Lymphocytes from one side of the bovine mammary gland migrate to the contra lateral gland and lymph node tissue

The four quarters of bovine mammary glands are completely separated and two quarters on each side (right or left) are connected to ipsi lateral supra mammary lymph nodes. It is not clear whether cells infused into the cistern of the mammary gland are capable of migrating to lymph nodes or the general circulation. To examine cell migration, a prescapular lymph node was removed from each of two lactating and three non-lactating dairy cows, and isolated lymphocytes were stained with Hoechst 33342. Autologous stained cells were infused into the mammary gland and then activated by intramammary infusion of zymosan-stimulated serum (source of C5a). After 17 h, Escherichia coli J5 bacterin was infused into the contra lateral mammary gland to mimic infection. After 43 h cows were euthanized and tissue samples (mammary quarters, right and left supra mammary, mesenteric, ileocecal and prescapular lymph nodes, liver and spleen) were collected for microscopic examination as well as flow cytometric analysis. Hoechst stained cells were detected not only in infused quarters, but also in contra lateral quarters as well as in both supra mammary lymph nodes. This indicates that cells infused into the mammary gland migrate to contra lateral tissues and supra mammary lymph nodes.     

Elimination kinetics of chlorhexidine in milk following intramammary infusion to stop lactation in mastitic mammary gland quarters of cows

OBJECTIVE: To evaluate the elimination kinetics of chlorhexidine in milk when used as an intramammary infusion to stop lactation in cows. DESIGN: Prospective study. ANIMALS: 6 cows. PROCEDURE: The study was performed in 2 phases. Three cows were studied in each phase. All cows were treated with chlorhexidine suspension by infusion into a mastitic mammary gland quarter after 2 milkings 24 hours apart. Foremilk samples (100 mL) were collected from treated and untreated (controls) mammary gland quarters of each cow. Chlorhexidine was extracted from raw milk, and residue concentrations were quantified by use of high-performance liquid chromatography. Foremilk samples from days 2, 5, and 8 were analyzed in phase I, and samples from time 0 and days 3, 7, 14, 21, 28, 35, and 42 were analyzed in phase II. RESULTS: In phases I and II, there was no quantifiable transference of chlorhexidine to milk in untreated mammary gland quarters. Measurable chlorhexidine residues were found in milk from treated mammary gland quarters of 2 cows throughout the 42-day sample period in phase II. Estimated mean elimination half-life for chlorhexidine in milk was 11.5 days. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of the long elimination half-life of chlorhexidine in milk from treated mammary gland quarters, the lack of human dietary exposure data to suggest a food tolerance for chlorhexidine in food products, and the Food and Drug Administration's published zero tolerance for chlorhexidine in uncooked edible calf tissues, we do not recommend extralabel use of chlorhexidine suspension as a treatment to stop lactation in mastitic mammary gland quarters of cows.     

Induction by endotoxin of the inflammatory response in the lactating and dry bovine mammary gland

Quarters of three lactating and three dry cows were infused with 10 micrograms endotoxin and the inflammatory response induced in the mammary gland was compared. The response of the dry glands was much less than that shown by the lactating glands. The swelling in the lactating quarters was severe after four hours and declined slowly; in the dry quarters the swelling was mild and transient. Antitrypsin levels, which reflect vascular permeability, were much greater in the lactating quarters, and the somatic cell counts were similarly much higher in the lactating quarters. One dry quarter gave no response other than a slight increase in antitrypsin after four hours.     

