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Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability
Thesis (MScAgric)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613891449585664 |
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| access_status_str | Open Access |
| author | Harms, Nicole Greta |
| author2 | Lambrechts, Helet
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| author_browse | Harms, Nicole Greta Lambrechts, Helet |
| author_facet | Lambrechts, Helet
Harms, Nicole Greta |
| author_sort | Harms, Nicole Greta |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132409 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:43:20.403Z |
| 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:10019.1/132409 Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability Harms, Nicole Greta Lambrechts, Helet Grobler, B. J. Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science. Rams -- Breeding Spermatozoa -- Quality Climatic changes Dohne Merino sheep -- Reproduction -- Seasonal variations Rams -- Reproduction -- Climatic factors Merino sheep -- Effect of temperature on Rams -- Feeding and feeds Rams -- Feeding and feeds Rams -- Effect of stress on Sheep -- Effect of heat on Sheep -- Water requirements UCTD Thesis (MScAgric)--Stellenbosch University, 2025. Harms, N. G. 2025. Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/59e40b9e-5fde-4ae4-9e0f-a5105fc256c3 ENGLISH ABSTRACT: Climate change is inevitable and the increases in ambient temperature, radiation and relative humidity, predisposes animals to heat stress. In recent years, the livestock sector has solely been focusing on improving the productivity and nutrition of livestock, rather than on the improvement of stress resistance. This has led to an increase in production but has also negatively impacted the sensitivity of livestock towards the warming environment. The identification and selection of breeds and individual animals that are resilient to a higher-than-normal ambient temperature, will become vital for animal production systems to contribute to food security. This study was aimed at determining the seasonal variation in testicular temperature, and how this is related to the quality of sperm samples produced. And also, what the effect was of short-term heat stress which can be considered a representative of a typical fever response, within different seasons and how spermatozoa quality recovered from the induced heat via scrotal insulation. The study consisted of four phases. Phase 1 involved the ranking of 20 adult Dohne Merino rams in terms of the reslieince towards cryopreservation at a sperm level, namely a high (HR) and low resilience (LR) group, and only 16 rams were then used for the rest of the study. The HR and LR groups were kept outdoors during a winter period (Phase 2) and summer period (Phase 3), after which both groups were maintained under indoor conditions (Phase 4). Testes data loggers were implanted into four HR rams and four LR rams to monitor testes temperature during the trial phases and these rams were also subjected to scrotal insulation for two days during each phase. Each phase consisted of 11 weeks, during which rectal temperature, testes temperature, and body surface temperature, were recorded weekly. Ambient temperature was recorded during the entire study period, and relative humidity and wind speed was measured for the outdoor phases. Semen samples were collected every fortnight over the entire study period and cryopreserved and frozen-thawed spermatozoa were subjected to a functional test. Sperm parameters recorded during the entire study period included sperm viability, sperm abnormal morphology, and acrosome integrity. Significant correlations were observed between the ambient temperature and the body surface- and testes temperature during the different housing conditions, indicating that ambient temperature influenced the manner in which rams maintained their core temperature and regulated their testes temperature in response to ambient conditions. It was determined, based on the differences observed between individual rams in terms of their testicular thermoregulation, certain rams may be more efficient in testicular thermoregulation than others. It was observed that HR and LR groups differed in terms of the quality of semen samples produced during the different seasons. This could be attributed to the high resilience rams having a higher tolerance towards changes in the ambient conditions and this tolerance is reflected in the semen samples produced. Significant differences were also observed between the different environmental phases suggesting seasons and ambient conditions played a role in the resilience of rams when subjected to different conditions. It was observed that ambient conditions played a role in how the testes were able to thermoregulate during scrotal insulation and seasons influenced the rate at which sperm quality parameters could be restored to pre-insulation values. AFRIKAANSE OPSOMMING: Klimaatsverandering is onvermydelik en die toenames in omgewingstemperatuur, bestraling en relatiewe humiditeit maak diere vatbaar vir hittestres. Tot onlangs, het die