Behandlingsresultat av kliniska mastiter
en studie av mastitbehandlingar utförda i mjölkkobesättningen på Jälla naturbruksgymnasium 1997-2008
Mastitis is an important disease in dairy cattle. It is very costly for the farmers and affects a large number of animals. Few studies have been made investigating the outcome of treatment for acute clinical mastitis under Swedish conditions, and it can be problematic to use the results in foreign studies since both the microbial flora as well as treatments may be different from the situation in Sweden. In this project we have investigated data on clinical mastitis and antibiotic treatment in the dairy herd at Jällaskolan, Uppsala based on recordings during the last ten years. The material includes both Swedish Red (SRB) and Swedish Holstein (SLB) breeds, which have been kept at the farm under similar conditions. The data contains registrations concerning the mastitis: date of outbreak, antibiotic treatment and bacteriological examination; as well as registrations regarding the individual cow such as cow-number, lactation number, date of calving and the interval between calvings. We have studied cases of acute clinical mastitis and the evaluation of treatment has been made based on bacteriological testing of the milk five weeks after treatment. In cases where this has not been applicable it has been registered if the cow e.g. was dried off, culled or got new mastitis.
The data of cows which have had mastitis show that, the frequency of mastitis was higher in SLB-cows compared to SRB-cows. Furthermore, the proportion of mastitis during the first lactation was larger for the SLB, while the distribution was more evenly spread over the first lactations for the SRB-breed. The hind udder quarters were more often infected than the front quarters. There was no difference in the results of the treatments or infecting agents between front and hind quarters, respectively. Most of the mastitis occurred early in lactation, 25 % during the first week after parturition and 40 % of the total number of mastitis cases debuted between one week before and three weeks after calving.
When comparing the microbial flora causing mastitis at Jälla with that found in studies at a national basis we discovered some differences. The proportion of mastitis caused by coagulase negative staphylococci (KNS) was higher at Jälla (19 %) than in a nationwide study (6 %). The cases of mastitis caused by Staphylococcus aureus (Sa; 15 %) and Streptococcus dysgalactiae (Srd; 10 %) were on the contrary fewer than reported in the national investigation (21 % and 16 %, respectively). Not only were the KNS-infections more common at Jälla, additionally a high proportion of the infecting strains were producing penicillinase (+), i.e. resistant to penicillin (34 % to be compared with 12.5 % reported in a national study).
When investigating which bacteria that caused mastitis in animals that had mastitis for the first time compared to animals with previous cases of mastitis we found that the proportion of KNS infections as well as cases with no bacterial growth in the milk-sample were larger in cases with first-time-mastitis. In animals that had more than one previous case of mastitis the proportion of infections caused by KNS + as well as Streptococcus uberis (Sru) was higher than among cows with mastitis for the first time. When the animals five weeks after treatment had growth of the same agens that caused the acute mastitis it was most often infections by Sa and KNS. If other bacteria were found in the milksample it was in most cases KNS +.
The most common antibiotic treatment was penicillin (pc) (77 %) followed by a combination of pc and fluoroquinolone (9 %) and fluoroquinolone alone (6 %). When studying treatment of Escherichia coli (Ec) mastitis we found no differences between the treatment results when using pc, fluoroquinolone, or pc and fluoroquinolone in combination.
Overall, 29 % of the treated animals were bacteriologically negative in milk five weeks after treatment. Twentytwo % had growth of another bacteria than the one causing the acute mastitis episode and 9 % had growth of the same bacteria. A difference was seen comparing Ec and Sa mastitis. After Ec mastitis more animals were free of Ec bacteria in milk (44 % vs 21 %) and less animals had any kind of mastitisbacteria in the milk sample (23 % vs 39 %). After KNS infection only 31 % of the animals were bacteriologically negative in milk 5 weeks after treatment.