Effects of UV irradiation in a continuous turbulent flow UV reactor on microbiological and sensory characteristics of cow's milk.

The dairy industry under current pasteurization conditions (15 s at 72°C) and sanitary standards achieves a safe product with excellent quality. In an ever-competitive market there is still a need to improve product quality and extend shelf life of dairy products to increase competitiveness and open up new markets. In an attempt to test the effect of UV irradiation on microbiota of fluid milk, a continuous flow UV system at 254 nm was used to treat 3.5 and 2% fat milk at two UV doses (880 and 1,760 J liter(-1)). Milk was obtained from three processors, and two lots from each processor were assessed. To assess the impact on the most descriptive native microbiota in pasteurized milk after UV illumination, the product was held at two storage temperatures (4 and 7°C) and tested weekly for 5 weeks for aerobic plate counts (psychrotrophic and mesophilic bacteria), laboratory pasteurization counts, aerobic sporeformers, coliform organisms, and titratable acidity. Microbial counts for all tested microorganisms were lower in UV-treated milk when compared with control throughout storage at 4 and 7°C in both 3.5 and 2% fat milk. Sensory analysis indicated that there is a sensory defect associated with UV treatment at the wavelength used.

Effect of selected dairy starter cultures on microbiological, chemical and sensory characteristics of swine and venison (Dama dama) nitrite-free dry-cured sausages.

The aim of this study was the evaluation of selected lactic acid bacteria (LAB) starter culture of dairy origin in the production of nitrite-free low-acid fermented venison (Dama dama) sausage (salame di daino) produced in a small-scale plant in Umbria (Italy), and their effect on microbiological, physico-chemical and sensorial properties of the products. Salame di daino was obtained with two different processes: with and without the addition of selected LAB starter cultures. Microbial counts of Enterobacteriaceae, coliform organisms and Pseudomonas spp. were lower in salami made with the addition of starter cultures. Staphylococcus aureus, Salmonella spp, and Listeria monocytogenes after the first week of ripening were only detected from control salami. Control salami were paler and harder, whereas those made with the addition of starter cultures were slightly saltier, juicier and in general more acceptable. Selected dairy-origin starter (SDS) cultures did prevent the growth of both indicators of food safety and of process hygiene and increased the acceptability of full-ripened salami.

Biological markers of neonatal calf performance: the relationship of insulin-like growth factor-I, zinc, and copper to poor neonatal growth.

Raising a heifer calf to reproductive age represents an enormous cost to the producer. Poor neonatal growth exacerbates the costs incurred for rearing, and use of blood variables that may be associated with poorly growing calves may offer predictive value for growth and performance. Thus, the principal objective of the present study was to describe changes in serum IGF-I, zinc, and copper from birth to 90 d in Holstein calves, while accounting for sex and twin status, in poorly growing calves and calves growing well. A second objective was to test the hypothesis that an association exists between these serum variables and morphometric indicators of growth. Measurements of BW, length, and height were recorded at birth and at 30, 60, and 90 d of age. Jugular blood (12 mL) was collected from each calf on d 1 to determine serum total protein, serum IgG, packed cell volume, serum zinc, serum copper, serum IGF-I, and CD18 genotype for bovine leukocyte adhesion deficiency; serum zinc, serum copper, and serum IGF-I (predictor variables) were also determined for each calf on d 2 through 10 and on d 30, 60, and 90. Stepwise multiple regression and logistic regression analyses were used to examine the relationships between the predictor variables and the dependent variables (BW, height, and length at d 30, 60, and 90 of life). Birth weight, sex, serum IGF-I (at all ages), serum copper, and the serum copper-to-zinc ratio were associated, to varying degrees, with the dependent growth variables. Birth weight was consistently the dominant predictor. In conclusion, these results suggest that lighter birth weight, reduced serum IGF-I, and inflammation may be important causes of poor growth in neonatal Holstein dairy calves.

Short communication: Attempts to identify Clostridium botulinum toxin in milk from three experimentally intoxicated Holstein cows.

Three adult lactating Holstein cows were injected in the subcutaneous abdominal vein with 175 ng/kg of body weight of Clostridium botulinum type C toxin (451 cow median toxic doses) to determine if this botulinum toxin crosses the blood-milk barrier. Whole blood (in sodium heparin) and clotted blood serum samples were taken at 0 min, 10 min, and 3, 6, 9, and 12 h postinoculation. Milk samples were taken at 0 min and at 3, 6, 9 and 12 h postinoculation. All samples were tested for the presence of the toxin using the mouse bioassay and immunostick ELISA test. The immunostick ELISA identified the toxin in whole blood and the mouse bioassay identified the toxin in serum at all times examined in all 3 animals. Toxin was not identified by either detection method in milk samples collected from the 3 animals. From these results, it appears that Clostridium botulinum type C toxin does not cross from the blood to the milk in detectable concentrations.

