Mastitis is one of the most economically important diseases in dairy cattle worldwide. Not only does it have a negative effect on milk production, it also is one of the main reasons for culling dairy cattle.
Pathogens causing mastitis in dairy cattle can be grouped into either contagious (or host adapted) or environmental pathogens. In different parts of the world it was shown that the prevalence of these differently grouped pathogens is dependent on various risk factors. Furthermore, it was shown that control measures implemented against contagious intramammary infections caused a relative shift over time towards a higher prevalence of environmental intramammary infections. In this study udder health data from the Onderstepoort Milk Laboratory (OML) was compared over two different years, 2008 and 2013, with regards to the prevalence of specified mastitogenic pathogens in total mixed ration (TMR) dairies and pasture-based dairies. Furthermore, the within-herd prevalence of Streptococcus uberis (Str. uberis) in Str. uberis positive herds was compared between the two years and the two management systems.
Statistically significant differences were found in the prevalence of most of the major contagious and environmental mastitogenic pathogens between 2008 and 2013 and between the TMR and pasture-based dairies. Coagulase-negative staphylococci (CNS) has the highest prevalence in both TMR and pasture-based for both 2008 and 2013. Streptococcus uberis overall showed an increase in prevalence from 2008 to 2013, with the highest prevalence in pasture-based dairies in 2013. Staphylococcus aureus (S. aureus) showed a statistically significant decrease in TMR and pasture-based dairies from 2008 to 2013.
The within-herd prevalence of Str. uberis increased from 2008 to 2013 with the highest within-herd prevalence in pasture-based dairies in 2013.
Dissertation (MMedVet)--University of Pretoria, 2016.