Short communication: Effects of supplementing diets of Holsteins with copper, zinc, and manganese on blood neutrophil function.

The effects of supplementing diets with sulfate or glycinate Cu, Zn, and Mn on blood neutrophil function were examined in 27 late-lactation Holstein cows having a mean (± standard deviation) days in milk at time of neutrophil assays of 216 ± 31 d. Cows were assigned to 9 blocks of 3 and were grouped by parity, milk production, and days in milk. Cows within each block were randomly assigned to 1 of 3 treatments: (1) control diet devoid of supplemental Cu, Zn, and Mn; (2) diet supplemented with Cu, Zn, and Mn via sulfates; and (3) diet supplemented with Cu, Zn, and Mn via glycinate form. All cows were initially fed a control total mixed ration with basal mineral concentrations of 8 mg/kg of Cu, 35 mg/kg of Zn, and 35 mg/kg of Mn for 30 d. During the treatment period, cows fed diets with mineral supplementation via sulfates or glycinate forms had target total dry matter dietary concentrations of 18 mg/kg of Cu, 60 mg/kg of Zn, and 60 mg/kg of Mn for 30 d. Control cows were fed the control diet devoid of supplemental minerals for an additional 30 d. In vitro neutrophil functions were measured after 30 d on experimental or control diets. Percentage of neutrophils phagocytizing, intracellular kill, and phagocytic index did not differ among treatments. Serum concentrations of Cu, Zn, and Mn were also not affected by dietary treatment after 30 d. Results from this study demonstrated that dietary Cu, Zn, and Mn supplemented either as sulfates or glycinate form for 30 d had no effect on either in vitro blood neutrophil function or serum concentrations of Cu, Zn, and Mn in late-lactation Holstein cows.

Relative bioavailability of all-rac and RRR vitamin E based on neutrophil function and total alpha-tocopherol and isomer concentrations in periparturient dairy cows and their calves.

The objective of this experiment was to determine whether source of supplemental alpha-tocopherol fed to periparturient dairy cows affects neutrophil function and vitamin E status of the cow and the neonatal calf. Starting 14 d before anticipated calving and continuing until 14 d post-parturition, cows were fed diets with no supplemental vitamin E or with 2,500 IU/d of vitamin E from all-rac alpha-tocopheryl acetate or RRR alpha-tocopheryl acetate. All-rac alpha-tocopherol contains equimolar amounts of all 8 stereoisomers, whereas the RRR contains only the RRR isomer. Concentrations of alpha-tocopherol in cow plasma, colostrum, milk, and blood neutrophils were greatest for the RRR treatment, intermediate for all-rac, and lowest for cows fed no supplemental vitamin E. The concentration of alpha-tocopherol in plasma of newborn calves was very low and not affected by treatment but after 6 feedings of their dam's colostrum or milk, concentrations in calf plasma followed the same treatment pattern as cow plasma. The number of bacteria phagocytized was greater by neutrophils from cows fed all-rac vitamin E than for the other 2 treatments, which resulted in a greater number of bacteria being killed. For cows fed all-rac vitamin E, the RRR isomer comprised about 20% of the alpha-tocopherol consumed but approximately 60% of the alpha-tocopherol in plasma and milk. This enrichment was caused mostly by an almost complete discrimination against the 2S isomers. Because all-rac alpha-tocopherol is 50% 2S isomers, these data suggest that 1 g of all-rac tocopheryl acetate is equivalent to 0.5 g of RRR tocopheryl acetate.

Effects of dietary vitamin C on neutrophil function and responses to intramammary infusion of lipopolysaccharide in periparturient dairy cows.

