Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this study, five trials were conducted to examine in vitro and in vivo degradation, excretion and absorption parameters of melamine (MEL) in dairy cows that have not been studied before or where limited information is available. The first two trials were in vitro studies conducted to determine the extent of MEL degradation in rumen liquor and the effects of MEL on ruminal ammonia (NH3) and volatile fatty acid (VFA) concentrations. For both trials, rumen liquor was collected from ruminally cannulated lactating Holstein cows. For the first and second trial, rumen liquor was collected from three and two cows, respectively. For both trials, Erlenmeyer flasks contained 1 g substrate and 100 mL incubation medium consisting of 20 mL rumen liquor and 80 mL reduced buffer solution. In the first trial, each flask contained 100 mg of MEL, resulting in an initial MEL concentration of 1000 mg/L. The flasks were incubated at 39° C for 0 (Control), 6, 24 or 48 hours under strictly anaerobic conditions. In all the trials, MEL concentrations were determined by LC/MSMS. MEL degradation was low after 6 and 24 h of incubation (3.2 and 5.5%, respectively) and increased to 13.6% after 48 h of incubation. In the second trial where VFA and NH3 concentrations were determined, the flasks contained either 0 (Control), 0.2 (T1) or 0.4 mg (T2) of MEL. The flasks were incubated for 6, 24 or 48 h. Treatment had no effect on individual or total VFA concentrations or NH3 concentrations at 6 and 48 h. At 24 h, T2 resulted in an inexplicable higher NH3 concentration. This study showed that the addition of melamine would not result increased rumen NH3 concentrations in vitro. Melamine would also not affect the production of different VFA’s. Therefore, it was concluded that the rumen micro-organisms present in rumen liquor would be unable to utilize MEL as a source of nitrogen and that the microbial production of VFA’s remains unaffected by the presence of MEL. In the third trial, MEL excretion in lactating cows was determined. Five cows were randomly allocated to treatments according to a 5 x 5 Latin square design. Cows received the treatment diets for 7 d followed by 8 d of MEL withdrawal during each of the five periods. The experimental treatments were formulated to provide a daily MEL intake of 0 (M0), 500 (M1), 1000 (M2), 5000 (M3) or 10000 mg (M4) via 15 kg of dairy concentrate pellets. Calculations based on the work of Newton & Utley (1978) suggested that a melamine intake of 0.16 g/kg of live weight would not result in detrimental health effects of ruminant animals. Therefore, a 600 kg lactating dairy cow should not be at risk when consuming 100 g of melamine. In this trial, the highest melamine treatment (M4 = 10 g/d) included a 10-fold safety factor from the suggested safe amount from the work of Newton & Utley (1978) and should not pose a health risk to the cows. Treatments had no effect on DMI, milk yield or milk composition. MEL was detected in the milk 8 h after initial MEL ingestion, increased rapidly and peaked on d 3 and was undetectable after 8 d. Treatments had no effect on MEL excretion efficiencies which ranged from 1.5 to 2.1%. The mean apparent digestibility of MEL was 78%. Mean faecal and urinary MEL excretions were 22 and 54 % of ingested MEL, respectively. Higher milk, urine and faecal MEL concentrations were observed with higher levels of dietary MEL. It was concluded that MEL appeared in the milk soon after first ingestion and a withdrawal period of 8 d was required for all milk, faecal and urine samples to reach undetectable levels of MEL. Urine and faeces were the primary routes for MEL excretion. The fourth trial was conducted to determine MEL absorption by the mammary gland in lactating dairy cows through arterio-venous (A-V) difference. Five cows received 10 g of MEL/d for three consecutive days. Day 3 of the trial was selected for commencement of blood sampling as previous studies (Cruywagen et al., 2009; Shen et al., 2010; Sun et al., 2011) reported the milk melamine concentration to reach a peak on d 3 of continuous melamine consumption by dairy cows. Early on d 3, catheters were inserted into the caudal superficial epigastric vein (milk vein) and caudal auricular artery. The blood sampling period commenced after residual milk removal from the udder following oxytocin administration. Blood from both locations were collected hourly for 9 hours. Following the final blood collection, oxytocin was administered again, catheters were carefully removed and cows were milked immediately thereafter. All blood samples were centrifuged and the decanted plasma was analysed for MEL, as well as for amino acid contents to calculate mammary blood flow. The positive MEL flux (calculated from A-V difference) confirmed net absorption of MEL into the mammary gland with an efficiency of absorption of 0.29%. Melamine excretion into milk was 5.63 mg/h. The mean plasma and milk MEL concentrations were 5.2 and 3.9 mg/kg, respectively. Melamine excretion efficiency to milk, expressed as percentage of the ingested amount, was 1.47%. It was concluded that melamine ingested by cows will result in net MEL absorption by the mammary gland, but that the absorption efficiency is low. The final trial of the study aimed to determine the effects that fermentation processes during the manufacturing of cheese, yoghurt and kefir would have on their MEL content if these products were made from MEL contaminated milk. Another objective was to determine if MEL in cheese would be degraded during the curing process. Cheese, yoghurt and kefir were made from milk with a MEL content of 6.77 mg/kg. The cheese was then cured for 2 wk at 6° C. The MEL contents of the yoghurt and kefir were 6.76 and 6.78 mg/kg, respectively, indicating that the different fermentation processes used in yoghurt and kefir production had no effect on their MEL content and that MEL was not degraded during the short fermentation periods. The percentage of milk MEL partitioned to whey and cheese were 97.4 and 6.5 %, respectively. It was concluded that the different fermentation processes involved during the manufacturing of yoghurt and kefir from MEL tainted milk did not decrease the MEL concentration. The milk MEL was predominantly partitioned to whey, with little MEL transferred to cheese. It was also concluded that MEL was not degraded in cheese during a 2-wk curing period. It was finally concluded that dietary MEL is readily absorbed by dairy cows and mainly excreted via the urine. The mammary gland has a low affinity for MEL absorption and approximately 2% of ingested MEL is excreted in the milk. When cheese is made from MEL tainted milk, the majority of MEL will concentrate in the whey fraction and only 6.5% will be present in the cheese. / AFRIKAANSE OPSOMMING: Vyf proewe is gedoen om in vitro- en in vivo-degradering, uitskeiding en absorpsie parameters van melamien (MEL) na te gaan waaroor daar min of geen inligting bekend