Outcome of clinical mastitis in dairy heifers assessed by reexamination ofcases one month after treatment

Heifers that were treated for clinical mastitis prior to parturition or wit hin 14 d postpartum were reexamined approximately 1 mo after treatment. Cli nical examination of the heifers and microbiological examination of quarter milk samples were carried out on both occasions. Of the 1000 heifers inclu ded in the study, 10.9% were culled within 28 d after treatment. Udder dama ge caused by mastitis was the only or main reason for culling in 96% of tho se heifers, In comparison, 4.5% of nonmastitic heifers from the same herds were culled within 30 d postpartum. Twenty-five percent of those heifers th at were not culled at d 28 after treatment had at least one nonfunctional q uarter at that time. One thousand one hundred twenty-two quarters that were clinically affected at the time of treatment were reexamined; 22% were non functional, 14% were still affected by clinical mastitis, 12% had subclinic al mastitis, 5% had a latent infection with coagulase-positive staphylococc i or Streptococcus dysgalactiae, and 46% were bacteriologically negative an d had a normal cell count at the time of reexamination. High percentages of nonfunctional quarters were observed among those quarters that were infect ed with Arcanobacterium pyogenes or with coagulase-positive staphylococci a t treatment. When all quarters that were clinically affected at treatment w ere considered, 40% of quarters were cured and were still in lactation at r eexamination. Quarters infected with coagulase-negative staphylococci had a higher cure rate than quarters infected with other organisms. At reexamina tion, clinical signs of thelitis were observed in many of those quarters th at were nonfunctional following the episode of clinical mastitis and also i n 25% of lactating quarters in which clinical mastitis persisted.