicated that the breed inspectors selected larger and heavier rams throughout. It is however, still the case in the Dorper industry that rams that perform below average are sometimes classified and used as stud breeding material. Body width and shoulder height were the body measurements that received the highest and lowest approval as visual selection criteria, respectively. A possible reason for this is that the tendency of a smaller Dorper sheep can be attributed to the decreasing shoulder height, as the latter is an indication of body frame size. Visual appraisal should therefore be used in conjunction with scientific methods. Optimum size for the Dorper should be established. / AFRIKAANSE OPSOMMING: ‘N BEOORDELING VAN PRESTASIE-EVALUERINGSPROSEDURES VAN DORPERRAMME ONDER EKSTENSIEWE BESTUURSTOESTANDE Dorperramme (n=2565) is vanaf 1988 tot 2000 te Kalahari Proefplaas in prestasietoetstydperke van ongeveer 180 dae onder ekstensiewe toestande volgens sekere liggaamsparameters en rasstandaarde geëvalueer. Die onderskeie liggaamsmates het lewende gewig, skouerhoogte, liggaamsbreedte, liggaamslengte, skrotumomtrek en gemiddelde daaglikse toename (GDT) ingesluit. Die parameters is aan die begin en einde van elke toetsperiode gemeet. Die ramme is visueel deur rasinspekteurs geëvalueer en volgens rasstandaarde geklassifiseer. Die lewende gewig van die ramme wat aan die begin van die toetsperiodes aangeteken is, was matig tot hoog en positief met meeste van die liggaamsparameters gekorreleerd. Die uitsondering was GDT, waar ʼn negatiewe korrelasie (-0.25) gevind is. Die lewende gewig van die ramme aan die einde van die toetsperiodes was matig en positief met beide skrotumomtrek (0.57) en die hoogste met liggaamsbreedte (0.76) gekorreleerd. Gemiddelde daaglikse toename was hoog en positief (0.63) met lewende gewig aan die einde van die toetsperiode gekorreleerd. Groot variasie binne toetsperiodes, wat aan ouderdomsverskille en variasie tussen toetsgroepe toegeskryf kan word, het genoodsaak dat die data vir die effek van jaar/seisoen gekorrigeer word. Ramme is volgens begingewig in bo- en ondergemiddelde groepe gerangskik. Groeipatrone van die ramme is met gekorrigeerde einddata ondersoek en gevind dat 75% van ramme gedurende die toetsperiode in hul onderskeie groepe gebly het. Hierdie bevinding verleen steun aan die positiewe korrelasie van 0.58 wat vir lewende gewig aan die begin en einde van toetsperiodes hierbo gevind is. Die liggaamsmates wat aan die begin en einde van die toetsperiodes gemeet is, was in die meeste gevalle matig tot hoog en positief (P < 0.0001) met mekaar gekorreleerd. Die uitsondering was GDT, wat laag en negatief met liggaamsmates, wat aan die begin van toetsperiodes aangeteken is, gekorreleerd was. Die seisoenseffek het die grootste bydrae tot lewende gewig aan die einde van die toetsperiodes gemaak, d.i. nadat elke meting deur die somme van kwadrate gekwantifiseer is. Dit is gevolg deur liggaamsbreedte, -lengte, skouerhoogte, skrotumomtrek en GDT (R² = 31.62%). Nadat daar vir jaarseisoen gekorrigeer is, was die bydrae van die onderskeie parameters tot lewende gewig aan die einde van toetsperiodes nog in dieselfde volgorde. Nadat ʼn stapsgewyse prosedure vir gekorrigeerde lewende gewig aan die einde van toetsperiodes gedoen is, is gevind dat liggaamsbreedte die grootste bydrae tot lewende gewig aan die einde van toetsperiodes gemaak het. Gemiddelde daaglikse toename het die derde grootste bydrae, d.i. na liggaamsbreedte en –lengte tot gekorrigeerde lewende gewig aan die einde van toetsperiodes gemaak. Vanweë die hoë korrelasies wat tussen die onderskeie liggaamsmates gevind was, is daar ook vir multi-kollineariteit getoets om vas te stel of die parsiële bydraes van die onderskeie liggaamsmetings verander. Dit het egter onveranderd