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

Localized mammary gland changes in milk composition and venous blood metabolite concentrations result from sterile subclinical mastitis

Subclinical mastitis reduces milk yield and elicits undesirable changes in milk composition, but the mechanisms resulting in reduced milk production in affected mammary glands are incompletely understood. This study investigated the effects of sterile inflammation on mammary gland metabolism by assessing changes in milk and venous blood composition. Mid-lactation primiparous Holstein cows (n = 4) had udder halves randomly allocated to treatments; quarters of 1 udder half were infused with 2 billion cfu of formalin-fixed Staphylococcus aureus (FX-STAPH) and quarters of the opposite udder half were infused with saline (SAL). Blood samples were collected from the right and left subcutaneous abdominal veins in 2.6 h intervals until 40 h postchallenge and analyzed for blood gas and metabolite concentrations. Milk from FX-STAPH udder halves had significantly increased SCS by the first milking at 8 h postchallenge. By 16 h postchallenge, FX-STAPH udder halves had increased concentrations of protein and lactate and lower lactose concentrations than SAL udder halves. Milk fat concentrations, milk yields, ECM yields, and the ferric reducing antioxidant power of milk were not significantly different between SAL and FX-STAPH udder halves. Venous blood of FX-STAPH halves had marginally greater concentrations of saturated O2, partial pressures of O2, and glucose concentrations than SAL halves. Conversely, total and partial pressures of CO2 did not differ between udder half treatments, suggesting a shift in local metabolite utilization in FX-STAPH udder halves. These results indicate that changes in milk composition resulting from mastitis are accompanied by changes in some key blood metabolite concentrations. The shift in venous blood metabolite concentrations, along with the marked increase in milk lactate, suggests that local mammary tissue or recruited immune cells, or both, alter metabolite usage in mammary tissues. Future studies are needed to quantify the uptake of key milk precursors during mastitis.

Intramammary administration of lipopolysaccharides at parturition enhances immunoglobulin concentration in goat colostrum

In newborn ruminants, transfer of passive immunity is essential to obtain protection against pathogens. This study aimed to increase the permeability of the blood-milk barrier using intramammary lipopolysaccharides (LPS) in goats at parturition to modulate colostrum composition. Twenty multiparous Majorera dairy goats were randomly allocated in one of the two experimental groups. The LPS group (n = 10) received an intramammary administration (IA) of saline (2 mL) containing 50 µg of LPS from Escherichia coli (O55:B5) in each half udder at parturition. The control group (n = 10) received an IA of saline (2 mL). Rectal temperature (RT) was recorded, and a blood sample was collected at parturition (before IA). In addition, RT was measured, and blood and colostrum/milk samples were collected on day (d) 0.125 (3 hours), 0.5 (12 hours), 1, 2, 4, 7, 15 and 30 relative to the IA. Goat plasma immunoglobulin G (IgG) and M (IgM) and serum β-hydroxybutyrate, glucose, calcium, free fatty acids, lactate dehydrogenase and total protein concentrations were determined. Colostrum and milk yields as well as chemical composition, somatic cell count (SCC), IgG and IgM concentrations were measured. The MIXED procedure (SAS 9.4) was used, and the model included the IA, time, and the interaction between both fixed effects. Statistical significance was set as P < 0.05. Goats from the LPS group showed higher RT on d 0.125, 0.5 and 4 relative to the IA compared to the control group (PIA×Time = 0.007). Goat serum biochemical variables and plasma IgG and IgM concentrations were not affected by the IA. Colostrum and milk yield as well as chemical composition were not affected by the IA, except for milk lactose percentage that was lower in the LPS group compared to the control group (4.3 ± 0.08 and 4.6 ± 0.08%, respectively PIA = 0.026). Colostrum SCC was higher in the LPS group than in the control group (3.5 ± 0.09 and 3.1 ± 0.09 cells × 106/mL, respectively; PIA = 0.011). Similarly, milk SCC increased in the LPS group compared to the control group (PIA = 0.004). The LPS group showed higher IgG (PIA = 0.044) and IgM (PIA = 0.037) concentrations on colostrum than the control group (31.9 ± 4.8 and 19.0 ± 4.8 mg/mL, 0.8 ± 0.08 and 0.5 ± 0.08 mg/mL, respectively). No differences in milk IgG and IgM concentrations between groups were observed. In conclusion, the IA of LPS at parturition increases RT, SCC and IgG and IgM concentrations in colostrum without affecting either yield or chemical composition.

