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A multilocation clinical trial in lactating dairy cows affected with clinical mastitis to compare the efficacy of treatment with intramammary infusions of a lincomycin/neomycin combination with an ampicillin/cloxacillin combination.

A study was conducted to compare the efficacy in lactating dairy cows of intramammary infusions in quarters affected with clinical mastitis between a formulation containing 330 mg lincomycin and 100 mg neomycin in a 10-mL aqueous solution (LINCOCIN FORTE S, Pharmacia & Upjohn) and a formulation containing 75 mg ampicillin and 200 mg cloxacillin in an oil suspension (AMPICLOX, Pfizer Animal Health). This study was designed as a multicentre clinical trial involving investigators in France, Germany and Belgium and carried out according to the European Commission guidelines on Good Clinical Practices. Cows in the herds were monitored for clinical mastitis. When evidence of clinical mastitis was detected in a single quarter, a pretherapy milk sample was collected from the affected quarter. After milk sampling, the cow was assigned to one of the two treatment groups at random and treated with an intramammary infusion of one syringe of either LINCOCIN FORTE S or AMPICLOX for three successive milkings in the mastitic quarter. At 4-5, 13-15 and 20-22 days after first infusion, the veterinarian returned to the farm to conduct a clinical examination and collect milk samples from the affected quarter. Milk samples were cultured for the presence of mastitis organisms and somatic cell count (SCC) was measured. Following a 10-month study period, 256 cases were enrolled in the study. A total of 232 and 189 cases were analysed for clinical cure and for clinical-plus-bacteriological cure, respectively. The proportions of cases cured clinically and cured clinically-plus-bacteriologically were compared between the two treatment groups. Somatic cell count differences between treatment groups were also tested. The clinical cure rate for LINCOCIN FORTE S (62.5%) was significantly better than for AMPICLOX (51.8%) (P = 0.035). The clinical-plus-bacteriological cure rate was also significantly better for LINCOCIN FORTE S (38.1%) than for AMPICLOX (21.7%) (P = 0.005). Among bacteriologically cured cases, the SCC declined in both treatment groups but the SCC was significantly higher for the AMPICLOX group than for the LINCOCIN FORTE S group (P = 0.036). In conclusion, clinical cure rate, clinical-plus-bacteriological cure rate, and SCC level were significantly better with LINCOCIN FORTE S than for AMPICLOX.

Ampicillin↗

Effect of teat dipping with a germicide barrier teat dip in late gestation on intramammary infection and clinical mastitis during the first 5 days post-partum in primiparous cows.

The effect of teat dipping with a barrier teat dip prior to parturition on intramammary infection (IMI) and clinical mastitis during the first 5 days post-partum was investigated in a split udder trial in 149 Holstein-Frisian heifers. Their left front and right hind quarters were dipped three times weekly (i.e. Monday, Wednesday and Friday) with a barrier teat dip containing 0.1% polyvidon iodine from day 260 of gestation until parturition. The opposite quarters (right front and left hind quarter) served as untreated control. Bacteria were isolated from 52.2% of quarter milk samples collected immediately after parturition prior to first machine milking. Staphylococcus aureus and coagulase-negative staphylococci (CNS) were predominantly found in the samples (29.2 and 35.6% of the positive samples, respectively). At parturition 6.7% of the heifers showed signs of clinical mastitis and another 27.5% developed signs of clinical mastitis during the first five days of lactation. No significant differences were found between treated and control quarters regarding IMI and incidence of clinical mastitis. Teat dipping prior to parturition in primigravid dairy heifers did not improve udder health in this trial.

Administration, Topical↗

Efficacy of a herd-specific vaccine against Staphylococcus aureus to prevent post-partum mastitis in dairy heifers.

A placebo-controlled field study was performed to evaluate the effect of a herd-specific vaccine against Staphylococcus aureus on intramammary infection (IMI), somatic cell count (SCC) and clinical mastitis. Three hundred and twenty-one heifers were assigned to two groups. Heifers in the vaccination group (n = 164) were vaccinated twice, i.e. 5 and 2 weeks before their expected calving date. Animals of the control group (n = 157) received the same treatment with a placebo containing no bacterial antigen. Quarter milk samples were collected immediately after parturition prior to the first machine milking, 3-4 weeks after calving and before the onset of treatment in animals with signs of clinical mastitis during the first 3 months after calving. For comparison of SCC the data from the monthly milk test records were evaluated. The prevalence of S. aureus in quarter milk samples taken at calving and 3-4 weeks post-partum did not differ significantly between the vaccine and control group. Incidence of clinical mastitis during the first 3 months after calving and the prevalence of S. aureus in quarter milk samples taken before the onset of treatment did not differ significantly between the groups. The SCC was lower in vaccinated than in control heifers. However, the difference was only significant on the third milk test day. Regarding prevalence of IMI with S. aureus and incidence of clinical mastitis the use of a herd-specific vaccine against S. aureus did not prove to be efficient on this farm.

