Biomedical subjects

J S Hogan

Publications and source records attributed to J S Hogan.

At least 19 recordsLinked to original sources

PubMed2006

Effects of prepartum intramammary antibiotic therapy on udder health, milk production, and reproductive performance in dairy heifers.

Preparturient heifers (n = 561) from 9 herds in 6 US states and 1 Canadian province were enrolled in a study to test the hypothesis that prepartum intramammary therapy would cure existing intramammary infections (IMI) and lead to increased milk production, reduced linear somatic cell count (LSCC), and improved reproductive performance. Mammary secretions were collected 10 to 21 d before expected calving from each quarter. Heifers were then assigned by identification number to receive intramammary therapy consisting of infusion of one tube per mammary quarter of a lactating cow commercial antibiotic preparation containing cephapirin or to a nontreated control group. Overall, 34.1% of mammary quarters were infected with a mastitis pathogen before parturition and 63.4% of heifers had at least one mammary quarter infected. The coagulase-negative staphylococci (CNS) caused the majority (74.8%) of prepartum IMI. Coagulase-positive staphylococci, environmental streptococci, and coliforms accounted for 24.5% of prepartum infections. Treatment had a significant effect on the cure rate of infected mammary quarters. Mammary quarters that were infected prepartum and treated with antibiotics had a 59.5% efficacy of cure rate and the percentage reduction in heifers with IMI was 51.9. Control quarters had a spontaneous cure rate of 31.7%. Treatment did not significantly affect milk production or LSCC in the first 200 d of lactation; however, there was a significant treatment by herd interaction for milk production. Quarters cured of either CNS or major pathogens had a lower LSCC in the first 200 d of lactation. No significant effect on services per conception or days open between treatment and control groups was observed. This trial demonstrated that prepartum intramammary antibiotic therapy did reduce the number of heifer IMI postpartum. Milk production, LSCC, and reproductive performance during the first 200 d of the first lactation were not significantly affected by treatment. Given these results, use of prepartum intramammary antibiotic therapy in heifers as a universal strategy to increase milk production in first-lactation dairy cows may not be warranted.

Animals↗

PubMed2005

Effects of adjuvants on safety and efficacy of an Escherichia coli J5 bacterin.

The effects of using a water-soluble adjuvant or an emulsified oil-based adjuvant on the safety, antibody titer, and clinical responses of an Escherichia coli J5 bacterin were tested in an experimental infection trial. Fifty-one cows were assigned to 17 blocks of 3. Two cows within each block of 3 were vaccinated with a commercially prepared E. coli J5 bacterin containing either a water-soluble adjuvant or the same bacterin preparation emulsified in oil. One cow in each block was an unvaccinated control. Cows were immunized at drying off and 42 d later. The right or left front mammary quarter of each experimental cow was challenged by intramammary infusion of E. coli 727 between 14 and 35 DIM. Areas of inflammation at the primary injection site were greater 1, 2, and 3 d following primary vaccination for bacterin containing oil-in-water adjuvant compared with bacterin containing water-soluble adjuvant. Whey anti-E. coli J5 IgG titers were higher at calving for cows vaccinated with bacterin containing oil-in-water adjuvant than for cows either vaccinated with bacterin containing water-soluble adjuvant or unvaccinated controls. Serum x-E. coli J5 IgG titers were higher at calving for vaccinated cows than for unvaccinated controls. Peak bacterial counts in milk from challenged quarters were greater for unvaccinated controls than for cows vaccinated with bacterin containing water-in-oil adjuvant. Bacterial counts in milk from challenged quarters and clinical score both were greater in unvaccinated controls than cows vaccinated with bacterin containing water-in-oil adjuvant between 12 and 24 h postchallenge. Clinical responses were similar between unvaccinated controls and cows vaccinated with bacterin containing water-soluble adjuvant.

Adjuvants, Immunologic↗

PubMed2005

Short communication: association between milk yield at dry-off and probability of intramammary infections at calving.

The association between milk yield at dry-off and intramammary infections at calving was evaluated from 116 lactations in one herd. Duplicate quarter samples were collected within 3 d after calving to estimate prevalence of intramammary infection at calving; information on cows' parity, daily milk yields, weekly somatic cell counts, and dry-off and calving dates were available for the data analyses. Generalized linear models with logit link were used to model the probability of a cow or a quarter being infected at calving, accounting for the clustered data. Increasing milk production at dry-off was a significant risk factor for both a cow and a quarter being infected with environmental pathogens at calving, but infections caused by coagulase-negative staphylococci at calving were not associated with milk yield at dry-off. For every 5-kg increase in milk yield at dry-off above 12.5 kg, the odds of a cow having an environmental intramammary infection at calving increased at least by 77%.