Neutrophil function and the severity and incidence of mastitis in dairy cows is related to the intake of many antioxidant nutrients. Because vitamin C is the major water-soluble antioxidant in mammals, we examined the effect of dietary vitamin C on neutrophil function and responses to intramammary infusion of lipopolysaccahride (LPS) in periparturient dairy cows. At 2 wk before anticipated calving, Holstein cows were fed diets that provided 0 (16 cows) or 30 (15 cows) g/d of supplemental vitamin C (phosphorylated ascorbic acid). Treatments continued until 7 d after cows received an infusion of 10 microg of LPS into one quarter of the mammary gland (on average, this occurred 32 d postcalving). Supplementation of vitamin C increased plasma concentrations of vitamin C at calving, but no differences were observed in samples taken 24 h postinfusion. Concentrations of vitamin C in milk (24 h postinfusion) and in neutrophils (calving and 24 h postinfusion) were not affected by treatment, but vitamin C concentrations in neutrophils isolated from milk were about 3 times greater than concentrations in blood neutrophils. The LPS infusion did not alter concentrations of vitamin C in plasma or milk, suggesting that the LPS model did not produce the same effects as a bacterial infection of the mammary gland with respect to antioxidant effects. Supplemental vitamin C had no effect on neutrophil phagocytosis or bacterial kill. Dietary vitamin C reduced the milk somatic cell count but did not affect the febrile response or milk production following LPS infusion.

Effect of selenium source on selenium status, neutrophil function, and response to intramammary endotoxin challenge of dairy cows.

The effects of feeding dry and early lactation dairy cows diets with selenate or selenized yeast (Se-yeast) on concentrations of Se in serum, milk, and newborn calves, neutrophil function, and inflammatory response were determined. At 60 d before anticipated calving until approximately 30 d in milk (DIM), cows were fed diets that contained 0.3 mg of supplemental Se/kg of DM from sodium selenate or Se-yeast. Diets also contained 0.2% supplemental S (as sulfate) because it has been shown to reduce absorption of Se by dairy cows. The concentration of Se in serum at calving and 28 DIM was about 1.4 times greater for cows fed Se-yeast than for those fed selenate. Serum concentrations decreased 45 and 23% from dry-off to calving for cows fed selenate or Se-yeast, respectively. Selenium concentrations in serum from newborn calves were also about 1.4 times greater when the dams were fed Se-yeast. Concentrations of Se in colostrum and milk were about 1.8 times greater when cows were fed Se-yeast. Blood neutrophils were isolated from cows at 28 DIM and were used in an in vitro kill assay. Selenium treatment did not affect bacterial kill or the percentage of neutrophils that phagocytized bacteria. At approximately 28 DIM, one quarter from each cow was infused with a solution containing endotoxin. Peak body temperature (40.7 degrees C) occurred 6 h postinfusion, and peak somatic cell count (6.5 log10/mL) occurred at 12 h postinfusion. Neither measure was influenced by Se treatment.

Effect of immunoglobulin G from cows immunized with ferric citrate receptor (FecA) on iron uptake by Escherichia coli.

The effects of immunoglobulin (Ig) G from cows immunized with the ferric citrate receptor (FecA) on iron uptake by Escherichia coli were investigated. Receptor FecA was purified from E. coli UT5600/pSV66. Cows were immunized with 400 microg purified FecA three times at 21 d intervals during late lactation and the nonlactating period. Immunoglobulin G was purified by protein G affinity chromatography from colostral whey from cows immunized with FecA and from unimmunized control cows. The purified IgG from FecA immunized cows had higher IgG titers against FecA compared with control IgG. Fifteen E. coli isolated from intramammary infections and E. coli UT5600/pSV66 were grown in an iron-depleted medium containing 1 mM citrate to induce FecA. The bacterial cells were mixed with 0, 2, and 4 mg/ml purified IgG, and 55Fe was added to the assay. After 5, 10, and 15 min incubations at 37 degrees C, samples were passed through 0.45-pm pore size filters. Filters were washed with saline three times, and the radioactivity of 55Fe taken up by the bacterial cells on the filters was measured by a liquid scintillation counter. The measurements were expressed as numbers of 55Fe atoms per colony-forming unit and transformed to log10. The assay was repeated three times for each isolate in a partially balanced incomplete block design. The presence of IgG decreased 55Fe uptake by E. coli mastitis isolates and E. coli UT5600/pSV66. Anti-FecA IgG reduced 55Fe uptake by E. coli greater than IgG from unimmunized cows.

