Proteomic analysis of differentially expressed proteins in bovine milk during experimentally induced Escherichia coli mastitis

The objectives of the current study were to profile changes in protein composition using 2-dimensional gel electrophoresis on whey samples from a group of 8 cows before and 18 h after infection with Escherichia coli and to identify differentially expressed milk proteins by peptide sequencing using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry post source decay. Only proteins present in whey fractions of all 8 cows were sequenced to avoid reporting a protein response unique to only a subset of infected cows. Despite the overwhelming presence of casein and β-lactoglobulin, the low abundance proteins transthyretin, lactadherin, β-2-microglobulin precursor, α-1-acid glycoprotein, and complement C3 precursor could be identified in whey samples from healthy cows. Whey samples at 18 h postinfection were characterized by an abundance of serum albumin, in spots of varying mass and isoelectric point, as well as increased transthyretin and complement C3 precursor levels. Also detected at 18 h postinoculation were the antimicrobial peptides cathelicidin, indolicidin, and bactenecin 5 and 7, and the proteins β-fibrinogen, α-2-HS-glycoprotein, S100-A12, and α-1-antiproteinase. Most notable was the detection of the acute phase protein α-1-acid glycoprotein in mastitic whey samples, a result not previously reported. In contrast to methods used in previous proteomic analyses of bovine milk, the methods used in the current study enabled the rapid identification of milk proteins with minimal sample preparation. Use of a larger sample size than previous analyses also allowed for more robust protein identification. Results indicate that examination of the protein profile of whey samples from cows after inoculation with E. coli could provide a rapid survey of milk protein modulation during coliform mastitis and aid in the identification of biomarkers of this disease.     

Effect of carprofen treatment following experimentally induced Escherichia coli mastitis in primiparous cows

Acute Escherichia coli mastitis is one of the major sources of economic loss in the dairy industry due to reduced milk production, treatment costs, discarded milk, and occasional fatal disease. Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used as adjunctive therapy to antibiotics. The objective of the current study was to evaluate the effect of carprofen treatment following infusion of Escherichia coli into the mammary glands of primiparous cows during the periparturient period. Severity of mastitis was scored based on the average milk production in the uninfected quarters on d +2 postinoculation and a clinical severity score. Carprofen was administered intravenously at 9 h postchallenge, when clinical signs of mastitis appeared. In previous work, efficacy of NSAIDs was mainly evaluated using clinical symptoms. In the present study, the effect of carprofen on innate immune response was also assessed by quantification of inflammatory mediators. All primiparous cows reacted as moderate responders throughout the experimental period. Primiparous cows were intramammarily inoculated with 1 × 10⁴ cfu of E. coli P4:O32 in 2 left quarters. Analysis of blood and milk parameters, including IL-8, complement component C5a, lipopolysaccharide-binding protein (LBP), soluble CD14, prostaglandin E₂, and thromboxane B₂ was performed from d 0 to d +6 relative to intramammary inoculation. Rectal temperature in carprofen-treated animals was lower than in control animals at 3 and 6 h posttreatment. Treatment also restored the decreased reticulorumen motility that occurs during E. coli mastitis to preinfection levels faster than in control animals. Carprofen treatment resulted in an earlier normalization of the clinical severity score. Eicosanoid (prostaglandin E₂ and thromboxane B₂) production in milk tended to be inhibited by carprofen. No significant differences in the kinetic patterns of somatic cell count, IL-8, complement component C5a, LBP, and soluble CD14 were observed. In conclusion, carprofen treatment improved general clinical condition by effective antipyrexia and restoration of reticulorumen motility but did not significantly inhibit eicosanoid production. Carprofen treatment did not result in a significant decrease of chemotactic inflammatory mediators, IL-8 and C5a, and early innate immune molecules, sCD14 and LBP. Therefore, major modulatory effects from NSAID administration were not observed in this mastitis model, although a larger study might confirm some apparent trends obtained in the present results.     

Effect of interferon-gamma on the production of tumor necrosis factor during acute Escherichia coli mastitis.