was nie. Die eerste twee proewe was in vitro-studies, uitgevoer om die mate van MEL degradeerbaarheid in rumenvloeistof na te gaan, asook die invloed van MEL op rumen-NH3 en vlugtige vetsuur (VVS)-konsentrasies. Vir beide proewe is rumenvloeistof van lakterende, rumengekannuleerde Holsteinkoeie verkry. Vir die eerste en tweede in vitro-studies, was rumenvloeistof verkry vanaf drie en twee koeie, onderskeidelik. In albei proewe is 1 g substraat in Erlen-meyerflessies afgeweeg en 100 mL inkubasiemedium bygevoeg wat uit 20 mL rumenvloeistof en 80 mL van ‘n buffermedium bestaan het. In die eerste proef is 100 mg MEL by die substraat gevoeg, sodat die aanvanklike MEL konsentrasie in die flessies 1000 mg/L was. Die flessies is by 39° C geïnkubeer vir 0 (Kontrole), 6, 24 of 48 ure, onder streng anaerobiese kondisies. Met die beïndiging van die inkubasieperiode is 100 mL van ‘n 0.2 M perchloorsuuroplossing bygevoeg om enige melamien wat nie gedegradeer was nie, op te los. In al die proewe is melamienbepalings by wyse van LC/MSMS gedoen. Melamiendegradering was laag na 6 en 24 h inkubasie (3.2 en 5.5%, respektiewelik) en teen 48 h inkubasie het dit toegeneem tot 13.6%. In die tweede proef het die flessies 0 (Kontrole), 0.2 (T1) of 0.4 mg (T2) melamien bevat. Behandeling het geen invloed op individuele of totale VVS-konsentrasies by enige van die inkubasietye gehad nie en ook nie op NH3-konsentrasies by 6 en 48 h nie. Om een of ander onverklaarbare rede het die T2-behandeling gelei tot hoër NH3-konsentrasies by 24 h. Die gevolgtrekking is gemaak dat die byvoeging van MEL geen effek op rumen NH3-konsentrasies het nie en dat die mikroorganismes in die rumen nie daartoe in staat sal wees om MEL as ‘n stikstof-bron sal kan benut nie. In die derde proef is die uitskeiding van MEL in melkkoeie ondersoek. Vyf lakterende Holsteinkoeie is ewekansig aan vyf behandelings toegeken in ‘n 5 x 5 Latynsevierkantontwerp. Gedurende elke periode het koeie die behandelings vir 7 d ontvang, gevolg deur ‘n 8 d MEL-onttrekkingsperiode. Die eksperimentele diëte is geformuleer om ‘n daaglikse MEL-inname van 0 (M0), 500 (M1), 1000 (M2), 5000 (M3) of 10000 mg (M4) per koei/dag te verseker, toegedien via 15 kg/d van ‘n suiwelkonsentraat in pilvorm. Berekeninge gebasseer op die werk van Newton & Utley (1978) stel voor dat ‘n MEL inname van 0.16 g/kg lewende massa, geen negatiewe effek op herkouers se gesondheid sal hê nie. Dus, ‘n koei wat 600 kg weeg, sal geen skade lei deur die inname van 100 g MEL nie. In hierdie proef was die hoogste MEL behandeling (M4 = 10g/d) tien keer laer as die voorgestelde veiligheidsvlak van Newton & Utley (1978). Behandeling het geen invloed op DMI, melkopbrengs of melksamestelling gehad nie. Melamien is so gou as 8 h na eerste inname in die melk waargeneem, waarna die konsentrasie vinnig toegeneem het en ‘n piek na 3 d bereik het. Behandeling het geen invloed op die uitskeidingsdoeltreffendheid van melamien in melk gehad nie en waardes het gewissel van 1.5 tot 2.1%. Die gemiddelde skynbare verteerbaarheid van MEL was 78%. Die gemiddelde mis- en uriene-MEL-konsentrasies was 22 en 54%, onderskeidelik. Hoër melk-, mis- en uriene-MEL-konsentrasies is waargeneem namate die MEL-inhoud van die diëte gestyg het. Die gevolgtrekking is gemaak dat MEL spoedig na eerste inname in die melk verskyn en dat ‘n onttrekkingsperiode van 8 d benodig word voordat melk-, mis- en uriene-MEL onwaarneembare vlakke bereik. Uriene en mis is die primêre uitskeidingsroetes van ingenome MEL. Die vierde proef is onderneem om MEL-absorpsie in die melkklier met behulp van arterio-veneuse (A-V) verskille te ondersoek. Vyf koeie het elk 10 g MEL/d vir drie agtereen-volgende dae ontvang. Dag 3 van die proef is gekies vir bloedkolleksies aangesien vorige studies (Cruywagen et al., 2009; Shen et al., 2010; Sun et al., 2011) gewys het dat melk MEL op dag 3 van MEL inname, piek konsentrasies beryk. Vroeg gedurende die oggend van d 3 is kateters in die kaudale oppervlakkige epigastriese aar (melkaar) en die kaudale aurikulêre slagaar geplaas. Die bloedtrekkingsperiode het ‘n aanvang geneem direk nadat die koeie volledig uitgemelk is na toediening van oksitosien om te verseker dat soveel as moontlik residuele melk verwyder word. Monsters van veneuse-, sowel as arteriële bloed, is 9-uurliks geneem. Na die finale bloedtrekking is oksitosien weer toegedien, die kateters is versigtig verwyder en die koeie is direk daarna weer gemelk. Al die bloedmonsters is gesentrifugeer en plasmamonsters is ontleed vir MEL, asook vir aminosuursamestelling ten einde bloedtoevoer na die uier te bereken. Die positiewe fluks (bereken van A-V verskil) het bevestig dat netto MEL absorpsie in die melkklier plaasvind, met ‘n doeltreffendheid van 0.29%. Melamienuitskeiding in die melk was teen ‘n tempo van 5.63 mg/h. Die gemiddelde plasma- en melk-MEL konsentrasies was 5.2 en 3.9 mg/kg, onderskeidelik. Die uitskeidingsdoeltreffendheid van MEL na melk, uitgedruk as persentasie van ingenome MEL, was 1.47%. Die gevolgtrekking is gemaak dat MEL wat deur koeie ingeneem word, tot netto MEL-absorpsie in die melkklier sal lei, maar dat die absorpsiedoeltreffendheid baie laag is. In die finale proef is daar gepoog om die invloed van fermentasieprosesse gedurende die vervaardiging van kaas, joghurt en kefir op die produkte se melamieninhoud na te gaan indien die produkte van melamienbevattende melk gemaak sou word. ‘n Tweede doel van hierdie proef was om te bepaal of MEL in kaas gedegradeer kan word tydens rypwording. Kaas, joghurt en kefir is gemaak van melk wat ‘n MEL-inhoud van 6.77 mg/kg gehad het. Die kaas is vervolgens vir twee weke by 6° C rypgemaak. Die MEL-inhoud van die joghurt en kefir was 6.76 en 6.78 mg/kg, onderskeidelik, wat daarop dui dat die onderskeie fermentasieprosesse wat tydens die bereiding van joghurt en kefir plaasvind, geen invloed op hul MEL-inhoud gehad het nie en dat MEL nie gedurende hierdie kort fermentasieperiodes gedegradeer is nie. Die persentasie MEL na wei en kaas versprei was 97.4 en 6.5%, onderskeidelik. Die gevolgtrekking is gemaak dat die verskillende fermentasieprosesse betrokke tydens die vervaardiging van joghurt en kefir wat van melamienbesmette melk gemaak word, nie die MEL-konsentrasie verlaag het nie. Tydens die vervaardiging van kaas, word die MEL hoofsaaklik na die weikomponent versprei en baie min na kaas. Melamien word ook nie in kaas afgebreek gedurende ‘n verouderingsproses van twee weke nie. Die finale gevolgtrekkings is gemaak dat MEL maklik deur melkkoeie geabsorbeer word en dat die hoof uitskeidingsroete via urine is. Die uier het ‘n lae affiniteit vir MEL absorpsie en ongeveer 2% van ingenome MEL is in die melk uitgeskei. Wanneer kaas van MEL besmette melk gemaak word, sal die meerderheid van die MEL in die weifraksie konsentreer, met slegs 6.5% teenwoordig in die kaas. / The Hennie Steenberg Trust Fund, the Ernst and Ethel Erickson Trust and the National Research Foundation (NRF) for their financial support

