Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: When modern man assumed the responsibility of domesticating animals for his own purposes, he directly accepted the responsibility associated with feeding and caring for them. Considering intensive production systems, nutrition is one of the most important aspects in maintaining healthy livestock as well as ensuring profitability is achieved. This is due to the fact that the feeding of the livestock is often the most expensive overhead cost encountered. In ostrich production systems, nutrition costs total an estimated 70 – 80% of the costs associated with rearing the birds from chick to slaughter. When dissecting the typical composition of these ostrich diets, it becomes evident energy and protein are two of the most important, and abundant, nutrients found. Therefore, this study was conducted to investigate the effects of different concentrations of protein and energy in the diets of slaughter ostriches, on their production parameters. In the first study (Chapter 3), five diets with different protein concentrations were formulated across the four feeding phases of slaughter ostriches (pre-starter, starter, grower and finisher). Three replications per treatment were conducted resulting in 15 camps of ostriches. Significant differences (P < 0.05) were found in the live weights of the birds at the end of each feeding phase except the finisher phase. In terms of the production parameters, differences (P < 0.05) were found for the dry matter intake (DMI), average daily gain (ADG) and the feed conversion ratio (FCR). Results indicated that the birds on the middle diet (control) and on the diets containing proportionally higher protein concentrations, although not different from each other, consistently outperformed those on diets containing lower concentrations of protein. These trends were also evident when comparing the cold carcass and thigh weights of the treatment birds post-slaughter. Therefore, from a financial standpoint, it could be concluded that increasing the protein content of the diets beyond that level currently used in industry (control) is not sensible. The second study (Chapter 4) was an evaluation on the primary products harvested from the birds utilized in the first study, namely the feathers, skin and meat. The aim of the investigation was to determine if the dietary protein concentrations had any effect on these products. No differences (P > 0.05) were observed across the feather yields or classes measured, except for the ‘tail feathers’, where the birds fed the lowest protein levels in their diets yielded the fewest. Differences (P < 0.05) were however found in selected skin parameters measured. Decreased dietary protein resulted in smaller wet skin size, smaller sizes of the feather nodules, as well as smaller crust size after the tanning process was completed. However, this had no impact (P > 0.05) on the skin grades achieved. Hence it became clear that dietary protein has an impact on the skin size achieved, which did not translate into differences in skin quality. Similarly, it did not affect the feather yields or quality. Energy is the most important nutrient in livestock diets as it is the first limiting nutrient influencing intake. Therefore, in the third study (Chapter 5), treatments in the form of five different levels of energy in the diets of ostriches, were investigated. Structurally, the layout was similar to the first study with three replications per treatment yielding 15 camps of ostriches. Significant differences (P < 0.05) were found between the live weights of the birds after the pre-starter phase, but not overall after the completion of the trial. The middle diet (diet 3) containing 14.5 MJ ME/kg displayed the highest gains per day of 216.0 ± 8.08 g per chick. The results of the growth were mirrored in the production parameters (DMI, ADG, FCR), where no differences (P > 0.05) were found for the rest of the feeding phases. In a follow up investigation of the effects of dietary, this chapter focused on the impact these different energy levels (Chapter 5) had on the primary products harvested after slaughter (Chapter 6). In particular, the feather yield and quality, skin yield and selected quality parameters, as well as the chemical composition of the meat was studied. No differences were found (P > 0.05) across any of the feather yields or classes measured. Concerning the skin yields and quality, similar results were found with no differences (P > 0.05) between the crust sizes or grades. With regards to the proximate composition of the meat, no major effect (P > 0.05) was found as a result of the treatment diets. Therefore, dietary energy content exhibited little influence over the feather, skin and meat parameters measured in this study. / AFRIKAANSE OPSOMMING: Die oomblik toe die nuwerwetse mens die verantwoordelikheid aanvaar het vir die mak maak van diere vir sy eie gebruik, het hy direk die verantwoordelikheid aanvaar wat geassosieer word met hul voeding en versorging. Met inagneming van intensiewe produksiestelsels is voeding een van die belangrikste aspekte in die handhawing van gesonde vee asook om winsgewendheid te verseker. Dit is as gevolg van die feit dat die voeding van diere dikwels die grootste oorhoofse uitgawe is. In volstruisproduksiestelsels bereik die voedingskostes ‘n totale geskatte hoeveelheid van 70 – 80% van die kostes wat geassosieer word met die grootmaak van die voëls vanaf kuiken tot slagvoël. Wanneer die tipiese samestelling van hierdie volstruisdiëte ontleed word, is dit duidelik dat energie en proteïene twee van die mees belangrike en volopste voedingstowwe is wat gevind word. Hierdie studie was dus onderneem om die effek van verskillende konsentrasies proteïene en energie in die diëte van slagvoëls en hulle produksieparameters te ondersoek. Vir die eerste studie (Hoofstuk 3) is vyf diëte met verskillende proteïenkonsentrasies geformuleer vir die vier voedingsfases van slagvolstruise (voor-aanvangs, aanvangs, groei en afronding). Drie herhalings per behandeling is gebruik wat 15 volstruiskampe tot gevolg gehad het. Betekenisvolle verskille (P < 0.05) in die lewende gewig van die voëls is aan die einde van elke voedingsfase gevind, behalwe vir die afrondingsfase. In terme van die produksieparameters is verskille (P < 0.05) gevind vir die droë materiaalinname (DMI), gemiddelde daaglikse toename (GDT) en die voeromsetverhouding (VOV). Resultate het getoon dat voëls wat die middelste dieet (kontrole) en diëte wat proporsioneel hoër proteïenkonsentrasies bevat het, alhoewel hulle nie van mekaar