The effects of recombinant interferon-gamma on the production of tumor necrosis factor in 10 dairy cows with Escherichia coli mastitis were determined. Prophylactic administration of recombinant interferon-gamma prior to the experimental E. coli challenge was effective in modifying the production of endogenous tumor necrosis factor during acute stages of disease. Elevated tumor necrosis factor concentrations were especially evident in cows that developed severe clinical symptoms and eventually died from endotoxemia. These results indicate that both milk and sera tumor necrosis factor concentrations are associated closely with the manifestation of peracute signs of coliform mastitis and are important factors contributing to morbidity and mortality of endotoxic shock. Pretreatment of cows with recombinant interferon-gamma possibly may down-regulate the generation of this potent endogenous inflammatory mediator within infected quarters. Controlling severe inflammation with recombinant interferon-gamma may prevent the tremendous loss in milk production and death that often accompany acute coliform mastitis during the periparturient period.     

Proteolysis in milk during experimental Escherichia coli mastitis

This work consisted of the intramammary infections (IMI) of 8 heifers by high doses of Escherichia coli to study both the proteolytic activity in milk and the resulting peptides. Therefore, a milking kinetic has been followed, and several parameters have been studied, such as proteose peptones (PP) fraction (quantitative and qualitative changes), plasmin activity (PA), milk somatic cell count (SCC), and bacterial count. A qualitative study of milk proteins and PP was performed by sodium dodecyl sulfate-PAGE, and the peptides recovered in PP during the acute phase of inflammation were amino-terminal micro-sequenced. A BSA increase in milk over time supported the hypothesis of an increase in the permeability of the epithelial barrier. A significant increase in PP content, considered to be an indicator of proteolysis, was observed from postinfusion hours (PIH) 12 to 48. Both the E. coli bacterial count and the SCC increased from PIH 3 to 216. Plasmin activity was increased noticeably from PIH 15 to 24. The respective increases in SCC, bacterial count, and PA suggest their involvement in a global mechanism responsible for the increase in proteolysis in milk after E. coli challenge. Somatic cell count and E. coli may be involved from PIH 3 to 216, and PA involvement might be highlighted during the maximum proteolysis, from PIH 15 to 24. A qualitative study of PP fraction by electrophoresis revealed the apparition of 5 peptide bands: P1 and P2 previously recovered during the lipopolysaccharide challenge, and E1 (27.0 kDa), E2 (15.5 kDa), and E3 (9.0 kDa) were specific to E. coli challenge; E1, E2, and E3 contained casein fragments. The roles played by leukocytes and E. coli are discussed.     

Evaluation of the efficacy of systemic danofloxacin in the treatment of induced acute Escherichia coli bovine mastitis

The objective was to evaluate the efficacy of a single dose of danofloxacin (6 mg/kg bodyweight) given by the intravenous route for the treatment of acute bovine mastitis induced by intra-cisternal infusion of an Escherichia coli strain (26 cfu into one rear quarter of each cow). Twenty-three Prim'Holstein lactating cows were inoculated. To be challenged, the mammary glands had to be productive, free of pathogenic bacteria, and with somatic cell counts (SCC) of <200,000 cells/ml. The cows were treated on an individual basis when predetermined criteria involving both systemic and local clinical signs were satisfied. Allocation to treatment, danofloxacin or negative saline control, was performed according to a randomized treatment allocation plan. Monitoring during a 21-d period after inoculation included individual clinical examination, bacteriological examination and determination of SCC. Esch. coli was isolated from the milk of all inoculated quarters at the first milking post-inoculation and, together with reference to the clinical scores; the challenge was considered to be successful in 20 of the 23 cows. On study day 7 bacteriological cure rates with danofloxacin and saline control were 89% (8/9) and 44% (4/9) respectively. On days 14 and 21 all milk samples that could be collected were negative for Esch. coli in both groups of animals. Beneficial statistically significant differences were found at the end of the observation period (days 19-21 post treatment) between cows treated with danofloxacin and saline for SCC (P=0.0091) and earlier in the study for milk production (P=0.0003) and udder inflammation (P=0.004). Obvious beneficial trends were recorded in the danofloxacin group for rectal temperature, milk quality, general behaviour and appetite. Danofloxacin-treated cows showed statistically significant lower local clinical scores and a more rapid return to pre-inoculation values. It was concluded that systemically administered danofloxacin is effective in terms of bacteriological results, milk production and both systemic and local signs when used in the treatment of induced acute Esch. coli mastitis. Danofloxacin hastens recovery and return to productivity compared with potential self cure.     

