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.     

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.     

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.     

A comparison of two commercially available Escherichia coli J5 vaccines against E. coli intramammary challenge

The efficacy of two commercially available Escherichia coli J5 bacterins was investigated. Jersey cows were randomly assigned to one of three treatment groups: 1) unvaccinated controls, 2) vaccinated with J.VAC (Merial Limited, Athens, GA), and 3) vaccinated with J5 bacterin. All cows were vaccinated at drying off and at 2 wk before anticipated calving. Cows that were vaccinated with the J5 bacterin also received a third immunization at calving. One quarter of each cow was challenged with approximately 64 cfu of E. coli at 14 to 30 d postcalving. Immunization by either vaccine did not influence the severity of coliform mastitis; however, the mean number of colony-forming units of E. coli recovered from challenged quarters was significantly lower for immunized cows than for control cows at 144 h postchallenge. Serum and mammary secretion immunoglobulin (Ig)G, IgG1, and IgG2 titers against E. coli J5 whole-cell antigens were enhanced in vaccinated cows. Serum and mammary secretion IgM were not different among treatment groups. Somatic cell counts in milk from challenged quarters, rectal temperatures, and the clinical status of cows following intramammary challenge were not different among treatment groups.     

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.     

Intramammary challenge with Escherichia coli following immunization with a curli-producing Escherichia coli

Holstein and Jersey cattle were immunized with a curli-producing strain of Escherichia coli (pCRL65/A012) or a noncurli-producing strain (pUC18/HB101) to determine differences in resistance to establishment of experimental intramammary infection. Cows (n = 6 per group) were immunized at 14 d prior to drying off, 7 d of involution, and at calving with 3 x 10(10) E. coli in Freund's Incomplete Adjuvant. At 30 d of lactation, one mammary quarter of each cow was infused with a wild strain of E. coli (727). Escherichia coli 727 was isolated from a naturally occurring intramammary infection and produced curli. All challenged quarters became infected, and all cows developed acute clinical mastitis. Geometric mean duration of intramammary infections was 6 d for both immunization groups. All infections were spontaneously eliminated within 10 d. No differences occurred between immunization groups in blood selenium and glutathione peroxidase activity, plasma selenium, number of E. coli 727 isolated from secretion after challenge, rectal temperature and SCC response, clinical status of mammary quarters, or DMI. Reduction in milk production after challenge was greater for cows immunized with E. coli pCRL65/A012. Immunization of dairy cattle with a curli-producing strain of E. coli did not protect against experimental intramammary challenge during lactation.     

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.     

Opsonic activity of bovine serum and mammary secretion after Escherichia coli J5 vaccination.

Six pairs of cows were used to determine the effects of immunization with an Escherichia coli (O111:B4) J5 bacterin on in vitro opsonization of a smooth heterologous strain of E. coli. One cow in each pair was either immunized with the vaccine or sham-immunized at drying off, 30 d after drying off, and at calving. Opsonizing bacteria with serum collected from vaccinated cows 21 d after calving resulted in higher mean number of intracellular bacteria per phagocytosing neutrophil than opsonizing bacteria with serum collected from control cows. Phagocytic parameters using serum collected at drying off and calving did not differ between treatment groups. A trend for enhanced opsonic activity of colostrum from vaccinates was noted. Enhanced opsonization by serum from vaccinated cows coincided with higher serum IgM titer to E. coli J5 whole cell antigen compared with controls. Serum IgG titers to E. coli J5 did not differ between groups. Colostrum IgG titers to E. coli J5 were greater at calving in vaccinated than in control cows. Colostrum and milk collected 21 d after calving from vaccinated cows had higher IgM titers to E. coli J5 than did mammary secretions from control cows. Numbers of intracellular bacteria per phagocytizing neutrophil were correlated positively with IgM titers to E. coli J5 in both serum and colostrum.     

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.     

Efficacy of an Escherichia coli J5 mastitis vaccine in an experimental challenge trial.