Endotoxin Triggers Tumor Initiation Events in Nontumorigenic Breast Epithelial Cells and Enhances Invasion-Related Phenotype in Pretumorigenic and Tumorigenic Breast Epithelial Cells

Inflammation is associated with the development of several cancers, including breast cancer. However, the molecular mechanisms driving breast cancer initiation or enhancement by inflammation are yet to be deciphered. Hence, we opted to investigate the role of inflammation in initiating and enhancing tumor-like phenotypes in nontumorigenic, pretumorigenic, and tumorigenic breast epithelial cells. Noncytotoxic endotoxin (ET) concentrations capable of inducing an inflammatory phenotype were determined for the different cell lines. Results showed that short-term ET exposure upregulated matrix metalloproteinase-9 (MMP-9) activity in nontumorigenic mammary epithelial cells of mouse (SCp2) and human origins (HMT-3522 S1; S1) and upregulated inflammatory mediators including nitric oxide (NO) and interleukin 1-β in tumorigenic human breast cells (MDA-MB-231), all in a dose-dependent manner. Long-term ET treatment, but not short-term, triggered the migration of SCp2 cells, and proliferation and migration of tumorigenic human breast cells MCF-7 and MDA-MB-231. Both short- and long-term ET exposures preferentially enhanced the invasion of pretumorigenic S1-connexin 43 knockout (Cx43-KO S1) cells compared to their nontumorigenic S1 counterparts. Moreover, both ET exposures disrupted lumen formation and apicolateral distribution of β-catenin in 3D cultures of S1 cells. In conclusion, ET treatment at concentrations that elicited inflammatory phenotype triggered tumor initiation events in nontumorigenic and pretumorigenic breast cells, and increased tumorigenicity of breast cancer cells. Our findings highlight the role of inflammation in enhancing migration, invasion, and loss of normal 3D morphology and suggest that such inflammatory insults can "add injury" to pretumorigenic and tumorigenic breast epithelial cells.

Short communication: Diagnosis and classification of clinical and subclinical mastitis utilizing a dynamometer and a handheld infrared thermometer

In times of ongoing automatization of dairy cow husbandry, objective and reliable tools for mastitis diagnostic are highly in demand. The objective of this study was to investigate the diagnostic value of a handheld dynamometer and an infrared thermometer to diagnose and score clinical and subclinical mastitis and to compare those values with results from palpation of the udder tissue. Overall, 218 cows with clinical mastitis (i.e., 46 mild, 106 moderate, and 66 severe cases), 142 with subclinical mastitis, and 68 healthy cows were enrolled. Our data provide evidence that the dynamometer is an accurate diagnostic tool to differentiate between healthy udder quarters, and those with subclinical and clinical mastitis. Furthermore, the severity score of clinical mastitis can be estimated by dynamometer. The firmness threshold for the detection of clinical mastitis was 1.002 kg. Using a threshold of 1.175 kg in clinical mastitis quarters, it was possible to differentiate between negative and positive bacteriological results. A differentiation between healthy and clinical mastitis quarters with the infrared thermometer was possible, albeit udder surface temperatures were highly influenced by ambient temperature. Udder surface temperature increased by 0.15 to 0.18°C for each degree of ambient temperature. In conclusion, the utility of an infrared thermometer to estimate the udder health status of dairy cows is limited, whereas the handheld dynamometer appeared to be an accurate and objective method.

Therapeutic effect of ginsenoside Rg1 on mastitis experimentally induced by lipopolysaccharide in lactating goats