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.     

Respiratory burst activity in activated and unstimulated isolated bovine blood neutrophils during experimentally induced Escherichia coli mastitis.

The respiratory burst activity, measured as H2O2 production, of isolated bovine polymorphonuclear leucocytes (PMN) was evaluated during experimentally induced Escherichia coli mastitis by means of flow cytometry in cells activated by phorbol 12-myristate 13-acetate (PMA) and in unstimulated cells. As expected, a significantly reduced respiratory burst activity was observed in PMA-activated PMN 18 h after intramammary inoculation with Escherichia coli. At this time only 75% of the PMA-activated PMN showed a respiratory burst, but with a higher intensity than that measured before and later after infection with Esch. coli. In addition, an increase in the respiratory burst activity was observed in unstimulated blood PMN during a short period at 18 h after infection, when up to 30% of the unstimulated PMN had a respiratory burst activity. The increase in the respiratory burst intensity of PMA-activated PMN and the spontaneously augmented production of reduced oxygen species by the unstimulated PMN during infection with Esch. coli might indicate the production of a natural stimulator of burst activity in circulation, most probably originating from the inflamed udder.     

Haptoglobin and serum amyloid A in milk and serum during acute and chronic experimentally induced Staphylococcus aureus mastitis

Local and systemic changes in the acute phase proteins, haptoglobin and serum amyloid A (SAA), were studied in six dairy cows during the acute and chronic phases of experimentally induced Staphylococcus aureus mastitis. Haptoglobin and SAA were measured in serum, and in milk from infected and healthy control udder quarters within each cow. Concentrations of haptoglobin and SAA increased rapidly in both serum and milk during the acute phase of mastitis and followed a similar pattern. Significantly raised milk concentrations of SAA were also found during chronic subclinical mastitis. Serum concentrations of SAA also tended to be higher during the chronic phase than pre-infection. Increases in milk haptoglobin and SAA were specific for the infected udder quarters. In conclusion, measurement of SAA in milk samples could be a useful tool in diagnosing mastitis.     

Interaction between the respiratory burst activity of neutrophil leukocytes and experimentally induced Escherichia coli mastitis in cows

The respiratory burst activity of neutrophil leukocytes from bovine peripheral blood was studied before and during an experimentally induced Escherichia coli mastitis. The competence of neutrophils to generate reactive oxygen species following stimulation with opsonized particles prior to infection was negatively correlated with severity of subsequently induced E. coli mastitis. In the presence of the soluble activator, phorbol myristate acetate, no such correlation was obtained. However, combination of blood neutrophil numbers with phorbol myristate acetate induced respiratory burst competence, called reactive oxygen species-generating capacity, displayed a negative correlation with the intensity of a subsequent inflammation of the bovine mammary gland. At the onset of mastitis, a concomitant reduction in blood neutrophil numbers, a strong shift in cell types, and a substantial decrease in production of reactive oxygen species occurred. Reestablishment and even enhancement of the respiratory burst activity coincided with the reappearance of mature neutrophils. Possible stimulatory effects on neutrophil superoxide generation are discussed. Data suggest that generation of reactive oxygen species by mature neutrophils may be of primary importance for microbial killing during the onset and recovery from mastitis.     

Short communication: The effects of experimentally induced Escherichia coli clinical mastitis on lying behavior of dairy cows

Clinical mastitis is a commonly occurring and economically important problem in the dairy industry. Researchers have suggested that changes in lying behavior could be useful as early indicators of cow discomfort and poor welfare. The objective of this study was to determine the associations between the onset of illness resulting from experimentally induced clinical mastitis and measures of lying behavior. Clinical mastitis was induced in 21 lactating dairy cows (parity=2.0±1.0, range=1 to 4; days in milk=61±18) by intramammary infusion of 25 or 100 μg of Escherichia coli lipopolysaccharide (LPS) into 1 uninfected mammary quarter. Lying behavior was monitored from 2 d before through 3 d after the LPS challenge by fitting each cow with a data logger. Calculated outcome measures were total lying time, lying time on the side of the intramammary infusion, number of lying bouts, and average lying bout duration. Cows spent less time lying down on the day of the challenge compared with the 2 d before (633.3 vs. 707.0 min/d; SE=29.6), particularly during the 4 to 7h following LPS infusion. However, no significant relationship was found between the mammary quarter challenged and cow preference for lying side throughout the episode of induced clinical mastitis. Given that lying is a high-priority behavior in dairy cows and that increased lying time is an adaptive sickness behavior to facilitate recovery, we infer that this reduction in lying time may present a concern for cows with clinical mastitis. Although additional studies with larger numbers of animals are needed, automated monitoring of lying behavior could be an important component of the on-farm early detection of health problems, such as mastitis, in the future.     