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The ostrich industry is a predominantly quantitative industry; focused mainly on the production of large numbers of slaughter birds for maximum meat and leather yield. Competing in the international market in the current economic environment necessitates a more qualitative approach. Productivity and product quality are aspects that need to be improved in order to stay competitive and economically viable. Genetic parameters for ostrich slaughter traits are lacking, however, and breeding programs are yet to be developed. Data on quantitative and qualitative production and slaughter traits from a commercial ostrich breeding flock was consequently analysed to establish the relative importance of genetic and non-genetic influences on these traits. Genetic and environmental (co)variances as well as estimates of heritability, genetic and phenotypic correlations were estimated for and among the various traits using standard software for multi-trait genetic analyses. Substantial variation, high and favourable genetic correlations as well as moderate to high heritability estimates were found among, and for distinguished body weight traits of growing ostriches. Heritability estimates of 0.14, 0.22, 0.33, 0.43 and 0.43 for 1-month, 4-month, 7-month, 10-month and 13-month-old ostrich weights were estimated in a five-trait animal model analysis. All carcass component weight traits, with the exception of the weight of the liver, showed significant genetic variation. No significant maternal permanent environmental variance was evident for these traits. Heritability estimates ranged from 0.21 (for subcutaneous fat weight) to 0.45 (for neck weight) in multi-trait analyses. The only potentially unfavourable correlation was a high genetic correlation between live weight and subcutaneous fat weight, as fat is considered as a waste product in the present system. The heritability estimates for individual muscle weights ranged from 0.14 to 0.43, while the genetic correlation between these weights and pre-slaughter live weight were all positive, ranging from 0.59 to 0.82. When meat quality traits were analysed it was evident that lightness (L*) and ultimate pH (pHu) showed significant genetic variation, with heritability estimates of 0.37 and 0.42, respectively. L* and pHu were negatively correlated (-0.65 ± 0.19). Since pH is an indicator of various meat quality parameters, it could be considered as an appropriate selection criterion for enhanced meat quality. With the exception of skin grading and crown length, all quantitative and qualitative skin traits showed significant genetic variation. Nodule traits were accordingly moderate to highly heritable. A negative, but favourable, correlation between weight and hair follicle score was ascertained, as hair follicles is a defect that should be selected against. This study demonstrated that sufficient genetic variation exists for most slaughter traits to allow sustained genetic progress for these traits, should it be desired as part of the overall selection objective. Combining some of the current economically important slaughter traits in a provisional selection index, it was clear that weight and crust skin size contributed most to monetary gain (approximately 54 and 38%, respectively). It was also demonstrated with this simple index that monetary gains in slaughter bird production should be easy to achieve at all levels of production performance and data recording. / AFRIKAANSE OPSOMMING: Die volstruisbedryf is hoofsaaklik ‘n kwantitatiewe bedryf wat meerendeels fokus op die produksie van groot getalle slagvolstruise vir die produksie van vleis en leer. Siende dat die bedryf hoofsaaklik op uitvoere fokus, word aanvaar dat ‘n verandering in strategie na ‘n meer kwalitatiewe benadering nodig is, in ag geneem die huidige ekonomiese situasie en marktoestande. Produktiwiteit sowel as produkgehalte moet in ag geneem word vir die bedryf om lewensvatbaar te bly. Daar is egter ‘n gebrek aan genetiese parameters vir volstruisslageienskappe, terwyl doeltreffende teeltstelsels nog ontwikkel moet word. Data van kwantitatiewe en kwalitatiewe produksie- en slageienskappe is gevolglik van ‘n kommersiële volstruis teeltkudde verkry en ontleed om die relatiewe belang van genetiese en nie-genetiese effekte op die eienskappe te kwantifiseer. Genetiese- en omgewings (ko)variansies, asook beramings van oorerflikheid sowel as genetiese en fenotipiese korrelasies, is vervolgens vir en tussen die onderskeie eienskappe beraam deur van standaard sagteware vir veelvuldige-eienskap genetiese ontledings gebruik te maak. Aansienlike variasie, hoë en meestal gunstige korrelasies, sowel as matige tot hoë oorerflikhede, is tussen en vir die onderskeie ligaamsgewigte van groeiende volstruise gevind. Oorerflikheidsberamings van 0.14, 0.22, 0.33, 0.43 en 0.43 is vir 1-maand, 4-maande, 7-maande, 10-maande en 13-maande-oue volstruise in ‘n vyf-eienskap dieremodel ontleding gekry. Alle karkaskomponentgewigte, met die uitsondering van die gewig van die lewer, het betekenisvolle genetiese variasie getoon. Oorerflikheidsberamings het tussen 0.21 (vir onderhuidse vetgewig) en 0.45 (vir nekgewig) gevarieer in veelvuldige-eienskapontledings. Die enigste moontlike ongunstige korrelasie was tussen liggaamsgewig en onderhuidse vetgewig, siende dat vet as ‘n afvalproduk gereken word in die huidige stelsel. Die oorerflikhede van die gewigte van indiwiduele spiere het van 0.14 tot 0.43 gevarieer, terwyl die genetiese korrelsies tussen hierdie gewigte en voorslaggewig deurgaans positief was, met waardes wat van 0.59 tot 0.82 gewissel het. Tydens die ontleding van vleisgehalte eienskappe was dit duidelik dat ligtheid (L*) en uiteindelike pH (pHu) genetiese variasie getoon het, met oorerflikheidsberamings van onderskeidelik 0.37 en 0.42. L* en pHu was negatief gekorreleerd op die genetiese vlak (-0.65 ± 0.19). Aangesien pH ‘n aanduiding is van verskeie vleisgehalteparameters, kan dit moontlik as ‘n indirekte seleksie-kriterium vir verbeterde vleisgehalte gesien word. Alle kwantitatiewe en kwalitatiewe veleienskappe het genetiese variasie getoon, met die uitsondering van velgradering en kroonlengte. Knoppie-eienskappe van die veerfollikels op die vel was ooreenstemmend matig tot hoog oorerflik. ‘n Negatiewe, maar gunstige, genetiese korrelasie is tussen liggaamsgewig en haarfollikelpunt beraam, siende dat haarfollikels ‘n defek is waarteen daar geselekteer moet word. Hierdie studie dui op voldoende genetiese variasie vir die meeste slageienskappe om voldoende genetiese vordering te verseker indien dit verlang sou word. Somminge van hierdie eienskappe wat tans van ekonomiese belang is, is vervolgens in ‘n voorlopige seleksie-indeks gekombineer. Dit was duidelik dat liggaamsgewig en velgrootte die meeste tot monetêre vordering bygedra het (onderskeidelik ongeveer 54 en 38%). Dit is vervolgens aangetoon dat monetêre vordering maklik haalbaar behoort te wees op alle vlakke van produksieprestasie en data-aantekening.