verskil nie, konsekwent beter presteer het as die wat diëte met laer proteïenkonsentrasies ontvang het. Hierdie tendense is ook waargeneem toe die koue karkas- en dygewigte van die eksperimentele voëls na-doods vergelyk is. Vanuit ‘n finansiële oogpunt kan daar dus tot die gevolgtrekking gekom word dat dit nie sinvol sal wees om die proteïeninhoud van volstruisdiëte te verhoog bo die vlak wat tans in die industrie (kontrole) gebruik word nie. Tydens die tweede studie (Hoofstuk 4) is die primêre produkte (vere, velle en vleis) wat vanaf die volstruise in die eerste studie geoes is, geëvalueer. Die doel van hierdie studie was om te bepaal of die verskillende proteïenkonsentrasies in die dieet enige effek op hierdie produkte het. Geen verskille (P > 0.05) is by die veeropbrengste of die verskillende veertipes wat gemeet is, waargeneem nie, behalwe vir die stertvere, waar die voëls wat die laagste proteïenvlakke in hulle diëte ontvang het, die laagste opbrengs gelewer het. Verskille (P < 0.05) is egter gevind in die geselekteerde velparameters wat gemeet is. ‘n Vermindering in die proteïenkonsentrasie het ‘n kleiner nat velgrootte tot gevolg gehad, asook ‘n afname in knoppiegrootte nadat die looiproses voltooi is. Hierdie waarneming het egter geen invloed (P > 0.05) op die gradering van die velle gehad nie. Dit het dus duidelik na vore gekom dat die dieetproteïen wel die velgrootte wat bereik is, beïnvloed het, maar nie tot verskille in velkwaliteit gelei het nie. Veeropbrengs en –kwaliteit is ook nie deur die dieetproteïen beïnvloed nie. Energie is die eerste beperkende voedingskomponent wat voerinname bepaal. Gegewe die groot invloed wat dit op voerinname het, is dit dus die mees belangrike komponent in die dieet van vee. Vandaar dan die derde studie (Hoofstuk 5) waar die behandelings in die vorm van vyf verskillende energievlakke in die diëte van volstruise ondersoek is. Die struktuur en uitleg van die studie was soortgelyk aan die eerste studie met drie herhalings per behandeling wat 15 volstruiskampe tot gevolg gehad het. Betekenisvolle verskille (P < 0.05) is gevind tussen die lewende gewigte van die voëls na die voor-aanvangsfase, maar nie nadat die hele proefneming voltooi is nie. Die middelste dieet (dieet 3) wat 14.5 MJ ME/kg bevat het, het die hoogste toename per dag van 216.0 ± 8.08 g per kuiken opgelewer. Groeiresultate is weerspieël in die produksieparameters (DMI, GDT, VOV), waar geen verskille (P > 0.05) in die res van die voedingsfases gevind is nie. Tydens ‘n opvolgondersoek rakende die effek van dieet, het hierdie hoofstuk gefokus op die impak wat die verskillende energievlakke (Hoofstuk 5) op die primêre produkte wat na-doods geoes is. Daar is in besonder na die vere-opbrengs en –kwaliteit, velgrootte en geselekteerde kwaliteitparameters, asook die chemiese samestelling van die vleis gekyk. Geen verskille (P > 0.05) is by die veeropbrengste of die verskillende veertipes wat gemeet is, gevind nie. Met betrekking tot die velgroottes en -kwaliteit, is soortgelyke resultate gevind met geen verskille (P > 0.05) tussen die knoppiegrootte en –gradering nie. Met verwysing na die proksimale samestelling van die vleis is geen betekenisvolle effek (P > 0.05) as gevolg van die eksperimentele diëte waargeneem nie. Die inhoud van die dieetenergie het dus ‘n klein invloed op die vere-, vel- en vleisparameters wat in hierdie studie geëvalueer is, gehad.

Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009. / Females of many bird species prefer to mate with males exhibiting elaborate ornamentation, which serves as an indicator of male quality. Such ornaments, called secondary sexual traits, could act as signals to females that males could confer direct and/or indirect genetic benefits (when offspring inherit superior genes), on offspring. In particular, it has been suggested that these signals relate to male ability to resist infections, as only high quality individuals are able to invest both in high immune defence and elaborate ornament expression. The ostrich (Struthio camelus) is the largest living bird and is a member of the family of flightless birds, the ratites. They are sexually dimorphic, males displaying black plumage, and a pink-coloured neck and bill; whereas females display dull-brown plumage (both sexes have white feathers). Little is known about the mating system of ostriches: they are promiscuous and in the wild, males and females have multiple partners. The communal nesting system of ostriches is unique in that only the major female and major male provide parental care, in the form of incubation and guarding the offspring until independence. Furthermore, a remarkable feature of cohorts is that offspring may differ greatly in size, and these size differences are likely to have a genetic basis arising from differing parental genotypic differences. As a trade-off between immune response and life-history traits has been documented in various bird species, I examined the relationships between male secondary sexual traits (and specifically colouration) and maternal investment; levels of immunocompetence in both parents and chicks; and chick growth. This study showed that females invest more at the egg stage in response to traits involved in the male courtship display: the colour of the neck, white and black body feathers, and the brightness of black feathers. As these traits, which are exposed during the courtship display as well as during male-male interactions, were related to male immune responses, I suggest that only high quality males will be able to display their condition optimally. Chicks with higher growth rates were found to have intermediate responses to stimulation of their humoral immune system with diphtheria and tetanus vaccines, suggesting that not only fitness benefits, but also costs are associated with mounting an immune response; and that variation in humoral responses and growth rates relates to how individuals trade off these costs and benefits. In addition, chick humoral responses were found to be related to the humoral response of both parents, but through different antibody responses (maternal responses to tetanus and paternal responses to diphtheria), suggesting that this component of the immune system is heritable. As the colouration of white feathers predicted chick growth rates, as well as a male’s ability to raise an antibody response, I suggest that this visual cue could serve as a signal to females of male humoral immunocompetence, therefore forming the basis of mate choice whereby females could increase the fitness of their offspring through higher growth rates.