Disinfection of dairy and animal farm wastewater with radiofrequency power.

Radiofrequency (RF) power was investigated as a new, physical (nonchemical), thermal process to disinfect wastewater from dairy and animal facilities. Samples (n = 38) from 8 dairy, 2 calf, and 3 swine facilities in California were collected over a 3-yr period and characterized for their dielectric properties, chemical composition, and suitability for thermal processing using RF power. To establish efficacy for disinfection, selected samples were inoculated with high levels (10(6) to 10(9) cfu/mL) of bacterial pathogens such as Salmonella sp., Escherichia coli O157:H7, and Mycobacterium avium ssp. paratuberculosis and processed with an RF prototype system. The capabilities of RF power as a method for thermal disinfection of wastewater were demonstrated when bacteria pathogens were completely and rapidly (<1 min) inactivated when temperatures of 60 to 65 degrees C were achieved. Furthermore, RF technology can be used for large-scale, batch or continuous and portable applications, allowing significant improvements in energy-use efficiencies compared with conventional thermal (surface heating) technologies. Therefore, RF power has potential as an alternative to disinfect dairy/animal farm wastewater before recycling.

Association of minimum inhibitory concentration cluster patterns with dairy management practices for environmental bacteria isolated from bulk tank milk.

Environmental bacteria have emerged over the past few years to become significant causes of mastitis. Bacteria in this group are often reported by practicing veterinarians to be increasingly resistant to intramammary therapy and responsible for elevated bulk tank somatic cell counts. The purpose of this study was to determine the extent of association of the minimum inhibitory concentrations for selected antimicrobial agents with environmental bacteria isolated from bulk tank milk on California dairies and their housing facilities, husbandry practices, and antimicrobic-use strategies. Bulk tank milk samples were collected from 2 dairy cooperatives that had their milk cultured at the Milk Quality Laboratory, University of California Davis, Veterinary Medicine Teaching and Research Center in Tulare, CA. Samples were collected from July 2001 through March 2002 on 88 d; and 404 environmental bacteria isolated from 93 dairies were found. Minimum inhibitory concentrations were determined on 337 of the isolates for 10 antimicrobial agents. Cluster analysis was performed on the minimum inhibitory concentration values for each organism, and 4 antimicrobial clusters with varying degrees of resistance were found.A 69-question survey questionnaire was completed on-farm for 49 of the 73 dairies that had at least 3 environmental bacterial isolates. The questionnaire sought information on housing facilities, milking management, mastitis prevention, antimicrobial usage strategies, and owner/veterinary involvement in disease control and prevention. Multinomial logistic regression analysis found significant associations between the antimicrobial agent-resistance cluster groups and some of the housing and bedding practices, failure to dry udders before milking, and antimicrobial treatment of nonmastitis conditions. No association was noted for antimicrobial agent treatment of mastitis and the resistance cluster patterns.

Efficacy of an Escherichia coli J-5 mutant strain bacterin in the protection of calves from endotoxin disease caused by subcutaneous challenge with endotoxins from Escherichia coli.

The purpose of this trial was to examine the potential of a new Escherichia (E) coli J-5 mutant strain bacterin to reduce the severity of clinical disease caused by subcutaneous challenge with endotoxins of Gram-negative bacteria in calves. Day-old to 3-day old calves (n = 40 per study phase) were randomly assigned to either of two treatment groups, i.e. a vaccinated or a placebo group. Calves in the vaccinated group received an inactivated bacterin containing a J-5 mutant strain of E. coli via subcutaneous route at 2-4 days of age and at 14 days thereafter. The placebo contained only adjuvant and saline in lieu of the antigen. Lipopolysaccharides (LPS) originating from E. coli were administered subcutaneously 3 weeks after the booster dose. The LPS challenge dosages were 1 and 8 microg/kg in study phases I and II, respectively. Various clinical, physiological, hematological, and serological parameters were measured at specific time intervals after challenge. The data were mostly analysed using peak changes from baseline recorded during the observation period. By the time of challenge the titers in vaccinated calves had increased significantly more than in the unvaccinated controls. Disease severity following subcutaneous challenge was dose dependent. In phase I, placebo calves were only mildly challenged whereas in phase II placebo calves showed a moderate challenge. After a mild challenge, there was little evidence of protection due to vaccination as only attitude was significantly improved in the vaccinates. In contrast, after a moderate challenge rectal temperature, hematocrit, blood glucose concentrations, and leukocyte changes were significantly better in the vaccinated group. In conclusion, the results of this study show that following a subcutaneous endotoxin challenge that induces a moderate clinical response, calves that were previously vaccinated with the E. coli J-5 bacterin were better protected than those in the placebo group.

