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Studies considering the effect of climate on extensive South African sheep production
Thesis (PhDAgric)--Stellenbosch University, 2024.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613829684264960 |
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| access_status_str | Open Access |
| author | Theron, Pieter Gert |
| author2 | Brand, Tertius Swanepoel |
| author_browse | Brand, Tertius Swanepoel Theron, Pieter Gert |
| author_facet | Brand, Tertius Swanepoel Theron, Pieter Gert |
| author_sort | Theron, Pieter Gert |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhDAgric)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/131932 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:42:21.587Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/131932 Studies considering the effect of climate on extensive South African sheep production Theron, Pieter Gert Brand, Tertius Swanepoel Cloete, Schalk Willem Petrus Van Zyl, Johan Hendrik Combrink Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. Climatic changes Sheep farming -- South Africa Sheep -- Effect of temperature on Sheep -- Effect of drought on -- Africa, Southern Lambs -- Productivity Sheep -- Productivity UCTD Thesis (PhDAgric)--Stellenbosch University, 2024. ENGLISH ABSTRACT: Global climate change could pose a significant challenge to the long-term sustainability of the South African sheep farming sector, but details regarding the exact impact climatic variation has on sheep production are lacking. The aim of this study was to gain a better understanding of the relationship between weather or climatic variables and the production of sheep. To achieve this aim, historical production data from seven flocks of four sheep breeds on five different research farms were analysed in relation to weather records to quantify potential weather effects on production. A trial to evaluate the efficacy of shearing as a heat stress mitigation strategy was also performed. Shearing Dohne Merino feedlot lambs under conditions of potential heat stress slightly improved thermal tolerance, but shorn animals grew significantly slower and displayed poorer feed conversion. Regression models using weather variables as independent variables to predict (re)production in the high and low line of the Elsenburg Merino flock were constructed and evaluated. The models could only explain modest amounts of the variation in production, although they did provide valuable insights into the nature and magnitude of weather effects on flock performance. Principal component analysis was used in an analysis of performance in the Elsenburg Dormer flock. The principal component methodology proved to be suitable, and it was concluded that weather conditions prior to conception could significantly impact subsequent performance in both ewes and lambs. Attempts were made to predict the difference in year-on-year performance in the Tygerhoek Merino flock using weather-based regression models, but it was found that performance could best be predicted based on the previous year’s performance. The interaction between ewe age and rainfall in the Tygerhoek Merino and Klerefontein Afrino and Namaqua Afrikaner flocks was also studied. Significant dam age effects were recorded in all three flocks. Rainfall impacted significantly but inconsistently on production. No beneficial interactions between age and rainfall were found, hence manipulation of flock age structure offers no potential as a drought mitigation strategy. The effects of rainfall during maternal gestation and the first year of life on reproductive performance in the two Klerefontein flocks was evaluated next. Rainfall affected the traits studied to a significant degree, but the effect was largely inconsistent. It appears that rainfall in excess of 275 mm during the first year of life led to an improvement in lifetime reproduction. Lamb performance in the Grootfontein Merino flock was found to be significantly affected by thermal conditions prior to maternal mating and gestation. Adverse effects were recorded when the temperature-humidity index (THI) in the year prior to mating or during gestation respectively exceeded 22.2 or 19.5. Evidence of fetal programming and carry-over effects resulting from heat stress was also uncovered in the Cradock Merino flock for lifetime reproductive traits. A THI exceeding 22.2 during gestation or 25.1 during the first year of life led to impaired lifetime performance. Overall, these results indicate that sheep are susceptible to the impacts of climate change while simultaneously offering potential for the development and implementation of targeted intervention strategies to mitigate such effects. AFRIKAANSE OPSOMMING: Wêreldwye klimaatsverandering kan ‘n beduidende uitdaging vir die langtermyn volhoubaarheid van Suid-Afrikaanse skaapboerdery inhou, maar besonderhede aangaande