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.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The nutrient requirements for breeding ostriches are currently not well-defined. Quantification of the nutrient requirements will improve the financial wellbeing of the industry. A study of the growth of the reproductive organs and liver, together with various production studies, were therefore undertaken in order to gain knowledge about the nutrition of breeding ostriches, thereby quantifying the nutrient requirements of breeding ostriches. Various studies were conducted to determine the influence of dietary protein, amino acids and energy on production levels of breeding ostriches. In a first study, five diets, varying in crude protein (CP) but with a constant energy content of 9.2 MJ ME/kg feed, were provided at a feed intake level of 2.5 kg/bird/day. The dietary CP levels were 7.5%, 9.1%, 10.8%, 12.3% and 14.0%. No differences (P>0.05) between treatments (total eggs per female per season) were found for number of unfertilized eggs (eggs per female per season; 8.9±0.8), dead-in-shell chicks (8.0±0.5), number of chicks hatched (19.1±1.1) and change in mass of females (-16.2±1.6kg). A tendency was observed for a difference in total egg production (mean and standard error; 39.1±3.6; P=0.08). The 12.3% CP diet caused the lowest (P<0.05) change in live mass (-3.8±2kg) for male birds. No interaction (P>0.05) occurred between the genotype of the bird and the dietary protein concentration for both egg and chick production. In a second study, six diets varying in ME (MJ ME/kg feed), were provided at an average feed intake level of 3.4 kg/bird/day. The levels were 7.5, 8.0, 8.5, 9.0, 9.5 and 10.0 MJ ME/kg feed respectively. No differences (P>0.05) were observed for total eggs produced per female per season (44.8±7.8), number of chicks hatched (15.4±4.1), number of infertile eggs (11.5±3.8), number of dead-in-shell eggs (12.1±3.2) and change in mass of females (10.7±3.6kg). Males increased linearly (y=2.4x + 2.45; R2=0.09; P<0.05) in live mass as the dietary energy content increased. Two eggs per diet per month were analyzed for crude protein, crude fat and trace elements, and one egg per diet per month was analyzed for fatty acid composition. Eggs from the first and last month of the season were subjected to amino acid analysis. Analysis of variance showed no difference in crude protein and fat (P>0.05) content of eggs between the experimental diets, as well as for the calcium content of eggshells. The proline content differed (P<0.05) between the diets. The C18:3n-3 (linoleic acid) content of the eggs increased (P<0.05) amongst the dietary treatments. Crude protein, fat and C18:3n-3 content in eggs increased (P<0.05) for the number of the egg in the laying cycle. In a third study, the feed intake of breeding ostriches, as affected by dietary energy content was investigated. Average feed intake (kg feed/bird/day) was not affected (P>0.05) at any dietary energy level when levels of 8.0, 8.7, 9.4, 10.1, 10.8 and 11.5 MJ ME/kg feed were provided. The mean and standard error was 3.7±0.2kg. The production of breeding female ostriches was not influenced by dietary ME and protein at these feed intake levels. Ostrich birds do not have the ability to regulate their feed intake at any dietary energy level as used in this study. The amount of nutrients deposited in the eggs had no influence on the reproductive efficiency of the breeding female ostrich. The experiments also revealed that female breeding ostriches were independent of dietary energy and protein as used in this study for the mean frequency of egg laying at various dietary protein and energy levels (P>0.05). In a fourth study, the growth and development of the reproductive organs of female birds at the onset of the breeding season were investigated. The amount of nutrients needs to be determined in order to support the growth of the reproductive organs during the breeding season, due to the fact that these organs are linked to egg production. It was thus necessary to investigate whether the reproductive organs grew and developed during a season. The first slaughter interval was conducted at the start of the breeding season. The ovary, oviduct and liver were collected, weighed after each slaughter and analyzed. Ovary and oviduct were analyzed for crude protein and fat. No differences (P>0.05) were observed between the different slaughter intervals for the mass, crude protein and fat content of both organs. No trend (P>0.05) in the weight of the oviduct could be observed over the 49-day period, this weight being highly correlated with body weight; whereas the ovary weight tended to be correlated with the time after the onset of the breeding period, although the variation in weights, both within and between weighings, was very high. The variation in the weight of the ovary probably reflects differences in the laying pattern of individuals. The number of follicles were not affected (P>0.05) by the number of days after mating. Livers were assessed for crude protein and fat, but no difference (P>0.05) was detected between the intervals, but the weight difference amongst the slaughter intervals was significant (P<0.05), suggesting that the ostriches used liver reserves to supplement nutrients that obtained from the diet for the development of the reproductive organs. This data will be used in an optimising model (Brand & Gous, 2006) to predict the nutrient requirements of female breeding ostriches. This study suggests that the female breeding ostrich might need additional protein during the first 7 weeks of the breeding season. Results from Chapter 4 and previous studies were used to calculate the energy, protein and amino acid requirements for the egg production and maintenance of the breeding female ostrich. Two methods were used to determine the energy requirement for egg production. The Metabolisable Energy requirement for egg production (MEe) and efficiency of ME utilization for energy deposition in the egg (ko) was calculated as 12.2 MJ (for an average size egg of 1.4kg) and 0.8 respectively. The Effective Energy requirement for egg production (EEe) and maintenance (EEm) was calculated as 15.9 MJ/day and 17.1 MJ/day respectively. Average total daily protein requirement (TPt) was calculated as 175g day. The amino acid requirements for maintenance and egg production is also provided, which is lower than previous studies. This study also provides evidence that the nutrient requirements are different for every month of the breeding season. / AFRIKAANSE OPSOMMING: Tans heers daar onsekerheid oor die voedingsbehoeftes van volstruis broeivolstruise. Kwantifisering van die voedingsbehoeftes sal ‘n finansiële hupstoot aan die industrie gee. ‘n Groeistudie van die reproduksie-organe en lewer, tesame met ‘n aantal produksie-studies, is uitgevoer om inligting oor die voedingsbehoeftes van volstruis broeivoëls te versamel. Daarby is die voedingsbehoeftes teoreties bereken. ‘n Aantal studies was uitgevoer om die invloed van dieët proteïen en aminosure en energie op produksie-data te bepaal. Eerstens is vyf diëte, wisselend in ru-proteïen (RP) en beperk tot ‘n inname van 2.5 kg/voël/dag, aan broeivolstruise gevoer. Die RP van elke dieët was 7.5%, 9.1%, 10.8%, 12.3% en 14.0%. Die energiewaarde van die voer is konstant by 9.2 MJ ME/kg voer gehou. Geen verskille (P>0.05) was tussen die behandelings waargeneem vir aantal geil eiers (totale eiers geproduseer per voël per seisoen; 8.9±0.8), aantal dood-in-dop (8.0±0.5), aantal kuikens (19.1±1.1) en verandering in massa van wyfies (-16.2±1.6kg) nie. ‘n Neiging (P=0.08) is wel waargeneem vir totale aantal eiers geproduseer. Die gemiddelde en standaard fout was 39.1±3.6. Die 12.3% dieët het tot die laagste verandering (P<0.05) in lewendige massa (-3.8±2kg) vir die mannetjies gelei. Geen interaksie (P>0.05) was tussen die genotipe en dieët proteïen konsentrasie vir beide eier- en kuikenproduksie opgemerk nie. In ‘n tweede studie is ses diëte, variërend in ME (MJ ME/kg voer), by ‘n gemiddelde tempo van 3.4 kg/voël/dag gevoer. Die verskillende ME-vlakke was 7.5, 8.0, 8.5, 9.0, 9.5 en 10.0 MJ ME/kg voer. Geen betekenisvolle verskille (P>0.05) is vir totale eiers geproduseer per voël per seisoen (44.8±7.8), aantal kuikens uitgebroei (15.4±4.1), aantal geil eiers (11.5±3.8), aantal dood-in-dop eiers (12.1±3.2) en massa verandering van wyfies (10.7±3.6kg) opgemerk nie. Die mannetjies het toegeneem in liggaamsmassa (P<0.05) soos daar ‘n toename was in die energievlak van die dieët. Twee eiers per dieët per maand is vir ru-proteïen, vet en spoorelemente, en een eier per diet per maand vir vetsure ontleed. Eiers van die eerste en laaste maand van die seisoen is ontleed vir aminosure. Analise van variansie het aangetoon dat daar geen verskille (P>0.05) bestaan vir die ru-proteïen en vetinhoud van die eiers by die verskillende eksperimentele diëte, asook die kalsiuminhoud van die eierdoppe. Prolien vlakke het tussen die diëte verskil (P<0.05). Die C18:3n-3 (linoleïensuur) inhoud van die eiers het verskil (P<0.05) tussen die dieët behandelilngs. Vir die hoeveelste eier in die lê siklus het die ru-proteïen-, vet- en C18:3n-3 inhoud van die eiers verhoog (P<0.05). In ‘n derde studie is ondersoek ingestel na die voerinname van die broeivolstruise soos moontlik beïnvloed deur die energievlak van die dieët. Gemiddelde voerinname (kg voer/voël/dag) is nie (P>0.05) deur die verskillende dieët energie vlakke van 8.0, 8.7, 9.4, 10.1, 10.8 en 11.5 MJ ME/kg voer beïnvloed nie. Die gemiddelde en standaardfout was 3.7±0.2kg. Die produksie van broeivolstruise nie deur verskillende dieëtvlakke van proteïen en energie by vlakke soos gevoer in hierdie studie geraak nie. Broeivolstruise in hierdie studie het nie die vermoë gehad om hul voerinname te beheer by enige dieët energievlak soos gebruik nie. Die aantal nutriënte wat in die eiers neergelê is, het geen bydrae tot die reproduksievermoë van die wyfie gehad nie. Die studie het verder bewys dat die gemiddelde frekwensie van eier-lê by wyfies onafhanklik was by dieët-energie en -proteïenvlakke (P>0.05) soos in hierdie studie gebruik. In ‘n vierde studie is die groei en ontwikkeling van die reproduksie-organe van die wyfies bestudeer tydens die aanvang van die broeiseisoen. Die hoeveelheid of konsentrasie van voedingstowwe moes bepaal word om die groei van die reproduksie-organe te ondersteun tydens die broeiseisoen, omdat hierdie organe aan eierproduksie gekoppel is. ‘n Studie is derhalwe uitgevoer om te bepaal tot watter mate die reproduksie organe groei en ontwikkel tydens die broeiseisoen. Die eerste slagting is uitgevoer op die dag van afkamp. Die ovaria, ovidukt en lewer is versamel, geweeg en ontleed. Die ovaria en ovidukt is ontleed vir ru-proteïen en vet. Geen verskille (P>0.05) is tussen die verskillende slagtings