Growth responses of coliform bacteria to purified immunoglobulin G from cows immunized with ferric enterobactin receptor FepA.

The ability of purified bovine immunoglobulin (Ig) G from cows immunized with ferric enterobactin receptor FepA to inhibit the growth of coliform bacteria derived from bovine intramammary infection was investigated in iron-restricted media. All isolates of Escherichia coli (n = 21) and Klebsiella pneumoniae (n = 21) were tested for growth in a chemically defined medium containing 0.5 mg/ml of apolactoferrin and in a pooled source of dry cow secretion. The addition of 4 mg/ml of purified bovine IgG directed against FepA in the synthetic medium resulted in significant growth inhibition for both E. coli and K. pneumoniae isolates. Growth reduction of E. coli was greater than that of K. pneumoniae. In dry cow secretions, the growth of each E. coli isolate but of less than half of K. pneumoniae isolates (43%) was inhibited by IgG from cows immunized with FepA. Purified bovine IgG from cows immunized with E. coli J5 had a minimal inhibitory effect on the growth of both E. coli and K. pneumoniae isolates in the synthetic medium. In dry cow secretions, IgG from cows immunized with E. coli and K. pneumoniae isolates. Supplementation with 50 microM of ferric chloride to the medium completely reversed the inhibitory effects of the antibodies and lactoferrin. Bovine IgG directed against FepA apparently inhibited the growth of coliform bacteria by interfering with the binding of the ferric enterobactin complex to the cell surface receptor FepA.

Effect of vitamin E supplementation in diets with a low concentration of selenium on mammary gland health of dairy cows.

Sixty-six cows and heifers (Holsteins and Jerseys) were assigned to one of three treatments at 60 d before anticipated calving. Treatment 1 consisted of 100 IU/d of supplemental vitamin E during the dry period and 100 IU/d during the first 30 d of lactation. Treatment 2 was 1000 IU/d of vitamin E during the dry period and 500 IU/d during lactation. Treatment 3 was 1000 IU/d of vitamin E during the first 46 d of the dry period, 4000 IU/d during the last 14 d of the dry period, and 2000 IU/d during lactation. Plasma concentrations of alpha-tocopherol decreased at calving for cows fed dietary treatments with low or intermediate concentrations of vitamin E, but not for cows fed the high vitamin E treatment. High dietary vitamin E increased concentrations of alpha-tocopherol in blood neutrophils at parturition, but no difference was found for the other two treatments. The percentage of quarters with new infections at calving was not different (32.0%) between cows receiving treatments that contained low and intermediate concentrations of vitamin E but was reduced (11.8%) in cows receiving the high vitamin E treatment. Clinical mastitis affected 25.0, 16.7, and 2.6% of quarters during the first 7 d of lactation for cows receiving the low, intermediate, and high vitamin E treatments, respectively. Cows with plasma concentrations of alpha-tocopherol < 3.0 micrograms/ml at calving were 9.4 times more likely to have clinical mastitis during the first 7 d of lactation than were cows with plasma concentrations of alpha-tocopherol > 3.0 micrograms/ml.

Dietary vitamin E and selenium affect mastitis and milk quality.

Vitamin E and selenium (SE) are essential nutrients that are integral components of the antioxidant defense of tissues and cells. Soils in many of the important dairy regions of the world are Se-deficient, and feedstuffs grown on these soils will not provide adequate dietary Se. Cattle consuming stored forages are likely to be low in vitamin E unless supplemented, and vitamin E deficiencies are frequently observed in peripartum dairy cows. Many new intramammary infections (IMI) occur in the 2 wk before and after calving. Deficiencies of either vitamin E or Se have been associated with increased incidence and severity of IMI, increased clinical mastitis cases, and higher somatic cell counts (SCC) in individual cows and bulk tank milk. Somatic cell counts are a primary indicator of mastitis and milk quality in dairy herds. The polymorphonuclear neutrophil (PMN) is a major defensive mechanism against infection in the bovine mammary gland. A know consequence of vitamin E and Se deficiency is impaired PMN activity and postpartum vitamin E deficiencies are frequently observed in dairy cows. Dietary supplementation of cows with Se and vitamin E results in a more rapid PMN influx into milk following intramammary bacterial challenge and increased intracellular kill of ingested bacteria by PMN. Subcutaneous injections of vitamin E approximately 10 and 5 d before calving successfully elevated PMN alpha-tocopherol concentrations during the periparturient period and negated the suppressed intracellular kill of bacteria by PMN that commonly is observed around calving.