An Escherichia coli (O111:B4) J5 bacterin was tested for efficacy in reducing IMI and severity of clinical coliform mastitis in an experimental challenge trial. Ten cows were immunized at drying off, 30 d after drying off, and at calving. Ten control cows were not immunized. Right front quarters of all cows were infused with a heterologous strain of E. coli approximately 30 d after calving. Vaccinated cows had lower bacterial counts in milk and lower rectal temperatures than unvaccinated controls following intramammary challenge. Milk production and DMI were more depressed in controls than in vaccinated cows. Milk SCC did not differ between experimental groups. Mean serum IgG titer to whole cell E. coli J5 was significantly greater in vaccinated than in unvaccinated cows at 30 d after drying off, day of challenge, and 7 d postchallenge. Milk IgG titer to E. coli J5 was higher at challenge in vaccinated than in control cows. Vaccination with the E. coli J5 bacterin did not prevent IMI but did reduce severity of clinical signs following intramammary experimental challenge with a heterologous E. coli strain.     

Production of antibodies to Staphylococcus aureus serotypes 5, 8, and 336 using poly(DL-lactide-co-glycolide) microspheres

Staphylococcus aureus is responsible for a major portion of the economic losses due to mastitis. Attempts to produce a vaccine to prevent S. aureus mastitis have been hampered by the low immunogenicity of the polysaccharide, which forms on the surface of the organism when it enters the mammary gland. The polysaccharide inhibits phagocytosis and destruction of the organism by neutrophils. This study was conducted to determine if S. aureus polysaccharide serotypes 5, 8, and 336 conjugated to a protein and incorporated in poly(DL-lactide-co-glycolide) microspheres would enhance the production of opsonizing antibodies to the polysaccharide. Cows were immunized with either polysaccharide conjugates emulsified in Freund's incomplete adjuvant or polysaccharide conjugates encapsulated in poly (DL-lactide-co-glycolide) microspheres emulsified in Freund's incomplete adjuvant. All cows produced sustained antibody titers to the three polysaccharide serotypes. Cows immunized with microspheres had higher antibody titers. Cows in both groups produced increased concentrations of IgG1 and IgG2 antibodies; neither group produced an increase in IgM. Immune sera from cows immunized with conjugates alone increased phagocytosis, which decreased at the end of the study. Sera from cows immunized with conjugates in microspheres increased phagocytosis, which was sustained at the end of the study. Immune sera from both groups decreased bacterial adherence to bovine mammary epithelial cells. These data showed that a single injection of antigen in microspheres produced higher titers and more sustained enhancement of phagocytosis, which could aid in the defense of the cow against S. aureus infections.     

Evaluation of an alternative dosing regimen of a J-5 mastitis vaccine against intramammary Escherichia coli challenge in nonlactating late-gestation dairy cows

The objective of the study was to evaluate the efficacy of an alternative vaccination regimen of a J-5 bacterin against intramammary Escherichia coli challenge in nonlactating late-gestation dairy cows. The parameters analyzed to assess the effect of vaccination were milk yield, milk conductivity, somatic cell count, J-5-specific serum IgG titers, and clinical signs. Twenty multiparous Holstein cows from the Cornell teaching and research dairy herd were paired by days in milk and were randomly selected to receive either the alternative off-label regimen of commercial J-5 bacterin or act as nonvaccinated controls. Cows received a first dose of bacterin 15 d before dry off, a second dose with the same product at the day of dry off, and the third dose 2 wk after dry off. The cows in both groups were challenged 10 d before the expected calving date. Serum IgG (total, IgG1 and IgG2) levels were higher in vaccinates compared with control cows. Eighty-five percent of challenged quarters became infected between both groups of animals. Eight of the 10 vaccinated and 9 of the 10 control cows showed signs of clinical mastitis postfreshening. A non-severe clinical mastitis was observed 24 to 48 h postparturition, characterized by flakes or clots in milk and mild swelling or pain. Off-label vaccination did reduce the clinical severity of clinical mastitis in the vaccinated group of cows as evidenced by reduced California mastitis test score, fewer flakes and lower overall clinical mastitis score. No significant differences between vaccinated and control groups were detected for rectal temperature. In conclusion, the alternative off-label vaccination scheme used in our study and evaluated in a novel E. coli challenge model did not prevent new intramammary infections but reduced clinical severity of experimentally induced E. coli mastitis.     