Interleukin-1β infusion in bovine mammary glands prior to challenge with <Emphasis Type="Italic">Streptococcus uberis</Emphasis> reduces bacterial growth but causes sterile mastitis

Dairy cows are especially vulnerable to intramammary infection by the bacterial pathogen Streptococcus uberis in the dry period. Use of immunotherapeutic agents at drying off could increase cellular defences in the gland and prevent establishment of new S. uberis infections. This study investigated the potential of infusing recombinant bovine interleukin-1 beta (rbIL-1beta) in the mammary glands as a prophylactic agent against subsequent intramammary challenge with S. uberis in the early dry period. Immediately after the last milking at commencement of the dry period, one cow from each of 10 monozygous twinsets was infused with 10 microg of rbIL-1beta in two quarters and the other twin was infused with the carrier agent, sterile phosphate buffered saline. Twenty-four hours later, the quarters were infused with 10(3) colony-forming units (CFU) of S. uberis. Bacteriology, somatic cell count (SCC), concentrations of specific cytokines and antibody responses were monitored in mammary gland secretions and sera for the next 21 days. Infusion of rbIL-1beta into mammary glands at commencement of the dry period was associated with less new S. uberis intramammary infections, as determined by the number of quarters with bacterial growth. However, high SCC in quarters following infusion of rbIL-1beta masked the full beneficial effect of this procedure.     

Controlling acute Escherichia coli mastitis during the periparturient period with recombinant bovine interferon gamma

The efficacy of recombinant bovine interferon (rBoIFN)-gamma against experimentally induced Escherichia coli mastitis during the periparturient period was investigated. Dairy cows intramammarily treated with rBoIFN-gamma 24 h before the E. coli challenge had fewer infected quarters, lower clinical scores, and infections of shorter duration when compared to placebo-treated animals. All rBoIFN-gamma treated cows survived the experimental E. coli challenge. However, placebo treated cows had a 42% mortality rate attributed to coliform mastitis within 3 days of the challenge. Results from this study suggest that intramammary infusion of rBoIFN-gamma can prevent the rapid, unrestricted growth of E. coli within the mammary gland and inhibit the subsequent development of an unlimited inflammatory response under experimental conditions. It is likely that controlling severe local inflammatory reactions may also decrease the pathological alterations to mammary parenchymal tissue that often accompanies acute coliform mastitis during the periparturient period. The potential for prophylactic treatment of perinatal dairy cows with rBoIFN-gamma to regulate the rate, severity, and duration of naturally occurring coliform mastitis during periods of heightened susceptibility is discussed.     

Assessment of antimicrobial transfer from treated to untreated mammary gland quarters by use of high-pressure liquid chromatography for detection of cloxacillin in milk samples from nonlactating dairy cows

OBJECTIVE: To determine whether half-udder intramammary infusion of cloxacillin results in transfer of cloxacillin from treated to untreated mammary gland quarters within nonlactating cows, and, if so, at what concentrations, and to determine whether selection of ipsilateral versus diagonal-contralateral quarters for treatment affects cloxacillin transfer among quarters. ANIMALS: 20 Holstein-Friesian cows from a dairy herd. PROCEDURES: A within-cow half-udder comparison trial was used in which 2 of 4 mammary gland quarters (ipsilaterally or diagonally) received an intramammary infusion of cloxacillin on day 1 of the nonlactating period. Three days later, milk samples were taken from all untreated quarters and high-pressure liquid chromatography was used to detect and quantify milk cloxacillin concentrations. RESULTS: Cloxacillin was detected in 25% of all untreated mammary gland quarters. Mean cloxacillin concentration in untreated quarters was below minimum inhibitory concentrations for targeted mastitis pathogens. No significant difference in cloxacillin concentrations was found in the ipsilateral or diagonal treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: Within-cow half-udder comparison trials are valid for antimicrobial trials in nonlactating cows, although transfer of antimicrobials does occur in trace concentrations. Ipsilateral or diagonal-contralateral treatment designs perform similarly. This type of design is economical for researchers, although care must be taken to account for within-cow clustering of mammary gland quarter data.     

Elimination kinetics of ceftiofur hydrochloride after intramammary administration in lactating dairy cows

OBJECTIVE: To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows. DESIGN: Prospective study. ANIMALS: 5 lactating dairy cows. PROCEDURE: After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination. RESULTS: Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 microg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE: Ceftiofur administered by the intramammary route as an extra-label treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times.     