Animals↗

PubMed2005

Comparison of bacteria populations in clean and recycled sand used for bedding in dairy facilities.

Bedding samples were collected twice from commercial dairy free-stall facilities that used recycled sand and clean sand in both the summer and winter. Collection began on the day sand was taken from the pile (d 0) and placed in the free stalls, and continued for 5 to 7 additional days. The number of colonies per gram of bedding of gram-negative bacteria, coliforms, Streptococcus spp., and Klebsiella spp. were estimated for each sand sample as well as amounts of dry and organic matter. Clean sand (CS) and recycled sand (RS) had the same bacterial counts when compared at any sampling time. The mean counts of bacterial populations did vary over the course of the study in both CS and RS. There was a significant increase in bacterial counts from d 0 to d 1 for gram-negative bacteria, coliforms, and Streptococcus spp. in both winter and summer. Counts of gram-negative bacteria, coliforms, Klebsiella spp., and Streptococcus spp. did not differ from d 1 to 7 in the winter. Total counts of gram-negative bacteria did not differ from d 1 to 7 in the summer. On d 1 in the summer, coliform counts were lower than at d 5 to 7, and Klebsiella spp. counts were lower than on d 3 to 7. Streptococcus spp. counts were high on d 1 and were constant through d 7 in both winter and summer trials. The number of coliform and Klebsiella spp. in both CS and RS was below the threshold thought to cause mastitis during the sampling times. The number of Streptococcus spp. was high in both CS and RS during the sampling periods. Other management factors need to be identified to decrease the number of Streptococcus spp. in bedding. Recycled sand had a higher organic matter and lower dry matter compared with CS in winter and summer. The results for this study were obtained from multiple herd comparisons, and herd was a significant effect suggesting that different management systems influence the number and types of bacteria in both CS and RS.

Animals↗

PubMed2005

Effect of selenium source on selenium status, neutrophil function, and response to intramammary endotoxin challenge of dairy cows.

The effects of feeding dry and early lactation dairy cows diets with selenate or selenized yeast (Se-yeast) on concentrations of Se in serum, milk, and newborn calves, neutrophil function, and inflammatory response were determined. At 60 d before anticipated calving until approximately 30 d in milk (DIM), cows were fed diets that contained 0.3 mg of supplemental Se/kg of DM from sodium selenate or Se-yeast. Diets also contained 0.2% supplemental S (as sulfate) because it has been shown to reduce absorption of Se by dairy cows. The concentration of Se in serum at calving and 28 DIM was about 1.4 times greater for cows fed Se-yeast than for those fed selenate. Serum concentrations decreased 45 and 23% from dry-off to calving for cows fed selenate or Se-yeast, respectively. Selenium concentrations in serum from newborn calves were also about 1.4 times greater when the dams were fed Se-yeast. Concentrations of Se in colostrum and milk were about 1.8 times greater when cows were fed Se-yeast. Blood neutrophils were isolated from cows at 28 DIM and were used in an in vitro kill assay. Selenium treatment did not affect bacterial kill or the percentage of neutrophils that phagocytized bacteria. At approximately 28 DIM, one quarter from each cow was infused with a solution containing endotoxin. Peak body temperature (40.7 degrees C) occurred 6 h postinfusion, and peak somatic cell count (6.5 log10/mL) occurred at 12 h postinfusion. Neither measure was influenced by Se treatment.

Animals↗

PubMed2004

Antimicrobial susceptibility of mastitis pathogens from first lactation and older cows.

Increasing antimicrobial resistance has become a serious concern worldwide and antimicrobial use in animal agriculture is currently under scrutiny. Mastitis is the most common reason for antibiotic use in dairy herds and thus, antimicrobial resistance of mastitis pathogens has received recent attention. The purpose of this study was to describe and compare antimicrobial susceptibility of mastitis pathogens isolated at calving from first lactation and older cows. A total of 202 bacteria were isolated from intramammary infections (IMIs) within 3 days after calving over a 16-month study period in the Krauss Dairy Research Herd at the Ohio Agricultural Research and Development Center (OARDC) in Wooster, OH. Of these IMIs, 78% were caused by coagulase-negative staphylococci (CNS). Forty-four percent of them were resistant to at least one antibiotic. Most resistance was observed against penicillin, 39% of the isolates from older cows and 26% from first lactation cows being resistant to penicillin (P > 0.05). Also MIC90 for penicillin was higher among isolates from older cows. On the other hand, resistance to tetracycline was more common and MIC90 higher among isolates from first lactation cows than from older cows. Differences in the proportions of resistant isolates between first lactation and older cows were not statistically significant, though. The resistance patterns of the CNS isolated during the study are concordant with antimicrobial usage in the study herd. This is in agreement with the generally accepted notion that selection pressure from the use of antibiotics is a main factor in development of antibiotic resistance.