alpha-Tocopherol concentrations in milk and plasma during clinical Escherichia coli mastitis.

Eighteen cows were challenged by intramammary infusion with Escherichia coli 727 to determine the effects of acute clinical mastitis on alpha-tocopherol concentrations in plasma and milk. Cows were fed diets supplemented with 1000 IU of vitamin E/d from calving through the experimental period. At challenge, geometric mean DIM was 33 d. Each mammary quarter was diagnosed with an IMI and clinical mastitis at 24 and 48 h after challenge. The alpha-tocopherol concentrations in milk from challenged quarters were approximately 60% greater by 24 and 48 h after challenge than concentrations at prechallenge and 168 h postchallenge. Plasma alpha-tocopherol concentrations did not change after intramammary challenge. The alpha-tocopherol in plasma and milk was correlated at 48 and 168 h postchallenge but not at prechallenge or 24 h postchallenge. Milk alpha-tocopherol and SCC were correlated positively across all sample periods. Milk fat and milk alpha-tocopherol concentrations were correlated at each sample period except 24 h postchallenge. Increases in milk alpha-tocopherol during clinical mastitis were not correlated to milk production, DMI, or BSA concentration in milk. Changes in milk alpha-tocopherol concentration during clinical mastitis were similar to the dynamics of milk SCC.

Effect of dietary fat and vitamin E on alpha-tocopherol and beta-carotene in blood of peripartum cows.

Nonlactating cows were fed diets containing 88% grass forage and 12% concentrate (DM basis). Starting 14 d prior to anticipated calving, the concentrate was changed to provide 0 or 200 g of supplemental fat and 0 or 890 IU of supplemental vitamin E daily. Following parturition, cows were fed for 14 d a 50% concentrate diet that provided the same amounts of supplemental fat and vitamin E that were fed during the dry period. Plasma was sampled and analyzed for alpha-tocopherol and beta-carotene. Supplemental dietary fat elevated plasma concentrations of both nutrients during the peripartum period. Supplemental dietary vitamin E elevated concentrations of alpha-tocopherol during that period. Dietary fat also increased concentrations of plasma cholesterol. When alpha-tocopherol and beta-carotene were expressed per unit of plasma cholesterol, fat supplementation did not affect concentrations. Dietary treatments did not influence concentrations of alpha-tocopherol in blood neutrophils and did not affect intracellular kill of bacteria by neutrophils. Essentially no beta-carotene was found in the neutrophils. For colostrum, dietary vitamin E increased concentrations of alpha-tocopherol and decreased concentrations of beta-carotene.

Role of vitamin E and selenium in host defense against mastitis.

Vitamin E and Se are essential nutrients that share common biological activities. Deficiencies in either of these micronutrients have been related in increased incidence and severity of mastitis. A known physiological consequence of alpha-tocopherol or Se deficiency is reduced neutrophil activity. Vitamin E and the Se-containing enzyme, glutathione peroxidase, and antioxidants that protect neutrophils from the destructive action of toxic oxygen molecules necessary for intracellular kill of ingested pathogens. Dietary supplementation of cattle with Se results in a more rapid neutrophil influx into milk following intramammary bacterial challenge and increased intracellular kill of ingested bacteria by neutrophils. Dietary supplementation of early lactation cows with vitamin E results in increased bactericidal activity by bovine blood neutrophils. Recently completed trials have shown that subcutaneous injections of vitamin E approximately 10 and 5 d prior to calving successfully elevated neutrophil alpha-tocopherol concentrations during the periparturient period and negated the suppressed intracellular kill of bacteria by neutrophils that is commonly observed at calving.

