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.     

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.     

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.     

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.     

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.     

Study of the efficacy of a Streptococcus uberis mastitis vaccine against an experimental intramammary infection with a heterologous strain in dairy cows

Streptococcus uberis is a worldwide pathogen that causes intramammary infections in dairy cattle. Nevertheless, commercial vaccines are currently not available and measures to control S. uberis mastitis are limited to the implementation of good management practices. The aim of the present study was to evaluate the efficacy of an S. uberis subunit vaccine against bovine mastitis (Laboratorios Hipra S.A., Amer, Spain) administered precalving against an experimental intramammary challenge with a heterologous S. uberis strain in dairy cows postcalving. With this objective, 25 gestating Holstein-Friesian heifers were randomly assigned to 1 of 2 groups: group 1 (n = 13), vaccinated by intramuscular route with the vaccine, and group 2 (n = 12), vaccinated by intramuscular route with phosphate-buffered saline as a control group. Both groups were immunized 60 and 21 d before the expected parturition date (75 and 36 d before challenge). Fourteen days after calving all cows were challenged by intramammary infusion of 100 colony-forming units of a heterologous S. uberis strain in 2 quarters per cow. Then, challenged quarters were monitored for clinical signs of mastitis, bacterial count, and somatic cell count for the following 21 d. Rectal temperature and daily milk yield per cow were also assessed. Results showed that all challenged quarters developed clinical mastitis. Nevertheless, vaccination significantly reduced the clinical signs of mastitis, bacterial count, rectal temperature, and daily milk yield losses after the intramammary infection and significantly increased the number of quarters with no bacterial isolation and somatic cell count <200,000 cells/mL at the end of the study (d 19, 20, and 21 after challenge). To confirm the efficacy of this vaccine, further studies under field conditions are needed.     

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.     

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.     

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.     

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.     

Bovine intramammary Escherichia coli challenge infections in late gestation demonstrate a dominant antiinflammatory immunological response

Coliform mastitis that presents itself at parturition or in the early weeks of bovine lactation is often characterized by severe inflammation and impaired milk production and can lead to death of the animal. Chronic intramammary infections caused by persistent strains of Escherichia coli may result in high production losses. The aim of this study was to determine the inflammatory response to a teat-canal challenge of bovine mammary glands with a persistent strain of E. coli during late gestation (dry period) and into early lactation. Two weeks before parturition, animals were challenged in 2 quarters with 30 cfu of a persistent strain of E. coli; control quarters were vehicle-infused and not infused, respectively. Samples of dry cow secretions were taken from all quarters before challenge and at 6, 12, 18, 24, 48, 72, 96, and 120 h following challenge. Colostrum samples and milk samples were taken from all quarters at parturition and 6, 12, 18, 24, 48, 72, 96 and 120 h postpartum. Bacterial culture, combined with random amplified polymorphic DNA genetic strain-typing analysis, indicated recovery of the bacterial challenge strain until 48 to 96 h postchallenge, and again at parturition and up to 6 and 12h postpartum. One animal exhibited clinical mastitis and the bacterial challenge strain was evident to at least 12 d postpartum. During twice-daily milkings, production levels were lower in bacteria-challenged quarters compared with controls. Somatic cell counts decreased to normal levels at a slower rate in challenged quarters compared with control quarters. Cytokine analysis indicated a minimal proinflammatory cytokine response, including interleukin-1β and tumor necrosis factor-α in challenged-quarter dry cow samples up to 120 h postchallenge. Interleukin-10 levels were significantly increased by 12h postchallenge in secretions from challenged and control quarters. These preliminary results in 2 cows indicate that proinflammatory signaling after intramammary bacterial infection may be actively suppressed during late gestation. We hypothesize that this immune-inhibitory response allows intramammary infections to become persistent in the dry period and cause clinical signs immediately after parturition.     

Evaluation of attenuated, live staphylococcal mastitis vaccine in lactating heifers

Four heifers were immunized in late pregnancy with two doses of attenuated, live Staphylococcus aureus and challenged during early lactation by intramammary infusion into one quarter of approximately 100 organisms of the same attenuated strain. Three unvaccinated control heifers were challenged similarly. At challenge immunoglobulins G1 and G2 antibodies against Staphylococcus aureus surface antigens were significantly greater in blood serum of vaccinated heifers than in controls. Also at challenge, serum from vaccinated heifers had a significantly greater opsonizing capacity for Staphylococcus aureus than did that of controls. The challenge dose of Staphylococcus aureus did not produce prolonged clinical signs of acute mastitis in any of the heifers; however, once of the control animals remained chronically infected. There was a decrease of milk production following challenge for controls but no such decrease for the immunized heifers. Taken together, results of clinical assessments, bacteriology, and measurements of milk production suggested that vaccinated heifers had higher resistance to the challenge dose than did controls.     

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.     

Mastitis prevalence in primigravid heifers at parturition

Prevalence of intramammary infection was determined for 382 primigravid heifers within 3 d postpartum on 11 Vermont dairy farms. Data collected during a 5-yr period are summarized. Duplicate quarter milk samples were cultured on tryptose-blood agar plates containing .1% esculin. Intramammary infections were diagnosed in 45.5% of the heifers and 18.7% of quarters. Staphylococcus species were the most prevalent bacteria isolated: they appeared in 25.4% of the heifers and 12.1% of quarters. Only 2.6% of the heifers were diagnosed with Staphylococcus aureus; 22.8% had udder infection caused by other staphylococcal species. Environmental mastitis pathogens, coliforms, and streptococci other than Streptococcus agalactiae were isolated from 14.9% of the heifers and 4.8% of quarters. The prevalence of mastitis among these primigravid heifers at parturition indicates a need to improve methods of diagnosis and control programs.     