Animals↗

Local and systemic effects of endotoxin mastitis on the chemiluminescence of milk and blood neutrophils in dairy cows.

The local and systemic effects of intramammary lipopolysaccharide (LPS) injection on the chemiluminescence (CL) of milk and blood polymorphonuclear leukocytes (PMN) were investigated in six healthy early lactation cows. Clinical signs of acute mastitis such as fever, increased heart rate and a decreased milk production were observed in all cows. Before LPS challenge, the CL activity of milk PMN was significantly lower than that of blood PMN (P < 0.01). A significant negative correlation was found between pre-challenge milk and blood PMN CL and, the decreased milk production in unchallenged quarters. The CL activity of milk PMN from LPS-injected quarters increased following LPS challenge, whereas it remained unchanged in control quarters. The CL activity of blood PMN showed a biphasic increase, with two peaks and a valley below pre-challenge CL activity (P < 0.01). At post-challenge hours (PCH) 6 and 12, the CL activity of milk PMN from LPS-injected quarters exceeded that of blood PMN (P < 0.05 and P < 0.001, respectively). The decreased CL activity of blood PMN and the enhanced CL activity of milk PMN during endotoxin-induced mastitis was reflected by changes in the shape of the CL curve. In blood PMN, a decrease of the second peak of the CL curve suggests that the myeloperoxidase (MPO)-H2O2 system is impaired during endotoxin-induced mastitis. In contrast, the MPO-H2O2 system was enhanced in milk PMN from challenged quarters. The highest duration and intensity of reactive oxygen intermediate (ROI) production was observed in milk PMN from LPS-injected quarters at PCH 12. The increased viability of PMN in LPS-injected quarters and to a lesser extent in control quarters suggests possible effects of both facilitated diapedesis and inflammatory mediators on milk PMN survival. In conclusion, our results suggest that a combination of local and systemic action of E. coli endotoxin is involved in the priming of milk PMN during mastitis.

Animals↗

The effect of milk production level on host resistance of dairy cows, as assessed by the severity of experimental Escherichia coli mastitis.

This study investigated the possible effects of milk production level on the host resistance of dairy cows. High (n = 18) and low (n = 18) producing cows on a research farm, which respectively produced 11 443 and 7 727 kg milk in their previous lactation, were compared. To enhance the possible differences in host resistance between high and low producing cows, the animals in both groups were metabolically stressed by overfeeding during the dry period or were fed according to requirements, resulting in four groups of nine cows. The metabolic status was monitored from two weeks pre-partum until 2.5-4.5 weeks post-partum. Host resistance was assessed by measuring the severity of experimentally induced Escherichia coli mastitis. Pre-partum blood glucose levels tended to be higher in overfed cows than in cows fed according to requirements. The post-partum energy balance was significantly more negative in high producing cows than in low producers, and tended to be more negative in overfed cows compared to cows fed according to the requirements. Post-partum plasma glucose, NEFA, beta-OH-butyrate and urea concentrations were similar in the four groups. Plasma glucose concentrations were significantly lower and liver triacylglycerol concentrations were significantly higher in third than in second parity cows. Host resistance was not affected by the production level or feeding regimen. There were no significant correlations between the metabolic status and the severity of experimental E. coli mastitis, except for the relatively more severe mastitis in the cows with beta-OH-butyrate concentrations above 1.4 mmol/L. In conclusion, milk production level did not affect host resistance in dairy cows, as measured by the severity of experimental E. coli mastitis. Even in a situation where cows were metabolically stressed by overfeeding, high producers were as able as low producers to cope with the demands of milk production, without consequences for host resistance.

3-Hydroxybutyric Acid↗

Granulomatous mastitis: imaging findings with histopathologic correlation.

