A comparison of the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts after calving in cows also given internal teat sealants.
AIM
To compare, in cows treated with an internal teat sealant, the effect of short-acting and long-acting cloxacillin-based dry-cow therapy on somatic cell counts (SCC) after calving.


METHODS
Cows from a spring-calving, pasture-based dairy farm in the Manawatu-Whanganui region of New Zealand were randomly allocated to receive either a short-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=291) or a long-acting cloxacillin and ampicillin dry-cow therapy and internal teat sealant (n=288) at the end of lactation. Cows were managed on-farm with routine husbandry procedures through the dry period and following calving. A multivariable logistic regression model was used to determine the association between length of action of dry-cow therapy and the proportion of cows with a SCC >150,000 cells/mL at the first herd test after calving.


RESULTS
Age of cow, mean SCC for the preceding season and interval from calving to the first post-calving herd test were all associated with the proportion of cows with an individual SCC >150,000 cells/mL at the first herd test (p<0.001) Treatment with the short-acting dry-cow therapy was not associated with decreased odds of cows having a SCC >150,000 cells/mL at the first herd test compared with treatment with long-acting dry-cow therapy (OR=0.724; 95% CI=0.40-1.30).


CONCLUSIONS AND CLINICAL RELEVANCE
In this herd, which routinely used internal teat sealants, the use of short-acting cloxacillin-based dry-cow therapy did not result in an increased proportion of cows with elevated SSC post-calving. This was a single farm, single year study but indicates that in this herd, changing from a long-acting to a short-acting antimicrobial may have no impact on the prevalence of subclinical mastitis.
['Whitfield|L K|LK|', 'Laven|R A|RA|']
D000667:Ampicillin D000818:Animals D000900:Anti-Bacterial Agents D002417:Cattle D002452:Cell Count D003023:Cloxacillin D003612:Dairying D004338:Drug Combinations D005260:Female D016015:Logistic Models D008321:Mammary Glands, Animal D008414:Mastitis, Bovine D009520:New Zealand D049590:Postpartum Period D011897:Random Allocation
short-acting long-acting Dry-cow therapy somatic cell count cloxacillin ampicillin