Hyperimmunization of steers with J5 Escherichia coli bacterin: effects on isotype-specific serum antibody responses and cross reactivity with heterogeneous gram-negative bacteria

Isotype-specific antibody responses and cross reactivity were profiled following hyperimmunization of steers with J5 Escherichia coli bacterin. The vaccine was administered at time 0, 30 d later, and every 2 wk for 10 subsequent immunizations. Blood was collected preimmunization and multiple times following each immunization. Isotype-specific anti-J5 Escherichia coli antibody response profiles in diluted sera harvested from each sample were assayed by ELISA and recorded as optical density. Selected sera were assayed for anti-J5 Escherichia coli antibody titers and used to determine cross reactivity against a variety of gram-negative bacteria. Immunization number and day postimmunization influenced response profiles for anti-J5 E. coli IgM, IgG(1)and IgG(2) antibodies. Two immunizations increased mean serum IgM and the IgG(1)antibody profiles above preimmunization levels, but 5 immunizations were required to detect significant IgG(2) antibody responses that were above preimmunization levels. Isotype-specific cross reactivity of the serum antibodies with a variety of heterologous gram-negative bacteria was also increased by hyperimmunization. However, no cross reactivity was observed for Staphylococcus aureus, purified lipopolysaccharide, or lipid A. Our results indicate that multiple booster doses of J5 E. coli bacterin may be required to elicit high levels of cross-reactive serum IgG(2) antibodies.     

Field trial to determine efficacy of an Escherichia coli J5 mastitis vaccine.

Efficacy of an Escherichia coli (O111:B4) J5 bacterin for preventing naturally occurring IMI and clinical mastitis was tested in a 2.5-yr field trial in a 225-cow commercial herd. Cows with odd-numbered identification were vaccinated, and cows with even-numbered identification served as unvaccinated controls for each lactation during the study. Immunizations were subcutaneous on the upper part of the rib cage just posterior to the scapula at drying off, 30 d after drying off, and at calving. Percentage of quarters infected at calving with Gram-negative bacteria did not differ between treatment groups. A total of 67% of Gram-negative bacterial IMI present at calving in control cows became clinical during the first 90 d of lactation compared with 20% in vaccinated cows. Rate of Gram-negative bacterial clinical mastitis was higher in control cows than in vaccinated cows during the first 90 d of lactation. Immunization with the E. coli J5 bacterin did not reduce level of Gram-negative bacterial IMI at calving but did reduce incidence of clinical mastitis.     

The effect of J5 bacterins on clinical,behavioral, and antibody response following an Escherichia coli intramammary challenge in dairy cows at peak lactation

Vaccination against coliform mastitis has become part of mastitis control programs in the past 3 decades, as a means of reducing the severity of clinical mastitis. Our study objective was to evaluate the effect of 2 commercially available vaccines on clinical, behavioral, and antibody response following Escherichia coli intramammary challenge in cows near peak lactation. Cows (n = 12 per group) were vaccinated with vaccine 1 (V1) or vaccine 2 (V2) at dry-off, 21 d pre-calving, and 14 d post-calving. Twelve cows served as unvaccinated controls (CTL). Cows were challenged with E. coli in a rear quarter at approximately 100 d in milk. Milk samples were collected pre- and post-challenge to enumerate E. coli and determine somatic cell count. Serum was collected before each vaccination and at d 0, 1, 2, 3, 6, 30, and 60 relative to challenge, to study antibody response. Milk IgA and tumor necrosis factor-α concentrations were determined in whey. Vaginal temperature, cow activity, and milk yield and components were monitored post-challenge. Bacterial count, somatic cell score, milk yield and component decline, vaginal temperature, activity measures, and antibody and cytokine response were analyzed for treatment differences. The effects of parity, breed, and a repeated measure of time were also tested. Seven cows had to be removed from the study post-challenge for antibiotic treatment (CTL and V1, n = 3 each; V2, n = 1), 2 of which were euthanized (both CTL). Vaccinated cows exhibited fever (vaginal temperature ≥39.4°C) 3 h earlier than CTL cows, but we found no differences between treatments for bacterial count, somatic cell score, or milk yield reduction. Vaccinated cows spent more time lying per rest bout 2 d post-challenge, but total daily lying time was not different from CTL cows during the 7 d post-challenge. The vaccines differed in antibody response: V1 cows had greater serum IgG₁ and IgG₂ post-challenge. A parity effect was also evident: primiparous cows had lower bacterial counts, somatic cell score and a smaller milk yield decline than multiparous cows, but also had lower antibody production. Immunization with either J5 bacterin did not reduce clinical signs of mastitis in cows challenged at 100 d in milk, demonstrating that the effects of J5 vaccination had diminished at peak lactation.     