vir die gewig, ru-proteïen en vetinhoud vir beide organe opgemerk nie. Geen betekenisvolle tendens in die gewig van die ovidukt is waargeneem oor die 49-dae periode nie, maar die gewig was hoogs gekorreleerd met liggaamsmassa. Ovaria-gewig het geneig om gekorreleerd te wees met die aantal dae na afkamp. Variasie binne en buite die gewigte was baie hoog. Die aantal follikels teenwoordig is nie beïnvloed (P>0.05) deur die aantal dae na paring. Die lewers is ontleed vir ruproteïen en vet, maar geen verskille (P>0.05) is tussen die intervalle opgemerk nie, maar die gewigte van dag 0 en 49 na paring het verskil (P<0.05). Dit kan aangevoer word dat die voëls moontlik lewer reserwes gebruik het om die voedingstowwe van die dieët te supplementeer vir die ontwikkeling van die reproduksie-organe. Data uit hierdie studie kan gebruik word in ‘n optimiseringsmodel (Brand & Gous, 2006) om die voedingsbehoeftes van broeivolstruise te bepaal. Hierdie studie beveel aan dat die broeiwyfie moontlik addisionele proteïen tydens die eerste sewe weke van die broeiseisoen benodig. Resultate van Hoofstuk 4 en vorige studies is gebruik om die energie- proteïen- en aminosuurbehoefte vir eierproduksie en onderhoud van broeivolstruise te bereken. Twee metodes is gebruik om die energiebehoefte vir eierproduksie te bereken. Metaboliseerbare Energie behoefte vir eierproduksie (MEe) en effektiwiteit van ME benutting vir energie deponering in eier (ko) is onderskeidelik as 12.2 MJ (vir ‘n eier wat gemiddeld 1.4kg weeg) en 0.8 bereken. Effektiewe Energie behoefte vir eierproduksie (EEe) en onderhoud (EEm) was onderskeidelik as 15.9 MJ/dag en 17.1 MJ/dag bereken. Die gemiddelde daaglikse proteïenbehoefte (TPt) is as 175g proteïen/dag bereken. ‘n Aanduiding van die aminosuur behoefte vir onderhoud en eierproduksie word ook gegee, wat laer is as vorige studies.

Eggshell of the African Ostrich, Struthio camelus, frequently occurs in African archaeological sites, some of which are beyond the limit of radiocarbon dating. In order to date those sites beyond the range of ¹⁴C dating using amino acid geochemistry, an understanding of the reaction kinetics governing amino acid chemistry must be achieved. The integrity of the eggshell matrix provides an excellent medium to investigate the kinetics of protein hydrolysis, amino acid decomposition, and isoleucine epimerization. Mathematical equations are derived from high temperature simulations of time and well-dated sites at ambient temperatures to determine rate constants for the reactions to a D/L ratio of 1.0. The reactions studied are Free and Total isoleucine epimerization, "classical" and "extended" hydrolysis, and the change in concentrations of free, bound, and total amino acids. Arrhenius plots aided in deriving the equations for each method which are then applied to predict kinetic parameters. Temperatures can be predicted within a 2°C range and time within 15% of its actual value if the appropriate method is used.

This study reports the isolation, purification and partial characterisation of the ostrich serpin, a2AP, as well as its target enzyme, ostrich plasmin, in its active and inactive proenzyme, viz. plasminogen, forms. Three different procedures were undertaken to isolate and purify ostrich a2AP. The first one involved L-lysine-Sepharose chromatography, ammonium sulfate fractionation, ion-exchange chromatography on Toyopearl Super-Q 650S, and ostrich plasminogen-Sepharose affinity chromatography. The second procedure replaced the latter chromatographic step with gel filtration on Sephadex G-200 and hydroxylapatite chromatography, while the third one employed instead the theoretically more efficient LBSI-Sepharose chromatographic step. The third procedure yielded purified ostrich a2AP, but the degree of purity and yield were relatively low. Ostrich plasminogen was highly purified after L-lysine-Sepharose chromatography and ostrich plasmin was obtained by the urokinase-activation of the purified ostrich plasminogen Ostrich a2AP revealed an Mr of 77-84 K and two isoelectric forms of pI 3.85 and 6.18. Nterminal sequence analysis showed ostrich a2AP to have only 2 out of 11 residues in common with both those of human and bovine a2AP. Ostrich a2AP showed the largest inhibitory effects on ostrich plasmin, followed by comm. bovine chymotrypsin, trypsin and plasmin, in that order, and it appeared to be a much less potent plasmin inhibitor than bovine aprotinin, but a much more potent one than the synthetic inhibitors, DFP and EACA. Ostrich plasminogen showed an Mr of 92 K and multiple isoelectric forms (~7) in the pI range 6.01-9.18, with a major one of pI 6.01. It showed a total of 775 amino acid residues and its N-terminal sequence showed ~53 percent identity with those of human, rabbit, cat, and ox plasminogens. Ostrich plasmin revealed an Mr of 78 K, two isoelectric forms of pI 4.07 and 6.01, and a total of 638 amino acid residues. N-terminal sequence analysis showed that 2-4 residues are identical to the 5 of human, cat, dog, rabbit, and ox plasmins. The pH and temperature optima of ostrich plasmin were determined as 8.0 and 40 oC, respectively. The thermodynamic and kinetic parameters of ostrich plasmin were computed, and plasmin was shown to prefer Lys to Arg residues in the S1 position. In conclusion, ostrich a2AP, plasminogen and plasmin showed definite similarities to their mammalian counterparts, but there were also significant differences.