Animals↗

PubMed2004

Iron uptake by Escherichia coli cultured with antibodies from cows immunized with high-affinity ferric receptors.

The synergistic effects of immunoglobulin G (IgG) from cows vaccinated with ferric citrate receptor (FecA) and IgG from cows vaccinated with ferric enterobactin receptor (FepA) were measured in an in vitro iron uptake assay. Serum was isolated and pooled within treatment from five cows each vaccinated with FepA or FecA or not vaccinated. Immunoglobulin G was isolated by ammonium sulfate precipitation and protein G affinity chromatography. Six Escherichia coli isolates from bovine intramammary infections were cultured in an iron-depleted medium to induce high-affinity iron acquisition systems and, in iron-depleted conditions, to specifically induce the expression of FecA. The bacterial cells were mixed with either 3 or 6 mg/mL of purified IgG and 55Fe. The radioactivity of 55Fe taken up by the bacterial cells was measured by a liquid scintillation counter after 5-, 10-, and 15-min incubations at 37 degrees C. The combination of anti-FecA IgG and anti-FepA IgG reduced 55Fe uptake compared with either anti-FecA or anti-FepA alone. Iron uptake was reduced more by anti-FecA IgG than by anti-FepA IgG when the ferric citrate system was induced. Reduction of iron uptake did not differ between anti-FepA alone and anti-FecA alone when citrate was absent from the medium.

Animals↗

PubMed2004

Changes in vitamin C concentrations in plasma and milk from dairy cows after an intramammary infusion of Escherichia coli.

Plasma and milk concentrations of ascorbic acid and dehydro-L-ascorbic acid (DHAA) were measured before and after 21 Holstein cows (approximately 26 DIM) were given an intramammary infusion of Escherichia coli. Blood, milk from the unchallenged quarters, and milk from the challenged gland were sampled immediately before challenge (d 0) and 24 h and 7 d postchallenge. Plasma vitamin C (ascorbic acid + DHAA) concentrations decreased 39%, and concentrations of vitamin C and ascorbic acid in milk from the challenged quarter decreased 52 and 62%, respectively, in samples taken 24 h postchallenge. No change was observed in vitamin C concentrations in milk from unchallenged quarters. The concentration of DHAA in milk from challenged quarters increased 67% 24 h postchallenge. The duration of clinical mastitis, peak body temperature, number of colony-forming units of E. coli isolated from the infected gland, and loss in milk yield were associated with a change in concentration of vitamin C in milk from the challenged quarter. Increased severity of clinical signs was associated with large decreases in concentration of vitamin C in milk from the challenged quarter. Similar, but statistically weaker, relationships were observed for changes in plasma vitamin C concentrations.

Animals↗

PubMed2004

Growth responses of Escherichia coli to immunoglobulin G from cows immunized with ferric citrate receptor, FecA.

Effects of purified immunoglobulin (Ig) G from cows immunized with ferric citrate receptor, FecA, on the in vitro growth of Escherichia coli were investigated. Twenty-one cows were assigned to one of 3 treatments: 1) FecA immunization, 2) E. coli J5 bacterin immunization, and 3) unimmunized control. FecA was derived from E. coli UT5600/pSV66. Immunoglobulin G was purified from pooled colostral whey for each treatment group. The IgG from FecA immunized cows had higher titers against FecA compared with other treatment groups. Bacterial isolates tested were 14 E. coli from intramammary infections and E. coli UT5600/pSV66. Iron depletion decreased the growth of E. coli compared with growth in Fe-replete medium. The presence of IgG further decreased the growth compared with the growth under iron restriction alone. Bacterial growth did not differ among IgG sources nor between IgG concentrations. Replenishing media with exogenous iron overrode the inhibitory effects of the Fe-depletion and IgG. Vaccinating cows with FecA had little effect on the growth inhibitory properties of IgG toward E. coli mastitis isolates cultured in Fe-deplete media.