Dynamics of experimentally induced Staphylococcus epidermidis mastitis in East Friesian milk ewes

The responses of five lactating East Friesian milk ewes to experimental mammary infection with Staphylococcus epidermidis and of five control ewes were examined over a period of 10 weeks. Infection caused an influx of neutrophils into milk, the numbers of which started to rise 4 h post infection and peaked 24 h after infection. The initial response was accompanied by mild fever and mild leucopaenia in blood (8 h after infection). No other signs of systemic infection were observed. Milk appeared normal at all times, although the milk yield of infected ewes tended to decline. Staphylococci were absent in milk from four ewes at 2 d and at 3 d after infection, but re-emerged intermittently in four of five ewes at subsequent samplings. Cytokines in milk were measured by ELISA. IL-8 was elevated in infected glands at 2 h and peaked at 8 h. In the four ewes intermittently shedding bacteria, IL-8 remained elevated until the final sampling at 10 weeks. IL-1beta was transiently elevated at 1 d and 2 d and showed a pronounced peak in one sheep. Milk samples from this ewe were bacteriologically negative, somatic cell count (SCC) was within the normal range and the concentrations of IL-1beta, as well as IL-8, were similiar to the control group (n=5) from 1 week after infection until the final sampling. Histological examination revealed leucocytic infiltrates in the four glands remaining infected at the end of the experiment, and a high level of CD5+ lymphocytes in three ewes. The results suggest that the relationship between the initial neutrophil influx and the proinflammatory cytokines may be responsible for determining the course of infection. Subclinical mastitis due to coagulase-negative staphylococci leads to minor changes in milk yield and milk constituents.     

Suppression of milk production during endotoxin-induced mastitis.

Healthy, midlactation cows were given intramammary infusions of 10 micrograms of endotoxin in two homolateral quarters. Productive, inflammatory, and systemic responses were studied to investigate the pathophysiological effects of mastitis on lactational performance. Endotoxin suppressed milk yield in all quarters of treated cows. A more severe and prolonged suppression occurred in infused quarters compared with uninfused quarters. The fat percentage of milk from all quarters was increased with a greater increase occurring in infused quarters. The protein composition of milk was elevated, and the lactose concentration was depressed in infused quarters. Mammary inflammation--as measured by milk SCC, NAGase, serum albumin, and lactoferrin--was limited to infused quarters. Changes in milk NAGase closely paralleled changes in milk SCC. Daily feed intake was unaffected, and serum glucose levels did not decline following infusion. The lactose concentration of urine increased rapidly after infusion. Reduction in milk yield in all quarters, but varying changes in milk composition in infused versus uninfused quarters suggest that mastitic hypogalactia is mediated by multiple pathophysiological events and is not solely due to inflammatory damage to the mammary epithelium. Part of the reduced lactational performance may result from escape of milk components from the udder into the circulation.     

All-trans retinoic acid is increased in the acute phase-related hyporetinemia during Escherichia coli mastitis