gebly. Regressie-analises het getoon dat liggaamsmates geneem aan die begin en einde van die toetsperiodes betekenisvol (P<0.0001) oor die hele tydperk (1988 – 2000) afgeneem het. Die grootste jaarlikse afnames was vir GDT (-2,5%) en liggaamsbreedte (-1,1%) bereken. Die negatiewe waardes wat verkry is, toon dat die Dorper oor tyd kleiner word. Die toepaslikheid van die visuele seleksiemetodes moet dus ernstig bevraagteken word. Die invloed van gekorrigeerde liggaamsmates en GDT op seleksie volgens rasstandaarde wat deur die rasinspekteurs gedoen is, is toe op puntediagramme aangetoon. Dit het getoon dat die rasinspekteurs deurentyd groter en swaarder ramme vir stoetseleksie selekteer. Daar is egter steeds ramme wat ondergemiddeld presteer en wat aan die Dorperbedryf as stoetramme beskikbaar gestel word. Liggaamsbreedte was die liggaamsmate wat die hoogste voorkeur van rasinspekteurs gekry het. Die liggaamsmate wat die minste deur die rasinspekteurs in ag geneem is, was dié van skouerhoogte. ʼn Moontlike verklaring vir laasgenoemde is dat die tendens van die kleinerwordende Dorper hieraan gekoppel kan word, omdat skouerhoogte 'n aanduiding van raamgrootte is. Visuele beoordeling behoort in samewerking met wetenskaplike metodes gebruik te word om sodoende ʼn optimum grootte vir die Dorper daar te stel.

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The Dorper is numerically the second most abundent of all the sheep breeds in South Africa. It is the most numerous sheep breed in the dry arid areas of South Africa which make out a very big portion of the natural grazing in South Africa. In this study the feedlot performance was specifically investigated since so little research has been done in this regard. In the first study (Chapter 1), the production efficiency, body components and commercial yield of 13 Dorper and 12 Merino lambs were investigated. A pelleted diet was fed ad lib and the water intake per day was measured. Lambs were slaughtered at 30kg and at 40kg live weight and cut up according to the South African commercial cuts. The weights of the organs, head, feet, skin and carcass were also recorded. Results from the first study showed that Dorpers had a lower (P<0.05) water efficiency (285.97 mVkgO75/day) than the Merinos (240.07 mVkg075/day), but had a higher (P<0.05) nitrogen retention. The head, feet, skin, heart, lungs, kidneys and diaphragm of Merino lambs were heavier (P<0.05). Merinos had heavier (P<0.05) breast and shank and thick rib (only at 40kg live weight) cuts. But the Dorper had a significantly heavier hindquarter (buttock and loin) which is the high-priced cut of any carcass. It seems that the Dorper will do well under feedlot conditions, and would possibly make a better commercial meat producer than the Merino under all circumstances. In the second study (Chapter 2), the free-ranging Dorper on natural grazing were compared with 7 Dorper lambs in the feedlot study. The essential amino acids in the duodenal contents were compared. The free-ranging Dorpers were randomly slaughtered at 40 kg live weight and a duodenal sample was collected. The feedlot Dorpers were also slaughtered at 40 kg live weight and a duodenal sample was taken. The second study indicated no significant differences between the EAA composition of the duodenal samples, whether protein quantity was taken into account (gAA/100g crude protein (CP)) or not (expressed as % of lysine). The chemical scores indicated that the two most limiting amino acids in the duodenal digesta for whole empty body growth were: arginine and histidine. Excess levels of amino acids tend to be present in all three duodenal digesta samples (isoleucine, leucine, lusine, methionine, phenylalaline, threonine and valine). The whole empty body EAA composition (g AA/100 g crude protein) was