Effective udder health management and high milk production can be obtained with low antimicrobial consumption

This Belgian study collected the antimicrobial usage of a convenience sample of 57 Belgian dairy herds with an average of 69 lactating cows per herd. Data were collected by using the "garbage can audit"", asking the farmers to throw away all empty drug vials and tubes used to treat adult dairy cattle into these cans. This method is considered the most reliable for this pupose, as it reduces mistakes in registration of drug administration and at the same time allows between-herd comparison and identification of risk factors.

Total antimicrobial consumption was 20.78 DDDA (Defined Daily Dosage Animal) per 1000 cow-days (which is 7.7 daily dosage per cow year), with a large variation between herds (range from 8,68 to 41,62 DDDA per 1000 cow-days). Since emergence of resistance to critically important antimicrobials for human health is a point of major concern, this study calculated the use of those critically important antibiotics separately. The average antimicrobial consumption of the 3rd and 4th generation cephalosporins and fluoroquinolones (critically important according to the OIE classification) was 8.59 DDDA per 1000 cow-days (3.18 daily dosage per cow per year). With the exception of one herd, all herds used critically important antimicrobials. Large between-herd variation existed in the use of critically important drugs. More than two thirds of the total amount of critically important antimicrobials used on the participating herds included 3rd and 4th generation cephalosporines. Compared with previous studies conducted in the Netherlands and Canada, the authors considered the use of critically important antibiotics in this study rather high. All authors observed a large variation in consumption of antimicrobials, both overall as in the use of critically important antibiotics. This suggests that it is possible to manage herds with limited use of (critically important) antimicrobials.

Each dry cow tube was calculated as 1 daily dose (so a cow dried off in all 4 quarters would account for 4 daily dosages. 80% of the herds applied blanket dry cow therapy. Not all herds that applied selective dry cow therapy were in the group of low-consuming herds, and that group also included herds that applied blanket dry cow therapy. In the low-consuming herds, most antimicrobials were being used in dry cow therapy, wheras in the high-consuming herds, most antimicrobials were administered systemically or as intramammary mastitis therapy, suggesting that a difference in strategy toward a reductino in antibiotic use is needed between these types of herds. The authors suggest that high consuming herds should first optimise general and udder heatlh and treatment approaches as this will result in a lower disease incidence.

Although high-producing cows are more suscpetible to mastitis, in this study no association was found between antimicrobial use and milk production, indicating that high production results can be obtained without high (critically important) antimicrobial use.

Mastitis prevention and control practices and mastitis treatment strategies associated with the consumption of (critically important) antimicrobials on dairy herds in Flanders, Belgium. Stevens, M. et al. Journal of Dairy Science, Volume 99 , Issue 4 , 2896 - 2903 DOI: http://dx.doi.org/10.3168/jds.2015-10496

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