Comparative pharmacokinetics of two florfenicol formulations following intramuscular and subcutaneous administration to sheep.

OBJECTIVE To compare the pharmacokinetics of 2 commercial florfenicol formulations following IM and SC administration to sheep. ANIMALS 16 healthy adult mixed-breed sheep. PROCEDURES In a crossover study, sheep were randomly assigned to receive florfenicol formulation A or B at a single dose of 20 mg/kg, IM, or 40 mg/kg, SC. After a 2-week washout period, each sheep was administered the opposite formulation at the same dose and administration route as the initial formulation. Blood samples were collected immediately before and at predetermined times for 24 hours after each florfenicol administration. Plasma florfenicol concentrations were determined by high-performance liquid chromatography. Pharmacokinetic parameters were estimated by noncompartmental methods and compared between the 2 formulations at each dose and route of administration. RESULTS Median maximum plasma concentration, elimination half-life, and area under the concentration-time curve from time 0 to the last quantifiable measurement for florfenicol were 3.76 µg/mL, 13.44 hours, and 24.88 µg•h/mL, respectively, for formulation A and 7.72 µg/mL, 5.98 hours, and 41.53 µg•h/mL, respectively, for formulation B following administration of 20 mg of florfenicol/kg, IM, and 2.63 µg/mL, 12.48 hours, and 31.63 µg•h/mL, respectively, for formulation A and 4.70 µg/mL, 16.60 hours, and 48.32 µg•h/mL, respectively, for formulation B following administration of 40 mg of florfenicol/kg, SC. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that both formulations achieved plasma florfenicol concentrations expected to be therapeutic for respiratory tract disease caused by Mannheimia haemolytica or Pasteurella spp at both doses and administration routes evaluated.

Effect of systematic parturition induction of long gestation Holstein dairy cows on calf survival, cow health, production, and reproduction on a commercial farm.

The objective of this study was to evaluate the effect of parturition induction on dairy cattle with long gestation (past due-date) single pregnancies on calf survivability, cow health, production, and reproduction. There was an induction period during which all cows and heifers reaching 282 days of gestation were induced with dexamethasone (n = 614). Control cows calved the year after, had a gestation length > 282 d and were not induced (n = 508). As the induced and non-induced groups were not contemporaneous, data were standardized using the ratio between the herd baselines for each period. Multivariate analyses of the data showed that induced cows were 1.41 times more likely (P = 0.020) to become pregnant in the lactation following the studied calving than non-induced cows with long gestation. There was no difference in the risk of difficult calvings, stillbirths, culling due to reproductive reasons, average milk production, average days open or risk of abortion in the following lactation between induced and non-induced cows. There seemed to be a relationship between parturition induction and a lower risk of post-partum death, although this was not statistically significant (P = 0.162), because including induction as a factor in the model markedly improved the fit of the data. There was no information on incidence of retained placenta (RP) for the non-induced group. In conclusion, parturition induction resulted in more cows becoming pregnant and a seemingly lower risk of post-spartum death without affecting calving difficulty, calf viability, or milk production.

Recombinant Moraxella bovoculi cytotoxin-ISCOM matrix adjuvanted vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis.

A randomized, blinded, controlled field trial was conducted during summer 2006 in a northern California, USA, herd of beef cattle to evaluate the efficacy of a recombinant Moraxella bovoculi cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK; pinkeye). A convenience sample comprised of 127 steers were administered a subcutaneous dose of either adjuvant alone (ISCOM matrices; control group) or recombinant M. bovoculi cytotoxin carboxy terminus adjuvanted with ISCOM matrices (MbvA group) and were boostered 21 days later. The steers were examined once weekly for 15 weeks for evidence of IBK. No significant difference in the cumulative proportion of corneal ulcerations was detected between groups. Compared to the control calves, the MbvA vaccinates had significantly higher increases in serum neutralizing titers to M. bovoculi hemolysin between week 0 and week 6. The prevalence of M. bovis isolations was higher from ulcerated eyes of calves vaccinated with MbvA as compared to control calves. Vaccination of calves against the carboxy terminus of M. bovoculi RTX toxin resulted in significant increases in serum hemolysin neutralizing titers and may modulate organism type cultured from ulcerated eyes of calves in herds where both M. bovis and M. bovoculi exist. Use of M. bovoculi antigens alone in vaccines to prevent IBK may not be beneficial in herds where IBK is associated with both M. bovoculi and M. bovis.