Ultrasonographic appearance of exogenous isobutane gas in the mammary glands of dairy cows.

OBJECTIVE: To determine whether exogenous isobutane gas infused into the udders of dairy cattle could be detected ultrasonographically, and if so, what effects volume of gas infused and infusion pressure had on how long after infusion exogenous isobutane gas could be detected. DESIGN: Randomized block design. ANIMALS: 8 Holstein cows 28 to 32 days after parturition. PROCEDURE: In each cow, 1 mammary gland was not treated and the other 3 received 1 of 3 treatments by means of intramammary infusion: low volume-high pressure, low volume-low pressure, and high volume-high pressure infusion of isobutane gas. Mammary glands were examined ultrasonographically 1 hour before and 1, 3, 12, 24, 36, 48, 72, and 96 hours after treatment. RESULTS: After intramammary infusion of isobutane gas, bright echoes and associated acoustic shadows were seen ultrasonographically; echoes were no longer seen 72 hours after gas infusion. Percentages of mammary glands in which bright echoes were detected were not significantly different among the 3 treatment groups at any time during the study. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that exogenous isobutane gas infused into the mammary glands to enhance the appearance of the udder of show dairy cattle can be readily detected by ultrasonography.     

Efficacy of extended pirlimycin therapy for treatment of experimentally induced Streptococcus uberis intramammary infections in lactating dairy cattle

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, around the time of calving, and during early lactation. Strategies for controlling S. uberis mastitis have not received adequate research attention and are therefore poorly defined and inadequate. Objectives of the present study were to evaluate the efficacy of extended therapy regimens with pirlimycin for treatment of experimentally induced S. uberis intramammary infections in lactating dairy cows during early lactation and to evaluate the usefulness of the S. uberis experimental infection model for evaluating antimicrobial efficacy in dairy cows. The efficacy of extended pirlimycin intramammary therapy regimens was investigated in 103 mammary glands of 68 dairy cows that became infected following experimental challenge with S. uberis during early lactation. Cows infected with S. uberis in one or both experimentally challenged mammary glands were randomly allocated to three groups, representing three different treatment regimens with pirlimycin, including 2-day (n = 21 cows, 31 mammary quarters), 5-day (n = 21 cows, 32 quarters), and 8-day (n = 26 cows, 40 quarters). For all groups, pirlimycin was administered at a rate of 50 mg of pirlimycin hydrochloride via intramammary infusion. A cure was defined as an experimentally infected mammary gland that was treated with pirlimycin and was bacteriologically negative for the presence of S. uberis at 7, 14, 21, and 28 days after treatment. Experimental S. uberis intramammary infections were eliminated in 58.1% of the infected quarters treated with the pirlimycin 2-day regimen, 68.8% for the 5-day regimen, and 80.0% for the 8-day regimen. Significant differences (P <.05) in efficacy were observed between the 2-day and 8-day treatment regimens. The number of somatic cells in milk decreased significantly following therapy in quarters for which treatment was successful in eliminating S. uberis. However, there was no evidence to suggest that extended therapy with pirlimycin resulted in a greater reduction in somatic cell counts in milk than the 2-day treatment. The S. uberis experimental infection model was a rapid and effective means of evaluating antimicrobial efficacy during early lactation at a time when mammary glands are highly susceptible to S. uberis intramammary infection.     