OBJECTIVE: The purpose of this study is to evaluate the mammographic and ultrasonographic characteristics of granulomatous mastitis and to correlate the imaging features with the histologic findings. MATERIALS-METHODS: 15 patients with diagnosis of idiopathic granulomatous mastitis were examined with mammography and ultrasonography. The clinical, pathologic and imaging features were retrospectively reviewed and correlated in all patients. RESULTS: Mammographic examination showed an asymmetric density with no distinct margins in 8 patients and an ill-defined mass in 3 patients. In 4 cases, no abnormal finding was detected on the mammography. Sonographic examination demonstrated an irregular mass with tubular connections in 5 patients, single or multiple hypoechoic tubular/nodular structures in 6, and focally or segmentally decreased parenchymal echogenity with acoustic shadowing in 4 patients. The imaging findings suggested a malignant tumor in 7 patients, while an inflammatory process or intraductal papilloma was considered in the differential diagnosis of the other patients. CONCLUSION: Granulomatous mastitis usually presents with clinical findings mimicking a carcinoma. The most common mammographic appearance of the lesion is an asymmetrically increased density, which is not characteristic for this entity. Sonographic patterns of the disease are varied and appear to relate to the histologic features. Findings include a mass-like appearance, tubular/nodular hypoechoic structures and focal decreased parenchmal echogenicity with acoustic shadowing. With awareness of the findings granulomatous mastitis can be considered in the differential diagnosis.

Adult↗

[Non-puerperal mastitis. Etiology, clinical aspects and therapy].

Non-puerperal mastitis was diagnosed in 79 patients (aged 12-77 years) over the years 1974-1984. Malignant neoplasm was not present. Bacterial infection in the region of the areola was the most frequent finding (40%), followed by abacterial inflammation without involvement of the nipples (29%). The other cases, bacterial or nonbacterial, occurred at different sites. The histological picture or clinical features of an increased secretory activity of the mammary gland (galactorrhoea, mastodynia) in addition to the mastitis was noted in 54 women. Causative organisms were proven in 53% of cases: Staph. aureus (41%) and coagulase-negative staphylococcus (41%), or anaerobic organisms (11%). Physical measures, antibiotics and bromocriptine were used as treatment. At the onset of treatment abscesses were already present or developed in 34 instances. In 28 cases one to six recurrences set in after the end of the treatment period. In 22 patients treated with bromocriptine prophylactically there were only two recurrences. In the majority of patients an increased alveolar secretion was important in the pathogenesis of the bacterial or abacterial inflammation. Prolactin-lowering treatment seems reasonable by itself in cases of abacterial mastitis, or in combination with antibiotics in bacterial mastitis. Recurrences can be prevented by long-term lowering of the peripheral prolactin level.

Adolescent↗

A chronic indurative mastitis in sheep, associated with maedi/visna virus infection.

A possible association of a chronic indurative mastitis with mvv (maedi visna virus) infection in sheep was investigated. Sheep of four flocks (group A), in which insufficient lamb growth apparently associated with insufficient milk production and probably related to udder induration, was a serious problem, were clinically examined in mid-lactation. The results were compared with four mvv-free flocks (group B) without such complaints. The incidence of udder induration in group A (n = 263) was about eight times higher than in group B (n = 206): 63.1 versus 8.0%. The clinical picture differed essentially between the groups. In group A the udder abnormalities were of a diffuse and indurative nature, involving both udder halves, while in group B the udder lesions were mainly nodular and often limited to one udder half. Bacteriological examination revealed a difference in infection rate of the udders (6.8% in group A versus 14.1% in group B). A substantial difference was observed in a comparison of the bacteriological infection rate of the clinically abnormal udders (5.4% in group A, versus 47.0% in group B). Serological examination with an indirect ELISA revealed 81% seropositive sheep in group A, versus 0% in group B. Twelve sheep of group A and five of group B, called for reason of mastitis, were selected for pathological examination. The gross and microscopic lesions showed a pronounced difference between both groups. In group A a diffuse interstitial mastitis with slight to moderate fibrosis and a pronounced lymphoid hyperplasia was observed. In group B the mastitis had a nodular character, with a chronic galactophoritis, extensive fibrosis, and in some cases chronic abscesses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Indurative lymphocytic mastitis in sheep after experimental infection with maedivisna virus.