Animals↗

PubMed2003

Effect of immunoglobulin G from cows immunized with ferric citrate receptor (FecA) on iron uptake by Escherichia coli.

The effects of immunoglobulin (Ig) G from cows immunized with the ferric citrate receptor (FecA) on iron uptake by Escherichia coli were investigated. Receptor FecA was purified from E. coli UT5600/pSV66. Cows were immunized with 400 microg purified FecA three times at 21 d intervals during late lactation and the nonlactating period. Immunoglobulin G was purified by protein G affinity chromatography from colostral whey from cows immunized with FecA and from unimmunized control cows. The purified IgG from FecA immunized cows had higher IgG titers against FecA compared with control IgG. Fifteen E. coli isolated from intramammary infections and E. coli UT5600/pSV66 were grown in an iron-depleted medium containing 1 mM citrate to induce FecA. The bacterial cells were mixed with 0, 2, and 4 mg/ml purified IgG, and 55Fe was added to the assay. After 5, 10, and 15 min incubations at 37 degrees C, samples were passed through 0.45-pm pore size filters. Filters were washed with saline three times, and the radioactivity of 55Fe taken up by the bacterial cells on the filters was measured by a liquid scintillation counter. The measurements were expressed as numbers of 55Fe atoms per colony-forming unit and transformed to log10. The assay was repeated three times for each isolate in a partially balanced incomplete block design. The presence of IgG decreased 55Fe uptake by E. coli mastitis isolates and E. coli UT5600/pSV66. Anti-FecA IgG reduced 55Fe uptake by E. coli greater than IgG from unimmunized cows.

Animals↗

PubMed2003

Opsonic activity of serum and whey from cows immunized with the ferric citrate receptor.

The effects of immunizing dairy cows with the ferric citrate receptor, FecA, on the opsonic activity of serum and whey were measured in a phagocytosis assay. Fifteen cows were assigned to five blocks of three cows based on date of expected parturition. Cows within a block were randomly assigned to one of three treatments: 1) FecA immunization, 2) immunization with a commercially available Escherichia coli J5 bacterin, and 3) unimmunized controls. Cows were challenged at approximately 21 DIM by intramammary infusion of E. coli 727 into one mammary quarter. Escherichia coli 727 were opsonized for the phagocytosis assay with either 10% heat-inactivated serum or 50% heat-inactivated whey collected from each cow at calving, immediately before challenge and 7 d after challenge. Cows immunized with FecA or the E. coli J5 bacterin had increased IgG titers against FecA and E. coli 727 compared with unimmunized control cows. However, sera and whey collected from cows immunized with FecA did not enhance opsonization of E. coli 727 compared with sera and whey from control cows. Immunization with the E. coli J5 bacterin increased opsonization of sera greater than immunization with FecA. Immunoglobulin M antibody titer against E. coli 727 in whey and phagocytic indexes were positively correlated. The phagocytic index of whey immediately before challenge and 7 d after challenge were negatively associated with peak bacterial counts in mammary quarters challenged with E. coli 727. Results of the current trial suggest that the immune response resulting from immunization with FecA did not enhance opsonization and in vitro phagocytosis of E. coli 727.

Animals↗

PubMed2002

Efficacy of immunization with ferric citrate receptor FecA from Escherichia coli on induced coliform mastitis.

The effects of immunization with the ferric citrate receptor FecA on antibody responses and on experimentally induced mastitis following intramammary challenge were investigated. Twenty-one cows were assigned to seven blocks of three cows based on expected parturition. Cows within block were randomly assigned to one of three treatments: 1) FecA immunization, 2) Escherichia coli J5 immunization, and 3) unimmunized controls. Challenge was by infusion of approximately 60 cfu of E. coli 727 into one uninfected mammary gland between 13 and 31 d after parturition. Cows within block were challenged on the same day. Cows immunized with FecA had higher immunoglobulin (Ig)G titers against FecA in serum and in mammary secretions at calving, immediately before challenge, and 7 d after challenge than did cows immunized with E. coli J5 or control cows. Immunization with FecA also increased IgG titers against whole-cell E. coli 727 in serum and in mammary secretions at calving. Serum IgM titers against FecA were higher in FecA immunized cows than in other treatment groups immediately before challenge. Bacterial counts in milk, duration of bacterial isolation in milk, rectal temperature, and milk somatic cell counts following intramammary challenge were similar among treatments. Milk production and dry matter intake did not differ among treatments. The ferric citrate receptor FecA was immunogenic in cows, but immunization had minimal effect on the clinical severity of experimentally induced E. coli mastitis.