Thesis (PhD(Agric) (Agriculture))--University of Stellenbosch, 2009. / Traditionally, agricultural land was regarded mainly as a production factor. Accordingly, in their application of the market sales comparison approach to agricultural land, valuers relied on a set of attributes related to agricultural production as the primary determinants of an agricultural property’s highest and best use (HBU) and market value. These characteristics were measurable and related to the property’s income-generating capacity. The emergence of a multi-functional rural land market with alternative uses of agricultural land, such as for lifestyle purposes, has transformed this concept. Lifestyle inspired buyers often focus on a wider range of attributes not necessarily related to income, but associated more with satisfaction derived from the property. This creates a measurement problem for agricultural land valuers, as the characteristics valued by lifestyle buyers are more intangible and subjective, which leave valuers without a base from which to value such properties. The presence of lifestyle inspired buyers makes agricultural land valuations more demanding as it implies different interpretations of the same farm and complicates the choice of a single HBU. The continued use of familiar conventional farming attributes by valuers when valuing farms where lifestyle motivations are present, and the omission of less measurable characteristics, implies that the market sales comparison method cannot be executed accurately. The objectives of the study were twofold: to reveal the dominance of value attributes applicable to farming as HBU when valuing farms bought primarily for lifestyle purposes and to identify the characteristics of land important to lifestyle inspired farm buyers.

Dissertation (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Pine sawdust-shavings (Pinus spp.) is at present a very popular soilless substrate in South African greenhouses. Growers use fresh pine sawdust-shavings as a substrate, which is biologically highly unstable. The greenhouse industry is looking at alternative organic substrates such as coco peat, which already went through a decomposition process and is more stable. A biological inactive substrate such as sand was included to compare microorganism activity with organic substrates. The main objective of this study was to compare the growth, yield and quality of hydroponically grown tomatoes in response to different growth mediums in combination with nitrogen source, irrigation frequency, period of substrate use and liming. In general the drainage water pH declined with an increase in NlLt+-N in the nutrient solution. Low pH values in the drainage water, especially when coco peat was used, had a detrimental effect on marketable yield. The drainage water pH of pine sawdustshavings increased during the growing season when 100 % N03--N was used. Due to the higher cation exchange capacity of coco peat, the drainage water electrical conductivity tends to increase more rapidly than with pine sawdust-shavings, during conditions with high temperatures and when insufficient irrigation volumes per irrigation cycle is applied. As expected the drainage water N03--N content decreased as the NlLt+-N content increased in the nutrient solution. Pine sawdust-shavings recorded a much lower N03--N and NlLt+-N content than sand and coco peat and thus supports the hypothesis that microbiological activity is higher in pine sawdustshavings, especially in the second season of substrate use. Coco peat produced the highest number of marketable fruit and yield per plant, followed by pine sawdustshavings and sand in the first season of substrate use. The number of marketable fruit and yield decreased with an increase in NlLt+-N content in the nutrient solution during production in warmer, summer conditions. Contrary to these fmdings, production in cooler, winter conditions recorded high yields when only N03--N or 80% N03--N : 20% NRt +-N was applied. The unmarketable yield increased with an increase in NlLt+-N in the nutrient solution. Visual evaluations showed that blossom-end rot (BER) was the main contributor to unmarketable yield. Increasing levels ofN03--N as nitrogen source in the nutrient solution, reduced weight loss and increased the loss of fruit firmness of tomatoes during storage. Increasing levels of N03 --N also increased fruit pH and reduced total titratable acidity. Coco peat produced fruit with a higher pH than pine sawdust-shavings. An increase in irrigation frequency affected fruit firmness negatively when coco peat was used as substrate. Different irrigation and fertigation practices are needed for different growth mediums and management needs to be adapted according to the growing season (winter vs. summer). / AFRIKAANSE OPSOMMING: 'n Mengsel van dennesaagsels en -skaafsels (Pinus spp.) word tans deur Suid- Afrikaanse kweekbuisprodusente gebruik as grondlose groeimedium. Hierdie groeimedium word nie vooraf gekomposteer nie en is dus biologies onstabiel. Die kweekbuisindustrie ondersoek tans die gebruik van alternatiewe, gekomposteerde en stabiele organiese groeimediums soos kokosveen. 'n Biologies onaktiewe groeimedium soos sand is ook ingesluit om met organiese groeimediums te kan vergelyk. Die hoof doelwit van die studie was om plantontwikkeling, opbrengs en kwaliteit van hidroponies geproduseerde tamaties te evalueer in verskillende groeimediums en in kombinasie met stikstofbron-verhouding, periode van groeimedium gebruik, besproeiingsfrekwensie en bekalking. Oor die algemeen het die pH in die dreinaat gedurende die groeiseisoen toegeneem soos die NH/-N inhoud verhoog het in die voedingsoplossing. Lae pH waardes in die dreinaat, veral waar kokosveen gebruik was, het 'n nadelige effek op bemarkbare opbrengs gehad. Die pH in die dreinaat van dennesaagsels en -skaafsels het gedurende die groeiseisoen toegeneem met die gebruik van 100% NO)--N in die voedingsoplossing. Die elektriese geleiding in die dreinaat van kokosveen neem vinniger toe gedurende toestande waarin hoë temperature en onder besproeiing voorkom, as in dreinaat van dennesaagsels en -skaafsels. Die NO)--N inhoud in die dreinaat het soos verwag afgeneem soos die NRt+-N inhoud in die voedingsoplossing toegeneem het. 'n Baie laer NO)--N en NRt+-N inhoud is by dennesaagsels en -skaafsels aangeteken wat dus die hipotese ondersteun dat mikrobiologiese aktiwiteit, veral in die tweede seisoen van gebruik, hoër is in dennesaagsels en -skaafsels as in sand en kokosveen. Kokosveen het die hoogste aantal bemarkbare vrugte en massa per plant geproduseer, gevolg deur dennesaagsels en -skaafsels en sand. Die aantal bemarkbare vrugte en opbrengs het verlaag met 'n verhoging in NRt+-N in die voedingsoplossing gedurende warm, somer toestande. In teenstelling met vorige resultate is gevind dat 100% NO)-- N of 80% NO)--N : 20% NRt+-N hoë opbrengste gelewer het gedurende koeler, winter toestande. Die onbemarkbare opbrengs het verhoog met hoër NRt+-N vlakke. Visuele waarnemings het aangedui dat blom-end verrotting die grootste bydrae tot onbemarkbare opbrengs gelewer het. 'n Verhoging in NO)--N vlakke het massaverlies beperk en die verlies in fermheid verhoog gedurende opberging. Hoër NO)--N vlakke het ook die pH van vrugte verhoog en die totale titreerbare suur verlaag. Kokosveen het vrugte met 'n hoër pH as dennesaagsels en -skaafsels geproduseer. 'n Toename in besproeiingsfrekwensie het vrug fermheid negatief beïnvloed wanneer kokosveen as groeimedium gebruik was. Verskillende besproeiings- en voedingspraktyke word benodig vir verskillende groeimediums en bestuur van die groeimediums moet aangepas word by klimaatstoestande gedurende die spesifieke produksieseisoen.