In order to provide further evidence for the association of an indurative lymphocytic mastitis in sheep with MVV (maedi-visna virus) infection, an experimental study was performed. Fourteen MVV-free pregnant ewes, 2 years of age, were divided into two groups. Eight were intravenously inoculated with MVV (strain ZZV-1050); six ewes served as sham-inoculated controls. Post-mortem examinations were carried out at 8, 16 and 28 months. After 8 months, the 3 infected ewes had indurated udders with extensive lymphoid proliferation around lactiferous ducts and in the acinar tissue. The ducts were often partially obliterated. After 16 months, one of the two infected ewes suffered from indurative lymphocytic mastitis. The other was free of specific udder lesions. After 28 months only one of three infected ewes had mild lymphocytic infiltration in the udder. None of the controls, two in each post-mortem session, had lesions typical of this form of mastitis. The lesions were most severe 8 months after infection. At 16 and 28 months lesions were of a lesser degree or were absent. The lung lesions in the infected ewes 8 months after inoculation were similar to the changes in the udder regarding the lymphoid accumulation, although the proliferation around bronchial tree and blood vessels was less pronounced. After 16 and 28 months all infected ewes had peribronchial and perivascular lymphocytic infiltration though of a lesser degree than after 8 months. From these results it is concluded that in addition to the lung and brain lesions MVV infections may cause a specific indurative lymphocytic mastitis.

Animals↗

Human immunodeficiency virus load in breast milk, mastitis, and mother-to-child transmission of human immunodeficiency virus type 1.

Human immunodeficiency virus (HIV) type 1 load in breast milk and mastitis were examined as risk factors for vertical transmission of HIV-1. Six weeks after delivery, HIV-1 load and sodium (an indicator of mastitis) were measured in breast milk from 334 HIV-1-infected women in Malawi. Median breast milk HIV-1 load was 700 copies/mL among women with HIV-1-infected infants versus undetectable (<200 copies/mL) among those with uninfected infants, respectively (P<. 0001). Elevated breast milk sodium levels consistent with mastitis occurred in 16.4% of HIV-1-infected women and were associated with increased vertical transmission of HIV-1 (P<.0001). Median breast milk HIV-1 load was 920 copies/mL among women with versus undetectable among those without elevated breast milk sodium levels, respectively (P<.0001). Mastitis and breast milk HIV-1 load may increase the risk of vertical transmission of HIV-1 through breast-feeding.

Adult↗

Idiopathic granulomatous mastitis: case report and review of the literature.

We report a case of idiopathic granulomatous mastitis in a 35-year-old Japanese woman, who came to our hospital complaining of a tender mass in her right breast. Because the results of initial aspiration cytology were considered highly suspicious for carcinoma, modified radical mastectomy was performed. However, the final histological diagnosis was granulomatous lobular mastitis with no evidence of malignancy. Idiopathic granulomatous mastitis is a rare inflammatory breast disease of unknown etiology. Since the clinical manifestations are similar to those of mammary carcinoma, this condition has been misdiagnosed as carcinoma and treated as such. A review of the literature revealed that idiopathic granulomatous mastitis has tended to occur in young patients with a history of childbirth or oral contraceptive usage. Clinical or imaging diagnosis has often been difficult. Complete resection or corticosteroid therapy can be recommended as the optimal treatment. Since 38% of patients experience recurrence, long-term follow-up is indicated.

Adrenal Cortex Hormones↗

Effect of antibiotic treatment of subclinical mastitis on human immunodeficiency virus type 1 RNA in human milk.

Although subclinical mastitis is associated with increased HIV load in breast milk, it is not known whether empirical treatment with antibiotics will reduce breast milk HIV load. We examined the effect of antibiotic treatment for subclinical mastitis on HIV load in breast milk. Seventy-five HIV-infected post-partum women in Malawi with subclinical mastitis were treated with oral amoxicillin/clavulanic acid and were followed between 1 and 24 weeks later. Breastmilk HIV-1 load and sodium concentration were measured and microbiological studies were performed at presentation. At 1 week (n = 34), the proportion of women with elevated breast milk leukocyte counts decreased significantly to 41.2% (p < 0.0001) and there was a nonsignificant increase in breast milk HIV-1 RNA load (p = 0.9264) and sodium concentration (p = 0.08) in the affected breast. At 4 to 12 weeks (n = 63), breast milk HIV-1 RNA load and sodium concentration decreased significantly (p < 0.05) and 17.5% had elevated breast milk leukocyte counts. Treatment with amoxicillin/clavulanic acid was associated with a significant decrease in inflammation of the breast, but breast milk HIV load remained elevated despite a significant decrease from baseline. These findings have important implications regarding how mothers should be counselled on safety of resuming breastfeeding after resolution of subclinical mastitis.