Vitamin E as an adjuvant in an Escherichia coli J5 vaccine.

Vitamin E was tested as an adjuvant in an Escherichia coli (O111:B4) J5 vaccine. Twenty cows were assigned to five groups of 4 cows. Cows in four groups were vaccinated with an E. coli J5 bacterin containing 5 ml of 10(9) boiled cells/ml. Vaccinations were at drying off, 30 d after drying off, and within 48 h after calving. Vaccine adjuvants differed among groups. The four treatment adjuvants were 5 ml of Freund's incomplete adjuvant, 5 ml of vitamin E, 2.5 ml of Freund's plus 2.5 ml of vitamin E, and 5 ml of PBS. Cows in the fifth group were unimmunized controls. A front mammary quarter of each cow was challenged by infusion of 10 micrograms of E. coli J5 lipopolysaccharide approximately 4 wk into lactation. Vitamin E alone enhanced serum IgM titers but had no effect on milk IgM or serum and milk IgG titers. The mixture of Freund's plus vitamin E resulted in peak IgG titers in serum and milk comparable with that of Freund's alone. Persistency of IgG titers in cows immunized with the Freund's plus vitamin E mixture was greater than the persistency of titers for cows immunized with the vaccine containing Freund's alone as the adjuvant. The mixture of Freund's plus vitamin E had a synergistic effect in reducing severity of systemic clinical signs.

Effect of supplementing periparturient cows with vitamin E on distribution of alpha-tocopherol in blood.

Holstein cows were fed 0 or 1000 IU/d of supplemental vitamin E during the dry period and injected with placebo or 3000 IU of vitamin E at 10 and 5 d prior to anticipated calving. Blood was collected at various times, starting at 60 d prepartum (dry off) and concluding 30 d postpartum, and separated into plasma, red blood cells, and neutrophils. Oral supplementation increased concentrations of alpha-tocopherol in plasma and red blood cells on 10 d, but not on 5 d prepartum. Injection of vitamin E increased alpha-tocopherol in plasma, red blood cells, and neutrophils at d 5 prior to and on the day of parturition. Concentrations of alpha-tocopherol and cholesterol in plasma were correlated, and both were at their nadir at parturition. Concentrations of alpha-tocopherol in plasma and red blood cells were correlated, but the correlation increased when plasma alpha-tocopherol was expressed per unit of cholesterol. alpha-Tocopherol in plasma and neutrophils had a low correlation. Injection of alpha-tocopherol increased its concentration in plasma, red blood cells, and neutrophils during the periparturient period. Concentration of alpha-tocopherol in plasma of periparturient cows may be limited by its low lipid content, and transport mechanisms for alpha-tocopherol may differ between red blood cells and neutrophils.

Bovine neutrophil responses to parenteral vitamin E.

Twenty-eight Holsteins were tested to determine effects of dietary and parenteral vitamin E supplementation during the dry period on plasma alpha-tocopherol and in vitro neutrophil functions at calving. Cows were assigned to one of four experimental groups receiving either supplemental dietary vitamin E, injections of vitamin E, both dietary and injections of vitamin E, or neither source of supplemental vitamin E during the dry period in a 2 x 2 factorial arrangement. Cows receiving parenteral vitamin E were injected subcutaneously with 3000 IU of vitamin E (dl-alpha-tocopherol) at 10 and 5 d prior to anticipated calving. Cows not receiving parenteral vitamin E were injected with a placebo. Experimental groups receiving dietary vitamin E during the dry period were supplemented with 1040 IU/d compared with none for controls. Cows injected with vitamin E had greater plasma alpha-tocopherol concentration 5 d after the first injection, at calving, and 1 wk after calving than did cows injected with placebo. Plasma alpha-tocopherol concentrations did not differ between dietary vitamin E treatment groups from calving through 4 wk postpartum. No interaction was found between dietary and parenteral supplementation of vitamin E on plasma alpha-tocopherol concentration. Neutrophils from cows injected with vitamin E had greater intracellular kill of bacteria at calving than did neutrophils from placebo-injected cows. Neither phagocytic index nor percentage of neutrophils phagocytizing differed between vitamin E-injected and placebo-injected cows. Dietary vitamin E during the dry period had no effect on neutrophil function at calving. Intracellular kill and plasma alpha-tocopherol were correlated at calving.