Animals↗

PubMed2002

Phagocytosis and serum susceptibility of Escherichia coil cultured in iron-deplete and iron-replete media.

The susceptibility of Escherichia coli cultured in either iron-deplete or iron-replete media to phagocytosis by bovine neutrophils and the bactericidal activity of bovine serum was tested in vitro. Fourteen E. coli isolates from naturally occurring intramammary infections (IMI) were cultured overnight at 37 degrees C in iron-replete media and iron-deplete media. The iron-replete media were trypticase soy broth or a chemically defined medium. The iron-deplete media were either trypticase soy broth plus 0.2 mM alpha, alpha' dipyridyl and 1mM citrate, or the chemically defined medium plus 0.2 mM alpha, alpha' dipyridyl, and 1 mM citrate. Iron-replenished medium was the chemically defined iron-deplete medium plus 40 mM ferric citrate. Bacteria grown in iron-deplete media were less susceptible to phagocytosis compared with bacteria grown in iron-replete media. Replenishing the chemically defined iron-deplete medium with ferric citrate obliterated the decreased susceptibility to phagocytosis observed in iron-deplete media. The iron availability in media used to culture E. coli before assay did not affect the bactericidal action of either the classical pathway of complement or the antibody independent alternative pathway of complement in serum. The growth of bacteria in iron-deplete medium did not alter the expression of capsule compared with growth in iron-replete medium. Iron availability during culture of E. coli altered the susceptibility of isolates to phagocytosis by neutrophils, but had no effect on the susceptibility of isolates to the bactericidal activity of serum.

Animals↗

PubMed1999

Antigenic homology of the inducible ferric citrate receptor (FecA) of coliform bacteria isolated from herds with naturally occurring bovine intramammary infections.

Expression of ferric citrate receptor FecA by Escherichia coli and Klebsiella pneumoniae isolated from bovine mastitis was investigated. Transformant E. coli UT5600/pSV66, which produces large quantities of FecA in the presence of citrate, was constructed. The FecA of E. coli UT5600/pSV66 was purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and used to prepare polyclonal antiserum in rabbits. All coliform isolates of E. coli (n = 18) and K. pneumoniae (n = 17) from naturally occurring bovine intramammary infections in five herds induced iron-regulated outer membrane proteins when grown in Trypticase soy broth containing 200 microM alpha-alpha'-dipyridyl and 1 mM citrate. Polyclonal antiserum against FecA was used in conjunction with an immunoblot technique to determine the degree of antigenic homology of FecA among isolates. In the presence of citrate, each isolate expressed FecA that reacted with the anti-FecA polyclonal antiserum. The molecular mass of FecA ( approximately 80.5 kDa) was also highly conserved among isolates. Therefore, the ferric citrate iron transport may be induced in coliform bacteria and utilized to acquire iron in milk for survival and growth. The FecA is an attractive vaccine component for controlling coliform mastitis during the lactation period.

Animals↗

PubMed1999

Growth responses of coliform bacteria to purified immunoglobulin G from cows immunized with ferric enterobactin receptor FepA.

The ability of purified bovine immunoglobulin (Ig) G from cows immunized with ferric enterobactin receptor FepA to inhibit the growth of coliform bacteria derived from bovine intramammary infection was investigated in iron-restricted media. All isolates of Escherichia coli (n = 21) and Klebsiella pneumoniae (n = 21) were tested for growth in a chemically defined medium containing 0.5 mg/ml of apolactoferrin and in a pooled source of dry cow secretion. The addition of 4 mg/ml of purified bovine IgG directed against FepA in the synthetic medium resulted in significant growth inhibition for both E. coli and K. pneumoniae isolates. Growth reduction of E. coli was greater than that of K. pneumoniae. In dry cow secretions, the growth of each E. coli isolate but of less than half of K. pneumoniae isolates (43%) was inhibited by IgG from cows immunized with FepA. Purified bovine IgG from cows immunized with E. coli J5 had a minimal inhibitory effect on the growth of both E. coli and K. pneumoniae isolates in the synthetic medium. In dry cow secretions, IgG from cows immunized with E. coli and K. pneumoniae isolates. Supplementation with 50 microM of ferric chloride to the medium completely reversed the inhibitory effects of the antibodies and lactoferrin. Bovine IgG directed against FepA apparently inhibited the growth of coliform bacteria by interfering with the binding of the ferric enterobactin complex to the cell surface receptor FepA.