Neutrophil apoptosis during the resolution of bovine mammary gland injury

The role of neutrophil apoptosis in the resolution of bovine mammary gland injury induced by intramammary administration of physiological buffered saline (PBS) or lipopolysaccharide (LPS) was investigated. Twenty mammary glands of five non-pregnant heifers were used in the two studies and each animal received both stimuli. Samples of cell populations were collected by mammary gland lavages before and 24, 48, 72 and 96 hours after treatment and examined by light microscopy and staining for myeloperoxidase (MPO). A marked influx of neutrophils into the mammary gland was observed 24 hours after stimulation. At the same time, apoptotic neutrophils and MPO-positive macrophages (MAC) were identified in the samples. The numbers increased to reach maximum values at 48 hours after stimulation with PBS and at 72 hours after stimulation with LPS. The observed differences in the length of the resolution period indicate that neutrophil viability can be modulated by delaying the apoptotic process. Apoptosis of neutrophils and their subsequent phagocytosis by MAC can be regarded as a significant mechanism in the removal of neutrophils from the acutely injured mammary glands and, hence, in the resolution of bovine mastitis.     

Persistent Experimental Salmonella dublin Intramammary Infection in Dairy Cows

Experimental intramammary infections were induced in five post-parturient Holstein cows by inoculation of low numbers (5000 colony forming units) of virulent Salmonella dublin via the teat canal of mammary gland quarters. Rectal temperature, pulse and respiratory rates, milk yield, and milk quality as assessed by the California Mastitis Test (CMT) and somatic cell counts (SCC) were recorded every 12 hours at milking. Bacteriologic cultures of foremilk quarter samples and feces were obtained daily, as were complete blood counts. ELISA titers for IgG and IgM recognizing S. dublin lipopolysaccharide (LPS) were obtained weekly on serum and quarter milk samples. All cows excreted S. dublin intermittently from infected quarters, but no changes were detected in rectal temperature, appearance of the mammary gland or secretions, CBC, milk yield, and pulse and respiratory rates. Somatic cell counts were modestly increased in infected quarters as compared with uninfected quarters (P = .015, paired t test); however, CMT scores after infection remained low, and were not significantly different from pre-infection scores (P greater than .10, sign test). After infection, administration of dexamethasone resulted in signs of clinical mastitis and increased excretion of S. dublin from mammary quarters (P = .0004, paired t test). One cow had necrotizing mastitis and S. dublin septicemia and was euthanatized. In the four surviving cows, clinical improvement was observed after systemic gentamicin therapy and intramammary infusion with polymyxin B, but all cows continued to excrete S. dublin intermittently from one or more quarters and occasionally from feces for the remaining period of observation. All infected cows demonstrated a rise in IgG and IgM ELISA titers recognizing S. dublin LPS in serum and milk. At necropsy (13-25 weeks postinfection), S. dublin was recovered only from the mammary tissue or supramammary lymph nodes in three of four cows. In one cow, mammary gland and lymph-node samples were negative for S. dublin despite positive milk cultures. In all cows, histopathologic examination revealed multifocal areas of chronic active mastitis. These lesions were similar to histopathologic findings from mammary gland carriers with naturally acquired S. dublin infection.     

Pathogenesis of Staphylococcus aureus mastitis: bacteriologic, histologic, and ultrastructural pathologic findings

Three lactating cows were experimentally infected with Staphylococcus aureus ATCC 29740 (Newbould 305 strain). Cows were euthanatized 2 to 216 hours after inoculation. Bacteriologic and microscopic examinations showed that S aureus attached to epithelial cells of the mammary gland in vivo. The histopathologic changes observed were progressive swelling, vacuolar degeneration of epithelial layers, and multiple foci of epithelial erosions and ulcers throughout the ductal system. The cellular response of the infected glands was demonstrated by a rapid increase in the number of somatic cells in the secretion and by accumulation of neutrophils below, within, and on the epithelium of the teat and lactiferous sinuses. The inflammatory response did not prevent infection nor subsequent pathologic changes in the inoculated glands.     

