J. S. Hogan1, V. L. Bogacz, and K. L. Smith
The Ohio State University Department of Animal Sciences
The efficacy of an Escherichia coli J5 bacterin for reducing the incidence of intramammary infections (IMI) 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 days prior to calving, 28 days later, and within 48 hours after calving. Vaccinated and placebo-injected heifers were challenged by intramammary infusion of E. coli 727 in one mammary gland approximately 30 days after calving. All challenged quarters were diagnosed with an intramammary infection within six hours 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. Bacterial counts in milk from challenged quarters were lower in vaccinated heifers than in control heifers at 12, 15, and 48 hours after challenge. Serum immunoglobulin G (IgG) titers against whole-cell E. coli J5 antigen at calving was higher in vaccinated heifers than in controls. Vaccinated heifers had higher IgG 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 severity and duration of clinical signs following intramammary challenge with a heterologous strain of E. coli.
Escherichia coli J5 vaccines have effectively reduced the incidence and severity of clinical mastitis in multiparous cows. Protection offered by the vaccine has been greatest for cows in their fourth or greater lactation. This corresponds with older cows being at the greatest risk within a herd for clinical mastitis caused by coliform bacteria. However, surveys within the last decade have indicated that the incidences of IMI and the risk of clinical mastitis in heifers were previously underestimated. Specifically, risk of clinical coliform mastitis was comparable between multiparous cows and first-lactation heifers. The economic impact of mastitis in primipartum heifers is potentially immense because first-lactation heifers represent approximately 32% of the lactating cows in the United States. The high incidence of IMI in first-lactation heifers at calving may be attributed to the lack of hygiene and health-management practices for heifers; however, these practices are afforded to lactating and dry cows. For example, experiments to determine efficacy of E. coli J5 vaccines established a protocol whereby immunizations were given at drying off, approximately 30 days later, and at the subsequent calving. Therefore, data are minimal on the impact of vaccinating primigravid heifers with E. coli J5 vaccines. The purpose of the current study was to determine the efficacy of an E. coli J5 bacterin administered during the last trimester of gestation and at calving in primigravid heifers following intramammary challenge with a heterologous strain of E. coli.
Primigravid heifers were either vaccinated with an E. coli J5 bacterin (n = 10) (Escherichia Coli Bacterin J5 Strain; Pharmacia and Upjohn, Kalamazoo, Mich.) or a placebo containing adjuvant only (n = 4). Heifers were immunized approximately 60 days prior to anticipated calving, 28 days later, and within 48 hours after calving. Immunizations (5 cc) were subcutaneous on the upper part of the rib cage behind the shoulder blade. The right or left front mammary quarter of each experimental heifer was challenged by intramammary infusion of E. coli 727. The average day in milk at challenge was 30 days. Heifers were monitored for clinical responses to mastitis, bacteria counts in milk, SCC, milk production, dry-matter intake, and antibody titers in serum and whey.
Results of the current trial in which heifers were vaccinated prepartum and at calving were similar to those in which multiparous cows were tested using a similar challenge model. Immunization of primiparous heifers with an E. coli J5 bacterin in the current study did not prevent IMI but reduced severity of clinical signs following intramammary challenge with a heterologous strain of E. coli (Figure 1). All quarters challenged were diagnosed with an IMI within six hours after challenge. Average durations of IMI were 66.1 hours for vaccinated heifers and 87.1 hours for controls. Average duration of local clinical signs, including mammary swelling or abnormal milk, was 93.3 hours for controls and 44.7 hours for vaccinated heifers.
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| Figure 1. Mean clinical score following intramammary challenge with Escherichia coli 727 at 0 hour in first-lactation heifers immunized with E coli. J5 (d: n=10) and in placebo- immunized controls (s: n=4). Dispersion bars represent standard errors for each treatment at each sample time. |
Previous trials testing the efficacy of E. coli J5 bacterins in multiparous cows have demonstrated that vaccination reduced bacterial counts in milk from challenged quarters. Similar results were observed in the current trial, which tested efficacy of an E. coli J5 bacterin in primiparous heifers. Bacterial counts in milk from challenged glands of vaccinated heifers were lower than those from control heifers at 12, 15, and 48 hours after challenge (Figure 2). Bacterial counts in milk peaked at nine hours after challenge in both groups, but a more rapid clearance of bacteria from the gland was observed in vaccinated heifers.