Animals↗

PubMed1999

Efficacy of an Escherichia coli J5 bacterin administered to primigravid heifers.

The efficacy of an Escherichia coli J5 bacterin for reducing the incidence of intramammary infections and clinical signs of mastitis was tested in first lactation heifers. Ten primigravid heifers were immunized with an E. coli J5 bacterin. Four heifers received a placebo. The bacterin and placebo were injected subcutaneously approximately 60 d prior to calving, 28 d later, and within 48 h after calving. Vaccinated and placebo-injected heifers were challenged by intramammary infusion of E. coli 727 in one mammary gland between 23 and 37 d after calving. All challenged quarters were diagnosed with an intramammary infection within 6 h after bacteria were infused. The severity and duration of local signs of clinical mastitis were reduced in vaccinated heifers compared with placebo-injected heifers. Systemic signs of clinical mastitis were limited and did not differ between treatment groups. Bacteria counts in milk from challenged quarters were lower in vaccinated heifers than in control heifers at 12, 15, and 48 h after challenge. Serum immunoglobulin G titers against whole-cell E. coli J5 antigen at calving were higher in vaccinated heifers than they were in controls. Vaccinated heifers had higher immunoglobulin G titers than did controls in mammary secretions at calving and immediately prior to challenge. Immunization of primigravid heifers with an E. coli J5 bacterin during the last trimester of gestation and at calving reduced the severity and duration of clinical signs following intramammary challenge with a heterologous strain of E. coli.

Animals↗

PubMed1999

Bacterial counts associated with sawdust and recycled manure bedding treated with commercial conditioners.

Bacteria counts associated with untreated organic bedding materials were compared with those of bedding treated with either an alkaline commercial bedding conditioner, acidic commercial bedding conditioner, or hydrated lime. Bedding materials were recycled manure and kiln-dried sawdust. The effects of bedding treatments on bacteria counts differed between bedding types. Each of the bedding treatments significantly reduced bacteria in recycled manure prior to use. The alkaline conditioner and hydrated lime effectively inhibited bacteria in recycled manure for 1 d. Bedding counts and teat swabs of cows housed on recycled manure treated with the alkaline conditioner were reduced on d 2. The use of the acid conditioner in recycled manure had little effect on bacteria in bedding. Sawdust differed from recycled manure in that bacteria in untreated sawdust prior to use were minimal, and populations increased rapidly during the first 2 d after use as bedding. The acid conditioner had a bacteriostatic effect in sawdust, evident by the reduction of bacteria on d 2. The alkaline conditioner and hydrated lime did not alter bacteria counts in sawdust compared with untreated sawdust. Antibacterial activity of each conditioner deteriorated between d 2 and d 6 in both beddings. The antibacterial activities of conditioners were related to the pH of bedding materials. The use of commercial bedding conditioners initially reduced bacterial counts; however, the antibacterial effects had diminished between d 2 and 6 after use in bedding.

Animals↗

PubMed1999

Efficacy of intramammary immunization with an Escherichia coli J5 bacterin.

Intramammary immunization was investigated as a procedure to reduce the clinical signs of coliform mastitis. Twenty-four cows were equally distributed to the following Escherichia coli J5 immunization schedules: 1) Subcutaneous injection 14 d prior to the end of lactation, intramammary immunization 7 d after drying off, and subcutaneous injection 30 d into the dry period; 2) subcutaneous injections at drying off, at 30 d into the dry period, and within 12 h after calving; and 3) unimmunized controls. Intramammary immunizations were the infusion of vaccine via the teat canal into each of the four mammary glands. Cows were challenged by infusion of E. coli 727 into one uninfected mammary quarter at approximately 30 d after calving. Intramammary immunization enhanced antibody titers against E. coli J5 and E. coli 727 compared with subcutaneous immunization. Immunoglobulin G titers against E. coli J5 and E. coli 727 in whey were greater at the time of challenge and 7 d after challenge for cows that received the intramammary immunization than for cows immunized by only subcutaneous injections. Serum IgG titers against E. coli 727 were enhanced at 7 d after challenge for cows receiving intramammary immunizations compared with conventionally immunized cows. Serum IgM titers against E. coli 727 were higher at calving for cows receiving intramammary immunization compared with conventionally immunized cows. Immunization schedule had minimal effect on systemic and local signs of clinical mastitis following challenge.

Animals↗