Opsonic activity of bovine serum and mammary secretion after Escherichia coli J5 vaccination.

Six pairs of cows were used to determine the effects of immunization with an Escherichia coli (O111:B4) J5 bacterin on in vitro opsonization of a smooth heterologous strain of E. coli. One cow in each pair was either immunized with the vaccine or sham-immunized at drying off, 30 d after drying off, and at calving. Opsonizing bacteria with serum collected from vaccinated cows 21 d after calving resulted in higher mean number of intracellular bacteria per phagocytosing neutrophil than opsonizing bacteria with serum collected from control cows. Phagocytic parameters using serum collected at drying off and calving did not differ between treatment groups. A trend for enhanced opsonic activity of colostrum from vaccinates was noted. Enhanced opsonization by serum from vaccinated cows coincided with higher serum IgM titer to E. coli J5 whole cell antigen compared with controls. Serum IgG titers to E. coli J5 did not differ between groups. Colostrum IgG titers to E. coli J5 were greater at calving in vaccinated than in control cows. Colostrum and milk collected 21 d after calving from vaccinated cows had higher IgM titers to E. coli J5 than did mammary secretions from control cows. Numbers of intracellular bacteria per phagocytizing neutrophil were correlated positively with IgM titers to E. coli J5 in both serum and colostrum.

Antibodies to iron-regulated outer membrane proteins of coliform bacteria isolated from bovine intramammary infections.

Expression of iron-regulated outer membrane proteins (OMP) by Escherichia coli and Klebsiella pneumoniae initially isolated from bovine intramammary infections (IMI) was investigated. Additionally, the presence of antibodies in bovine serum and mammary secretion directed against the iron-regulated OMP was examined. Outer membrane proteins were separated by sodium-dodecyl polyacrylamide electrophoresis. Detection of immunoglobulin G directed against OMP was by immunoblotting. All Gram-negative bacteria expressed iron-regulated OMP when grown in skim milk or trypticase soy broth plus iron chelator, alpha-alpha'-dipyridyl. Immunoglobulin G directed against the iron-regulated OMP, as well as the major OMP and several other proteins, was detected in serum and milk of lactating cows with or without Gram-negative bacterial IMI. Antibody against the iron-regulated OMP was detected also in colostrum, secretion from the involuted gland, and in newborn calf serum 4 days after ingesting colostrum.

Intramammary challenge with Escherichia coli following immunization with a curli-producing Escherichia coli.

Holstein and Jersey cattle were immunized with a curli-producing strain of Escherichia coli (pCRL65/A012) or a noncurli-producing strain (pUC18/HB101) to determine differences in resistance to establishment of experimental intramammary infection. Cows (n = 6 per group) were immunized at 14 d prior to drying off, 7 d of involution, and at calving with 3 x 10(10) E. coli in Freund's Incomplete Adjuvant. At 30 d of lactation, one mammary quarter of each cow was infused with a wild strain of E. coli (727). Escherichia coli 727 was isolated from a naturally occurring intramammary infection and produced curli. All challenged quarters became infected, and all cows developed acute clinical mastitis. Geometric mean duration of intramammary infections was 6 d for both immunization groups. All infections were spontaneously eliminated within 10 d. No differences occurred between immunization groups in blood selenium and glutathione peroxidase activity, plasma selenium, number of E. coli 727 isolated from secretion after challenge, rectal temperature and SCC response, clinical status of mammary quarters, or DMI. Reduction in milk production after challenge was greater for cows immunized with E. coli pCRL65/A012. Immunization of dairy cattle with a curli-producing strain of E. coli did not protect against experimental intramammary challenge during lactation.

