Little research has focused on treatment of cows with subclinical
mastitis during lactation.
Ceftiofur is a new broad-spectrum,
third-generation cephalosporin antibiotic for veterinary use that inhibits bacterial cell wall synthesis by interfering with
enzymes essential for
peptidoglycan synthesis.
Ceftiofur should be effective against a wide range of contagious and environmental
mastitis pathogens. Objectives of the present study were to evaluate the efficacy of
ceftiofur for treatment of subclinical
mastitis in lactating dairy cows, and to determine if extended
therapy regimens enhanced efficacy of
ceftiofur. Holstein and Jersey dairy cows (n = 88) from 3 dairy research herds were used. Cows were enrolled in the study based on milk somatic cell counts >400,000/mL and isolation of the same
mastitis pathogen in 2 samples obtained 1 wk apart. Cows with one or more intramammary
infections (IMI) were blocked by parity and DIM and allocated randomly to 1 of 3 different
ceftiofur treatment regimens: 2-d (n = 49 IMI), 5-d (n = 41 IMI), and 8-d (n = 38 IMI) treatment regimens. For all groups, 125 mg of
ceftiofur hydrochloride was administered via intramammary infusion. Eighteen cows with 38 IMI were included as an untreated negative control group. A bacteriological cure was defined as a treated infected mammary quarter that was bacteriologically negative for the presence of previously identified bacteria at 14 and 28 d after the last treatment. Efficacy of
ceftiofur therapy against all subclinical IMI was 38.8, 53.7, and 65.8% for the 2-, 5-, and 8-d
ceftiofur treatment regimens, respectively. Four of 38 (10.5%) IMI in control cows were cured spontaneously without treatment. All 3
ceftiofur treatment regimens were significantly better than the negative control, and the 8-d extended
ceftiofur treatment regimen treatment group was significantly better than the standard 2-d treatment group. Pathogen groups had significantly different cure rates from one another. The cure rate for the 8-d extended
ceftiofur treatment regimen was 70% for Corynebacterium bovis, 86% for
coagulase-negative Staphylococcus species, 36% for Staph. aureus, 80% for Streptococcus dysgalactiae ssp. dysgalactiae, and 67% for Strep. uberis.