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| Figure 2. Bacteria counts in milk following intramammary challenge with Escherichia coli 727 at 0 hour in first-lactation heifers immunized with E coli. J5 (d: n=10) and in placebo- immunized controls (s: n=4). Dispersion bars represent standard errors for each treatment at each sample time. |
Protection against coliform mastitis afforded by vaccination with E. coli J5 bacterins has been ascribed to enhanced opsonization of bacteria and phagocytosis by neutrophils responding to the IMI. However, vaccination appears to have no effect on rate or magnitude of SCC response to intramammary challenge (Figure 3). Milk SCC did not differ between experimental groups. Milk SCC responses typically were initiated three to six hours after peak bacterial counts and reached their peak 24 hours after challenge. Milk SCC from vaccinated and control heifers had returned to prechallenge concentrations by 14 days after challenge.
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| Figure 3. The SCC following intramammary challenge with Escherichia coli 727 at 0 hour in first-lactation heifers immunized with E. coli J5 (d: n=10) and in placebo-immunized controls (s: n=4). Dispersion bars represent standard errors for each treatment at each sample time. |
The bacterial strain used in the current trial, E. coli 727, has been repeatedly used as a challenge strain to induce clinical mastitis with limited systemic signs. Systemic clinical signs again were limited following challenge with this strain. Vaccination had no effect on systemic clinical signs including rectal temperature, milk production, and dry-matter intake. Average peak rectal temperatures were 105.8° F for control heifers and 106.2° F for vaccinated heifers at 15 hours after challenge (Figure 4). Rectal temperatures had returned to prechallenge values in both groups by 24 hours after challenge. Milk production was reduced approximately 16% in controls and 23% in vaccinated heifers one day after challenge. Milk production returned to prechallenge yields by day two in vaccinated and control heifers. Preceding the transient decrease in milk production, dry matter intake decreased 12% the day control heifers were challenged. Dry matter intake was not altered by challenge in vaccinated heifers.
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| Figure 4. Rectal temperature foolowing intramammary challenge with Escherichia coli 727 at o hour in first-lactation heifers immunized with E. coli J5 (d: n=10) and in placebo-immunized controls (s: n=4). Dispersion bars represent standard errors for each treatment at each sample time. |
Titers for naturally occurring serum antibodies specific for E. coli J5 are negatively associated with risk for clinical coliform mastitis among cows within a herd. Immunization of primigravid heifers in the current study enhanced IgG titers against whole-cell E. coli J5 antigen at calving. Immunoglobulin G titers in colostrum (Figure 5) and serum (Figure 6) collected at calving were greater in vaccinated heifers compared with controls. Milk collected from mammary glands of vaccinated heifers immediately prior to challenge had higher IgG titers than did milk collected prior to challenge from mammary glands of controls. Immunization did not alter immunoglobulin M (IgM) titers against E. coli J5 in either serum (Figure 5) or mammary secretions (Figure 6).
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| Figure 5. Mammary secretion antobody titers [IgG (d, s); IgM (m,n)] to Escherichia coli J5 in first-lactation heifers immunized with an E. coli J5 bacterin (n=10; closed symbols) and placebo-immunized controls (n=4; open symbols). Samples were collected at calving (C + 0), on day 21 of lactation (C + 21), immediately prior to challenge (E + 0), and at 14 days after challenge (E + 14). Dispersion bars represent standard errors for each treatment at each sample time . |
![Figure 6. Serum antibody titers [IgG (d, s); IgM (m, n)] to Escherichia
coli J5 in first lactation heifers immunized with an E. coli](images/sc169_49.jpg) |
| Figure 6. Serum antibody titers [IgG (d, s); IgM (m, n)] to Escherichia coli J5 in first lactation heifers immunized with an E. coli J5 bacterin (n=10; closed symbols). Samples were collected at 60 days prior to anticipated calving (C - 60), 28 days later (C - 32), calving (C + 0), on day 21 of lactation (C + 21), immediately prior to challenge (E + o), and at 14 days after challenge (E + 14). Dispersion bars represent standard errors for each treatment at each sample time. |
Severity of clinical signs following intramammary infusion of E. coli was positively related to the peak bacterial count in milk from challenged quarters. Enhancing mammary secretion of IgG titers specific for E. coli J5 effectively reduced the peak bacterial counts in milk and subsequent clinical signs of mastitis. Correlations were not significant among serum IgG or IgM titers and peak bacterial counts.
First-lactation heifers represent a substantial population of animals within a dairy herd that are at risk for clinical coliform mastitis. Immunization of primigravid heifers during the last trimester of gestation and at calving with an E. coli J5 bacterin resulted in an enhanced humoral response and reduction in clinical coliform mastitis signs similar to that previously reported following immunization of multiparous cows.
1 For more information, contact at: The Ohio State University, Ohio Agricultural Research and Development Center, 302 Pounden Hall, 1680 Madison Avenue, Wooster, OH 44691; (330) 263-3792, Fax (330) 263-3949; email:hogan.4@osu.edu