Ultrasound scanning and body condition scoring as aids to reproduction management of sheep

Thesis (MScAgric)--Stellenbosch University, 2022.ENGLISH ABSTRACT: The body condition scoring (BSC) and ultrasound scanning of ewes with reference to their reproductive performance are management tools with potential to ease the management, nutrition and breeding of South African sheep. There is a paucity of data on condition scores and scanning figures of individual sheep in the local ovine genetic resource and relevant data were thus sourced from genetic resource flocks managed by science and research institutions. Data from the Elsenburg Merino, Dormer and South African Mutton Merino (SAMM) flocks were used to study genetic and environmental parameters for ewe mating weight, BCS at mating and lambing, as well as for correlations of these traits with reproduction. H Line Merino ewes were heavier than the L Line at mating, but no line differences were found for condition scores. The H Line was selected for reproduction while the L Line was selected against reproduction. Dormer ewes were heavier than SAMM ewes at mating, with the SAMM having higher condition scores. Ewe mating weight was highly heritable at 0.74 in Merinos, with lower estimates for BCS at mating (0.28) and lambing (0.18). Ewe mating weight was moderately heritable at 0.49 in Dormers and SAMMs, with lower estimates for BCS at mating (0.21) and lambing (0.27). Genetic correlations among these traits were positive and moderately high for all flocks, ranging from to 0.58 to 0.93. Genetic correlations of mating weight and condition scores with reproduction were mostly negative (i.e. unfavourable) across ewe age groups and analyses, significantly so in some cases. The unfavourable genetic correlations are probably related to complex interactions of age and current and previous reproduction in mature ewes, as well as the relationship of reproduction with BCS being characterised by an intermediate optimum. Further studies are indicated. On the other hand, ultrasound scanning was studied in Dohne Merino and SAMM ewes of the Mariendahl flock. Lambing year had a significant effect on all reproductive traits with values oscillating in both breeds. Number of embryos lost per ewe present at lambing was generally low (0.00 to 0.05). Number of lambs scanned per ewe available was moderately repeatable at 0.11 to 0.16, depending on breed and modelling. A comparable range of 0.16 to 0.19 was found for number of lambs born per ewe lambed. Repeatability estimates for embryonic losses were not significant. Scanning and lambing rate were highly correlated on the ewe level, suggesting that scanning figures would act as a good proxy for lambing rate in the absence of complete lambing data. Both ewe BCS and the outputs of ultrasound scanning may have a role to play in managing reproductive performance at the flock level. However, further refinement is needed before these managerial aids can be used with confidence in the broader South African sheep flock.AFRIKAANSE OPSOMMING: Kondisiepunte en die ultraklankskandering vir dragtigheid kan as bestuursmiddels gebruik word om die bestuur van reproduksie, voeding en teling van Suid-Afrikaanse teelooie te beheer. Daar is ‘n gebrek aan data aangaande kondisiepunte en skanderingsyfers van indiwiduele diere in die nasionale kleinveehulpbron en data vir die studie is van genetiese hulpbronkuddes onder institusionele bestuur bekom. Data van die Elsenburg Merino, Dormer en Suid-Afrikaanse Vleismerino (SAVM) kuddes is bekom om genetiese- en omgewingsparameters vir ooi paargewig, sowel as kondisiepunte by paring en lam te bestudeer. H-Lyn Merino-ooie was swaarder by paring as ooie in die L-lyn, maar daar was nie lynverskille vir kondisiepunte by paring of lam nie. Die H-Lyn was geselekteer vir reproduksie en in teenstelling was die L-Lyn geselekteer teen reproduksie. Dormerooie was swaarder as SAVMs by paring, maar SAVM-ooie het hoër kondisiepunte gehandhaaf. Ooi paargewig was hoogs oorerflik teen 0.74 in Merinos, met laer beramings vir kondisiepunt by paring (0.28) en lam (0.18). Ooi paargewig was matig oorerflik teen 0.49 in Dormers en SAVMs, met laer beramings vir kondisiepunt by paring (0.21) en lam (0.27). Genetiese korrelasies tussen die eienskappe was positief en matig-hoog in alle kuddes, met ramings wat tussen 0.58 en 0.93 gewissel het. Genetiese korrelasies van paargewig en kondisiepunte met reproduksie was meestal negatief (m.a.w. ongunstig) oor ooiouderdomsgroepe, met betekenisvole korrelasies in sommige gevalle. Hierdie ongunstige genetiese korrelasies is waarskynlik die gevolg van ingewikkelde interaksies van ooi-ouderdom met huidige en vorige reproduksieprestasie in volwasse ooie, sowel as ‘n verwantskap met ‘n intermediêre optimum tussen kondisiepunt en reproduksie. Verdere studies word voorgestel. Aan die ander kant is ultraklankskandering met Dohne Merino- en SAVM-ooie van die Mariendahlkudde bestudeer. Lamjaar het al die skanderingseienskappe betekenisvol beïnvloed met waardes wat baie tussen jare gewissel het. Die getal embrios verloor per ooi bekikbaar by lam was laag (0.00 tot 0.05) in albei rasse. Die getal lammers geskandeer per ooi beskikbaar was matig herhaalbaar teen 0.11 tot 0.16, afhangend van die ras en die gepaste model. ‘n Vergelykbare stel waardes van 0.16 tot 0.19 is gevind vir aantal lammers gebore per ooi gelam. Die herhaalbaarheid van embrionale verliese was nie betekenisvol nie. Skanderings- en lamtempo was hoogs gekorreleer op die ooivlak, wat daarop dui dat skanderingsresultate as ‘n goeie aanduiding van lamtempo gebruik kan word as volledige lamrekords nie bygehou word nie. Ooikondisiepunt sowel as die uitsette van ultraklankskandering kan moontlik ‘n belangrike rol in die reproduksiebestuur van skape op ‘n kuddevlak speel. Daar is egter verdere verfyning van die tegnologie nodig voordat hierdie bestuurshulpmiddels met vertroue in die breër Suid-Afrikaanse skaapkudde toegepas kan word.Master