Thesis (PhD(Agric) (Animal Sciences))--University of Stellenbosch, 2005. / As most researchers have foreseen, and many breeders have hoped, the in vivo and in vitro production of livestock embryos and the birth of subsequent offspring never really replaced artificial insemination during the past 30 years. This was, to a large extent, due to very variable and unreliable numbers of embryos produced using these two methods. The present study was therefore undertaken to investigate certain aspects of assisted reproductive techniques (ART) to try and solve some of these difficulties. Problems addressed were the management of follicular development on the ovary by controlling the dominant follicle, and investigating alternative and more cost-effective culture media and conditions for embryo culture. A method to control the development of the dominant follicle in a cohort of follicles as well as the waves of follicular development in the ovaries of sheep, goats and cows with an estrogenic product was investigated. Estradiol cypionate (ECP) was used for this purpose, injected intramuscularly after the insertion of the progesterone or progestagen implant. ECP has a negative feedback effect on the secretion of pituitary FSH, and therefore follicular development. The animals of the three different species were randomly divided into two groups each, the ECP-group receiving the estradiol cypionate injection, and the control group receiving a saline injection. Five days after the ECP injection a program of follicular multi-stimulation with FSH hormone was initiated. The females of the different species were bred by either natural service (goats) or inseminated by laparoscopy (sheep) or trans-cervically (cows) to fertilize the ovulated ova. Embryos and unfertilized ova were collected surgically at the 8 to 16- cell stage 3 to 4 d after breeding in the sheep and goats, and trans-cervically in the cows. Significantly more CL formed, and a total number of ova and embryos, as well as transferable embryos, were collected from the ECP-group of sheep ewes and goat does compared to the control group that received no ECP (p<0.01). There was, however, no difference in the average number of unfertilized ova that were collected in the two sheep or goat groups. In the cows the number of CL counted, the total number of embryos and ova and of transferable embryos collected, were significantly greater (p<0.05) in the group that were injected with ECP compared to the group that received no ECP. The control group also had a significantly larger number of unfertilized ova than the ECP-group (p<0.05). It could therefore be concluded that more reliable numbers of embryos can be produced in vivo if the development of the dominant follicle as well as the subordinate follicles is controlled with estradiol cypionate. Since more than half a century ago, attempts have been made to culture cells and embryos outside the body (in vitro or ex vivo). This was done with different culture media and in various "incubators". Chapter 2 deals with two different culture media used: a standard TCM-199 culture medium and first trimester amniotic fluid (BAF) collected sterilely from pregnant cows after slaughter. Two different culture conditions were also investigated, the standard laboratory CO2 incubator versus culturing bovine embryos in the vagina of a goat doe. Two experiments were done: Firstly the permeability of different receptacles to CO2 gas was analyzed for possible culture in the vagina. Four-well plates and straws were used to incubate TCM-199 and BAF for a period of 120 h in the presence or absence of 5% CO2 gas. The pH values were measured every 24 h and recorded. In the second experiment pre-compacted morula stage bovine embryos were incubated in the above culture media in sealed 0.25 mL straws in a standard laboratory incubator and in the vagina of a goat doe. Evaluation was done on (1) stage of development and (2) number of blastomeres after 96 h of culture. In experiment one it was shown that the CO2 gas diffused out of the 4-well plate as well as the straws in the absence of CO2 gas, while in the presence of CO2, the pH of both media stabilized between 7.3 and 7.5. This meant that the semen straws were permeable to CO2 gas and could therefore be used as receptacles for culturing early stage bovine embryos. In the second experiment no statistical differences (p>0.05) were found in the number of Grade 1 pre-compacted bovine embryos that developed to the blastocyst stage, or the hatched blastocyst stage, neither for the culture medium used, or the method of culturing in the two incubators. Neither was there any difference (p>0.05) in the number of blastomeres that developed at the blastocyst stage between the two types of incubators used. Embryos tended to develop more blastomeres when cultured in BAF than when cultured in TCM-199 in both the standard laboratory incubator and when using the vagina of a goat doe as an incubator (p<0.05). After the collection of in vivo produced livestock embryos, they are evaluated under high magnification (minimum of 80X) with the aid of an inverted or stereo microscope. The Grade 1 embryos will give the best conception results when transferred to synchronized recipient female animals, while the Grade 3 embryos will give the worst results. The aim of the next experiment was to culture all three quality grades of in vivo produced pre-compacted morula-stage embryos of sheep, goats and cows in two different culture media and then compare the development of the embryos by evaluating the number of embryos reaching the hatched blastocyst stage. The results have shown that there were no significant differences between the development of the Grade 1 and the Grade 2 embryos from any of the three species when either cultured in TCM- 199 or heat inactivated early pregnancy-stage (<60 d) bovine amniotic fluid (BAF) were used as culture media. Significantly more in vivo produced Grade 3 pre-compacted morula-stage sheep, goat and cow embryos, however, developed to the hatched blastocyst stage when cultured in BAF with 10% FBS and antibiotics, compared to culture in TCM-199 with 10% FBS and antibiotics (p<0.05). The effect of co-culture on the survival of caprine embryos post transfer to a synchronized recipient female goat was also assessed. A total of 120 Kashmir embryos at the blastocyst stage were divided into three groups after thawing and reconstitution in four steps in glycerol and sucrose medium. The first group of embryos (G1, n=40) was individually transferred semi laparoscopically in D-PBS with 10% FBS and antibiotics to the ipsilateral horn of the CL over a period of 3 d. The second group of caprine blastocysts (G2, n=40) was similarly transferred in TCM-199 with FBS and antibiotics. The third group of frozen-thawed caprine blastocyst-stage embryos (G3, n=40) were first co-cultured for ~24 h in TCM-199 with serum and antibiotics in groups of up to five embryos inside a ~50 mm length of a semen straw in a cylindrical sponge in the anterior part of the vagina of a goat doe in her luteal phase. After the culture period these embryos were transferred in a similar way in TCM-199 without the co-culture as in G1 and G2. Ultrasound scanning showed that significantly more of the blastocyst embryos that were cocultured in the vagina (G3) before transfer developed to a pregnancy compared with the embryos transferred in D-PBS (G1). The co-culture Group 3 blastocyst-stage caprine embryos produced significantly more offspring than the non-cultured embryos transferred in both D-PBS (G1) and TCM-199 (G2) (p<0.05). The maturation of bovine oocytes to allow the oocyte to resume meiosis, is the first step in in vitro fertilization to produce IVMFC embryos. The composition of the maturation medium plays an important role in the success achieved with maturation. An investigation was therefore launched to evaluate the maturation ability of first trimester bovine amniotic fluid (BAF) to mature prophase I oocytes collected from abattoir ovaries to metaphase II oocytes, compared to a standard maturation medium such as TCM-199. In the first experiment three groups of ~100 oocytes each were matured in TCM-199 with estrus cow serum (ECS). The first group of oocytes was matured in a 50 μL micro-drop in an incubator, while the other two groups were matured in semen straws, one group in an incubator and the other group in the vagina of a goat doe in di-estrus. Six further groups of ~100 oocytes each, with BAF as maturation medium, three groups with ECS and three without ECS, were matured in the same receptacles and under the same conditions as with the TCM-199. No significant differences in number of oocytes reaching the metaphase II stage could be found for any of the nine treatment groups. In the ...

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.