Enterotoxin production by Staphylococcus aureus isolated from mastitic cows.

Staphylococcus aureus is an important cause of mastitis in cows. The ability of S. aureus strains to produce one or more enterotoxins in milk and dairy products is linked to staphylococcal food poisoning. To determine whether staphylococci causing bovine mastitis could cause human foodborne intoxication, the production of staphylococcal enterotoxins A through D (SEA, SEB, SEC, and SED) by 160 S. aureus isolates was evaluated with the use of a reverse passive latex agglutination enterotoxin kit. All S. aureus strains were isolated over a 9-month period from 2,343 routine submissions of a composite quarter collection of individual mastitic cows at 18 dairy farms in the San Joaquin Valley in California. Prior to enterotoxin detection, isolates were grown by a method that enhances the in vitro synthesis of enterotoxin. Twenty-two of 160 S. aureus isolates produced enterotoxin. Seven produced SEC, 12 produced SED, and 3 produced both SEC and SED. None of the isolates produced SEA or SEB.

The use of spiral plating and microscopic colony counting for the rapid quantitation of Mycobacterium paratuberculosis.

AIMS: To evaluate a spiral plating and microscopic colony counting technique to hasten the quantitation of Mycobacterium paratuberculosis. METHODS AND RESULTS: Broth and milk cultures of M. paratuberculosis were spirally plated onto Middlebrook agar plates and microscopically counted at 8 and 14 days of incubation. The same plates were recounted at 27-28 days of incubation when grossly visible colonies were present. The results were statistically compared with no difference in CFU ml-1 derived from the shorter vs longer incubation times. Other mycobacteria isolates were also plated and microscopically examined and found to be easily distinguishable from M. paratuberculosis. CONCLUSIONS: Microscopic quantitation of spirally plated M. paratuberculosis cultures can be achieved within 8-14 days of plate incubation and compare favourably to counts derived after prolonged incubations. SIGNIFICANCE AND IMPACT OF THE STUDY: The technique could greatly hasten the quantitation of viable M. paratuberculosis.

The cytokine markers in Staphylococcus aureus mastitis of bovine mammary gland.

TaqMan real time PCR was used to study the transcriptional activity of the bovine IL-2, IL-6, IL-12p40, IFN-gamma, TNF-alpha and granulocyte-monocyte colony stimulating factor of whole milk cells in bovine mammary gland experimentally infected with Staphylococcus aureus. Cytokine transcriptional activity was monitored at 7, 24 and 32 h Post-infection (Pi). IL-12 and TNF-alpha levels were significantly elevated at 24 h Pi followed by sharp decrease at 32 h pi. IL-2 level was decreased at 32 h pi. IL-12 and IFN-gamma showed a significant interaction at 24 h pi. The significant elevations of the IL-12 and TNF-alpha transcriptional level most likely indicate their important role in regulation of the immune responses of bovine mammary gland in S. aureus infection. Depression of IL-2 could reflect the suppressive nature of the S. aureus mastitis.

Cytokines gene expression patterns of bovine milk during middle and late stages of lactation.

The cytokine mRNA profiles of the bovine mammary gland were investigated using newly developed TaqMan real-time polymerase chain reaction systems (Applied Biosystems, Foster City, CA, USA). Transcriptional activity of six cytokines, interleukin (IL)-2, IL-6, IL-12, interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and granulocyte-macrophage colony stimulating factor (GM-CSF) was studied during the mid- and late-lactation stages. Transcripts for TNF-alpha, GM-CSF, and IFN-gamma were detected in all samples of both stages. However, IL-12 was only detected in 80 and 58 % of late- and mid-lactation samples, respectively. IL-12 expression was up-regulated in late lactation in comparison with the corresponding level in mid-lactation. The cytokines interaction in late lactation was more co-ordinated and their transcriptional levels were significantly correlated among each other, whereas, in mid-lactation significant correlation of the cytokines transcription was only seen with the TNF-alpha, GM-CSF, and IFN-gamma. Cytokine mRNA profiles between mid- and late lactation showed significant differences, which can be attributed to the dramatic changes that the mammary gland is subjected to during late lactation. The significant elevation of IL-12 transcriptional activity in late lactation and its relevance to the mammary gland immunity is discussed.

