Sustainable management of breech flystrike in sheep by manipulating tail length: the effect of tail docking on lamb welfare as well as the genetics of ovine tail length

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dc.contributor.advisorCloete, Schalk W. P. en_ZA
dc.contributor.advisorDzama, Kennedyen_ZA
dc.contributor.advisorScholtz, Ansieen_ZA
dc.contributor.authorTeubes, Meganen_ZA
dc.contributor.otherStellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.en_ZA
dc.date.accessioned2024-03-05T15:58:58Z
dc.date.accessioned2024-04-26T19:58:57Z
dc.date.available2024-03-05T15:58:58Z
dc.date.available2024-04-26T19:58:57Z
dc.date.issued2024-03
dc.descriptionThesis (MScAgric)--Stellenbosch University, 2024. en_ZA
dc.description.abstractENGLISH ABSTRACT: It is expected that society will place more pressure on animal production systems to implement change, given increased awareness of ethical animal husbandry and global sustainability. Increased temperatures, due to climate change, are likely to provide favourable conditions for insect activity, thereby inducing favourable conditions for blowfly activity. Myasis following on the deposition of eggs by gravid females of the Australian sheep blowfly, Lucilia cuprina, in the breech area of Merino sheep compromises animal welfare and results in high production losses. Tail docking is a commonly accepted way to render lambs less attractive to breech flystrike as adult sheep, by reducing dag formation in the breech area. This procedure is considered as invasive and painful, with an immediate impact on lamb welfare. Therefore, this study assessed the degree of discomfort lambs experienced both during tail docking and after the procedure was conducted. A total of 228 lambs were randomly assigned to a treatment group whose tails were docked with a hot-blade and a control group where lambs were left intact after tail length was measured. Behavioural assessment of the two groups during tail docking recorded higher (P < 0.05) levels of agitation and vocalisation in the treatment group, while the control group were more likely to be calm. These behavioural patterns persisted in the post-procedural phase with no differences (P > 0.05) between recordings 2 or 10 minutes after docking. The second objective was to determine if there is sufficient genetic variation to select Merino sheep for shorter tail length, on the assumption that selection for shorter tails may provide the same benefits as docking without the painful docking procedure. Tail length had a moderate heritability of 0.30 ± 0.08 with a small maternal effect (0.08 ± 0.04) and nonsignificant permanent dam environmental effect. However, selection for shorter tails will reduce the size of lambs if breeding values are not adjusted for skeletal size by including docking weight as a covariate when breeding values are estimated. The final objective of the study was to assess the effect of breeding for shorter tails on other production traits by estimating genetic correlations between tail length and hogget traits. Tail length was genetically correlated to clean fleece weight (0.36 ± 0.18) and total wrinkle count (0.33 ± 0.15). Selection for a reduced tail length may thus compromise fleece weight and result in plainer (less wrinkly) sheep. The latter genetic correlation is favourable, given the well-recorded higher predisposition of wrinkly sheep to breech strike. It was concluded that tail docking results in at least temporary discomfort in young lambs, thereby compromising their welfare. This procedure could potentially be replaced by selection for shorter tails. However, the reduction of tail length to levels where breech strike is expected to be minimised may take several decades.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Daar word verwag dat die samelewing meer druk op diereproduksiestelsels sal plaas om verandering te implementeer, gegewe verhoogde bewustheid van etiese veeteelt en wêreldwye volhoubaarheid. Verhoogde temperature, as gevolg van klimaatsverandering, sal waarskynlik gunstige toestande vir insekaktiwiteit verskaf, en sodoende brommeraktiwiteit ondersteun. Myiase na die neerlegging van eiers deur Australiese skaapbrommerwyfies, of Lucilia cuprina, in die broekarea van Merinoskape benadeel dierewelsyn en lei tot hoë produksieverliese. Stertsny is 'n algemeen aanvaarde manier om lammers minder aantreklik vir vlieë te maak as volwasse skape, deur misklosvorming in die broekarea te verminder. Hierdie prosedure word as indringend en pynlik beskou, met 'n besliste effek op lammerwelsyn. Daarom het hierdie studie die graad van ongemak wat lammers ervaar het, beide tydens stertsny en nadat die prosedure uitgevoer is, geassesseer. Altesaam 228 lammers is ewekansig toegewys aan 'n behandelingsgroep waarvan die sterte met 'n warmyster afgesit is en 'n kontrolegroep waar lammers onbehandel gelaat is nadat stertlengte gemeet is. Gedragsevaluering van die twee groepe tydens stertsny het op hoër (P < 0.05) vlakke van agitasie en vokalisering in die behandelingsgroep gedui, terwyl die kontrolegroep meer geneig was om kalm te wees. Hierdie gedragspatrone het voortgeduur na stertsny, met geen verskille (P > 0.05) tussen opnames 2 of 10 minute na die prosedure nie. Die tweede doelwit was om vas te stel of daar genoegsame genetiese variasie is om Merinoskape vir ‘n korter stertlengte te selekteer, met die veronderstelling dat seleksie vir korter sterte dieselfde voordele kan inhou as stertsny, maar sonder die pynlike stertsnyprosedure. Stertlengte het 'n matige oorerflikheid van 0.30 ± 0.08 gehad met 'n klein maternale effek (0.08 ± 0.04) en nie-beduidende permanente moer-omgewingseffek. Seleksie vir korter sterte sal egter die grootte van lammers benadeel indien teelwaardes nie vir skeletgrootte aangepas word deur gewig tydens stertsny as 'n kovariant in te sluit wanneer teelwaardes beraam word nie. Die laaste doelwit van die studie was om die effek van teling vir korter sterte op ander produksie-eienskappe vas te stel deur genetiese korrelasies tussen stertlengte en jaaroud-eienskappe te voorspel. Stertlengte was geneties gekorreleerd met skoonvaggewig (0.36 ± 0.18) en totale plooitelling (0.33 ± 0.15). Seleksie vir 'n korter stertlengte kan dus vaggewig benadeel en moontlik kleiner skape tot gevolg hê. Die genetiese korrelasie met plooitelling is gunstig, gegewe die bewese hoër vatbaarheid van geplooide skape vir broekaanvalle. Daar is tot die gevolgtrekking gekom dat stertsny ten minste tydelike ongemak by lammers tot gevolg het, en sodoende hul welsyn benadeel. Hierdie prosedure kan moontlik vervang word deur seleksie vir korter sterte. Die vermindering van stertlengte tot vlakke waar broekaanvalle na verwagting tot die minimum beperk sal word, kan egter etlike dekades neem.af_ZA
dc.description.versionMastersen_ZA
dc.format.extent61 pagesen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130503
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshSheep -- Breeding -- Environmental aspectsen_ZA
dc.subject.lcshAnimal husbandry -- Effect of temperature onen_ZA
dc.subject.lcshMerino sheep -- Economic aspectsen_ZA
dc.subject.lcshClimatic changesen_ZA
dc.subject.lcshWool industry -- Economic aspectsen_ZA
dc.subject.lcshFlystrike -- Genetic aspectsen_ZA
dc.subject.lcshBlowfliesen_ZA
dc.subject.lcshLamb welfareen_ZA
dc.subject.lcshTail dockingen_ZA
dc.subject.nameUCTDen_ZA
dc.titleSustainable management of breech flystrike in sheep by manipulating tail length: the effect of tail docking on lamb welfare as well as the genetics of ovine tail lengthen_ZA
dc.typeThesisen_ZA
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