Amoxicillin↗

Lymphocytic mastitis and diabetic mastopathy: a molecular, immunophenotypic, and clinicopathologic evaluation of 11 cases.

Lymphocytic mastitis and diabetic mastopathy are uncommon fibroinflammatory breast diseases. The lesions seen in these entities are unique in that the associated lymphoid infiltrates are composed of predominantly B cells. In addition, B-cell lymphoepithelial lesions, a finding commonly associated with extranodal marginal zone B-cell/mucosa-associated lymphoid tissue (MALT) lymphomas, are also often present in lymphocytic mastitis and diabetic mastopathy. Although the clinical and immunomorphologic features are well characterized, the clonality of the B-cell infiltrate and the lymphomatous potential of lymphocytic mastitis and diabetic mastopathy have not been emphasized in the literature. We evaluated 11 cases of lymphocytic mastitis/diabetic mastopathy for immunoglobulin heavy chain gene rearrangement and correlated the findings with all available clinical data. A longstanding history of Type I diabetes mellitus was present in seven patients. One nondiabetic patient had Sjogren's syndrome, and two patients had no history of diabetes mellitus or other autoimmune disease. Clinical data were unavailable for one patient. B-cell-predominant lymphoid infiltrates were seen in all cases, and B-cell lymphoepithelial lesions were found in five. No evidence of a B-cell clone was found in any of the 11 cases by appropriately controlled immunoglobulin heavy chain gene rearrangement studies, and none of the patients developed lymphoma during follow-up intervals ranging from 2-126 months. These findings suggest that despite the presence of B-cell-predominant lymphoid infiltrates and lymphoepithelial lesions, lymphocytic mastitis and diabetic mastopathy do not appear to be associated with an increased risk for lymphoma.

Adult↗

Identification of staphylococcal and streptococcal causes of bovine mastitis using 16S-23S rRNA spacer regions.

Bovine mastitis is caused mainly by certain Staphylococcus and Streptococcus species. The sequences of the 16S-23S rRNA spacer regions were determined for the nine species which cause mastitis: Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus epidermidis, Staphylococcus hyicus, Staphylococcus simulans, Staphylococcus xylosus, Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis. Significant variation was found between the spacer sequences of different species with the lengths of the spacers varying from 240 to 461 bp. Between genera the spacers shared only short conserved regions (8-9 bp) and within genera the sequence identities varied from 53 to 85%. This variation made it possible to construct specific primer pairs for these species and genera. The specificities of these primers were tested with 25 bacterial species and 51 isolates from cattle with clinical mastitis. The DNA-based identification of the mastitis species was mostly successful.

Animals↗

Idiopathic granulomatous mastitis: time to avoid unnecessary mastectomies.

Idiopathic granulomatous mastitis is a rare disease of the breast. Clinically and radiologically it may mimic breast carcinoma. Awareness of surgeons, pathologists, and radiologists is essential to avoid unnecessary mastectomies. Data regarding 24 patients with histologically confirmed idiopathic granulomatous mastitis treated at our center over 8 years were analyzed. The mean age of patients was 34.3 years. Breast lump was the most common presentation. The right breast was affected in 16 cases. Four patients were pregnant at the time of presentation. Lactation within 6 months of presentation was documented in four patients. Two patients used contraceptives pills. A clinical suspicion of malignancy was present in 17 cases. Mammography was performed in 16 patients and showed focal asymmetrical dense lesions in 9, well-circumscribed opacity in 4, spiculated lesion in 1, and was normal in 2. Fine-needle aspiration was performed in 17 patients, of which 2 were reported as malignant. Wide local excision was the mainstay of treatment. One patient underwent mastectomy upon clinical, mammographic, and repeated cytologic findings consistent with malignancy, and the final histology confirmed idiopathic granulomatous mastitis with no evidence of malignancy. Four patients developed recurrence after a mean follow-up of 31.2 months. A greater awareness of the rare entity of idiopathic granulomatous mastitis is mandatory to avoid unnecessary mastectomies. Clinical, radiologic, and even cytologic findings are sometimes confused with malignancy. To the best of our knowledge, our patient who developed the disease at the age of 11 years is the youngest reported case.

