AHEAD IN ANIMAL HEALTH
Monitoring Udder Health: Evaluating Effects of changing Antimicrobial Policy Christian G.M. Scherpenzeel1, Ryan van Egmond1, Kristel W. van den Heuvel-van den Broek1, Inge M. Santman-Berends1, and Gerdien van Schaik1,2 1 GD Animal Health, the Netherlands 2 Utrecht University, Faculty of Veterinary Medicine, the Netherlands
Why? Antibiotic resistance is becoming increasingly important and given its potential association with antimicrobial use (AMU), continuous actions are taken to reduce AMU in the livestock industry. One of the most important measures to avert preventive antibiotic usage was implementation of selective instead of blanket dry cow therapy in 2013. In the Netherlands, both AMU and udder health parameters are monitored in the Dutch cattle health surveillance system (CHSS) based on routinely collected census data (17,000 dairy herds). Results
Aim The aim of our study was to determine whether we could monitor the effect of changing AMU on udder health in Dutch dairy farms.
Materials and methods Available data sources • Identification & registration data: on- and off-farm movements on animal level (RVO) • Antimicrobial supplies on herd, age group, product and delivery level (MediRund) • BTSCC: bi-weekly herd level data (Qlip) • Test-day records: animal and test-day level (CRV)
RVO
+ MediRund +
Qlip
+
CRV
higher probability to have >25% cows with a new HSCC during the start of lactation.
With the implementation of general regulations aiming to decrease AMU, the Animal Defined Daily Dosage (DDDA) in dairy herds decreased from 5.78 in 2009 to 4.03 in 2013 (SDA, 2014). After implementation of SDCT, DDDA in dairy herds decreased further to 3.06 in 2017 (SDA, 2018). Our results showed that both implementation of regulations for AMU in general (2009) and implementing selective dry cow therapy rather than blanket treatment (2013), did not result in a deterioration in most udder health indicators. The only indicator that was somewhat negatively influenced by the implementation of SDCT was the percentage of herds with >25% new HSCC in multiparous cows during the start of lactation.
Discussion The results indicate that even though total AMU (including intramammary AMU, Fig. 2) was decreased with 47% (from 5.78 DDDA in 2009 to 3.06 DDDA in 2017), a decrease in udder health indicators was not observed. Thus, application of SDCT did not seem to affect the general udder health in dairy herds. However, in dairy herds that did not use any antimicrobials the SCC of cows was significantly higher compared to the herds with an average AMU.
Conclusion
Even though most udder health parameters were not negatively influenced, the results of the multivariable models showed that not applying antimicrobials at all resulted in a higher BMSCC (+15.6 x103 cells/mL (95% CI: 15.1-16.1)), a higher incidence and prevalence of HSCC cows (OR=1.6) and a
2013
2014
It is advisable to closely monitor the effects on animal health when new policies to reduce AMU are implemented. The results provide confidence that AMU reducing measures lead to more prudent use of antimicrobials without jeopardizing animal health.
2015
2016
2017
DDDA
In total, six udder health indicators are monitored on a quarterly basis i.e. bulk milk somatic cell count (BMSCC), prevalence and incidence of high SCC cows (HSCC), herds with Fig. 1 Schematic overview of the 5 year period 2013-2017 with the implementation of selective dry cow treatment starting from 2014 a >25% incidence of HSCC primi- and multiparous cows during the start of the lactation and herds with a >25% 2,0 prevalence cows with a consistent HSCC before and after 1,8 calving. The association between udder health key indicators 1,6 and AMU was analysed using population average multi 1,4 1,2 variable regression techniques with appropriate distributions 1,0 and link functions. In addition, other variables that may be 0,8 related to udder health were included in the models. 0,6 • Dutch dairy herds (~ 17,000 herds) 0,4 0,2 • Complete data >75% of Dutch dairy herds 0,0 • 5 year period: 1st January 2013 – 31st December 2017 2013 2014 2015 2016 2017 AMU mastitis therapy
AMU dry cow therapy
Fig. 2 Intramammary antimicrobial use (AMU) in Annual Defined Daily Dosages (DDDA) on farm-level from 2013 - 2017
www.gdanimalhealth.com/udderhealth c.scherpenzeel@gdanimalhealth.com
GD2059/01-20