Escherichia coli is a cause of subclinical and clinical mastitis in dairy cattle and goats, and sometimes causes severe clinical disease that may result in death of the animal. Previous investigation showed that ginsenoside Rg1 extracted from Panax ginseng C.A. Meyer (Araliaceae) has an anti-inflammatory effect on the sepsis induced by E. coli lipopolysaccharide via competitive binding to toll-like receptor 4. We hypothesized that intravenous injection of Rg1 had therapeutic effect on mastitis experimentally induced by intramammary infusion of lipopolysaccharide in lactating goats. In this study, 9 lactating goats were randomly assigned to 1 of the 3 groups: (1) lipopolysaccharide intramammary infusion + saline intravenous injection, (2) lipopolysaccharide intramammary infusion + Rg1 intravenous injection, and (3) saline intramammary administration + saline intravenous injection. Because no adverse clinical signs were observed after intramammary infusion of saline and intravenous injection of Rg1 in a preliminary experiment, and available qualified goats were limited in this study, this treatment was not included in this study. One udder half of each goat received intramammary infusion of lipopolysaccharide (50 μg/kg of body weight; groups 1 and 2) or saline solution (group 3), and the other half was infused with 2 mL of saline solution at h 0. Afterward, intravenous injections of saline solution (groups 1 and 3) or Rg1 (2.5 mg/kg of body weight; group 2) were administered at h 2 and 4 post-lipopolysaccharide challenge. Blood and milk samples were collected 3, 6, 9, 12, 15, 18, 21, 24, 48, and 72 h post-lipopolysaccharide challenge, and clinical signs were monitored hourly after lipopolysaccharide challenge within the first 10 h and at the same time points as blood samples. The results showed that Rg1 treatment downregulated rectal temperature, udder skin temperature, udder girth, milk somatic cell count, and N-acetyl-β-d-glucosaminidase and upregulated milk production, lactose, and recovered blood components, such as white blood cells, neutrophils, lymphocytes, total proteins, albumin, and globulin. Considering the positive therapeutic effect on lipopolysaccharide-induced mastitis in goats presented in this study as well as the anti-inflammatory activity found previously, the botanical Rg1 deserves further study as a therapeutic agent in the treatment of E. coli mastitis in dairy animals.

Serotonin as a homeostatic regulator of lactation

Serotonin (5-HT), a neurotransmitter produced in mammary epithelial cells (MECs), acts via autocrine-paracrine mechanisms on MECs to regulate milk secretion in a variety of species. Recent studies in dairy cows reported that 5-HT ligands affect milk yield and composition. We determined the mRNA expression of bovine 5-HT receptor (5-HTR) subtypes in bovine mammary tissue (BMT) and cultured bovine MECs. We then used pharmacologic agents to evaluate functional activities of 5-HTR subtypes. The mRNAs for five receptor isoforms (5-HTR1B, 5-HTR2A, 5-HTR2B, 5-HTR4, and 5-HTR7) were identified by conventional reverse transcription PCR, real-time PCR, and in situ hybridization in BMT. In addition to luminal MEC expression, 5-HTR4 was expressed in myoepithelium, and 5-HTR1B, HTR2A, and HTR2B were expressed in small mammary blood vessels. Studies to date report that there are multiple 5-HTR isoforms in mammary tissue of rodents, humans, and cattle. Inhibition of the 5-HT reuptake transporter with selective 5-HT reuptake inhibitors (SSRIs) disrupted tight junctions and decreased milk protein mRNA expression in mouse, human, and bovine mammary cells. Selective 5-HT reuptake inhibitors act to increase the cellular exposure to 5-HT by preventing reuptake of 5-HT by the cell and eventual degradation. Increasing 5-HT concentration in milk via inhibiting its reuptake (SSRI), or by increasing the precursor for 5-HT synthesis 5-hydroxytryptophan, accelerated decline in milk synthesis at dry-off. We conclude that the 5-HT system in mammary tissue acts as a homeostatic regulator of lactation.

Variation of inflammatory dynamics and mediators in primiparous cows after intramammary challenge with Escherichia coli

The objective of the current study was to investigate (i) the outcome of experimentally induced Escherichia coli mastitis in primiparous cows during early lactation in relation with production of eicosanoids and inflammatory indicators, and (ii) the validity of thermography to evaluate temperature changes on udder skin surface after experimentally induced E. coli mastitis. Nine primiparous Holstein Friesian cows were inoculated 24 ± 6 days (d) after parturition in both left quarters with E. coli P4 serotype O32:H37. Blood and milk samples were collected before and after challenge with E. coli. The infrared images were taken from the caudal view of the udder following challenge with E. coli. No relationship was detected between severity of mastitis and changes of thromboxane B2 (TXB2), leukotriene B4 (LTB4) and lipoxin A4 (LXA4). However, prostaglandin E2 (PGE2) was related to systemic disease severity during E. coli mastitis. Moreover, reduced somatic cell count (SCC), fewer circulating basophils, increased concentration of tumor necrosis factor-α (TNF-α) and higher milk sodium and lower milk potassium concentrations were related to systemic disease severity. The thermal camera was capable of detecting 2-3°C temperature changes on udder skin surface of cows inoculated with E. coli. Peak of udder skin temperature occurred after peak of rectal temperature and appearance of local signs of induced E. coli mastitis. Although infrared thermography was a successful method for detecting the changes in udder skin surface temperature following intramammary challenge with E. coli, it did not show to be a promising tool for early detection of mastitis.