Comparison of bovine hematology reference intervals from 1957 to 2006.

BACKGROUND: The most commonly used bovine hematology reference intervals were published in 1965. We found the results from healthy cattle in 2001 differed from those in many ways. Discovery of the original laboratory book used to calculate the 1965 values gave us the opportunity to evaluate whether hematology values of healthy cattle have changed over time. OBJECTIVE: The purpose of this study was to establish hematology reference intervals for Holstein cows, compare selected hematologic results with similar population data from 1957, and compare these reference intervals with those of other North American veterinary schools and published values. METHODS: Reference intervals were developed in 2001 using clinically healthy, bovine leukemia virus-negative, mid-lactation Holstein cows. Selected parts of the hemograms and neutrophil:lymphocyte (N:L) ratio were compared with those from healthy, age-matched Holstein cows evaluated in 1957. Bovine reference intervals were solicited from clinical pathology laboratories in North American veterinary colleges and analyzed for population characteristics and method of analysis. RESULTS: Between 1957 and 2001, mean neutrophil counts increased significantly, whereas lymphocyte, monocyte, and eosinophil counts and hemoglobin concentration decreased significantly. Mean N:L ratio increased significantly to 1.17. Most surveyed laboratories were using the 1965 reference intervals. Two other institutions that had developed reference intervals after 2000 had results similar to ours. CONCLUSIONS: Continued use of older bovine hematology reference intervals could lead to misinterpretation of within-reference neutrophil counts as neutrophilia and under-recognition of neutropenia, eosinophilia, monocytosis, or lymphocytosis. Use of N:L>1 as evidence of inflammation should be discontinued or used with great caution.

Efficacy of tulathromycin for treatment of cattle with acute ocular Moraxella bovis infections.

OBJECTIVE: To evaluate the clinical efficacy of a single injection of tulathromycin, compared with saline (0.9% NaCl) solution-treated control calves, for treatment of induced infectious bovine keratoconjunctivitis in calves. DESIGN: Clinical trial. ANIMALS: 30 Holstein bull calves ranging from 5 to 6 months old and 75 to 200 kg (165 to 440 lb) with no history of Moraxella bovis infections, no history of M bovis vaccination, and negative results for M bovis on 3 consecutive ocular bacterial cultures. PROCEDURES: Both eyes of each calf were infected with 1 X 10(10) colony-forming units of piliated M bovis for 3 consecutive days prior to the trial. On day 0, ocular lesion scores were determined for each calf and the calves were weighed and assigned to a treatment (2.5 mg/kg [1.14 mg/lb] of body weight, SC) or control group according to a stratified random allocation based on weight and lesion score. Eyes were stained with fluorescein and photographed daily to record healing. Eyes were evaluated bacteriologically for M bovis on days 0 to 6 and at 3-day intervals thereafter. RESULTS: Median time to ulcer resolution in calves treated with tulathromycin was 9.1 days. More than 50% of control calves still had ulcers at the end of the trial (21 days). Moraxella sp was isolated less often from the eyes of treated calves than from the control calves. By day 10, the treated calves had lower ocular lesion scores than control calves. CONCLUSIONS AND CLINICAL RELEVANCE: A single dose of tulathromycin (SC) was an effective treatment of calves with experimentally induced infectious bovine keratoconjunctivitis. The long serum half-life of tulathromycin, along with the results of this trial, suggests that tulathromycin may be a rational choice as a single-injection treatment for infectious bovine keratoconjunctivitis.