Ceftiofur hydrochloride administered at a dosage of 2.2 mg of CE/kg, SC or IM, once daily for 5 days was efficacious for treatment of APM in dairy cows.

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.

A survey was conducted to determine and contrast prevalence of IMI in nulligravid and primigravid dairy heifers pre- and postpartum. Contrasts were made to evaluate the risk factors of location of dairy, trimester of gestation, and season of sampling on IMI. Twenty-eight dairies in California, Louisiana, Vermont, and Washington were studied. Lacteal secretions were collected aseptically from heifers at breeding age (8 to 19 mo) from one side of the gland and again at 4 d postpartum from all quarters. Of the quarters sampled, 65.6% prepartum and 64.0% postpartum were free of IMI. The percentages of quarters with IMI from coagulase-negative staphylococci or Staphylococcus aureus IMI were 27.1 and 9% prepartum and 21.8 and 2.9% postpartum. Staphylococcus aureus IMI were most prevalent in Louisiana during the months other than summer. Location, herd, and season significantly influenced prevalence of IMI. The prevalence of IMI was greatest during the last trimester of pregnancy, ranging from 49.2% in the winter to 36.8% in the summer. The significant effects of herd location and season suggest that management variables influence prevalence of heifer IMI. Because prevalence of IMI was greatest during the last trimester of pregnancy compared with prevalence during earlier stages of pregnancy, the heifer may be most susceptible to this disease during this period of first gestation.

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, the period around calving, and during early lactation. Strategies for controlling Strep. uberis mastitis are poorly defined and are currently inadequate. Objectives of the present study were to evaluate efficacy of ceftiofur, a new broad-spectrum cephalosporin antibiotic, for treatment of experimentally induced Strep. uberis intramammary infections (IMI) in lactating dairy cows during early lactation and to determine whether extended therapy regimens enhanced efficacy of ceftiofur. Efficacy of extended ceftiofur intramammary therapy regimens was investigated in 37 mammary quarters of 23 dairy cows that developed clinical mastitis following experimental infection with Strep. uberis during early lactation. Cows that developed clinical mastitis during the challenge period were allocated randomly to 3 groups representing 3 different ceftiofur treatment regimens: 2-d (n = 7 mammary quarters), 5-d (n = 16 mammary quarters), and 8-d (n = 14 mammary quarters) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. A bacteriological cure was defined as an experimentally infected quarter that was treated and was bacteriologically negative for the presence of Strep. uberis at 7, 14, 21, and 28 d posttreatment. Percentage of Strep. uberis IMI eliminated was 43, 88, and 100% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Both the 5- and 8-d ceftiofur extended therapy treatment regimens had significantly higher bacterial cure rates than the standard 2-d ceftiofur treatment regimen. The bacterial cure rate of the 8-d ceftiofur extended therapy group was marginally better (P = 0.052) than the 5-d ceftiofur extended therapy group. Results of this study indicate that ceftiofur therapy was effective for eliminating Strep. uberis experimental IMI, and 5- and 8-d extended ceftiofur therapy regimens were more effective than the standard 2-d treatment.

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