Effect on outcome of intramammary challenge exposure with Staphylococcus aureus of somatic cell concentration and presence of an intramammary device

Results of experimental Staphylococcus aureus intramammary challenge of all quarters of 6 cows, each fitted with an intramammary device (IMD) in 2 quarters, and of 10 quarters of 3 cows not fitted with an IMD were reported. Infection was established in all 34 quarters, regardless of presence or absence of an IMD. Neither the course nor severity of early S aureus intramammary infection were influenced by the presence of an IMD or by differences in milk somatic cell (MSC) concentration in the gland at the time of bacterial challenge infusion, up to a MSC concentration of nearly 1 million/ml. Cumulative success of experimental infection in this and a previous study from our laboratory was nearly 100% in glands in which the MSC concentration was less than 1 million/ml and about 17% when the MSC concentration exceeded 1 million/ml.     

Effects on adhesion molecule expression and lymphocytes in the bovine mammary gland following intra-mammary immunisation

Changes to adhesion molecule expression and lymphocyte populations were evaluated in alveolar mammary tissue collected from cows following an immunisation protocol that involved intra-mammary inoculation to induce an IgA response in mammary secretions. The right quarters of the udder were immunised; the left side acted as a control. Antibody titres in secretions showed that at least two animals responded with antigen-specific IgA. Numbers of T-lymphocytes were 4-fold higher in immunised glands compared with controls (P < 0.05). IgA-, IgM- and IgG-positive cell numbers were significantly higher (P < 0.01) in immunised glands compared with controls in three of the four cows. No mucosal addressin molecule-1 (MAdCAM-1), vascular cell-adhesion molecule-1 (VCAM-1) or peripheral node addressin (PNAd) protein expression was detected on smaller venules that stained positively for von Willebrand factor in alveolar mammary tissues, from either immunised or control glands. Both VCAM-1 and PNAd were detected on smaller venules in supramammary lymph nodes, however, there was no significant difference between immunised and control glands. Quantification of MAdCAM-1 mRNA showed very low expression in both immunised and control alveolar tissue compared with Peyer's patch positive-control tissue. These findings suggest that the bovine mammary gland is capable of a mucosal antibody response; however, MAdCAM-1 is not involved with lymphocyte homing to the mammary gland in this species.     

Intramammary administration of gentamicin as treatment for experimentally induced Escherichia coli mastitis in cows.

In 8 Holstein cows, 50 colony-forming units (CFU) of Escherichia coli was administered into 1 mammary gland. Infections were established in all inoculated glands. In 4 of the 8 cows, 500 mg of gentamicin sulfate was administered by intramammary infusion 14 hours after inoculation; the other 4 cows were untreated controls. Infusions of gentamicin also were given after each of the 3 successive milkings after the initial infusion, so that a total dose of 2 g of gentamicin was given to each of the treated cows. During the 33-hour treatment period and for the first milking after the last infusion of gentamicin, the treated cows had a mean gentamicin concentration of greater than or equal to 31.0 micrograms/ml in milk samples that were collected from inoculated quarters immediately before each milking. Concentrations of 0.34 and 0.69 micrograms of gentamicin/ml were detected in milk from 2 cows at 8 days after inoculation with E coli. Mean serum concentrations of gentamicin were greater than or equal to 0.37 micrograms/ml throughout the treatment period and the first 12 hours after the last infusion, with a mean peak concentration of 0.96 micrograms/ml at 24.4 hours. The range of peak concentration of gentamicin detected in urine from all treated cows was 42 to 74.4 micrograms/ml. Peak concentration of E coli in milk in the treated cows (6.08 +/- 1.02 log10 CFU/ml) did not significantly (P greater than 0.05) differ from that of the control cows (5.26 +/- 1.00 log10 CFU/ml). Similarly, mean duration of infection in the treated cows (54 hours) did not differ significantly from that of the control cows (48 hours).(ABSTRACT TRUNCATED AT 250 WORDS)     

Immune cell differentiation in mammary gland tissues and milk of cows chronically infected with Staphylococcus aureus