Investigation of mammary blood flow changes by transrectal colour Doppler sonography in anEscherichia colimastitis model

The objectives of this preliminary investigation were to evaluate the feasibility of transrectal colour Doppler sonography (TCDS) for determining blood flow of the pudendoepigastric trunk in cows with experimentally inducedEscherichia coliMastitis. Five primiparous Holstein dairy cows, 4–6 months after calving, were examined in two trials. All monitored udder quarters were initially clinically healthy, somatic cell count (SCC) was <50 000 cells/ml and bacteriologically negative. The blood flow of the left and the right pudendoepigastric trunk was described by the blood flow volume (BFV). In the methodological part of the study, the intra-observer precision of the method was evaluated. The coefficients of variation of the BFV were 7·1% for the left and 9·4% for the right pudendoepigastric trunk. The intraclass correlation coefficients of the BFV were 0·99 (P<0·001) for the left and 0·75 (P=0·004) for the right vessel. BFV did not differ significantly between the left and the right side nor between pre- and post-milking nor between oestrus and dioestrus. In the experimental part of the study, significant differences of increasing BFV between 0 and 12 h p.i. (post infectionem) (P=0·043) and decreasing BFV between 12 and 24 h p.i. (P=0·043) were discovered for the pudendoepigastric trunk of the infected right side. In the left-right (control-infection) comparison a significant increase of the right BFV was observed at 12 h p.i. (P=0·043). The difference of an increasing SCC correlated positively with the difference of an increasing BFV between 0 and 12 h p.i. (Spearman's ρ=1·00;P=0·043) for the right infected side. It was shown that TCDS is a reproducible technique for investigating pathological mammary blood flow changes at an early stage of acute mastitis.

Cumulative physiological events influence the inflammatory response of the bovine udder to Escherichia coli infections during the transition period

A high proportion of intramammary coliform infections present at parturition develop disease characterized by severe inflammatory signs and sepsis during the first 60 to 70 d of lactation. In the lactating bovine mammary gland, the innate immune system plays a critical role in determining the outcome of these infections. Since the beginning of the 1990s, research has increased significantly on bovine mammary innate defense mechanisms in connection with the pathogenesis of coliform mastitis. Neutrophils are key effector cells of the innate immune response to intramammary infection, and their function is influenced by many physiological events that occur during the transition period. Opportunistic infections occur when the integrity of the host immune system is compromised by physical and physiological conditions that make the host more susceptible. The innate immune system of many periparturient cows is immunocompromised. It is unlikely that periparturient immunosuppression is the result of a single physiological factor; more likely, several entities act in concert, with profound effects on the function of many organ systems of the periparturient dairy cow. Their defense system is unable to modulate the complex network of innate immune responses, leading to incomplete resolution of the pathogen and the inflammatory reaction. During the last 30 yr, most efforts have been focused on neutrophil diapedesis, phagocytosis, and bacterial killing. How these functions modulate the clinical outcome of coliform mastitis, and how they can be influenced by hormones and metabolism has been the subject of intensive research and is the focus of this review. The afferent (sensing) arm of innate immunity, which enables host recognition of a diverse array of pathogens, is the subject of intense research interest and may contribute to the variable inflammatory response to intramammary infections during different stages of lactation. The development of novel interventions that modulate the inflammatory response or contribute to the elimination of the pathogen or both may offer therapeutic promise in the treatment of mastitis in periparturient cows.

Mammary uptake and excretion of prostanoids in relation to mammary blood flow and milk yield during pregnancy-lactation and somatotropin treatment in dairy goats

