Research Phd ThesesVetoquinol

Antimicrobial consumption on Flemish dairy herds: quantification, associated factors and mastitis management input as a basis for appropriate use

The overall goals of this thesis were to picture the antimicrobial consumption (AMC) on dairy herds in Flanders, to identify associated factors and to explore whether AMC, udder health and milk quality can be influenced by intensive follow up.
The first study revealed that the average antimicrobial use was 20.78 defined daily dose animal (DDDA) per 1,000 cow-days, ranging from 8.68 to 41.62 DDA between herds. Large variation was also present in the use of for human health critically important antimicrobials. About two third of the total antimicrobials were used intramammary. On herds with a low total AMC, the majority of antimicrobials was typically used intramammary for dry-cow therapy while on herds with a high total AMC mainly intramammary antimicrobials for mastitis therapy or (long acting) systemic products (without withdrawal time for milk) were used. The AMC was negatively associated with the incidence rate of treated mastitis cases and to a lesser extent with the use of selective dry cow therapy, and was positively associated with the prevalence of heifers on the herd.
In a second part of the thesis, the use of selective dry-cow therapy was confirmed as being associated with lower AMC. Moreover, herds where (some)

mastitis cases were treated with homeopathic intramammary products had a lower AMC compared with herds not treating with homeopathic substances although further research is needed seen the lack of evidence of efficacy of this type of products. Besides, herds participating in veterinary herd health management programs had a lower AMC compared with herds not participating in such programs. The treatment of subclinical mastitis for at least 5 subsequent days was associated with an elevated use of for human health important compounds.
In the last part of the thesis, it was evaluated to what extent intensive udder health monitoring and providing advice to the farmer influences udder health, milk quality and AMC. Implementation of management measures concerning udder health was higher on herds that received intensive mastitis management input compared with herds without this input. Moreover, within the herds that received intensive mastitis management input, compliance was better when the herd veterinarian was attending (some of) the herd health visits performed by the PhD student. Further, a good or improved mastitis management was associated with a decrease in the use of for human health critically important antimicrobials.
In conclusion, a good udder health management can be supportive towards a more responsible use of antimicrobials without negative implications for milk quality and udder health.

Profile of Marina Stevens

Marina Stevens graduated in 2011 as a veterinarian at Ghent University, Belgium and started as a PhD student at the same university after graduation. She defended het PhD thesis October 2018. Marina is author of multiple peer-reviewed publications and gave presentations at (inter)national congresses as well as at local farmers meetings. After leaving Ghent University in 2015, she started working as a veterinary consultant on dairy herds as part of the Milk@vice team and in the veal industry. In August 2017 she started as product and technical manager food producing animals in Belgium and the Netherlands for Vetoquinol.