die presiese impak van klimaatsvariasie op skaapproduksie ontbreek. Die doel van hierdie studie was om ‘n beter begrip van die verwantskap tussen weers- of klimaatsveranderlikes en produksie in skape te verkry. Om hierdie doelwit te bereik is historiese produksiedata van sewe kuddes bestaande uit vier rasse op vyf verskillende navorsingsplase in verhouding tot weerrekords geanaliseer om potensiële weereffekte te kwantifiseer. ‘n Proef is ook uitgevoer om die doeltreffendheid van skeer as ‘n strategie om hittestres te versag te evalueer. Om Dohne Merinolammers wat potensieel hittestres in ‘n voerkraal ervaar te skeer het hulle effens meer hitte-verdraagsaam gemaak, maar geskeerde lammers het stadiger gegroei en swakker voeromset getoon. Regressiemodelle wat weersveranderlikes as onafhanklike veranderlikes gebruik om (re)produksie in die hoë en lae lyn van die Elsenburg Merinokudde te voorspel is ontwikkel en geëvalueer. Die modelle kon slegs ‘n relatief klein persentasie van die variasie in produksie verklaar, alhoewel hulle waardevolle inligting rakende die omvang en aard van weereffekte op kuddeprestasie verskaf het. Hoofkomponentontledings is in ‘n analise van produksie in die Elsenburg Dormerkudde gebruik. Die hoofkomponentmetodologie was gepas en daar is tot die gevolgtrekking gekom dat weersomstandighede voor konsepsie ‘n betekenisvolle uitwerking op die daaropvolgende produksie-uitset van beide ooie en lammers kon hê. Pogings is ook aangewend om die verskil in jaar- op-jaar prestasie in die Tygerhoek Merinokudde te voorspel deur weer-gebaseerde regressiemodelle te gebruik, maar daar was gevind dat prestasie die beste voorspel kon word aan die hand van die vorige jaar se produksie. Die interaksie tussen ooi-ouderdom en reënval in die Tygerhoek Merino- en die Klerefontein Afrino- en Namakwa Afrikanerkuddes is ook bestudeer. Betekenisvolle moerouderdomeffekte is in aldrie kuddes aangeteken. Reënval het ‘n betekenisvolle maar wisselvallige impak op produksie gehad. Geen voordelige interaksies tussen ouderdom en reënval is gevind nie, dus bied die manipulasie van die ouderdomstruktuur van ‘n kudde geen potensiaal as ‘n droogteverligtingstrategie nie. Die effek wat reënval tydens moederlike dragtigheid en in die eerste jaar van lewe op reproduktiewe prestasie in die twee Klerefontein kuddes uitoefen, is daarna geëvalueer. Reënval het die eienskappe wat bestudeer is betekenisvol beïnvloed, maar die effek was merendeels wisselvallig. Dit wil voorkom asof reënval hoër as 275 mm gedurende die eerste jaar van lewe tot ‘n verbetering in lewenslange reproduksie gelei het. Lammers in die Grootfontein Merinokudde se produksie is betekenisvol deur die hitte-toestande voor moederlike paring of gedurende dragtigheid beïnvloed. Nadelige effekte is aangeteken wanneer die temperatuur-humiditeitsindeks (THI) in die jaar voor paar of gedurende dragtigheid onderskeidelik hoër as 22.2 of 19.5 was. Getuienis van fetale programmering en oordrageffekte in lewenslange reproduksie-eienskappe as gevolg van hittestres is ook in die Cradock Merinokudde blootgelê. ‘n THI van meer as 22.2 gedurende dragtigheid of 25.1 gedurende die eerste jaar van lewe het tot verlaagde prestasie gelei. Hierdie resultate dui daarop dat skape vatbaar is vir die impak van klimaatsverandering, maar bied terselfdertyd geleenthede vir die ontwikkeling en implementering van geteikende intervensiestrategieë om hierdie impakte te versag. Doctoral 2025-04-29T09:44:29Z 2025-04-29T09:44:29Z 2024-12 Thesis https://scholar.sun.ac.za/handle/10019.1/131932 Stellenbosch University xix, 245 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Climatic changes Sheep farming -- South Africa Sheep -- Effect of temperature on Sheep -- Effect of drought on -- Africa, Southern Lambs -- Productivity Sheep -- Productivity UCTD Theron, Pieter Gert Studies considering the effect of climate on extensive South African sheep production |
| title | Studies considering the effect of climate on extensive South African sheep production |
| title_full | Studies considering the effect of climate on extensive South African sheep production |
| title_fullStr | Studies considering the effect of climate on extensive South African sheep production |
| title_full_unstemmed | Studies considering the effect of climate on extensive South African sheep production |
| title_short | Studies considering the effect of climate on extensive South African sheep production |
| title_sort | studies considering the effect of climate on extensive south african sheep production |
| topic | Climatic changes Sheep farming -- South Africa Sheep -- Effect of temperature on Sheep -- Effect of drought on -- Africa, Southern Lambs -- Productivity Sheep -- Productivity UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/131932 |
| work_keys_str_mv | AT theronpietergert studiesconsideringtheeffectofclimateonextensivesouthafricansheepproduction |