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.     

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.     

Evaluation of protein A and a commercial bacterin as vaccines against Staphylococcus aureus mastitis by experimental challenge

Protein A and a commercial staphylococcal bacterin were evaluated by experimental challenge with Staphylococcus aureus (ATCC 29740). Thirty cows in first lactation were in three treatment groups, protein A, bacterin, and nonvaccinated controls. Studies were through three lactations and included bacteriological and cytological analyses of quarter milk samples. Rate of intramammary infection with Staphylococcus aureus was similar for vaccinated and unvaccinated cows. Rates of spontaneous cure within each lactation were significantly higher for vaccinated cows. For all three lactations, spontaneous cure rates were 83, 73, and 47% for protein A, bacterin, and control cows. Somatic cell counts were significantly lower for vaccinated cows for quarters infected with Staphylococcus aureus, but no differences were demonstrated for milk production by lactation. Incidence of clinical mastitis was higher in unvaccinated cows, but too few developed for a valid comparison.     

Field survey of clinical mastitis in low somatic cell count herds

Nine commercial dairy herds, each with low herd milk somatic cell counts, were monitored for 1 yr to determine prevalence of intramammary infections and rates of clinical mastitis. Staphylococcus species was the bacterial group most frequently isolated from quarters at calving and at drying off. Environmental streptococci and coliform intramammary infections totaled less than 6% of quarters at both calving and at drying off. Staphylococcus aureus were isolated from less than 1% of quarters and Streptococcus agalactiae from 0% of quarters at both calving and drying off. A total of 646 clinical cases of mastitis were diagnosed in 548 quarters of 406 cows. Mean rate of clinical mastitis among herds was .457 clinical cases/305 cow-days. Rates of clinical mastitis ranged among herds from .273 to .748 clinical cases/305 cow-days. Coliforms and bacteriologically negative and environmental streptococci accounted for 82.3% of clinical cases. Rates of clinical mastitis and severity of clinical signs differed among herds, seasons of the year, parity groups, and stages of lactation. Rates of clinical mastitis were highest during summer, in first lactation cows, and during the first 7 d of lactation.     

Effect of dietary copper source on response to coliform mastitis in dairy cows

The effect of organic or inorganic dietary Cu on Escherichia coli mastitis was investigated in first-lactation heifers. Twenty-eight primigravid Holstein heifers were assigned to 3 treatments in a completely randomized block design with 10 blocks of 3 animals grouped by expected calving date. Treatments were as follows: basal diet [7.1 mg Cu/kg of dry matter (DM); CON] and diets supplemented with Cu (10 mg/kg of DM) as Cu sulfate (CUS) or as Cu proteinate (CUP). Treatments were fed individually from 60 d prepartum through 49 d of lactation. All heifers were marginally deficient at the onset of the experiment (liver Cu of 60 mg/kg) and did not differ between groups. Mean liver Cu concentrations were about 3-fold greater in CUS and CUP compared with CON at d 0, 21, and 42 of lactation. At d 34 postpartum, one pathogen-free quarter per cow was infused with Escherichia coli strain 727. Copper supplementation did not lower peak responses to challenge; however, CUP tended to offer some benefits: milk bacterial count with CUP was lower compared with CON at 24, 48, and 72 h and lower than CUS at 24 and 96 h, and postchallenge milk production tended to be greater for CUP. Clinical udder score was lower at 12 h for CUP and CUS compared with CON, and at 144 h CUP had lower clinical scores compared with CUS or CON. Somatic cell count, dry matter intake, plasma Cu, and plasma ceruloplasmin did not differ between treatments. Compared with the control diet or Cu sulfate supplement, supplementation with Cu proteinate tended to improve the clinical status of cows after live E. coli intramammary challenge.     

Administration of internal teat sealant in primigravid dairy heifers at different times of gestation to prevent intramammary infections at calving

Intramammary infections (IMI) are common in primigravid dairy heifers and can negatively affect future milk production. Bismuth subnitrate-based internal teat sealants (ITS) have been used to prevent prepartum IMI in dairy heifers by creating a physical barrier within the teat, preventing pathogens from entering the gland, though determination of when to administer ITS in heifers has yet to be investigated. The objectives of this study were to determine if administration of ITS in primigravid heifers reduced the odds of IMI at calving and if administration of ITS at different stages of gestation (75 vs. 35 d prepartum) affected the odds of IMI at calving. A total of 270 heifers were used at a single farm. One quarter of each heifer was randomly chosen to be aseptically sampled and administered ITS 75 d prepartum (ITS75), another quarter of each heifer was sampled and received ITS 35 d prepartum (ITS35), whereas the remaining 2 quarters of each heifer served as control quarters (CON) and were not sampled before calving. Within 12 h of calving, aseptic colostrum samples were collected from all quarters to determine quarter infection status. When an IMI was caused by mastitis pathogens other than non-aureus staphylococci (NAS), CON quarters were 3 times [95% confidence interval (CI): 1.4–6.3] and 2.5 times (95% CI: 1.2–4.9) more likely to be infected at calving than ITS75 and ITS35 quarters, respectively. For IMI with NAS, CON quarters were 5.8 (95% CI: 3.2–10.5) and 6.4 (95% CI: 3.4–12.0) times more likely to be infected than ITS75 and ITS35 quarters, respectively. Odds of IMI at calving was similar between ITS75 and ITS35 quarters for both NAS (odds ratio = 0.9) and other pathogens (odds ratio = 1.2). Results indicate that ITS administration at either 75 and 35 d prepartum reduced IMI prevalence at calving in primigravid dairy heifers. Farm specific factors may influence prevalence and timing of heifer IMI and earlier administration of ITS provides an extended period of protection for the developing gland.