The isolation and purification of calpastatin from ostrich liver is presented, along with its physicochemical and kinetic properties. By using extraction from liver, ion-exchange chromatography on DEAE-Toyopearl, heating to 90 °C for 10 min and rechromatography on Toyopearl Super-Q 650 S, ostrich calpastatin was isolated and purified from ostrich liver. The purified intact calpastatin showed homogeneity on SDS-PAGE (Mr of 105.6 K). Amino acid analysis showed that ostrich calpastatin resembled that of rabbit liver and human erythrocyte calpastatin. An N-terminal sequence could not be obtained because the N-terminus was found to be blocked by an as yet unknown amino acid residue. The Mr values of degradative forms of ostrich liver calpastatin were determined to be 56 K and 90 K. By using PAG-IEF the pI of the intact form was determined to be 5.1. Ostrich liver calpastatin behaved characteristically like other calpastatins during kinetic analysis. Calpastatin inhibited calpain from pH 6 to 9 and was found to be unaffected by temperatures as high as 100 °C. Calpastatin also inhibited calpain activity at Ca2+ concentrations ranging from 1 to 10 mM. The inhibitor was shown to be phosphorylated because after incubation with alkaline phosphatase there was a decrease in inhibitory activity. No inhibitory effects were detected against other proteases such as chymotrypsin and trypsin, with both proteases inactivating calpastatin completely. Ostrich liver calpain was shown to have a pH optimum of 7.5 and a temperature optimum of 30 °C. In terms of its thermodynamic properties it resembled that of other ostrich proteases; DH, DS and DG being 47.07 kJ/mol, -91.1 J/mol/K and 74.237 kJ/mol, respectively. Ostrich liver calpain showed a Km of 0.14 % (w/v). The enzyme was active at both milli- and micro-molar concentrations of Ca2+. Ostrich liver calpastatin showed many physical, chemical and kinetic properties similar to those of other known calpastatins.

Most descriptions of the ostrich oropharynx and oesophagus are superficial and supply little meaningful morphological data. It was therefore the aim of this study to address this deficiency by means of a macroscopic and histological study of this region. The results were supplemented by data obtained by scanning electron microscopy. Macroscopic observations confirmed that in the ostrich the oral and pharyngeal cavities formed a single structure and could not be separated using visual criteria. The most obvious components observed in the roof of the oropharynx were the palate, the choana, the infundibular cleft and the pharyngeal folds, and on the floor, the interramal region, the tongue and the laryngeal mound. The prominent median longitudinal fold running along the palate and the numerous folds in the interrammal region of the floor contained a concentration of Herbst (Pacinian) corpuscles. The ramphotheca forming the rim of the oral cavity carried a sharp tomium along the rostral aspect of the mouth. which would assist the ostrich in tearing off plant material. It was further observed that both the roof and floor of the oropharynx could be macroscopically divided into two regions based on colour differences in the mucosa. The pale rostral regions were lined by a keratinized stratified squamous epithelium whereas the darker, more caudally positioned regions demonstrated a thicker non-keratinised epithelium and, in the case of the roof, a glandular layer. None of the regions of the upper digestive tract sampled revealed structures resembling taste buds and it would appear as if taste plays no role in the selection of food in the ostrich. The presence of large numbers of Herbst corpuscles in the palate may indicate the importance of texture in the selection of food in this species. In addition to confirming the folded nature of the ostrich tongue, this study revealed that the deep pouch formed by the dorsal tongue fold is further subdivided by a smaller secondary fold into dorsal and ventral recesses. The function of this structural adaptation is unclear but the large increase in surface area produced by the folds, and by virtue of the numerous mucous producing glands found in the mucosa, would presumably enhance mucous production and secretion required for ingesting often dry and difficult to swallow plant material. In addition to the tongue, the entire caudal aspect of the oropharynx was well-equipped with glandular tissue. Other adaptations for swallowing food included the presence of a highly folded mucosa in the interramal region which would indicate that the floor of the oral cavity in the ostrich is capable of a certain degree of distension to accommodate the accumulation of food in the oral cavity prior to swallowing. In similar fashion the longitudinal mucosal folds present throughout the oesophagus, as in other avian species, would also allow for distension of this organ when swallowing bulky food items. The pharyngeal folds that lie caudal to and around the opening of the Eustachian tubes in ratites are often referred to as the “tonsils” although no histological information has been presented to support this observation. This study revealed that the pharyngeal folds are filled with masses of diffuse and nodular lymphatic tissue and that epithelial folds emanating from the infundibular cleft and retropharyngeal recess formed tonsillar crypts surrounded by the lymphatic tissue. It has been well documented that in most species of birds papillae are found throughout the oropharynx. Papillae have also been described in ratites, mainly on the tongue and at the caudal aspect of the larynx. Whether the projections observed on the laryngeal mound of the ostrich in this study can be viewed as pharyngeal papillae remains debatable. Likewise, the lingual papillae seen in the ostrich were poorly developed and