Thesis (PhD (Animal Sciences))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The current study was undertaken to determine the effectiveness of the current South African chicken conservation programmes in conserving the genetic diversity of village chicken populations. Village chicken farmer’s production constraints such as feed availability, chicken mortality, prevalence of diseases and chicken sales were influenced by gender, age, wealth status, production system, chicken flock size, type of chicken breed owned, accessibility of veterinary services, availability of supplements, vaccines and shelter. Considerable phenotypic heterogeneity in qualitative traits of indigenous chicken populations and their distributions in different regions of South Africa revealed the absence of selection on a preferred phenotype, showing that the population is not standardized. Genetic diversity studies using both microsatellites and mtDNA markers demonstrated that the conservation flocks of South African chickens displayed considerable genetic variability that is different from that of the assumed founder populations (field chicken populations). The indigenous chicken mtDNA further revealed multiple maternal lineages in South African chickens, where conservation flocks and field chicken populations shared these major haplotypes A, D and E which are presumed to be of Chinese, South East Asia and Indian subcontinent origin, respectively. The overall findings of the study increased awareness of the importance of genetic management and utilization of indigenous chicken genetic resources of South Africa. As a result, the study provides a base-line dataset to complement the decision-making process on designing proper conservation strategies for South African indigenous chicken genetic resources. / AFRIKAANSE OPSOMMING: Die huidige studie is onderneem om die doeltreffendheid van die Suid-Afrikaanse hoenderbewarings programme in die bewaring van genetiese diversiteit in dorphoender bevolkings. Dorp hoenderboere se produksie beperkinge soos voerbeskikbaarheid, hoender mortaliteit, die voorkoms van siektes en hoenderverkope word beïnvloed deur geslag, ouderdom, rykdom status, produksie sisteem, hoender kudde grootte, tipe hoenderras, toegang tot veeartsenydienste, beskikbaarheid van supplemente, inentstowwe en skuiling. Merkbare fenotipiese variasie in kwalitatiewe eienskappe van die inheemse hoenderbevolking en hul verspreiding in verskillende areas van Suid-Afrika, is aanduidend dat daar nie seleksie plaasvind vir ‘n voorkeur fenotipe nie, wat dus toon dat die bevolking nie gestandardiseer is nie. Genetiese diversiteit studies met behulp van beide mikrosatelliete en mtDNA merkers het getoon dat die bewaringskuddes van Suid- Afrikaanse hoenders vertoon merkbare genetiese variasie wat verskil van die veronderstelde stigter bevolkings (veldhoender populasies). Die inheemse hoenders mtDNA het verder onthul dat verskeie moederlike afstammelinge in die Suid Afrikaanse hoenders, major haplotipes A, D, E wat afkomstig is vanaf die Chinese, Suid-Oos Asië en die Indiese subkontitent onderskeidelik; gedeel word saam met die bewaringskuddes en die veldhoender populasie. Die algemene bevindige van die studie verhoog die bewustheid van die belangrikheid van genetiese bestuur en benutting van inheemse hoender genetiese hulpbronne van Suid-Afrika. As gevolg hiervan, verskaf die studie ‘n basis-lyn datastel vir die besluitnemingproses oor die ontwerp van ‘n ordentlike bewaring strategieë vir die Suid-Afrikaanse inheemse hoender genetiese hulpbronne.

Thesis (PhDAgric (Animal Sciences))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: A series of experiments were conducted to determine the effect of the replacement of oat silage by wheat straw in low forage diets for high producing dairy cows. In the first trial, 28 multiparous Holsteins were randomly assigned to two dietary treatments, namely silage and straw after completing a covariate period coinciding with the first 40 days of lactation and remained on these diets for the remainder of experimental period from 41 to 252 days. In order to evaluate the effect of substitution during different stages of lactation, the experimental period was divided into four phases. Diets were formulated to support similar levels of milk for both treatment groups and for all phases. The substitution of oat silage by wheat straw had a negative effect on dry matter intake, milk production and composition, as well as on feed and nitrogen efficiency, but had no effect on body weight and body condition. A rumen fermentation trial was also done, where six multiparous cannulated cows were randomly allocated in a changeover design to the same dietary treatments used in the animal performance trial. Despite a relatively low peNDF content and high NFC content of the diets, the mean rumen pH and time spent below pH 5.8 indicated that cows were actually not subjected to subclinical rumen acidosis, probably due to effective chewing activity. Forage source had no significant effect on rumen fermentation end products or mean daily rumen pH. However, the time spent below pH 5.8 was significantly lower for cows in the silage treatment than for those in the straw treatment, which could be related to a longer chewing time and more effective chewing activity that was observed on the straw treatment. Cows on the straw treatment sorted less against the medium sized particles, which was not expected, since straw inclusion is normally associated with a higher degree of sorting. In a third experiment, the effect of the replacement of silage by wheat straw was evaluated in terms of pre and postpartum animal performance. Dry cow diets were formulated with the objective to restrict intake, thus preventing cows from consuming metabolizable energy in excess of their requirements. Both treatments were successful in controlling intake and the replacement of oat silage by wheat straw in dry cow diets had no apprent effect on postpartum animal performance. Using the data from the lactation experiment, the adequacy of the CPM Dairy model to predict animal performance from low forage diets was also evaluated. The model was highly accurate in predicting adjusted milk production of cows consuming oat silage as basal forage, with a mean bias of only 0.05 kg milk/d, but it overpredicted milk production of cows receiving diets with wheat straw as the sole forage source, with a mean bias overprediction of 2.3 kg milk per day during the corresponding period of positive energy balance. Overprediction of energy balance from straw was confirmed in the dry cow experiment where a statistical analysis of the residuals between predicted and actual body condition score change indicated an overprediction on the straw treatment. / AFRIKAANSE OPSOMMING: Die invloed van die vervanging van hawerkuilvoer deur koringstrooi in diëte vir hoogproduserende melkkoeie is in ‘n reeks proewe nagegaan. In die eerste proef is 28 volwasse Holsteinkoeie ewekansig aan ‘n kuilvoer- of strooigebaseerde behandeling toegeken na die voltooiing van ‘n kovariaatperiode van 40 dae. Ten einde die invloed van die behandeling tydens verskillende stadia van laktasie te evalueer, is die proefperiode in vier fases verdeel. Diëte is geformuleer om vergelykbare melkproduksies vir beide behandelings tydens al die fases te ondersteun. Vervanging van hawerkuilvoer deur koringstrooi het ‘n negatiewe invloed op droëmateriaalinname, melkproduksie, melksamestelling, voeromset en stikstofbenutting gehad, maar geen invloed op ligaamsmassa- en kondisieverandering nie. In ‘n rumenfermentasieproef is ses volwasse, gekannuleerde Holsteinkoeie in ‘n omswaai-ontwerp aan twee diëte, soortgelyk aan dié wat tydens die laktasieproef gebruik is, in toegewys. Ten spyte van ‘n relatief lae peNDF-inhoud en ‘n relatief hoë NFC-inhoud van die diëte was daar, te oordeel aan die gemiddelde rumen pH en tyd waartydens die rumen pH onder 5.8 was, geen aanduiding van subkliniese rumenasidose nie, waarskynlik as gevolg van ‘n langer kou-tyd en meer doeltreffende kouaktiwiteit. Ruvoerbron het skynbaar ook geen invloed op rumenfermentasie-eindprodukte en gemiddelde rumen pH gehad nie. Die periode waartydens rumen pH laer as 5.8 was, was egter korter vir koeie in die kuilvoerbehandeling as vir dié in die strooibehandeling. Dit kan waarskynlik aan meer doeltreffende herkou-aktiwiteit toegeskryf word. Aangesien strooiinsluiting in herkouerdiëte normaalweg met ‘n groter mate van voerseleksie geassosieer word, was die kleiner mate van seleksie teen mediumgrootte partikels met die strooibehandeling verrassend. In ‘n derde proef is die invloed van van die vervanging van kuilvoer met koringstrooi in terme van pre- en postpartum diereprestasie ondersoek. Droëkoeidiëte is geformuleer met die doel om inname te beperk en koeie sodoende te verhoed om meer metaboliseerbare energie in te neem as wat hulle benodig. Albei behandelings was doeltreffend om inname te beheer en die vervanging van hawerkuilvoer met koringstrooi het geen invloed op postpartum diereprestasie gehad nie. Deur van die data van die laktasieproef gebruik te maak, is die toereikendheid van die CPM Dairy model om diereprestasie vanaf lae ruvoerdiëte te voorspel, ook bepaal. Die model was hoogs akkuraat in die voorspelling van melkproduksie in die geval van die kuilvoerbehandeling, maar dit het melkroduksie met 2.3 kg/dag oorskat in die geval van die koringstrooibehandeling. Hierdie oorberaming van energiebalans is tydens die droëkoeiproef bevestig.