Mammary arterious-venous differences (A-V) and excretion into milk of four prostanoids were related to changes in milk yield and milk vein blood velocity (MBV) in goats at different stages of pregnancy and lactation, and during somatotropin (ST) treatment in mid-lactation. Arterial concentrations and mammary A-V for the vasodilators prostacyclin (PGI(2)) and prostaglandin (PG) E(2) (measured as 6-keto-PGF(1 alpha) and bicyclic PGE(2), respectively) decreased from late pregnancy to lactation. A-V were negatively correlated to MBV (r = -0.32 to -0.34). Arterial concentrations of the vasoconstrictors PGF(2 alpha) and TXA(2) (measured as TXB(2)) changed similarly, but no A-V across the mammary gland were found. The vasodilator to vasoconstrictor ratio in plasma was around 1:1, and in skimmed milk around 0.29-0.49 due to significantly higher TXB(2) levels in milk compared to plasma. Close linear correlations were established between milk yield and excretion of TXB(2) into milk (r = 0.80, P < 0.001), and between MBV and PGE(2) excretion into milk (r = 0.69, P < 0.001). ST treatment stimulated MBV and mammary prostanoid supply, and decreased prostanoid concentration in milk vein plasma. The high arterial levels of prostaglandins during pregnancy most likely reflected uterine synthesis. Our results support a role for PGI(2) and PGE(2) in local mammary blood flow regulation during lactation. Increased mammary uptake of these two prostanoids may be involved in the mammary blood flow response to ST. TXA(2) may be synthesized by mammary epithelial as well as vascular cells, and TXA(2) may be an important factor in regulation of mammary function.

The effect of endotoxin on functional parameters of mammary CID-9 cells

The effect of endotoxin on mammary CID-9 cells, which differentiate in culture and express beta-casein, was investigated. Cells in culture supplemented with lactogenic hormones and dripped with EMS-Matrix (EMS-drip), were treated daily with endotoxin (0.5-500 microg/ml). Endotoxin at concentrations of less or equal to 10 microg/ml did not affect cell growth and viability up to 5 days post endotoxin treatment. Endotoxin (0.01-10 microg/ml) was added to the culture medium, upon confluence, and functional parameters were examined within 48 h post endotoxin treatment. Nuclear factor-kappaB (NF-kappaB) (p52) increased in nuclear extracts from endotoxin-stimulated cells within 1 h of treatment, while beta-casein mRNA and protein expression decreased in a concentration-dependent manner at 24 and 48 h post treatment. Zymography showed that the 72 and 92 kDa gelatinase activity increased in cells at 24 and 48 h post endotoxin treatment at 10 and 50 microg/ml. At the latter concentration, the active form of 72 kDa gelatinase was induced at 48 h. Interleukin-6 and tumor necrosis factor-alpha levels increased at 1-3 h post endotoxin treatment and peaked at 6 h in cells on plastic and EHS-drip. Nerve growth factor (NGF) levels increased in control and endotoxin-treated cells in a time-dependent manner, and endotoxin increased NGF levels in culture at 6 and 9 h post endotoxin treatment. This study shows that endotoxin activated NF-kappaB, suppressed beta-casein expression and upregulated gelatinases, cytokines and NGF. This model could be used to investigate the role of mammary cells in initiating and propagating inflammation and to test candidate molecules for potential anti-inflammatory properties.

Near-infrared spectroscopy evaluated as a technique for estimating udder haemodynamics in the lactating cow

Near-infrared spectroscopy (NIRS) that requires few compact instruments is a non-invasive and continuous method of monitoring haemodynamics in living organs. To assess the feasibility of using NIRS in evaluating the udder haemodynamics in six dairy cows, a probe component consisting of a light-emitting diode and a phototransistor was attached to the left side of the udder surface. Real-time variation of tissue haemodynamics was analysed and the data were transferred to the computer by way of a radiotelemetry system. On induction of temporary congestion by applying pressure with the hand pressed firmly against the left milk vein for 20 s, concentration of oxyhaemoglobin decreased throughout the 20-s duration of congestion, and concentration of deoxyhaemoglobin increased. A surge in blood volume was also observed from the beginning of congestion, then the volume attenuated to baseline. The data demonstrated that the reading seen on the monitor reflects the real-time status of the mammary gland. NIRS shows promise as a useful approach to physiological studies.

Modulation of the inflammatory reaction and neutrophil defense of the bovine lactating mammary gland by growth hormone

This review is focused on the possible interactions of prolactin and somatotrope hormone in the modulation of inflammation of the mammary gland. Several different models are examined: Escherichia coli, Streptococcus uberis, and endotoxin mastitis. Subsequently, the release of growth hormone and insulin-like growth factor during fever and mastitis, the immunophysiological effects of GH on E. coli mastitis, S. uberis and endotoxin mastitis, the galactopoietic action of rBST on healthy and mastitis cows as well as the immunologic effects of GH on leukocytes in healthy and diseased cows are discussed. It can be concluded that the underlying regulation of the neuro-endocrine network is fundamental in the normal function of the immune system.