rudimentary. Compared to other birds, therefore, it is clear that the oropharynx of the ostrich is poorly equipped with papillae. This study confirmed that the hyobranchial apparatus consists of both central and paired caudo-lateral components, the former represented by the paraglossum and fused basihyale and urohyale, and the latter by the ceratobranchiale and the epibranchiale. The most important finding was that the paraglossum of the ostrich consisted of paired caudo-laterally directed cartilages that were connected rostrally to each other by fibrous connective tissue, and which supported the ventro-lateral aspect of the tongue. This information on the paraglossum has not previously been reported. The horns of the hyobranchial apparatus did not pass close to the skull as previously reported but in fact curved downwards away from the skull. The larynx consisted of the cricoid, procricoid and two arytenoid cartilages as is found in birds in general. It can be concluded that the present study, in addition to confirming the basic features of the oropharynx previously described for the ostrich, clarified the contradictory information presented in the literature and also provided new, unreported morphological data, some of which may be important when studying nutrition in these birds. / Dissertation (MSc)--University of Pretoria, 2008. / Anatomy and Physiology / unrestricted

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Ostrich farming is of significant economical importance in South Africa. Three ostrich mycoplasmas, Ms01, Ms02 and Ms03 have been identified previously, and were provisionally named ‘Mycoplasma struthiolus’ (Ms) after their host Struthio camelus. Ostrich mycoplasmas are the major causative organisms of respiratory diseases, and they cause stock losses, reduced production and hatchability, and downgrading of carcasses and therefore lead to large economic losses to the industry. In order to be pathogenic to their host, they need to attach through an attachment organelle, the so-called tip structure. This structure has been identified in the poultry mycoplasma, M. gallisepticum, and is made up of the adhesin GapA and adhesin-related CrmA. Currently, no ostrich mycoplasma vaccine is commercially available and for this reason the need to develop one has arisen. Therefore the first part of this study was dedicated to the identification and isolation of vaccine candidate genes in the three ostrich mycoplasmas. Four primer approaches for polymerase chain reactions (PCR’s), cloning and sequencing, were used for the identification of adhesin or adhesin-related genes from Ms01, Ms02 and Ms03. The primer approaches revealed that the target genes could not be identified due to the high diversity of sequences that were generated. Therefore sequences were also compared with those of other mycoplasma species in BLAST searches. Results showed that the most significant hit was with the human pathogen M. hominis oppD, which is located in the same operon as the membrane protein P100 involved in adhesion. Other hits were with ABC transporters which may also play a role in cytadhesion. The second part of this study was aimed at testing whether two poultry mycoplasma vaccines, M. synoviae and M. gallisepticum, can be used in ostriches to elicit immune responses until an ostrich mycoplasma vaccine has been developed. Ostriches on three farms of different age groups in the Oudsthoorn district were therefore vaccinated with these vaccines in a vaccine trial. The enzymelinked immunosorbent assay (ELISA) was used to test the level of antibody response. Results showed that both vaccines elicited an immune response in all three age groups. A high percentage of the ostriches reacted positively, which indicates that both vaccines elicit antibody responses and may therefore give protection against ostrich mycoplasma infections. / AFRIKAANSE OPSOMMING: Volstruisboerdery is ‘n belangrike ekonomiese sektor in Suid-Afrika. Drie volstruismikoplasmas, Ms01, Ms02 en Ms03, is voorheen geïdentifiseer en voorlopig ‘Mycoplasma struthiolus’ (Ms) benaam na aanleiding van hul gasheer, Struthio camelus. Volstruismikoplasmas is die grootste oorsaaklike organismes van respiratoriese siektes, kudde verliese en die afgradering van karkasse wat lei tot groot ekonomiese verliese in die volstruisbedryf. Ten einde patogenies vir die gasheer te wees, moet mikoplasmas deur middel van ‘n aanhegtingsmeganisme vasheg – die sogenaamde puntvormige struktuur. Hierdie struktuur is in die pluimvee mikoplasma M. gallisepticum geïdentifiseer, en bestaan uit aanhegting proteïen GapA en die aanhegting verwante proteïen CrmA. Tans is geen volstruismikoplasma entstof kommersieel beskikbaar nie, en derhalwe het die behoefte ontstaan om so ‘n entstof te ontwikkel. Die eerste gedeelte van hierdie studie is dus gewy aan die identifisering en isolering van entstof kandidaat gene in al drie volstruismikoplasmas. Vier inleier benaderings vir polimerase ketting reaksies (PKR), klonering asook geenopeenvolging bepalings vir die identifisering van aanhegting of aanhegting verwante gene vanuit Ms01, Ms02 en Ms03 is gebruik. Die inleier benaderings het getoon dat die teikengene nie geïdentifiseer kon word nie as gevolg van hoë variasie in die gegenereerde geenopeenvolgings. Derhalwe is geenopeenvolgings met ander mikoplasma spesies deur middel van BLAST soektogte vergelyk. Resultate het getoon dat die betekenisvolste ooreenstemming dié met die menslike patogeen M. hominis oppD was, wat deel vorm van die membraan proteïen P100 operon wat betrokke is by aanhegting. Ander ooreenstemmings sluit ABC transporters in wat moontlik betrokke kan wees by aanhegting. Die tweede gedeelte van hierdie studie het ten doel gehad om te toets of twee pluimvee mikoplasma entstowwe, M. synoviae en M. gallisepticum, gebruik kan word in volstruise om immuunresponse te ontlok tot tyd en wyl ‘n volstruismikoplasma entstof ontwikkel is. Volstruise vanaf drie plase in verskillende ouderdomsgroepe in die Oudtshoorn distrik was ingeënt met hierdie entstowwe in ‘n entstof proefneming. Die ensiem-afhanklike immuno-absorpsie essaï (ELISA) was gebruik om antiliggaam response te toets. Die resultate het getoon dat beide entstowwe immuunresponse ontlok het in al drie ouderdomsgroepe. ‘n Groot persentasie van die volstruise het positief gereageer wat ‘n aanduiding is dat beide entstowwe immuunresponse ontlok het en kan dus beskerming bied teen volstruismikoplasma infeksies.