Antibiotic susceptibility patterns for environmental streptococci isolated from bovine mastitis in central California dairies.

Environmental streptococci are frequently isolated from bovine mastitis in dairy cows with only limited information available on the antimicrobial susceptibility of these organisms. A total of 362 environmental streptococci isolated from cases of bovine mastitis from the central San Joaquin Valley of California over a 3-yr period were used in the study. Overall, 39.9% of the strains tested were Streptococcus uberis, 42.2% were Streptococcus dysgalactiae, and 11.1% were Enterococcus spp. The antimicrobial susceptibility for these organisms was determined for the following antimicrobial agents: penicillin, ampicillin, cephalothin, ceftiofur, penicillin + novobiocin, erythromycin, pirlimycin, tetracycline, and sulfadimethoxine. Results demonstrate substantial differences in the susceptibility patterns for the various organisms collectively referred to as the environmental streptococci. The MIC90 for penicillin was 0.06 microg/ml for 152 strains of S. dysgalactiae compared with 0.25 microg/ml for 133 strains of S. uberis. However, the Enterococcus spp. were the most resistant organisms tested. These data also indicate that the use of interpretive criteria based on human data may provide misleading results. In conclusion, these data confirm that the environmental streptococci are a diverse group of organisms comprised of several different genera and species and that identification of environmental streptococci to the species level is needed to appropriately modify control methods. Moreover, the use of the agar disk diffusion (Kirby-Bauer) susceptibility test for agents with human-based interpretive criteria is contraindicated, and these tests should only be performed with agents with mastitis specific interpretive criteria.

Prevention of diseases caused by Staphylococcus aureus using the peptide RIP.

Staphylococcus aureus causes many diseases including cellulitis, keratitis, osteomyelitis, septic arthritis and mastitis. The heptapeptide RIP has been shown to prevent cellulitis in mice, which was induced by S. aureus strain Smith diffuse. Here we show that RIP can also significantly reduce the overall pathology and delay the onset of disease symptoms in several other models of S. aureus infections, including: keratitis (tested in rabbits against S. aureus 8325-4), osteomyelitis (tested in rabbits against S. aureus MS), mastitis (tested in cows against S. aureus Newbould 305, AE-1, and environmental infections) and septic arthritis (tested in mice against S. aureus LS-1). These findings substantiate that RIP is not strain specific in its inhibitory activity and that RIP is an effective inhibitor of bacterial pathology at multiple body sites following diverse routes and doses of administration. These findings strongly evidence the potential value of RIP as a chemotherapeutic agent.

Quantitation of bovine cytokine mRNA in milk cells of healthy cattle by real-time TaqMan polymerase chain reaction.

Here we present a novel methodology to quantitate bovine cytokines and growth factors contributing to immunity against bacterial infections of the mammary gland in cattle. Real-time TaqMan PCR systems were developed to overcome limitations of conventional quantitative PCR methods. The TaqMan method is based on the cleavage of fluorescent dye-labeled probes by the 5'-3' exonuclease activity of the Taq DNA polymerase during PCR and measurement of fluorescence intensity by an automated spectrophotometer integrated in a sequence detection system (Applied Biosystems, Foster City, CA). The bovine-specific TaqMan probes were designed to encompass an intron, thus allowing differentiation between complementary DNA (cDNA) and genomic DNA (gDNA) amplification products. Quantitative analysis of cytokine cDNA was performed in comparison to bovine glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Messenger RNA (mRNA) from the universally expressed housekeeping gene GAPDH proved to be useful as an amplification control and allowed for correction of variations in different numbers of cells in the starting material, in the efficiencies of RNA extraction and reverse transcription. With this method, high-throughput analysis of large numbers of samples was possible within a short time. In addition, decreasing the numbers of working steps shortened the time for analysis and increased accuracy. Profiles of cytokines (interleukin (IL)-2, IL-6, IL-8, IL-12 p40, TNF-alpha, IFN-gamma) and granulocyte-macrophage colony stimulating factor (GM-CSF) were established in normal lactating cattle. Differences of cytokine profiles obtained with the real-time TaqMan PCR system and conventional methods are discussed.

Oxygen radical production by Asian elephant (Elephas maximus) heterophils and Holstein cattle (Bos taurus) neutrophils.