Bovine acute mastitis: effects of intravenous sodium salicylate on endotoxin-induced intramammary inflammation

Effects of the nonsteroidal antiinflammatory agent sodium salicylate on endotoxin-induced mastitis were evaluated in lactating cows. Escherichia coli endotoxin was administered to a mammary quarter 1 h after initiation of a 12-h i.v. infusion of sodium salicylate. Milk SCC, BSA concentrations in milk, mammary inflammation, rectal temperature, appetite, milk production, and plasma and lymph PGF2 alpha were monitored. Gross mammary inflammation was not reduced by salicylate infusion, nor did sodium salicylate prevent increased milk SCC or BSA concentrations in milk, although treatment tended to decrease the magnitude of these responses. Sodium salicylate decreased subcutaneous abdominal vein PGF2 alpha metabolite, and PGF2 alpha metabolite tended to be reduced in lymph during the acute phase of inflammation. The increased rectal temperature after endotoxin infusion was reduced in cows treated with sodium salicylate. Appetite was reduced after endotoxin infusion in untreated cows and those treated with sodium salicylate. Milk production declined after endotoxin challenge in all cows. Although sodium salicylate did not substantially reduce mammary inflammation, it had an antipyretic effect and reduced PGF2 alpha metabolite in mammary blood.

Mammary blood flow and regulation of substrate supply for milk synthesis

In ruminants, mammary supply of substrate varies with rate of mammary blood flow and concentrations of blood substrates. Blood concentrations of most mammary substrates, except acetate and tryptophan, do not vary greatly with feed intake, short term. Fasting reduces mammary blood flow, whereas milking and injection of growth hormone or thyroxine increase flow. It is proposed that the fraction of cardiac output that perfuses the udder of lactating ruminants plays a role in regulation of nutrient partitioning between milk and body tissues. In fed animals this fraction is 15 to 16% of cardiac output, which declines on fasting to 8 to 9% and increases slightly following growth hormone treatment to 17.6%. Following realimentation of fasted cows or goats, mammary blood flow takes several hours to return to normal. Investigation of the mechanism of this response, in terms of the ability of the animal to recognize its nutritional status and partition nutrients accordingly, should prove fruitful to understanding causes of variations of milk production in response to feed quantity and quality. Several substrates show increased mammary arteriovenous difference with increasing blood concentrations. This may reflect differing ratios of blood flow:milk yield. The steep gradient of concentration of substrates across the mammary epithelial cell membrane suggests that a major impediment to substrate supply for milk synthesis is the rate of substrate transport across the membrane.

Lipid composition of milks from cows with experimentally induced mastitis

Changes in milk lipid composition were measured during the course of mastitis infections induced in cows by infusion of either Escherichia coli endotoxin or Streptococcus agalactiae into 2 quarters of the udder; untreated quarters were used as controls. Experiments were divided into 3 distinct phases: a pre infusion period during which several samples were collected before infusion; a post infusion period following infusion and corresponding to the occurrence of elevated cell counts in milk from infused quarters; a recovery period followed after a short pause and represented the return of the cell count in milk from infused quarters to the level in the corresponding controls. Milk total fatty acid composition was unaffected by the infusion. Free fatty acid (FFA) composition did, however, undergo some alteration. There was a significant increase in long-chain saturated acids in milk from infused quarters relative to the corresponding controls during the post infusion period. FFA concentration (mequiv./100 g fat) also increased significantly during this period although the net increase was only slight. Phospholipid and cholesterol concentrations were significantly higher post infusion in milk of infused quarters. The results suggest that changes in concentration and composition of those milk constituents synthesized and secreted by the mammary epithelium occur after secretion in the alveolar lumen and milk ducts.

Effect of Escherichia coli endotoxin-mediated inflammation of one mammary quarter of the bovine udder on diapedesis into other quarters

Implantation of 1 microgram Escherichia coli endotoxin into one papillary duct of a bovine udder frequently resulted in a mild inflammatory process in the treated quarter which was measured by use of the Wisconsin mastitis test (WMT) on quarter fore milk samples. Inflammation of a fore quarter was usually (18/24) accompanied by a transient elevation in WMT score from the homolateral hind quarter, but rarely (1/25) from the contralateral quarter. Inflammation in a hind quarter rarely (2/26) affected the homolateral fore quarter and never (0/25) the contralateral quarter. The pattern of responses suggests tha absorption and initial removal of endotoxin from the mammary gland occurs via the lymphatic rather than the blood system.