This study identifies and compares the distribution of mononuclear cells in the mammary gland tissues and milk of healthy and chronically infected with Staphylococcus aureus cows. Somatic cell counts (SCCs) during the 3 months before the study were > 1 x 10(6) cell/ml in the infected quarters and < 1 x 10(5) cell/ml in the infection-free quarters. Immediately after slaughter, samples from the tissues above the gland cistern and supra-mammary lymph node were collected. No histological differences were found between the supra-mammary lymph nodes of the healthy and infected udders, and both appeared normal. In the milk of the healthy infection-free mammary glands, SCC was < 50,000 cells/ml) while epithelial cells were the predominant type. The percentage of CD18+ was low than 45%, of which over three-quarters were polymorphonuclear (PMN), and less than one- quarter were mononuclear cells. The later comprised CD4+ or CD8+ T-lymphocytes, macrophages (Mo) but not B-cells. In the tissues, there were few CD18+ leukocytes, and most of the cells were T-lymphocytes. The number of B-lymphocytes bearing CD21+ was similar to that of CD8+ and were localized in the connective tissue as clusters of 2-5 cells, mainly in areas with no alveoli, or as single cell having a dendritic like form. The number of Mos was negligible. In the milk of the infected glands, SCC exceeded 700,000 cells/ml, of which > 95% were CD18+ positive. The distribution of the leukocytes had two patterns: one presented (> 80%) of PMN cells and a small number of mononuclear cells; the second had less than 50% PMN and many mononuclear cells. The CD8+ cells in these infected sections were observed throughout the mammary epithelial cells (MEc) around the alveoli and in the alveolar lumen (AL). The numbers and the location of CD21+ B-lymphocytes were similar to those in the infection-free mammary glands. The number of CD5+ positive cells was lower than T and B- cells combined and were located throughout the mammary epithelial cells, around the alveoli and within the connective tissue. Mo numbers were high in most of those infected quarters, and were localized around the connective tissue and within the AL.     

Somatic cell and innate immune responses in mammary glands of lactating cows to intramammary infusion of Bifidobacterium breve at pre-drying off period

Intramammary infusion of Bifidobacterium breve (B. breve)-induced somatic cell (SC) counts, chemiluminescent response (CL), lactoferrin (LF) concentrations and mastitis-causing pathogens from quarters with subclinical mastitis were measured to evaluate innate immune response of mammary glands in dairy cows at 3 to 4 weeks before drying off. SC counts in 7 quarters of 7 control cows and 5 quarters of 6 cows with mastitis increased markedly on day 1 and SC values in control cows were significantly (P<0.05) increased and returned to pre-infusion levels on day 5 after B. breve-infusion. CL values in both groups increased markedly on day 1 and then decreased after B. breve-infusion; however, CL values in cows with mastitis did not return to normal levels on day 5 and at postpartum. The CL values were highly correlated with their SC counts in milk from both groups. LF concentrations increased toward day 3 after B. breve-infusion and were higher in cows with mastitis. B. breve-infusion eliminated 16.6% (1/6) of pathogens from 6 quarters with chronic subclinical mastitis. B. breve-induced SC responses in quarters from 3 cows with mastitis showed characteristic patterns of recovery, persistent and new infections. B. breve-induced SC counts in quarters from the cows in the pre-drying off were lower (25.7–70.6%) than those of the cows in mid-lactation. The intrinsic innate immune response in cows on pre-drying off may be decreased and appears to be insufficient to eliminate pathogens from mammary gland in the pre-drying off.     

Infection following challenge of the lactating and dry udder of dairy cows with Actinomyces pyogenes and Peptostreptococcus indolicus

