"December, 2004." / Bibliography: leaves 229-251. / xvi, 265 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Disciplines of Animal Science and Biometrics SA, 2005?

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Porcine somatotropin (pST) is a naturally occurring protein (hormone), secreted by the pituitary gland of young pigs and is one of the major growth regulating factors. High levels of pST is found in circulating blood of young animals, resulting in the partitioning of nutrients into lean tissue and bone growth. Supplying an exogenous source of pST should increase the deposition of lean muscle and bone and decrease the deposition of fat in the older (above 60 kg) pig. To ascertain whether pST would have a positive influence on production- and meat characteristics in the South African scenario for pigs slaughtered at a high bodymass, a trail was conducted. For group housed animals pST had no significant effect on the following parameters: feed intake, calculated cumulatively on a weekly basis, ADG, live weight, carcass weight, carcass length, ham length or chest depth, intramuscular fat area, muscle depth and colour measured with a Hennessey probe and waterbinding capacity. However, when the FCR of pigs in this investigation were calculated, there was a significant (p<0.05) influence by sex and pST detected. Boars converted their feed to live weight better than barrows and gilts from week ten onwards. Boars had an increased FCR when treated with pST. A significant increase was found in muscle area and a significant decrease in extra muscular (back fat) area of boars and barrows. A significant pST (p< 0.05) effect (3 mm reduction) was seen for backfat depth measured by the Hennessey probe and the intrascope. Porcine somatotropin significantly (p<0.05) increased the muscle area of the loin-cut for all animals. The area covered by subcutaneous fat of boars and barrows were significantly (P<0.05) reduced by pST treatment, with no effect detected for gilts (p>0.05). Porcine somatotropin treatment increased the muscle percentage and decreased the extramuscular fat percentage in such a way that the differences between sexes was reduced. Thus, more uniform fat-muscle distribution between carcasses was obtained by pST treatment. Control animals had a significantly higher pH24 than pST treated animals (P=0.049). Lower values were found for animals receiving pST for L* (p=0.016), a* (p=0.002) and b* (P=0.016). The effect on b* (yellow-blue range) in the M longissimus thoracis of pST treated animals showed slightly (but significantly) less yellow and more green compared to control animals (p=0.016). This combined with the lower L* values (brightness) indicates that pST treated animals had a significantly darker colour meat compared to the control animals. Individually housed animals showed no significant differences for the following characteristics: live weight, carcass weight, head, trotters, shoulder, middle back, middle belly, loin belly, thigh, fillet, carcass fat and kidney. Whereas pST caused a significantly lower percentage of the middle back of boars and barrows, but not in gilts, pST could only precipitate a lower percentage (11.18%) loin back of treated animals (p=0.026) v.s. control animals (12.05%). A trend (p>0.1) was detected for percentage bone in the middle back, with the pST treated (14.17% vs. 13.18%) animals having more bone than that of control animals. pST animals had a higher percentage (p=0.024) skin (5.04%) than the control animals (4.28%). This study shows that there is no negative effect of pST on meat quality characteristics and carcass composition, in fact there is less variation between carcasses obtained from different sexes treated with pST. The producer can bring heavier animals to the market with a reduced backfat percentage and a greater percentage meat with the help of pST. / AFRIKAANSE OPSOMMING: Vark somatotropien (pST) is ‘n natuurlike hormoon wat deur die pituitêre klier in die brein afgeskei word by klein varkies en is een van die belangrikste hormone betrokke by groei regulering. Hoë vlakke van pST kom voor in die bloed van jong varkies, dit veroorsaak dan die verspreiding van nutriente in die liggaam van die varkie sodat dit meer vleis en beengroei toon en minder vet deponeer. Namate die varkie volwasse word neem die bloedvlakke van pST af en begin die liggam meer vet deponeer ten koste van proteien groei, terselfde tyd begin die seksuele kenmerke ontwikkel. Die toediening van ‘n eksterne bron van pST behoort die groei van been en vleis te bevoordeel in ouer diere (bo 60 kg). Vir die doeleindes van die ondersoek wou ons bepaal of pST ‘n positewe effek het op groei en vleiskwaliteitseienskappe van varke wat in Suid Afrikaanse kondisies gebruik word en teen ’n hoër liggamsmassa as gewoonlik geslag word. Vir varke wat in groepe behuis was was daar geen effek op die volgende eienskappe nie: voer inname weekliks bepaa, gemiddelde daaglikse toename, liggaamsmassa, karkasgewig, karkas lengte, ham lengte, bors diepte, intrmuskulêre vet en spierdikte bepaal met ‘n Hennessey sonde asook waterbindigs vermoë. Bere het egter ’n beter voeromsettings faktor gehat as burge en soggies, maar as pST toegedien is het hulle voeromsettingsfaktor toegeneem. ’n Betekenisvolle (p<0.05) toename in spier area van alle diere, met ’n gesamentlike afname in onderhuidse vet area van bere en burge (nie soggies nie) is gevind. ’n Betekenisvolle afname (3 mm) in rugvetdikte is gevind by diere wat met pST behandel is. Hierdie effekte is so in die lewe gebring dat die verskil tussen die geslagte minder prominent is en karkasse meer uniform is. Betekenisvolle hoër pH24 waardes is gevind by kontrole diere as by pST behandelde diere (p=0.049). L* (p=0.016), a* (p=0.002) en b* (p=0.016) waardes was betekenisvol laer vir pST behandelde diere as vir kontrole diere. Die effek op b* waardes (geel-blou reeks) in die M. longissimus thoracis van behandelde diere was in so ‘n mate dat die vleis ietwat minder geel en meer groen was in vergelyking met die kontrole diere (p=0.016), saam met laer L* waardes (helderheid) is ‘n indikasie van ietwat donkerder vleis van behandelde diere. Individueel behuisde diere het geen betekenisvolle effek getoon vir die volgende parameters nie: liggamsgewig, karkasgewig, kop, voete, skouer, middel rug, middel maag, lende maag, dy, haas en niere. ‘n Betekenisvolle laer persentasie middel rug is gevind in bere en burge, maar nie vir soggies nie, maar in die lende rug is ‘n betekenisvolle effek gevind vir alle diere (11.8% vir pST en 12.05% vir kontroe , p=0.026). ‘n Neiging (p>0,1) is gesien vir die hoeveelheid been in die middle rug van diere behandel met pST (14.17% vs. 13.18%) Dier met pSt behandel het’n betekenisvol hoer persentasie vel as kontrole diere gehat (5.04% vs. 4.28%, p=0.024. Die resultate van die ondersoek bewys dat daar geen negatiewe effekte van pST op vleis- en karkaseienskappe is nie, daar is self minder variasie tussen karkasse van verskillende geslagte. Die boer kan swaarder diere bemark met minder rugvet en meer vleis met behulp van pST.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of this study was to provide scientifically founded guidelines to enhance the understanding of beef production from natural pastures in arid sweet veld regions. Cattle from four breed types ranging from large to small frame sizes (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni) were compared in terms of cow production and efficiency as well as the growth performance, carcass and meat quality of steers slaughtered at 18, 24 and 30 months of age. Eighteen and 30 month old steers were slaughtered at the end of the wet summer season, while the 24 month old steers were slaughtered at the end of the dry winter season. The Afrikaner herd (59.8 ± 9.0 %) had lower (p < 0.05) pregnancy rates than the Simmentaler cross (79.3 ± 12.2 %), Bonsmara cross (76.5 ± 11.1 %) and Nguni herds (86.1 ± 5.8 %). Breed differences (p < 0.05) for weaning weight and preweaning gain were observed (Simmentaler cross > Bonsmara cross > Afrikaner > Nguni). The Nguni cow herd (46.5 ± 5.7 kg/100 kg mated) was more (p < 0.05) efficient than the Simmentaler cross (36.2 ± 5.5 kg/100 kg mated), Bonsmara cross (37.7 kg/100 kg mated) and Afrikaner herds (29.5 ± 5.9 kg/100 kg mated). During the dry winter season steers gained 23.4 ± 1.5 kg from 7 to 12 months of age and from 18 to 24 months of age they gained 20.9 ± 2.0 kg. During the wet summer season steers gained 109.7 ± 1.8 kg from 12 to 18 months and 120.3 ± 4.1 kg from 24 to 30 months of age. The best (p > 0.05) fat classification codes were attained at 30 months of age and the worst (p < 0.05) at 24 months of age. Simmentaler cross steers attained the lowest (p < 0.05) fat classification at all three age classes. At 30 months of age, 15 of the 63 steers slaughtered had 3 or 4 permanent incisors, while 47 steers had 2 permanent incisors. The total amount as well as the percentage kidney and omental fat were the highest (p < 0.05) at 30 months of age and the lowest (p < 0.05) at 24 months. Back fat thickness followed the same pattern. Although breed differences for some meat quality parameters were observed, slaughter age had a much more pronounced effect on meat quality parameters. The percentage cooking loss was the lowest (p < 0.05) at 30 months of age. The meat was also darker (p > 0.05) and more red (p < 0.05) at 30 months than at 18 or 24 months of age. The pH24 was higher (p < 0.05) at 24 (5.68 ± 0.05) and 30 months (5.65 ± 0.03) than