Blood vitamin A profiles, including concentrations of retinol and its active metabolite retinoic acid, were assessed during the peripartum period and during experimentally induced Escherichia coli mastitis in heifers. Serum retinol decreased in all animals in the immediate postpartum period and normalized within 1 wk after parturition. No significant changes were detectable in the concentrations of retinoic acid isomers during puerperium. Following intramammary E. coli infusion, all cows showed moderate symptoms of systemic disease besides the local signs of inflammation. The presence of a systemic acute-phase reaction was documented by fever, increase in serum amyloid A, and decrease in serum albumin. Retinol concentration in serum also decreased spectacularly during coliform mastitis, and the decline was clearly related to the timing of the acute-phase response. Moreover, a significant increase of all-trans retinoic acid, mirrored by a lowering of 13-cis retinoic acid, was detected during the same time period. The 9-cis isomer of retinoic acid was present in all samples, but it remained below the quantification limit. Results confirmed the decrease in serum retinol during the peripartum period of dairy cows. Furthermore, the study established that profound changes in vitamin A metabolism occur during the acute-phase reaction of coliform mastitis in heifers. The bovine infection model reproduced the acute phase-related hyporetinemia, as previously observed in humans and rats. In addition, all-trans retinoic acid was found to be the most abundant circulating acid isomer during mastitis, providing an indication for a possible key role of all-trans retinoic acid in the modulation of the immune response.     

Effect of dexamethasone on experimental Escherichia coli mastitis in the cow

The effect of intramuscular administration of dexamethasone on milk production and on several clinical and hematologic indicators in cows with experimental Escherichia coli mastitis was studied. Two groups of three cows each were intramammarily inoculated with 20 x 10(5) cfu E. coli 0101 K99 F41 in rear quarters. Immediately after inoculation one groups received 30 mg dexamethasone intramuscularly, whereas the other group was injected similarly with pyrogen-free saline. Fourteen days later milk production losses were markedly less in the dexamethasone-treated group. Dexamethasone treatment reduced local clinical signs of inflammation, significantly increased rectal temperatures, and diminished inhibition of rumen amplitude during the acute phase of infection. Moreover, cows treated with dexamethasone showed diminished neutropenia, more pronounced hypozincemia, and delayed onset in the decrease in plasma iron concentrations. Possible mechanisms by which these changes are accomplished are discussed.     

Kinetics and characteristics of bovine neutrophil alkaline phosphatase during acute Escherichia coli mastitis.

Alkaline phosphatase activity of isolated bovine blood neutrophils was investigated before and during experimentally induced Escherichia coli mastitis. Activities markedly increased 1 wk after infection in neutrophils of cows suffering from moderate or from severe disease. Elevated neutrophil alkaline phosphatase activity did not correlate with a specific stage of maturating postmitotic neutrophils appearing in circulation during mastitis. Neutrophil alkaline phosphatase from healthy cows before infection and from mastitic cows was characterized by means of thermostability, specific inhibitor patterns, slab gel electrophoresis, and kinetic parameter analysis. The leukocyte enzyme from healthy and mastitic cows displayed very similar characteristics, suggesting that the increase in activity during mastitis is most probably related to the enhanced expression of the normal alkaline phosphatase enzyme.     

Treatment of acute Escherichia coli mastitis in cows with enrofloxacin: effect on clinical signs and chemiluminescence of circulating neutrophils

We have studied the effect of treatment with enrofloxacin on local and general clinical signs and chemiluminescence of circulating polymorphonuclear leucocytes during experimentally induced Escherichia coli mastitis in cows immediately afer parturition. Twelve cows were infected with 10(4) cfu Esch. coli P4:032 into both left quarters. Six cows received an intravenous injection of 5 mg enrofloxacin/kg at 10 h after infection and a second enrofloxacin treatment administered subcutaneously at 30 h post infection. The other six cows were controls that received no treatment. General clinical signs (fever, tachycardia, loss of appetite, reduced rumen motility and depression) were similar in both groups. Local clinical signs, such as swelling, pain and firmness of the inflamed mammary quarters, were less severe in the treated cows. We saw no difference in the appearance of the milk: flecks and watery or purulent milk were observed in both groups. The beneficial effects of treatment with enrofloxacin were mainly on milk production and composition. The decline in milk production and the changes in milk concentrations of lactose, Na+ and bovine serum albumin were less pronounced in the treated cows. Treatment with enrofloxacin accelerated the clearance of bacteria from the infected quarters, but had no effect on the chemiluminescence response of isolated polymorphonuclear leucocytes. The changes in the number of circulating leucocytes and the appearance of immature neutrophils in the circulation of the treated cows indicated possible beneficial effects on migration of neutrophils into the inflamed glands. Higher milk somatic cell counts in the treated cows supported this hypothesis. The results of this study indicated that treating cows that have been experimentally infected with Esch. coli mastitis after parturition with enrofloxacin reduced the severity of the disease, especially the decline in milk production and the changes in milk composition.     