Oxidative metabolic burst activity by Asian elephant (Elephas maximus) heterophils and Holstein cattle (Bos taurus) neutrophils was indirectly evaluated by measuring the oxidation of nonfluorescent intracellular 2',7'-dichlorofluorescein (DCFH) to fluorescent 2',7'-dichlorofluorescein (DCF) with flow cytometry. The results were recorded as mean channel fluorescence intensity. Phorbol myristate acetate at 50 ng/ml was used to activate the cells. Elephant heterophils and bovine neutrophils exhibited similar abilities to oxidize intracellular DCFH to DCF, a fluorescent product. A wide range of mean channel fluorescence intensity (1,803-7,393) was observed among individual elephants, and the range of intensities was similar to that observed in bovine neutrophils, supporting the concept of functional heterogeneity of heterophils among elephants.

Evaluation of the Delvo-X-Press assay for detecting antibiotic residues in milk samples from individual cows.

Performance of the Delvo-X-Press beta-lactam antibiotic assay was examined using bulk-tank milk samples and milk samples from individual cows. Bulk-tank milk samples fortified with bovine lactoferrin at a concentration of 1 mg/ml or more consistently tested positive. False-positive results were also obtained from bulk-tank milk samples fortified with bovine plasma at concentrations of 20 and 40%. The assay yielded positive results for milk with antibiotic concentrations as low as 2 ppb. Individual milk samples were collected from 144 healthy lactating cows and from 34 cows with chronic Staphylococcus aureus mastitis. Specificity estimates for samples from healthy and mastitic cows were 0.88 (95% confidence interval [CI], 0.82, 0.93) and 0.94 (95% CI, 0.86, 1.00), respectively. Individual milk samples were collected from three cows with experimentally induced mastitis for 21 consecutive days. False-positive results occurred as late as 12 days postchallenge. A moderate but significant (P < 0.01) positive linear correlation (r = 0.61) was observed between test result and somatic cell count (SCC) values in milk samples with SCCs of >10(6)/ml.

Cloning and expression of bovine neutrophil beta-defensins. Biosynthetic profile during neutrophilic maturation and localization of mature peptide to novel cytoplasmic dense granules.

beta-Defensins are microbicidal peptides implicated in host defense functions of phagocytic leukocytes and certain surface epithelial cells. Here we investigated the genetic structures and cellular expression of BNBD-4, -12, and -13, three prototypic bovine neutrophil beta-defensins. Characterization of the corresponding cDNAs indicated that BNBD-4 (41 residues) derives from a 63-amino acid prepropeptide and that BNBD-12 (38 residues) and BNBD-13 (42 residues) derive from a common 60-amino acid precursor (BNBD-12/13). The peptides were found to be encoded by two-exon genes that are closely related to bovine epithelial beta-defensin genes. BNBD-4 and BNBD-12/13 mRNAs were most abundant in bone marrow, but were expressed differentially in certain non-myeloid tissues. In situ hybridization and immunohistochemical studies demonstrated that BNBD-4 synthesis is completed early in myelopoiesis. BNBD-12 was localized exclusively to the novel dense granules, organelles that also contain precursors of cathelicidins, antimicrobial peptides that undergo proteolytic processing during phagocytosis. In contrast to cathelicidins, Western blot analyses revealed that mature beta-defensins are the predominant organellar form in myeloid cells. Stimulation of neutrophils with phorbol myristate acetate induced secretion of BNBD-12, indicating that it is co-secreted with pro-cathelicidins. The exocytosis of BNBD-12 by activated neutrophils reveals different mobilization pathways for myeloid alpha- and beta-defensins.

The observation of reactive thrombocytosis in New Zealand white rabbits in response to experimental Pasteurella multocida infection.