Challenge of 12 mammary glands of cows in mid-lactation with 10(7) colony forming units (cfu) of Peptostreptococcus indolicus on two occasions led to clinical mastitis in only four quarters. The bacteria were rarely recovered and disappeared from the secretion within 14 days. In challenges 7 days prior to drying off eight of 12 quarters became infected and at drying off all quarters challenged became infected. The infections established at drying off persisted well into the dry period. P. indolicus infection was also established in all of 12 dry glands challenged, but usually eliminated at calving or early in the next lactation. Isolation of P. indolicus was accompanied in about one-third of cases by changes in the appearance of the secretion. Intramammary challenge with Actinomyces (formally Corynebacterium) pyogenes led to clinical and subclinical infections in nine of 12 lactating glands and in all of six dry glands. Dry period infections with A. pyogenes were more severe and rarely eliminated even by antibiotic therapy. Infections during lactation were often eliminated either naturally or by antibiotic therapy. Intermittent recovery of A. pyogenes from the lactating mammary gland, without clinical signs of infection, was possible for up to 90 days after challenge. Combined infections with A. pyogenes and P. indolicus were clinically more severe with a higher frequency of systemic involvement. It was shown that in the non-lactating gland an acute mastitis, similar to 'summer mastitis' could be established either by simultaneous inoculation with A. pyogenes and P. indolicus or by subsequent inoculation of quarters excreting P. indolicus with A. pyogenes.     

Persistence of antibiotics in bovine mammary secretions following intramammary infusion at cessation of milking

A study was conducted to determine the persistence of antibiotic preparations for use in nonlactating cows in bovine mammary secretions following intramammary infusion at cessation of milking. Five commercially available antibiotic formulations were evaluated using 311 cows. All quarters of each cow were sampled once only during the nonlactating period and most cows were sampled at or near parturition. Antibiotic residues were detected qualitatively by the Bacillus stearothermophilus disc assay. Great variation between different antibiotics in persistence in mammary secretion was observed. In general, mammary secretions from most mammary glands infused with cloxacillin or penicillin-dihydrostreptomycin were positive at 28–35 days after infusion and some were positive at 42–49 days after infusion. On the other hand, <13% of mammary secretions at 7 days after infusion of novobiocin and 50% of mammary secretions at 14 days after infusion of penicillin-novobiocin were positive for antibiotics. Cephapirin benzathine persisted for about 21 days after infusion. Some samples that were positive for antibiotics after initial testing were negative following heating of samples, suggesting that component(s) of dry secretion can inhibit growth of B. stearothermophilus and influence the interpretation of results. Colostrum samples from all quarters except one were negative for antibiotics. These data suggest that nonlactating-cow antibiotic formulations persist primarily during the early to mid-nonlactating period. Based upon present methods of formulation, it would appear that antibiotic preparations for use in nonlactating cows most likely provide little protection during the periparturient period, at a time when mammary glands are highly susceptible to new intramammary infections.     

Proinflammatory cytokines and CD14 expression in mammary tissue of cows following intramammary inoculation of Panax ginseng at drying off

The lack of efficacy of conventional strategies for the maintenance of healthy udders in domestic cattle has prompted studies on the use of immunomodulators or biological response modifiers (BRM) for this purpose. These compounds are agents that modify the host's response to pathogens leading to beneficial effects on disease outcome. The objective of this study was to evaluate the effects of a single intramammary infusion of Panax ginseng (GS) extract on the amount of pro-inflammatory cytokines and the number of monocytes/macrophages present in bovine mammary tissues at drying off. Eight mammary quarters from six nonpregnant cows in late lactation were infused with 10 mL of GS (3mg/mL), six quarters were treated with 10 mL of placebo (vehicle alone) and six quarters were maintained as uninoculated controls. The analyses of tumor necrosis factor-alpha (TNF-α) by immunohistochemistry revealed that the production of this proinflammatory cytokine significantly increased (P<0.05) in the inoculated mammary glands of cows following BRM inoculation, whereas the interleukin-1 alpha (IL-1α) and IL-6 staining area was not affected by BRM treatment. The number of monocytes/macrophages detected with CD14 antibody was significantly higher (P<0.05) in BRM-treated quarters than in placebo and uninoculated control quarters. These results indicated an immunomodulator potential of the BRM used. The beneficial effect of the extract could be used as alternative therapy in the control of mastitis at drying off, either alone or in conjunction with dry cow antibiotic therapy.