Adolescent↗

Milk transfer of phenoxymethylpenicillin during puerperal mastitis.

1 The milk excretion of phenoxymethylpenicillin (PMP) was studied from both breasts in patients with mastitis (n = 12) and healthy volunteers (controls, n = 4) to investigate the hypothesis that milk transfer of PMP is higher in mastitic than in non-mastitic breasts. 2 Patients were included according to clinical symptoms of mastitis. Milk (and serum from controls) were sampled 0, 1, 2, 3, 4, 6 and 8 h after a single oral dose of 1320 mg PMP. Penicillin concentrations in milk and serum were measured by an agar diffusion technique. 3 Maximum milk concentrations (Cmax) of PMP in patients were higher (P less than 0.05) in mastitic than in non-mastitic breasts. The latter concentrations were higher (P less than 0.05) than those in breast milk from healthy controls. In milk from the mastitis patients (both breasts) the Cmax was reached after 2 h with a subsequent rapid decline in concentration. In milk from the healthy controls the PMP concentration reached a plateau after 4 h. The area under the milk concentration vs time curve (AUC0-8h) was not different for mastitic vs non-mastitic breast milk in patients nor for mastitic vs control breast milk. This can be explained by higher rates of appearance and disappearance of PMP in the breast milk of mastitis patients compared with healthy controls. In mastitic breast milk there was a moderate (P less than 0.01) increase in sodium and albumin compared with non-mastitic milk. However, milk potassium, glucose and lactose values were within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Risk factors for subclinical mastitis among HIV-infected and uninfected women in Lusaka, Zambia.

Subclinical mastitis, defined as raised milk sodium/potassium (Na/K) ratio, is associated with poor infant growth and, among HIV-infected women, with increased milk HIV viral load. We conducted a longitudinal cohort study in Lusaka, Zambia, in order to investigate the relative importance of several potential causes of subclinical mastitis: maternal infection, micronutrient deficiencies and poor lactation practice. Women (198 HIV-infected, 189 HIV-uninfected) were recruited at 34 weeks' gestation and followed up to 16 weeks postpartum for collection of information on their health, their infant's health, infant growth and infant feeding practices. Milk samples were collected from each breast at 11 postpartum visits and blood at recruitment and 6 weeks postpartum. The geometric mean milk Na/K ratio and the proportion of women with Na/K ratio > 1.0 in one or both breasts were significantly higher among HIV-infected than among uninfected women. Other factors associated with the higher mean Na/K ratio in univariable analyses were primiparity, high maternal alpha(1)-acid glycoprotein (AGP) at 6 weeks, maternal overall morbidity and specific breast symptoms, preterm delivery, low infant weight or length, infant thrush and non-exclusive breast feeding. In multivariable analyses, primiparity, preterm delivery, breast symptoms, HIV status and raised AGP were associated with the raised Na/K ratio. Thus the main factors associated with subclinical mastitis that are amenable to intervention are poor maternal overall health and breast health. The impact of improved postpartum health care, especially management of maternal infections and especially in primiparous women, on the prevalence of subclinical mastitis and its consequences requires investigation.

Adult↗

Giving selenium supplements to dairy cows strengthens the inflammatory response to intramammary infection and induces a growth-suppressing effect on mastitis pathogens in whey.

Supplementing the feed of selenium-deficient diary cows with selenium (Se)-yeast or selenite at a level of 0.2 p.p.m. induced self-cure of subclinical mastitis; the prevalence of quarters harbouring subclinical mastitis (bacteriological criteria) decreased to about one half during the 8 week supplementation period. Three phenomena became apparent to explain the beneficial effect of selenium on mastitis: 1. The recruitment of phagocytes to the infected milk compartment of the udder was improved due to Se-supplementation; the correlation between infection and the respective inflammatory response, as indicated by the somatic cell count (SCC) and the N-acetyl-beta-D-glucosaminidase activity (NAGase) of milk, was poor in selenium-deficient cows. Selenium supplementation significantly improved the correlation; 2. Selenium supplementation induced an unspecified antibacterial activity in milk lactoserum (whey), restricting in vitro growth of the mastitis pathogens Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae and Streptococcus uberis, bacterial growth rates in whey samples became inversely correlated with the respective blood glutathione peroxidase activities (GSH-Px); and 3. Selenium supplementation had an effect on redox activities and sulfhydryl activities in whey. These changes were correlated with in vitro bacterial growth rates.

Animals↗