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The ostrich industry has overcome many challenges since it originated. However, it is still vulnerable to sudden changes in customer preferences and economic cycles. As feed costs are the greatest expense in ostrich production, optimising feed formulations is vital. This will be possible if the growth and development of the ostrich can be simulated by modelling software. Various studies were conducted to describe ostrich growth in the form of equations that can be used in modelling software to increase the accuracy of predictions. In the first study, birds were given the choice of four diets with varying energy (8.5 or 13.5 MJ ME/kg feed) and protein (180 or 120 g/kg feed) levels. The birds preferred the high density diet (high energy and protein) in each growth phase. A growth curve of assumed optimal growth was constructed. The chemical fractions of the body were shown to increase non-linearly with advancing age and equations were established to predict the change of the body composition over time. In the second trial, birds received a formulated growth diet and were fed according to their nutrient requirements. Growth data was collected on the separate body components of maturing birds. Feather and skin nodule growth was defined for birds hatched in the summer. Allometric equations were set up to determine, predict and model the ostrich skin size and skin weight, some bones, some organs and the commercially valuable muscles through the growth cycle. The final trial was conducted to determine the effect of diet density (energy and amino acid level) on the growth of ostrich body components. A four-stage, 3 x 5 (energy x protein) factorial design was developed with varying energy and protein feeding regimes. Protein (amino acid) level had no influence on body component growth. Energy level had no effect on feather growth, skin nodule growth, bone and organ growth and muscle growth. Increased levels of dietary energy increased the skin size and skin weight. Increasing the dietary energy level also had a significant effect on the total body fat of the birds. Allometric equations were set up for each variable to predict the effect of diet on ostrich growth. Results in this study provide a framework for simulation modelling. Predicting ostrich growth and development is paramount to accurate diet formulations and lower feeding costs. / AFRIKAANSE OPSOMMING: Die volstruisindustrie het reeds vele struikelblokke oorkom, maar bly steeds kwesbaar vir skielike veranderinge in die ekonomiese klimaat asook in die voorkeure van die verbruiker. Een van die belangrikste insetkostes in volstruisproduksie is voer en daarom is dit noodsaaklik om voerformulerings te optimiseer. Die doel van hierdie tesis was om by te dra tot die ontwikkeling van modellering sagteware wat die groei en ontwikkeling van die volstruis naboots. Die spesifieke doel was om volstruisgroei te bestudeer en te bespreek deur middel van vergelykings wat gebruik kan word om die akkuraatheid van die simulasiemodelle te verhoog. Tydens die eerste studie is die voëls die keuse van vier diëte gegee waarvan die energie- (8.5 of 13.5 MJ ME/kg voer) en proteïen- (180 of 120 g/kg voer) vlakke verskil het. Die voëls het in die hoëdigtheid voer (hoog in energie en proteïen) in elke groeifase gekies. Uit hierdie data, wat aanvaar is om optimale groei te verteenwoordig, is ‘n groeikurwe gekonstrueer wat getoon het dat die chemise komponente van die liggaam nie-linieêr toegeneem het oor tyd. Vergelykings is hieruit afgelei wat die verandering in die liggaamsamestelling oor tyd kan voorspel. In die tweede studie het die voëls ʼn vier-fase geformuleerde groeidieët ontvang en is na gelang van hulle voedings behoeftes gevoer. Groeidata is ingesamel van die individuele liggaams-komponente van die groeiende volstruise. Veer- en velgroei is gedefinieer vir die voëls wat in die somer uitgebroei het. Allometriese vergelykings is opgestel om te bepaal hoe die volstruis se velgrootte, velgewig, sekere bene en organe, asook die kommersiële belangrike spiere gedurende die groei-siklus verander. Die finale studie is uitgevoer om die effek van voedingsvlak (energie- en aminosuurvlak) op die groei van die volstruis se liggaamskomponente te bepaal. ʼn Vier-fase, 3 x 5 (energie x proteïen) faktoriale ontwerp is gebruik met veranderende energie- en proteïenvlakke. Proteïen- (aminosuur) vlakke het geen invloed op die groei van die liggaamskomponente gehad nie. Energievlak het geen effek op die veer-, vel-, velknoppie-, been-, organe- en spiergroei gehad nie. Toenemende vlakke van energie het wel gelei tot ʼn toename in die velgrootte en massa. Die toename in voedingsengergie-vlakke het ook ʼn betekenisvolle effek op die totale liggaamsvet van die voëls gehad. Allometriese vergelykings is opgestel vir elk van die veranderlikes om die effek van dieët op elke komponent van die volstruis te bepaal. Die resultate van hierdie studies verskaf ‘n raamwerk vir die simulering en modellering van die groei en ontwikkeling van die volstruis. Akkurate voorspellings van die groei en ontwikkeling van die volstruis is noodsaaklik vir akkurate dieëtformulering en verlaagde voedingskostes.