Experimental challenge of bovine mammary glands with Enterococcus faecium during early and late lactation

Mammary glands of early and late lactation cows were challenged with Enterococcus faecium of bovine origin to determine in vivo pathogenicity and milk somatic cell count (SCC) responses. A total of 20 early lactation and 18 late lactation mammary glands were challenged. Two isolates highly adaptive and 2 isolates poorly adaptive for in vitro growth in mammary secretion were used as challenge strains of bacteria. Challenged quarters of early lactation cows were more susceptible to intramammary infection caused by E. faecium than those of late lactation cows. Intramammary challenge with isolates poorly adaptive for in vitro growth in mammary secretions resulted in 94.7% of quarters infected compared with 36.8% of the quarters infused with the isolates highly adaptive for in vitro growth in mammary secretions. Milk from quarters infused with the isolates poorly adaptive for in vitro growth had higher SCC and bacterial counts compared with quarters challenged with the isolates highly adaptive for in vitro growth. A stage of lactation effect within treatment groups was measured when milk SCC were compared between early and late lactation cows. Milk SCC in uninfused (negative control) quarters were lower in early lactation cows compared with late lactation cows. Conversely, in quarters infused with isolates poorly adaptive for in vitro growth, SCC were higher in early lactation cows compared with late lactation cows on d 2, 3, 4, 15, 16, and 17 postchallenge. In quarters infused with isolates highly adaptive for in vitro growth, SCC response did not differ between early and late lactation cows. In vitro growth of E. faecium in mammary secretion was inversely related to in vivo pathogenicity in the mammary glands of early and late lactation cows.     

Influence of involution on intramammary phagocytic defense mechanisms.

Mammary secretions (n = 34 cows) and mammary phagocytes (n = 18 cows) were collected throughout the nonlactating (dry) period to determine changes in intramammary phagocytic defense mechanisms. Mammary secretions were evaluated for their ability to support phagocytosis of Staphylococcus aureus by neutrophils from donor cows and mammary phagocytes for phagocytic and chemiluminescence activity. Ability of secretions to support phagocytosis decreased with advancing length of the dry period. This effect was more pronounced when dry cow secretions constituted 50% of the phagocytic mixture. Phagocytic activity of mammary phagocytes decreased with advancing dry period when autologous secretion was used in the incubation mixture. With homologous secretion, the percentage of phagocytosis increased 5 to 6 d after drying off compared with before drying off and then gradually decreased throughout the remainder of the dry period. Chemiluminescence activity (log10 counts per minute) of mammary phagocytes was lower during the dry period and decreased with advancing dry period. Results indicated diminishing ability of secretions to support phagocytosis and diminished phagocytic and bactericidal mechanisms during the dry period.     

Effect of anticapsular antibodies on neutrophil phagocytosis of Staphylococcus aureus.