Thesis (PhD (Animal Sciences))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Local pigs in Southern Africa are an important component of resource-based subsistence farming systems and contribute substantially to the improvement of livelihoods of farmers. The objective of the study was to characterise indigenous pigs through the following specific objectives: to characterise the production systems, to give a physical description and to evaluate the genetic differentiation of the indigenous pigs. Surveys were carried out in Chirumhanzu and Mutoko Districts of Zimbabwe, Afred Nzo, OR Tambo and Vhembe districts of South Africa. Blood samples were collected in all of the above and additional three districts in Malawi (Mchinji, Dedza and Salima). The first study showed that most of the indigenous pigs were kept by women. The farmers kept small herd sizes (<7 pigs) to match the available resources. Income was the main determinant of farmer production objectives and breed preference. Several constraints that would militate against in situ conservation included poor quality and quantity of feeds, diseases, lack of housing, lack of markets and lack of support services. The pigs were generally small and black resembling the Windsnyer-Mukota type of pigs. The pigs apparently had a high foraging ability and high thermo-tolerance that made them suitable for production in low-intensity management free range production systems. These types of pigs were distributed throughout the study area. A microsatellite analysis showed high diversity but very little population differentiation among the pig populations from Southern Africa, with 93 % of variety occurring within subpopulations. Development of markets can be a feasible way of mainstreaming the indigenous pigs into the general economy. This will achieve the twin objectives of conserving and improving the breed while, at the same time, benefitting the farmers that keep these genetic resources. Farmers faced similar production constraints and the pigs were similar across the study areas. / AFRIKAANSE OPSOMMING: Plaaslike varke speel ‘n belangrike rol in hulpbron-gebaseerde bestaansboederye in Suider- Afrika, en maak ‘n aansienlike bydrae tot verbetering van die lewensbestaan van bestaansboere. Die studie het die volgende doelwitte: om die produksie van inheemse varke te karakteriseer, die varke fisies te beskryf, en om die genetiese differensiasie van die inheemse varke te evalueer. Opnames is uitgevoer in die Chirumhanzu en Mutoko distrikte van Zimbabwe, Afred Nzo, OR Tambo en Vhembe distrikte in Suid-Afrika. Bloedmonsters is in al die bogenoemde en nog drie distrikte in Malawi (Mchinji, Dedza en Salima) versamel. Die eerste studie het getoon dat die meeste inheemse varke deur vroue aangehou word. Die boere het klein trop groottes vir aanpasbaarheid by die beskikbare hulpbronne. Inkomste en varkras voorkeur was die hoof bepalende faktore vir hierdie boere se produksie doelwitte. Verskeie beperkings wat bots teen in situ instandhouding sluit in swak kwaliteit- en kwantiteit voere, siektes, gebrek aan behuising, die gebrek aan markte en die gebrek aan ondersteunende dienste. Die varke is oor die algemeen klein en swart en vertoon soos die Windsnyer-Mukoto tipe varke. Hierdie varke het blykbaar ‘n hoë voer-soekende vermoë en hitte-verdraagsaamheid wat hulle geskik maak vir die produksie in lae-intensiteit bestuur en vry-weidende produksie sisteme. Hierdie tipe varke was versprei oor die studie area. ‘n Mikrosatelliet analise het aangedui dat daar hoë genetiese variasie is binne die vark populasie, maar daar is klein differensiasie tussen die verskillende vark populasies van Suider-Afrika, met 93% variasie wat voorkom binne sub-populasies. Die ontwikkeling van markte kan ‘n haalbare manier wees om die inheemse varke toegang te gee tot die algemene ekonomie. Hiermee kan beide doelwitte, bewaring en verbetering van hierdie varkras, tergelyktydig bereik word, ten goede van die boere wat hierdie genetiese hulpbronne aanhou.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The first study (Chapter 3) evaluated the growth response of ostrich chicks on diets containing three different levels of protein and amino acids. Linear and nonlinear models were fitted to the data and compared by using Akaike’s information criterion (AIC). The linear polynomial of the third degree had the lowest AIC value for all three treatments thus making it the most suitable model for the data. Significant differences were found between treatments for growth data. The results from this study can aid in describing the growth of ostriches subjected to assumed optimum feeding conditions. In the second study (Chapter 4), a range of diets was formulated for the five growth stages of ostriches (pre-starter, starter, grower, finisher and maintenance) according to their nutrient requirements. The diets were diluted with wheat straw. Three dilution levels (0%, 10% and 20%) were used for the pre-starter and starter phases, five dilution levels (0%, 15%, 30%, 45% and 60%) were used for the grower and the finisher phases, and five dilution levels (0%, 20%, 40%, 60% and 80%) were used for the maintenance phase. Weekly intake data were collected throughout each phase. Feed bulk restricted intake by 21% and 52% at the 10% and 20% dilution level, respectively (P < 0.05) in the pre-starter phase, whereas intake was not restricted during the starter phase(P > 0.05). Intake was constrained by 39% and 42% at the 45% and 60% dilution levels in the grower phase, respectively (P < 0.05), and by 17% and 39% at the 45% and 60% dilution levels (P < 0.05) in the finisher phase, respectively. Feed bulk restricted intake by 60% and 69% for the 60% and 80% dilution levels (P < 0.05), respectively, in the maintenance phase. Defining the bulk density that will constrain feed intake, as established in this study, will aid in least-cost feed formulations, feed intake modelling and growth predictions. In the third study (Chapter 5) the effect of three different dietary protein (with a specific associated amino acid content) concentrations on certain production parameters in growing ostriches were investigated. Significant differences were found for the final live weight of birds, cold carcass weight, thigh weight as well as for most of the weighed muscles at slaughter (350 days old). Concerning the growth and feed related parameters, only average daily gain (ADG) was influenced by dietary treatment (P < 0.05). Results indicated that birds on the diet with the medium protein performed optimally. One exception is the starter phase (26 – 47 kg) where chicks on the high protein diet outperformed those on the medium protein diet. In the fourth study (Chapter 6) the effects of different dietary energy concentrations on ostrich production