Reactive thrombocytosis is an increase in the circulating thrombocyte count secondary to a physiologic process within the body, often an infection. Reactive thrombocytosis is different than primary or essential thrombocytosis which is usually related to myeloproliferative neoplasia. Essential thrombocytosis is most common in adults, whereas reactive thrombocytosis is most frequently observed in children. Reactive thrombocytosis has been occasionally reported in cats, dogs and horses but has not been previously reported in the rabbit. Rabbits were challenged with virulent Pasteurella multocida. Hematologic, clinical, and culture assessments were performed prior to challenge, enabling each animal to serve as its own control. The questions asked were whether reactive thrombocytosis was a consistent phenomena and whether its presence and/or intensity was related to disease severity. All challenged rabbits demonstrated some degree of thrombocytosis in response to the infection, but individual rabbits were varied in their pattern of thrombocytosis. Elevations varied from intense to mild to undulating with durations of 1 to 11 days above 500 x 10(9)/L and 0 to 5 days above 650 x 10(9)/L. Correlation analysis was unable to demonstrate significant association between thrombocytosis, body temperature, leukocyte count, or the granulocyte lymphocyte ratio (all r < 0.2). No significant association between intensity of thrombocytosis and degree or type of pathologic lesions was observed. Thrombocytosis does not appear predictive of disease intensity or outcome. The data indicate that in the rabbit thrombocytosis is a consistent response to infection with P. multocida. Rabbits may serve as a model for the study of reactive thrombocytosis, in humans especially in children infected with Haemophilus sp., which are also a members of the bacterial family Pasteurellaceae.

Evaluation of commercially available Escherichia coli J5 bacterin as protection against experimental challenge with Pasteurella multocida in rabbits.

OBJECTIVE: To evaluate the ability of commercially available Escherichia coli J5 bacterin to protect rabbits from experimental challenge with Pasteurella multocida. ANIMALS: 40 P multocida-free New Zealand White rabbits. PROCEDURES: Rabbits were assigned to 1 of 4 groups of 10 rabbits each. Three of the groups were inoculated SC with J5 bacterin at 8 weeks old. Inoculation was repeated 3 and 6 weeks later. The fourth group was not inoculated and served as controls. Groups 1, 2, and 3 were given 10(9), 10(8), and 10(7) colony forming units (CFU), respectively. Response was monitored by titer assessment, using an E coli J5 antigen capture ELISA. Five weeks after the last inoculation, all rabbits were challenged with P multocida and observed for an additional 5 weeks. Clinical, hematologic, serologic, culture, and necropsy data were collected. RESULTS: Inoculation of rabbits with 10(9) CFU of E coli J5 bacterin-induced titers that were significantly greater than titers of rabbits vaccinated with 10(8) or 10(7) CFU or those in controls. The incidence of acute bacteremia was lower in rabbits with high titers. At necropsy, prevalence of lesions typical of P multocida was not significantly different among groups. Prevalence of histologic lesions was also not significantly different among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Although the bacterin induced considerable antibody response and possibly reduced the rate of bacteremia, antibodies were not protective against long-term colonization or infection of the frontal sinuses or tympanic bullae by the challenge strain of P multocida. This bacterin in its currently available form is unlikely to aid in reducing the prevalence of pasteurellosis in rabbits.

Seroprevalence of antibodies against gram-negative core antigens in rabbits, using an Escherichia coli J5 antigen-capture enzyme-linked immunosorbent assay.

OBJECTIVE: To determine the seroprevalence of antibodies to gram-negative core antigens (GNCA) in specific-pathogen-free (SPF) rabbits (ie, free of Pasteurella multocida) and rabbits of undefined bacterial status (conventional). SAMPLE POPULATION: Serum samples were obtained from 7 groups of rabbits. The SPF rabbits comprised 2 adult groups and 1 immature group, whereas the 4 groups of conventional rabbits were all adults. PROCEDURE: A seroprevalence survey was conducted on rabbit sera for antibodies against GNCA, using an Escherichia coli J5 antigen-capture ELISA. RESULTS: Collective geometric mean titer (GMT) of adult rabbits was 1:6,463. The GMT of each of the 6 groups of adult rabbits was 1:956, 1:1,133, 1:4,525, 1:5,338, 1:7,669, and 1:25,600. Titers of populations differed significantly. CONCLUSION: Data analysis revealed there were anti-GNCA antibodies in rabbits. Similar to other species, the prevalence of IgM and IgG anti-GNCA antibodies increased with age. The IgG response was more marked than the IgM response. The SPF rabbits had lower IgG anti-GNCA titers than conventional rabbits, indicating possible cross-reactive epitopes between P multocida and Enterobacteriaceae. Rabbits with the highest anti-GNCA titers were those used in polyclonal antibody production, possibly stemming from endotoxin contamination of antigen or adjuvant. CLINICAL RELEVANCE: The possible cross-reactive antibodies directed at homologous wall components of Pasteurellaceae and Enterobacteriaceae could prove to be a possible heterotypic vaccination strategy for the protection of rabbits against pasteurellosis. Investigators should determine whether antigen impurity (endotoxin contamination) influences epitope focus during polyclonal antibody production and whether it affects sera variability among rabbits.