One of the major virulence factors of Staphylococcus aureus is development of an exopolysaccharide capsule in vivo, which inhibits recognition of antibodies to highly antigenic cell wall by neutrophils. To circumvent this inhibition, an attempt was made to produce anticapsular antibodies. Three cows per group were immunized in midlactation by injections in the area of the supramammary lymph node and intramuscularly and were boosted on d 14, 42, and 70 with three variants of Smith S. aureus: compact, unencapsulated; diffuse, rigid capsule; and diffuse large clearing, exceptionally large flaccid capsule using dextran sulfate as adjuvant. Serum agglutination and ELISA titers of cows immunized with diffuse and diffuse large clearing increased after immunization and after each boost and remained elevated to the end of the experiment at 112 d. Phagocytosis of diffuse and diffuse large clearing, measured by flow cytometry, was enhanced by immunization with either organism. No antibody response to capsule or enhanced phagocytosis of diffuse developed in cows immunized with compact. However, anticompact antibodies were opsonic for diffuse large clearing. These data show that bovine antibodies to S. aureus capsule are opsonic for bovine neutrophils and that capsule plays a role in inhibition of cell-wall opsonization of S. aureus.     

The effects of experimentally induced Escherichia coli mastitis and flunixin meglumine administration on activity measures, feed intake, and milk parameters

The use of flunixin meglumine (FM), a nonsteroidal antiinflammatory drug, during experimentally induced Escherichia coli mastitis was evaluated. Twenty-four primiparous and multiparous lactating dairy cows were challenged with 1×10(2)cfu of E. coli 727 in 1 uninfected quarter. Of the 24 E. coli-challenged animals, 12 were administered FM [ECF; 100mg (2cc)/45.5kg of body weight) at the onset of clinical mastitis signs. The remaining 12 challenged cows were untreated (EC). An additional 11 cows were infused with 1mL of sterile phosphate-buffered saline and served as the nonchallenged control (CTL) group. Activity measures, dry matter intake (DMI), milk production, milk bacterial counts from challenged mammary glands, and somatic cell score (SCS) were collected on all animals. Activity measurements were collected using both a behavior-monitoring system and data loggers. Activity was summarized by day (behavior-monitoring system) and in 3-h time periods (data loggers). An examination of animal activity indicated that EC and ECF cows stood more and lay less as compared with the CTL animals in the first 6h after FM administration. When DMI was analyzed, CTL and ECF animals had greater DMI than the EC animals on d 1 postchallenge. However, by d 2 postchallenge, DMI for ECF and EC cows was significantly less than for the CTL cows. The ECF cows had greater milk yield than did EC animals by d 3 and 4 postchallenge, and no significant difference in yield was observed between the ECF and CTL animals. No differences in SCS were observed between the parity groups. Yet, bacterial counts in milk were greater in multiparous animals compared with the primiparous cows. Therefore, it can be concluded that E. coli mastitis does alter animal activity and may have a negative effect on animal well-being. However, the improvement in DMI and milk production for ECF animals provides evidence for using a nonsteroidal antiinflammatory drug as supportive therapy in alleviating the adverse effects associated with E. coli mastitis.     

Relationships among vitamin E, selenium, and bovine blood neutrophils

Effects of vitamin E and selenium supplementation on in vitro phagocytosis and intracellular kill of bacteria by bovine neutrophils were investigated. Diets were not supplemented with vitamin E and selenium during the dry period and first 21 d of lactation. Cows were then assigned to one of four treatment diets for 30 d. Treatment diets were either unsupplemented or supplemented with vitamin E, selenium, or both vitamin E and selenium, in a 2 x 2 factorial arrangement. Peripheral blood neutrophils were isolated from each cow on lactation d 51. Vitamin E supplementation of diets increased intracellular kill of Staphylococcus aureus and Escherichia coli by neutrophils. Intracellular kill of S. aureus was greater in neutrophils isolated from selenium supplemented cows than in neutrophils from cows without supplemental selenium. Intracellular kill of E. coli did not differ between neutrophils from selenium supplemented and selenium unsupplemented cows. Ability of neutrophils to phagocytize either S. aureus or E. coli was independent of vitamin E and selenium.