Behaviour of Escherichia coli strains during semi-hard and hard raw milk cheese production

The behaviour of two Escherichia coli strains, one with a high and the other with a low thermotolerance phenotype, was investigated during production and ripening of Swiss semi-hard and hard raw milk cheese. In semi-hard cheese, counts of E. coli increased during production, before a log-linear decrease occurred during ripening, with a faster rate of reduction in core than in rind samples, and faster reduction of the more heat-sensitive strain in rind samples. Nevertheless, at the end of semi-hard cheese ripening, E. coli were present at least at 1.3 log₁₀ cfu g⁻¹ in rind samples and remained detectable by enrichment of core samples. During the first day of hard cheese production, both E. coli strains were almost completely inactivated. Detection by enrichment was possible in one of twelve spiked cheeses after 16 weeks, indicating the potential of a thermotolerant E. coli strain to survive until the end of ripening.     

Mammary blood flow during experimental Escherichia coli endotoxin induced mastitis in goats and cows.

The effect of intramammary infusion of Escherichia coli endotoxin upon mammary blood flow was studied in lactating goats and cows. Blood flow was recorded by means of an electromagnetic flow probe chronically implanted around one mammary artery. Endotoxin mastatis was always accompanied by a significant increase in mammary blood flow, characterized by 2 conspicuous peaks. The flow returned to control values by the thirteenth hour after infusion. Other symptoms of acute mastitis were: fever, increased heart rate, swelling, heat and pain of the gland, increased chloride and total cell count in milk.     

Growth of Escherichia coli in milk from endotoxin-induced mastitic quarters and the course of subsequent experimental Escherichia coli mastitis in the cow

The objective of this study was to assess growth of Escherichia coli in milk from endotoxin-induced mastitic quarters and to relate the in vitro findings to the course of experimental E. coli mastitis. Whole and skim milks from 24 rear quarters of 12 cows were inoculated with E. coli 0:157 and incubated at 38 degrees C. Growth of E. coli 0:157 was not inhibited in milk collected from rear quarters immediately prior to endotoxin infusion. However, growth inhibition occurred in all but one whole mastitic milk samples collected from mastitic quarters 18 h after infusion of .1 mg of endotoxin. Skim milk samples from mastitic quarters were bactericidal in four cows (7 quarters), whereas growth occurred in skim mastitic milk from 17 quarters of nine cows. Rear quarters of all cows were inoculated with 10(4) cfu of E. coli 0:157 19 h after the quarters had been infused with endotoxin. Clinical parameters and milk production were monitored during 36 h and 21 d, respectively. None of the inoculated quarters developed signs of inflammation, and secreta from inoculated quarters were bacteriologically negative after 48 h. Therefore, growth-inhibitory property of skim milk from endotoxin-induced quarters was apparently not a suitable parameter to monitor differences in susceptibility to E. coli mastitis.     

Effect of steroidal anti-inflammatory drugs on Escherichia coli endotoxin-induced mastitis in the cow

Effects of intramammary infusion of prednisolone (40 mg) or intramuscular injection of dexamethasone (30 mg) or flumethasone (5 mg) on local and systemic signs in Escherichia coli endotoxin-induced mastitis were studied. The effect of varying intervals (0, 2, and 4 h) between intramammary infusion of endotoxin and prednisolone in the same quarter was determined. Intramammary infusion of endotoxin (.01 mg lipopolysaccharide of E. coli) produced inflammation of the infused quarter, fever, tachycardia, and leukopenia followed by a neutrophilic leukocytosis in the blood and a decrease in plasma zinc and iron concentrations. All corticosteroid treatments, except intramammary administration of prednisolone 4 h after endotoxin infusion, enhanced leukocytosis and diminished local signs of inflammation. Intramuscular injection of dexamethasone or flumethasone together with intramammary infusion of endotoxin and intramammary administration of prednisolone 2 h after lipopolysaccharide infusion completely abolished the febrile response. Abolishment of fever and attenuation of several hematologic and blood biochemical changes may be explained by diminished synthesis of endogenous mediators within the inflamed quarters due to glucocorticosteroid action.