Effects of antimicrobial treatment at drying off on bacteriological cure rate, new infection rate, and somatic cell count during the subsequent lactation in dairy cows with subclinical or unspecific mastitis - a comparative study

Quarter milk samples from 117 dairy cows with elevated somatic cell counts at the end of lactation were bacteriologically and cytologically analysed 1 4 days and 7 days before drying off and on the day of dry off. 147 quarters showed subclinical mastitis, 224 with unspecific mastitis, and 93 were hea lthy. On the day of drying off, the cows were therapied intramammary in all quarters with one of the following long-acting antimicrobial suspensions: No 1, containing 1g Cloxacillin, an oily and dynomilled suspension (Orbenin (R) extra), No 2, containing 0,8g Oxacillin, 200mg Oxacillin-Sodium-Monohyd rate, an oily suspension (Stapenor retard(R)), No 3, containing 100 000 I.U . Penethacillin, 300 000 I.U. Benethamin-Penicillin, 100 mg Framycetinsulfa t, an oily suspension (Benestermycin(R)), No 4, with 1g Cloxacillin, an oil y suspension (Vetriclox(R)). 25 cows were left untreated as a control group . Quarter milk samples were taken from these animals on the day of parturit ion for bacteriological investigation and on days 7 and 14 after parturitio n for bacteriological examination and measuring somatic cell count. The ant ibiotic dry cow therapy, regardless the used preparation, resulted in a sig nificant higher grade of bacteriological curing rate and newinfection-rate compared with untreated cows. The cure rate concerning the somatic cell cou nt in quarters with subclinical and unspecific mastitis before drying off w as significantly higher than in untreated ones. Such an effect was not seen in healthy udder quarters. Comparison between the four antibiotic suspensi ons in relation to the grade of somatic cell count depression and somatic c ell count cure rates showed qualitative differences between them: Suspensio n No1 ranked above No2, No2 above No3, followed by No 4. The results provid e strong evidence that the therapy of cows with subclinical and unspecific mastitis or the end of lactation with antimicrobial long-acting suspensions at the time of during off is strongly recommended.