Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Although small, the South African ostrich industry contributes 60% to the total world production of slaughter ostriches. Ostrich leather contributes more than 50% of the R2.1 billion turnover of this industry. This study is the first structured investigation into the characteristics of ostrich leather focussing on factors such as age, nutrition, slaughter weight, and genetics, and the influence thereof on intrinsic leather traits.
Large variation in terms of skin quality was found between producers, month of the year and production years. The effect of age suggested that leather thickness and tensile strength increased with age while the number of nodules declined by 2.8 for every month increase in slaughter age. Slit tear strength and tensile strength increased with heavier slaughter weights. Older ostriches had higher values for slit tear strength and skin thickness. Nodule diameter increased at a rate of 0.08mm per month increase in age. Nodules with an average diameter of more than 4.0mm were only obtained in the combination of old heavy birds, while nodule diameter of the other age-weight combinations ranged between 3.3mm and 3.5mm.
Subjective assessment of nodule traits by participants with or without prior knowledge of age suggested that slaughter age accounted for 46% of the variation in estimated slaughter age. Nodule acceptability scores generally increased with an increase in slaughter age. Moderately acceptable scores were found in skins from birds 11 months and older.
The effect of energy and protein concentrations of ostrich diets suggested that raw skin areas were 19.4% and 21.8% larger at slaughter for birds receiving a diet containing 10.5 MJ/ME and 12.0 MJ ME/kg DM respectively, compared to that of birds receiving a 9.0 MJ ME/kg DM diet. Leather thickness taken parallel to the spine was increased by 13% when birds were fed the higher energy diet. Dietary protein concentrations failed to influence skin weight, skin area or any physical leather properties.
The genetic variation in nodule size measured at different sampling sites on the skin suggested that nodule size increased chronologically with age at the neck, back, upper leg, and flank and butt areas. Estimates of h² for nodule size ranged from 0.09 ± 0.07 on the flank region to 0.24 ± 0.10 on the upper leg region. Preliminary results seem to suggest that nodule size on different locations of the skin is not necessarily the same genetic trait. It was concluded that measurements at any specific site is unlikely to predict measurements at other sites with a high degree of accuracy due to the large variation that exists between measurement sites.
This dissertation provides an insight into the complexity of ostrich leather quality, and the interaction of leather traits, such as nodule size and shape, leather thickness and tensile strength, that determine ostrich leather quality. / AFRIKAANSE OPSOMMING: Alhoewel klein, produseer die Suid-Afrikaanse volstruisbedryf 60% van die totale wêreldproduksie van slagvolstruise. Volstruisleer is verantwoordelik vir meer as 50% van die R 2.1 biljoen omset van die bedryf. Hierdie studie is die eerste gestruktureerde ondersoek na die intrinsieke eienskappe van volstruisleer en die invloed van ouderdom, voeding, slagmassa en genetika op hierdie eienskappe.
Groot variasie t.o.v. leerkwaliteit is waargeneem tussen produsente, maande van die jaar en produksiejare. Die effek van ouderdom toon dat leerdikte en treksterkte verhoog het met toename in ouderdom, terwyl die aantal knoppies afneem met 2.8 vir elke maand toename in slagouderdom. Skeur- en treksterkte het verhoog met ʼn swaarder slagmassa (64kg vs. 99kg). Hoër waardes vir skeursterkte en veldikte is vir ouer voëls (384 dae vs. 234 dae ouderdom) verkry. Knoppie deursnit het teen ʼn tempo van 0.08mm per maand toename in ouderdom verhoog. Knoppies met ʼn gemiddelde deursit van groter as 4.0mm is slegs waargeneem in swaar-ou voëls, terwyl die knoppie deursnit van die ander massa-ouderdom kombinasies tussen 3.3mm en 3.5mm gewissel het.
Die subjektiewe waarneming van 28 respondente, ingelig of oningelig oor die betrokke slagouderdom, dui daarop dat die werklike slagouderdom verantwoordelik is vir 46% van die variasie in geskatte slagouderdom. Die puntetoekenning vir knoppie-aanvaarbaarheid het verhoog met ‘n toename in slagouderdom. Aanvaarbare puntetoekenning vir knoppie-ontwikkeling is verkry vir voëls vanaf 11 maande en ouer.
Die effek van energie- en proteïenkonsentrasies in volstruisdiëte toon dat die rouveloppervlakte onderskeidelik 19.4% en 21.8 % groter was met slagting vir voëls wat onderskeidelik ‘n 10.5 MJ/ME en 12.0 MJ ME/kg DM diëte gevoer is, in vergelyking met voëls wat ‘n 9.0 MJ ME/kg DM dieet ontvang het. Leerdikte, geneem parallel met die ruggraat, het met 13% toegeneem wanneer die hoër energie dieet gevoer is. Dieetproteïen konsentrasies het geen invloed op velmassa, veloppervlakte of enige fisiese leerkwaliteitseienskappe gehad nie.
Die genetiese variasie in knoppiegrootte geneem op verskillende lokaliteite op die vel toon ʼn chronologiese toename met ouderdom in die nek-, rug-, boud-, sy- en stuitjie gebiede. Beraamde h² vir knoppiegrootte wissel vanaf 0.09±0.07 op die sye tot 0.24±0.10 op die boudgedeelte. Voorlopige resultate dui aan dat knoppiegrootte op verskillende lokaliteite nie noodwendig dieselfde genetiese basis het nie. Die gebruik van een lokaliteit vir die voorspelling van die eienskappe van ʼn ander, blyk nie sinvol te wees nie a.g.v. die groot variasie wat tussen verskillende lokaliteite bestaan.
Hierdie studie verskaf insig oor die kompleksiteit van volstruisleerkwaliteit en die interaksie van leereienskappe soos knoppiegrootte en –deursnit, veldikte en treksterkte, in die bepaling van leerkwaliteit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/19547 |
| Date | 03 1900 |
| Creators | Van Schalkwyk, Salmon Jacobus |
| Contributors | Hoffman, L. C., Cloete, S. W. P., Mellett, F. D., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiii, 91 leaves : ill. |
| Rights | Stellenbosch University |
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