Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Mastitis is the most prevalent and costly production disease of dairy cattle; hence mastitis
incidence is a distinctly important trait in dairy cattle. The primary objective of the study
was to determine the economic value, and develop a model for genetic prediction of clinical
mastitis in South African Holstein cattle. These procedures are a prerequisite to including
this trait in the breeding objective. The cost of clinical mastitis per incident was calculated as
the sum of revenue loss due to discarded milk during the infection period and the
associated treatment costs. Economic value (ZAR/incident) was calculated as the change in
profit (increase in costs) resulting from a simulated marginal increase in mastitis incidence in
an average herd. Average economic losses due to clinical mastitis were estimated at
ZAR919.96/cow/year and the average incidence was 0.9cases/cow/year. The economic
value of clinical mastitis was ‐ZAR1079.51/incident. A model for predicting estimated
breeding values (EBVs) for clinical mastitis using somatic cell score (SCS), fore teat length
(FTL), udder depth (UD) and rear udder height (RUH) was developed, using genetic
(co)variances among these traits. Since EBVs for SCS, FTL, UD and RUH are routinely
estimated under the national genetic evaluation programme, EBVs for clinical mastitis can be predicted from the model developed in the current study. Thus, the results of the study
provide the basis for including clinical mastitis in the breeding objective for South African
Holstein cattle. / AFRIKAANSE OPSOMMING: Mastitis is die mees algemeenste en duursteproduksie siekte wat voorkom by melkbeeste,
daarom is die voorkoms van mastitis 'n belangrike eienskap in melkbeeste. Die primêre doel
van die studie was om die ekonomiese waarde te bepaal, asook die ontwikkeling van 'n
model vir genetiese voorspelling van kliniese mastitis in Suid‐Afrikaanse Holstein beeste.
Hierdie prosedures is 'n voorvereiste vir insluiting van hierdie eienskap as ‘n teeldoelwit in
seleksie programme. Die koste van kliniese mastitis per voorval is bereken as die som van
die inkomste verlies weens melk weggegooi tydens die infeksie periode en die
gepaardgaande koste vir die behandeling. Ekonomiese waarde (ZAR / voorval) is bereken as
die verandering in wins (toename in koste) wat voortspruit uit 'n gesimuleerde marginale
toename in mastitis voorkoms in 'n gemiddelde kudde. Gemiddelde ekonomiese verliese as
gevolg van kliniese mastitis was beraam op ZAR919.96/koei/jaar en die gemiddelde
voorkoms was 0.9gevalle/koei/jaar. Die ekonomiese waarde van kliniese mastitis was ‐
ZAR1079.51/geval. 'n Model vir die voorspelling van beraamde teelwaardes (EBV’s) vir
kliniese mastitis is ontwikkel deur gebruik te maak van die ko‐variansies tussen die
onderskeie eienskappe: somatiese sel telling (SST), voorspeen lengte (VSL), uier diepte (UD)
en agter uier hoogte (AUH). Aangesien teelwaardes vir SST, VSL, UD en AUH gereeld beraam
word onder die Nasionale genetiese evaluasie program, kan teelwaardes vir kliniese mastitis
voorspel word vanuit die model wat ontwikkel is in die huidige studie. Dus verskaf die
resultate van hierdie studie ‘n basis vir die insluiting van kliniese mastitis as ‘n teeldoelwit in
seleksie programme van die Suid‐Afrikaanse Holstein beeste.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/86396 |
| Date | 04 1900 |
| Creators | Man'ombe, Edson |
| Contributors | Dzama, K., Banga, C., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | ix, 58 p. |
| Rights | Stellenbosch University |
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