as follows 7.10 arginine; 2.40 histidine; 3.31 isoleucine; 7.22 leucine; 6.61 lysine; 1.62 methionine; 3.91 phenylalanine; 3.77 threonine and 4.85 valine. The composition can serve as an example of the ideal EAA requirements for whole empty body growth between 30 and 40 kg live weight of Dorper ram lambs. The duodenal amino acid concentrations of the free-ranging Dorper compared well with those of the feedlot Dorpers which suggests that the microbial organisms have a big influence on the amino acid concentration which reaches the intestines. / AFRIKAANSE OPSOMMING: Die voerkraal prestasie en essentiele aminosuur behoeftes van groeiende Dorper lammers: The Dorper is getalgewys die tweede mees talryke skaapras in Suid-Afrika. Dit is die mees talryke skaapras wat in die drce woestynagtige gebiede van Suid-Afrika aangetref word. Die gebiede beslaan die grootste oppervlakte van Suid-Afrika se natuurlike weiveld. In die studie is voerkraal prestasie van die Dorper nagevors, spesifiek omdat daar so min navorsing op hierdie gebied gedoen is. In die eerste studie (Hoofstuk 1) is die produksie doeltreffendheid, liggaams komponente en kornrnersiele produksie van 13 Dorper- en 12 Merino lammers ondersoek. 'n Verpilde rantsoen is ad lib gevoer en die water inname per dag is ook gekontroleer. Die lammers is geslag op 30 en 40 kg lewende gewig en die karkasse is daarna opgesny volgens die Suid-Afrikaanse kornmersiele karkassnitte. Die resultate van die eerste studie het getoon dat Dorpers 'n laer water potentiaal (P<0.05) (285 97 mflkgO 75/dag) as die Merinos (240.07 mVkg075/dag) het. Dorper lammers het ook 'n hoer (P<0.05) stikstof retensie. Die kop, vel, pote, hart, longe, niere en diafragma van Merino lammers was swaarder (P<0.05). Merinos se brisket en dikrib snitte weeg ook swaarder (P<0.05). Die Dorper het 'n beduidende swaarder agterkwart (len de en boud) gehad, wat die duurste snit is van enige karkas. Die Dorper het baie goed gedoen in die voerkraal toestande en sal waarskynlik onder aile omstandighede 'n hcer vleisproduksie op die Merino lewer. In die tweede studie (Hoofstuk 2), is die vryweiende Dopers op natuurlike weiding vergelyk met die Dorpers in 'n voerkraal. Die twee groepe Dorpers se essensiele aminosuur samestelling in hul dunderms is bepaal en vergelyk om te bepaal of daar enige tekorte teenwoordig is. Die Dorpers in die veld en in die voerkraal is op 40 kg lewende gewig geslag en monsters van die dunderm inhoud is gekollekteer. Die monsters is ontleed om te bepaal of daar enige betekenisvolle verskille in die essensiele aminosure van die dunderm inhoud tussen die veld Dorpers en voerkraal Dorpers was. Die tweede studie het geen betekenisvolle verskille getoon tussen die dunderm monsters se essensiele aminosure, of die hoeveelheid proteien (gAA/100g) in aanmerking geneem is of nie (uitgedruk as % lisien). Die chemiese telling dui aan dat die twee mees beperkende aminosure in die dunderm inhoud vir lee liggaam groei arginien en histidien was. Oormaat vlakke van aminosure kom voor in al drie dunderm inhoud monsters (isoleusien, leusien, lisien, metionien, femielalanien, treonien en valien). Die totale lee liggaam essensiele aminosuursamestelling (g aminosuur/100g ruprotein) was soos volg: 7.10 arginien; 2.40 histidien; 3.31 isoleusien; 7.22 leusien; 6.61 lisien; 1.62 metionien; 3.91 fenielalanien; 3.77 treonien en 4.85 valien. Hierdie aminosuursamestelling kan as 'n aanduiding dien vir die ideale aminosuurbehoeftes van Dorper ram lammers vir totale lee liggaamsgroei vanaf 30 tot 40 kg lewende massa. Die dunderm aminosuur konsentrasie van die Dorper in die veld stem goed ooreen met die van die voerkraal Dorper. Dit toon waarskynlik dat die mikrobe organismes in die rumen In groot invloed het op die aminosuur samestelling wat die dunderm bereik.