at 18 months of age (5.48 ± 0.04). A trained sensory panel only detected that Longissimus muscle samples from 18 month old steers were more tender (p < 0.05) than that from 30 month old steers. Similar results were found for Warner-Bratzler shear force values. Marketing steers at 30 months of age resulted in higher production outputs for all the breed types than marketing weaners. For marketing both weaners and 30 month old steers the Nguni herd produced more marketable kilograms live weight than the Simmentaler cross, the Bonsmara cross and the Afrikaner herds. Different marketing systems suitable to the Arid Sweet Bushveld were identified. Each marketing system is discussed in terms of its application, advantages, disadvantages and adaptability to arid regions. It is maintained throughout that a conservative approach to grazing as well as cattle management is critical to ensure stable production systems in arid regions with erratic rainfall patterns. / AFRIKAANSE OPSOMMING: Die oogmerk van hierdie studie is om wetenskaplik gefundeerde riglyne daar te stel wat die begrip van beesvleis produksie vanaf natuurlike weidings in ariede soetveld streke sal verbeter. Beeste van vier ras tipes wat wissel van groot- tot kleinraam tipes (Simmentaler kruis > Bonsmara kruis > Afrikaner > Nguni) is vergelyk in terme van koeiproduksie en effektiwiteit sowel as die groei prestasie, karkas- en vleiskwaliteit van osse op 18-, 24- en 30-maande ouderdom. Osse wat op 18 en 30 maande ouderdom geslag is, is aan die einde van die nat somerseisoen geslag, terwyl osse wat op 24 maande ouderdom geslag is, aan die einde van die droë winterseisoen geslag is. Die Afrikaner kudde (59.8 ± 9.0 %) het ’n laer (p < 0.05) reproduksietempo as die Simmentaler kruis (79.3 ± 12.2 %), Bonsmara kruis (76.5 ± 11.1 %) en die Nguni kuddes (86.1 ± 5.8 %) gehandhaaf. Ras verskille (p < 0.05) ten opsigte van speenmassas en voorspeense groeitempo’s is waargeneem (Simmentaler kruise > Bonsmara kruise > Afrikaners > Ngunis). Die Nguni koei kudde (46.5 ± 5.7 kg/100 kg gedek) was meer (p < 0.05) effektief as die Simmentalerkruis (36.2 ± 5.5 kg/100 kg gedek), Bonsmarakruis (37.7 kg/100 kg gedek) en die Afrikaner kuddes (29.5 ± 5.9 kg/100 kg gedek). Gedurende die droëwinter seisoen het die osse vanaf 7 to 12 maande ouderdom 23.4 ± 1.5 kg in liggaamsmassa toegeneem en vanaf 18 tot 24 maande ouderdom het hulle 20.9 ± 2.0 kg toegeneem. Gedurende die nat somerseisoen het die osse vanaf 12 tot 18 maande ouderdom 109.7 ± 1.8 kg in liggaamsmassa toegeneem en van 24 tot 30 maande ouderdom het hulle 120.3 ± 4.1 kg toegeneem. Die beste (p < 0.05) vetklassifikasie kodes is op 30 maande ouderdom verkry en die swakste (p < 0.05) op 24 maande ouderdom. Simmentalerkruisosse het by alle ouderdomsgroepe die swakste (P < 0.05) vetklassifikasie kodes behaal. Op 30 maande ouderdom het 15 van die 63 osse wat geslag is 3 of 4 permanente snytande gehad, terwyl 47 osse 2 permanente snytande gehad het. Die totale hoeveelheid sowel as die persentasie nier- en omentumvet was die hoogste (p < 0.05) op 30 maande ouderdom en die laagste (p < 0.05) op 24 maande ouderdom. Rugvetdikte het dieselfde patroon gevolg. Alhoewel rasverskille vir sommige vleiskwaliteitsparameters waargeneem is, het slagouderdom’n groter effek hierop. Die persentasie kookverlies was die laagste (p < 0.05) op 30 maande ouderdom. Die vleis was ook donkerder (p < 0.05) en meer rooi (p < 0.05) op 30 maande ouderdom as op 18 en 24 maande ouderdom. Die pH24 was hoër (p < 0.05) op 24 (5.68 ± 0.05) en 30 maande ouderdom (5.65 ± 0.03) as op 18 maande ouderdom (5.48 ± 0.04). Behalwe vir sagtheid, is geen ander ras- of slagouderdomsverskille in die longissimus spiermonsters vir enige van die sensoriese eienskappe wat geëvalueer is, waargeneem nie. ’n Opgeleide sensoriese paneel het slegs waargeneem dat die longissimus spiermonsters van 18 maand oue osse sagter (p < 0.05) was as dié van 30 maand oue osse. Soortgelyke resulte is vir die Warner-Bratzler snyweerstand gevind. Die bemarking van 30 maand oud osse het hoër produksie uitsette vir al die ras tipes opgelewer as die bemarking van speenkalwers. Met die bemarking van beide speenkalf en 30 maand oue osse, het die Ngunikudde meer bemarkbare kilogram lewendige massa as die Simmentalerkruis, die Bonsmarakruis en die Afrikaner kuddes geproduseer. Verskillende bemarkingstelsels wat as geskik vir die Ariede Soet Bosveld beskou word, is geïdentifiseer. Elke bemarking stelsel is in terme van sy toepassing, voor- en nadele asook die toepaslikheid daarvan in ariede streke bespreek. Dit word deurgaans aanbeveel dat ’n konserwatiewe benadering tot beide weidings- en kuddebestuur, krities is om stabiele produksiestelsels in ariede streke met wisselvalige reënvalpatrone te verseker.