Heightened public concern over the presence of antibiotic residues has forced the dairy industry to consider alternatives to antimicrobials in the treatment of clinical mastitis. One such alternative is the use of immune modulators which enhance cell mediated immunity and lymphokine production (Cox 1988; McCall 1989). Anecdotal reports indicated that a killed extract of Propionibacterium acnes (Propionibacterium Acnes, Immunostimulant; ImmunoVet Inc) was being successfully used to treat chronic clinical mastitis (Douglas 1990). However, no controlled trials have yet been reported that document the success of this treatment.
Summary We gave gonadotropin-releasing hormone (GnRH) or an analog of GnRH to 264 lactating cows with cystic ovaries. The effects of milk progesterone concentration ( mpc ) and days after parturition ( dap ) at diagnosis on clinical response 30 days after treatment and on subsequent fertility were examined. Palpation per rectum revealed ovarian cysts in 264 cows; 118 had true follicular cysts ( mpc < 1 ng/ml). Clinicians with more than 3 years of experience reported significantly more true cysts than did less experienced clinicians. Clinical response 30 days after treatment did not differ in 3 groups of cows (divided on the basis of mpc at treatment), but fewer cows with mpc <1 ng/ml were bred or conceived than were cows with mpc ≥33 ng/ml. Days after parturition at diagnosis did not affect 30-day clinical response rate, but cows treated <35 dap had significantly more days to first estrus and to conception than did cows treated >90 dap . Significantly more cows treated <35 dap had mpc <1 ng/ml at treatment.
To establish the maximum concentration and duration of oxytetracycline residues in milk from cows with retained fetal membranes given the antimicrobial via intrauterine infusion, and to investigate whether the number of infusions or the presence of fever (> 39.7 C) affected the duration of residues.Prospective study.54 Holstein cows with retained fetal membranes on a single 1,400-cow commercial dairy.Cows were treated once a day with 5 g of oxytetracycline (50 ml of 100 mg/ml solution in a povidone base) by intrauterine infusion for at least 2 days, or until the membranes were expelled. Cows that became febrile (rectal temperature > or = 39.7 C) were also given 20,000 IU of procaine penicillin G/kg of body weight, i.m., for 2 to 4 days. Milk samples were collected at 24-hour intervals during treatment. and at 12-hour intervals after the last treatment. All samples were frozen and submitted every 2 weeks for high performance liquid chromatography analysis for oxytetracycline.Oxytetracycline was detected in milk of all cows during treatment, at a maximum concentration ranging from 47.2 to 1,804.6 micrograms/kg (mean, 316.9 micrograms/kg). Duration of oxytetracycline residues after the last infusion ranged from 0 to 144 hours (mean, 52.3 hours). Neither the number of infusions received, nor development of rectal temperature > 39.7 C, affected the maximum concentration or the duration of oxytetracycline residues in milk.Milk obtained from cows that had been treated for retained fetal membranes by intrauterine infusion of oxytetracycline should be discarded to avoid illegal residues.
Abstract Objective —To estimate seroprevalence of Mycobacterium avium subsp paratuberculosis (MAP) infection among adult dairy cows in Colorado and determine herd-level factors associated with the risk that individual cows would be seropositive. Design —Cross-sectional observational study. Animals —10,280 adult (≥ 2 years old) dairy cows in 15 herds in Colorado. Procedure —Serum samples were tested with a commercial ELISA. A herd was considered to be infected with MAP if results of mycobacterial culture of ≥ 1 individual cow fecal sample were positive or if ≥ 1 culled cow had histologic evidence of MAP infection. Results —424 of the 10,280 (4.12%) cows were seropositive. Within-herd prevalence of seropositive cows ranged from 0% to 7.82% (mean, 2.6%). Infection was confirmed in 11 dairies. Cows in herds that had imported ≥ 8% of their current herd size annually during the preceding 5 years were 3.28 times as likely to be seropositive as were cows in herds that imported < 8%. Cows in herds with ≥ 600 lactating cows were 3.12 times as likely to be seropositive as were cows in herds with < 600 lactating cows. Cows in herds with a history of clinical signs of MAP infection were 2.27 times as likely to be seropositive as were cows in herds without clinical signs. Conclusions and Clinical Relevance —Annual importation rate, herd size, and whether cows in the herd had clinical signs typical of MAP infection were associated with the risk that individual cows would be seropositive for MAP infection. ( J Am Vet Med Assoc 2004;225:97–101)
Preculture incubation, preculture freezing, and increased plate inoculation volumes were tested in an attempt to increase the recovery rate of pathogens in milk from cases of clinical bovine mastitis. Culture of milk from 291 cases of clinical bovine mastitis was performed using standard milk culture techniques (.01 ml of fresh milk streaked on trypticase soy agar plates with 5% sheep blood and .1% esculin). The sensitivity of this method was compared with that of cultures performed using augmented techniques: 4 and 18 h of preculture incubation; preculture freezing of samples overnight at -20 degrees C; and increasing the plate inoculation volume to .05 and .1 ml for fresh, incubated, and frozen samples. Preculture incubation and larger plate inoculation volumes significantly increased the recovery rate of bacterial pathogens over the standard culture method. The greatest improvement in sensitivity without a concomitant increase in contamination was achieved when samples were incubated for 4 h and plates were inoculated with .1 ml of the sample. Recovery was enhanced significantly by this method for several organisms, including environmental streptococci and coliform bacteria. Freezing milk before culture yielded a significantly higher positive culture rate overall, but freezing did not affect the positive culture rate of any individual bacterial species.
The sensitivity, specificity, and positive and negative predictive values were compared for six methods of collecting or culturing milk samples for the diagnosis of chronic Streptococcus agalactiae intramammary infection. Cows in four dairy herds were cultured three times in 2 wk to determine infection status. At the second sample period, individual quarter and composite milk samples were taken before and immediately after milking, and two volumes of milk from the composite samples were streaked on culture plates. The sensitivity, specificity, and predictive values for these cultures ranged between 95 and 100% for all diagnostic methods, and no significant differences were found between methods. The results indicate that when either quarter or composite samples are collected before or immediately after milking, 95 to 100% of S. agalactiae culture-positive cows will be infected with S. agalactiae in herds with a prevalence of S. agalactiae between 35 and 55%. A similar proportion of culture-negative cows will be uninfected.