parameters were examined in two different trials. The first trial included measurements from the pre-starter phase through the starter phase until the grower phase. The second trial was based on the finisher phase per se. Overall dietary levels provided in the pre-starter, starter and grower phases indicated better growth, FCR, skin size and grade, thigh weight, live weight, and carcass weight for the birds fed the medium energy diet. Dietary energy levels provided during the finisher phase indicated that the energy level above the medium level used improved growth rate and tanned skin size. The gender of the birds influenced carcass weight, growth rate, and certain feather parameters (P < 0.05). In the fifth study (Chapter 7) the effect of feather clipping at six to eight months of age on the production parameters of ostrich chicks were investigated. The study was conducted in three different trials. In each of the trials the feathers of half the amount of birds were clipped at six to eight months of age. Significant differences (P < 0.05) were found for the feed conversion ratio (FCR), the average daily gain (ADG) and for the quantity of valuable feathers. Results indicated that the growth rate and FCR was better for the birds which had their feathers clipped at six to eight months of age. Results also showed that the quantity of feathers with commercial value were significantly higher for the clipped group. This study showed that there may be an advantage for ostrich producers concerning the harvesting of feathers at six to eight months of age. The work in this thesis is a follow up on the framework set by Kritzinger (2011) and is part of the same project. Most of the results obtained in these studies will be incorporated in to the mathematical optimisation model of Gous and Brand (2008) for more accurate predictions concerning feed intake and other production parameters that may lower feeding costs. / AFRIKAANSE OPSOMMING: Die eerste studie (Hoofstuk 3) evalueer die groei van volstruiskuikens op diëte met drie verskillende vlakke van proteïene en aminosure. Liniêre en nie-liniêre regressiemodelle is op die data gepas en met Akaike se inligting kriterium (AIC) vergelyk. Die liniêre polinoom van die derde graad het die laagste AIC waarde vir al drie behandelings gehad. Daarom is die voorspellings van hierdie model gebruik om die groeidata te interpreteer. Beduidende verskille tussen behandelings vir groeidata (P < 0.05) is gevind. Die resultate van hierdie studie kan help met die beskrywing van die groei van volstruise, onderworpe aan aangeneemde optimale voedingsbehoeftes. In die tweede studie (Hoofstuk 4) is 'n verskeidenheid diëte geformuleer vir die vyf groeistadiums van volstruise (voor-aanvangs, aanvangs, groei, afronding en onderhoud) volgens hul voedingsbehoeftes. Die diëte is verdun met koringstrooi. Drie verdunningsvlakke (0%, 10% en 20%) is gebruik vir die voor-aanvangs- en aanvangsfase, vyf verdunningvlakke (0%, 15%, 30%, 45% en 60%) is gebruik vir die groei- en die afrondingsfase en vyf verdunningsvlakke (0%, 20%, 40%, 60% en 80%) is gebruik vir die onderhoudsfase. Weeklikse inname-data is ingesamel gedurende elke fase. In die voor-aanvangsfase het voerlywigheid (verhoging van ruvesel) inname beperk met 21% en 52% vir die 10% en 20% verdunningsvlakke (P < 0.05) onderskeidelik, terwyl inname nie beperk is gedurende die aanvangsfase nie (P > 0.05). Inname is beperk met 39% en 42% op die 45% en 60% verdunningsvlakke in die groeifase (P < 0.05) onderskeidelik, en met 17% en 39% op die 45% en 60% verdunningsvlakke in die afrondingsfase (P < 0.05), onderskeidelik. Voerdigtheid het inname beperk met 60% en 69% vir die 60% en 80% verdunningsvlakke, onderskeidelik, in die onderhoudsfase (P < 0.05). Die definiëring van die digtheid of ruvoerinhoud van voer wat inname beperk, soos in die studie bepaal, sal help met die optimering van voerformulasies, voerinname-modellering en groeivoorspellings. In die derde studie (Hoofstuk 5) is die effek van drie verskillende dieëtproteïenkonsentrasies (met 'n spesifieke gepaardgaande aminosuurinhoud) op sekere produksieparameters in die groei van volstruise ondersoek. Beduidende verskille is gevind vir die finale lewende gewig, koue karkasmassa, boudgewig sowel as vir die meeste van die geweegde spiere van voëls op slagouderdom (350 dae oud). Met betrekking tot die groei en voedingsverwante parameters, is slegs die gemiddelde daaglikse toename (GDT) beïnvloed deur die dieet (P < 0.05). Resultate het aangedui dat voëls op die medium-proteïendieet optimaal presteer. Een uitsondering is die aanvangsfase (26 – 47 kg), waar kuikens op die hoë-proteïendieet beter gevaar het as die voëls wat die medium-proteïendieet ontvang het. In die vierde studie (Hoofstuk 6) is die invloed van verskillende dieet-energiekonsentrasies op volstruis-produksieparameters in twee verskillende proewe ondersoek. Die eerste proef het gestrek vanaf die voor-aanvangsfase, deur die aanvangsfase tot en met die einde van die groeifase. Die tweede proef is gedoen vir die afrondingsfase. In die voor-aanvangs-, aanvangs- en groeifase is beter groei, voeromsetverhouding (VOV), velgrootte en -graad, boudgewig, lewende gewig en karkasgewig verkry vir die voëls wat die standaard-energie dieet ontvang het (P < 0.05). Dieet-energievlakke wat tydens die afrondingsfase fase verskaf is, het aangedui dat die energievlak bo die medium-vlak verbeterde groeitempo en gelooide velgrootte tot gevolg het (P < 0.05). Die geslag van die voëls het ’n invloed gehad op karkasgewig, groei, en sekere veerparameters. In die vyfde studie (Hoofstuk 7) is die effek van die knip van vere, op die ouderdom van ses tot agt maande, op die produksieparameters van volstruiskuikens ondersoek. Die studie is uitgevoer in drie verskillende proewe. In elk van die proewe is die vere van die helfte van die hoeveelheid voëls geknip op ses tot agt maande ouderdom. Beduidende verskille is gevind vir die VOV, die gemiddelde daaglikse toename (GDT) en vir die hoeveelheid waardevolle vere (P < 0.05). Die groeitempo en VOV was beter vir die voëls waarvan die vere op ses tot agt maande ouderdom geknip is (P < 0.05). Resultate het ook getoon dat die hoeveelheid waardevolle vere aansienlik hoër was vir die groep waarvan die vere op ses tot agt maande ouderdom geknip is (P < 0.05). Hierdie studie het getoon dat daar 'n voordeel mag wees vir volstruisprodusente indien vere geknip word op die ouderdom van ses tot agt maande. Die werk in hierdie tesis volg op die raamwerk van Kritzinger (2011) en was deel van dieselfde projek. Die meeste van die resultate wat verkry is in die studies sal in die wiskundige optimeringsmodel van Gous en Brand (2008) geïnkorporeer word vir meer akkurate voorspellings van voerinname en produksieparameters wat die voerkostes kan verlaag.