veesektor net gefokus op die verbetering van die produktiwiteit en voeding van vee, in plaas van die verbetering van stresweerstand. Dit het gelei tot 'n toename in produksie, maar het ook die sensitiwiteit van vee teenoor die warm omgewing negatief beïnvloed. Die identifisering en seleksie van rasse en individuele diere wat bestand is teen 'n hoër as normale omgewingstemperatuur, sal noodsaaklik word vir diereproduksiestelsels om tot voedselsekerheid by te dra. Hierdie studie was daarop gemik om die seisoenale variasie in testikulêre temperatuur te bepaal, en hoe dit verband hou met die kwaliteit van spermmonsters wat geproduseer word. En ook, wat die effek was van korttermyn hittestres, wat beskou kan word as 'n verteenwoordiger van 'n tipiese koorsreaksie, binne verskillende seisoene en hoe spermatozoa kwaliteit herstel het van die geïnduseerde hitte via skrotum isolasie. Die studie het uit vier fases bestaan. Fase 1 het die rangorde van 20 volwasse Dohne Merino ramme in terme van die weerstand teenoor kriopreservering op 'n spermvlak behels, naamlik 'n hoë (HR) en lae veerkragtigheid (LR) groep, en slegs 16 ramme is toe vir die res van die studie gebruik. Die HR- en LR-groepe is gedurende 'n winterperiode (Fase 2) en somerperiode (Fase 3) buite gehou, waarna beide groepe onder binnenshuise toestande onderhou is (Fase 4). Testes dataloggers is in vier HR ramme en vier LR ramme ingeplant om testes temperatuur te monitor tydens die proef fases en hierdie ramme is ook vir twee dae gedurende elke fase aan skrotum isolasie onderwerp. Elke fase het bestaan uit 11 weke, waartydens rektale temperatuur, testes temperatuur en liggaamsoppervlak temperatuur weekliks aangeteken is. Omgewingstemperatuur is gedurende die hele studieperiode aangeteken, en relatiewe humiditeit en windspoed is vir die buitefases gemeet. Semenmonsters is elke twee weke oor die hele studietydperk versamel en gevriesde en bevrore-ontdooide sperme is aan 'n funksionele toets onderwerp. Spermparameters wat gedurende die hele studieperiode aangeteken is het sperm-lewensvatbaarheid, sperm-abnormale morfologie en akrosoom-integriteit ingesluit. Beduidende korrelasies is waargeneem tussen die omgewingstemperatuur en die liggaamsoppervlak- en testestemperatuur tydens die verskillende behuisingstoestande, wat aandui dat omgewingstemperatuur die wyse waarop ramme hul kerntemperatuur handhaaf, en hul testestemperatuur gereguleer het in reaksie op omgewingstoestande beïnvloed het. Daar is vasgestel, gebaseer op die verskille waargeneem tussen individuele ramme in terme van hul testikulêre termoregulering, dat sekere ramme meer doeltreffend in testikulêre termoregulering as ander wees. Daar is waargeneem dat HR- en LR-groepe verskil in terme van die kwaliteit van semenmonsters wat gedurende die verskillende seisoene geproduseer is. Dit kan toegeskryf word aan die hoë veerkragtigheid ramme wat 'n hoër toleransie teenoor veranderinge in die omgewingstoestande het en hierdie verdraagsaamheid word weerspieël in die semenmonsters wat geproduseer word. Beduidende verskille is ook waargeneem tussen die verskillende omgewingsfases wat daarop dui dat seisoene en omgewingstoestande 'n rol gespeel het in die veerkragtigheid van ramme wanneer hulle aan verskillende toestande onderwerp is. Daar is waargeneem dat omgewingstoestande 'n rol gespeel het in hoe die testes in staat was om te termoreguleer tydens skrotum isolasie en seisoene het die tempo beïnvloed waarteen sperm kwaliteit parameters na voor-isolasie waardes herstel kon word. Masters 2025-06-06T07:55:22Z 2025-06-06T07:55:22Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132409 Stellenbosch University xxi, 8 pages unnumbered, 223 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Rams -- Breeding Spermatozoa -- Quality Climatic changes Dohne Merino sheep -- Reproduction -- Seasonal variations Rams -- Reproduction -- Climatic factors Merino sheep -- Effect of temperature on Rams -- Feeding and feeds Rams -- Feeding and feeds Rams -- Effect of stress on Sheep -- Effect of heat on Sheep -- Water requirements UCTD Harms, Nicole Greta Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title | Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title_full | Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title_fullStr | Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title_full_unstemmed | Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title_short | Heat stress resilience in rams, and the relationship with seasonal variation in sperm quality and viability |
| title_sort | heat stress resilience in rams and the relationship with seasonal variation in sperm quality and viability |
| topic | Rams -- Breeding Spermatozoa -- Quality Climatic changes Dohne Merino sheep -- Reproduction -- Seasonal variations Rams -- Reproduction -- Climatic factors Merino sheep -- Effect of temperature on Rams -- Feeding and feeds Rams -- Feeding and feeds Rams -- Effect of stress on Sheep -- Effect of heat on Sheep -- Water requirements UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132409 |
| work_keys_str_mv | AT harmsnicolegreta heatstressresilienceinramsandtherelationshipwithseasonalvariationinspermqualityandviability |