Effect of duration of supplementation of selenium and vitamin E on periparturient dairy cows.

Cows were fed diets either supplemented with .2 ppm Se and 70 IU vitamin E/kg diet DM (21 cows) or unsupplemented (40 cows) during the dry period (approximately 60 d). From parturition to 21 d of lactation, cows were fed diets that were either supplemented with .3 ppm Se and 40 IU/kg vitamin E or unsupplemented. At d 21 following parturition, 18 cows fed the unsupplemented diet were switched to diets containing 0 or .3 ppm supplemental Se and 0 or 40 IU/kg supplemental vitamin E arranged factorially. These diets were fed for the next 32 d. The remaining cows continued their respective diets for 32 d. Plasma Se concentrations averaged .1 microgram/ml for supplemented cows but were .05 micrograms/ml for unsupplemented cows. Plasma Se concentration from cows fed supplemental Se from 21 to 53 d postpartum increased rapidly and were not different from long-term supplemented cows. Whole blood glutathione peroxidase activity was lower in unsupplemented than in supplemented cows. Short-term Se supplementation increased glutathione peroxidase activity above that for unsupplemented animals, but activity was still less than that in long-term supplemented animals. Plasma alpha-tocopherol concentrations at parturition and d 21 postpartum were lower in unsupplemented than in supplemented animals. On d 53 postpartum, no differences in plasma alpha-tocopherol concentrations were found between long-term supplemented and unsupplemented cows. Supplementing vitamin E during the dry period increased alpha-tocopherol content of colostrum.

Relationships among vitamin E, selenium, and bovine blood neutrophils.

Effects of vitamin E and selenium supplementation on in vitro phagocytosis and intracellular kill of bacteria by bovine neutrophils were investigated. Diets were not supplemented with vitamin E and selenium during the dry period and first 21 d of lactation. Cows were then assigned to one of four treatment diets for 30 d. Treatment diets were either unsupplemented or supplemented with vitamin E, selenium, or both vitamin E and selenium, in a 2 x 2 factorial arrangement. Peripheral blood neutrophils were isolated from each cow on lactation d 51. Vitamin E supplementation of diets increased intracellular kill of Staphylococcus aureus and Escherichia coli by neutrophils. Intracellular kill of S. aureus was greater in neutrophils isolated from selenium supplemented cows than in neutrophils from cows without supplemental selenium. Intracellular kill of E. coli did not differ between neutrophils from selenium supplemented and selenium unsupplemented cows. Ability of neutrophils to phagocytize either S. aureus or E. coli was independent of vitamin E and selenium.

Relationships among selenium, vitamin E, and mammary gland health in commercial dairy herds.

Nine well-managed dairy herds were monitored for 1 yr to determine if bulk tank SCC and rate of clinical mastitis were associated with dietary and plasma Se and vitamin E status. Intakes of Se and vitamin E were 1 to 16 mg/d and 100 to 900 mg/d, respectively. Plasma Se concentrations were correlated positively with intakes of Se below 5 mg/d but were independent of Se intakes above 5 mg/d. Feeding vitamin E increased plasma concentrations of tocopherol, but the influence of dietary vitamin E on plasma concentrations was four times greater for dry cows than for lactating cows probably due to secretion of tocopherol into colostrum and milk. Bulk tank SCC averaged 5.4 log10/ml and decreased significantly as Se concentration in plasma increased. Plasma glutathione peroxidase was correlated positively to Se intake but negatively to SCC. Rate of clinical mastitis was negatively related to plasma Se concentration and concentration of vitamin E in the diet. An apparent interaction between dietary Se and vitamin E was evident since herds fed high amounts of Se tended to have high rates of clinical mastitis, but not if high amounts of vitamin E were fed. These data confirm earlier findings that Se and vitamin E status of dairy cows are related to mammary gland health.