Costs associated with selected preventive practices and with episodes of clinical mastitis in nine herds with low somatic cell counts

Nine dairy herds (mean size, 149 cows) with bulk-tank milk somatic cell counts of less than 300,000 cells/ml and greater than 80% of cows with Dairy Herd Improvement Association linear somatic cell counts less than or equal to 4 were selected for study. Each herd was monitored for 12 consecutive months. Duplicate quarter-milk specimens were collected from each cow for bacteriologic culturing at beginning of lactation, cessation of lactation, and at the time of each clinical episode of mastitis. Streptococcus agalactiae was never isolated and Staphylococcus aureus was isolated from less than 1% of all quarters. There were 554 episodes of clinical mastitis. During the year of study, the incidence rate of clinical mastitis varied from 15.6 to 63.7% of cows among the 9 herds. Mean costs per cow per year in herd for mastitis prevention were: $10 for paper towels, $3 for nonlactating cow treatment, and $10 for teat disinfectants. Mean cost associated with clinical mastitis was $107/episode. Approximately 84% ($90) of the costs attributed to a clinical episode were associated with decreased milk production and nonsalable milk. Costs of medication and professional veterinary fees per clinical episode varied significantly among the 9 herds. Three of the herds did not have a veterinarian treat a clinical episode of mastitis during the year of study even though 2 of these herds had the first and third highest incidence rates of clinical mastitis. When calculated on a per cow in herd basis, mean costs of $40/cow/year were attributed to clinical mastitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Serratia species isolated from bovine intramammary infections

Intramammary infections from which Serratia spp. were isolated were studied over a 32-mo period in a research dairy herd consisting of approximately 120 lactating cows. A total of 29 Serratia spp. intramammary infections were detected and accounted for 9% of all Gram-negative bacterial intramammary infections. Serratia marcescens was the most common Serratia spp. isolated. Origin of intramammary infections was 48.3% during the first half of the dry period, 31% during the last half of the dry period, and 20.7% during lactation. A total of 64% of intramammary infections that were first detected during the first half of the dry period persisted to calving. Geometric mean number of lactation days infected for all infections was 55. Intramammary infections that originated during the first half of the dry period were present in lactation for a significantly greater number of days compared with intramammary infections new during the last half of the dry period or lactation. A total of 48% of infections were clinical. Serratia spp. intramammary infections tended to be of long duration compared with other Gram-negative bacterial intramammary infections and were highly associated with the dry period.

Ultrastructural investigation of neurons identified and localized using the confocal scanning laser microscope

Studies of labeled neurons at the light-microscopic level often pinpoint a substructure of particular interest, i.e., a synapse or a spine. An ultrastructural investigation would explain a lot about how these structures arose, how they function, and how they are regulated. Finding a small region in a large block can require constant checking during sectioning, until past the structure. In our pursuit of the synaptic structure of varicosities on the axons of neurons identified physiologically and morphologically at the light level, we have combined confocal scanning laser microscopy (CSLM) with conventional and high-voltage electron microscopy (EM). CSLM images were collected in the reflection mode to view neurons filled with horseradish peroxidase and stained with nickel-intensified diaminobenzidine, which is compatible with EM. The CSLM optical sections provided a record of what one should expect to see at regular intervals throughout the depth of the tissue block. We have shown that the CSLM greatly simplified the task of localizing small structures in brain tissue prepared for EM.

Nonunion of a pathologic juvenile scaphoid fracture after osteomyelitis

A patient with osteomyelitis of the scaphoid in childhood resulting in a pathologic fracture with nonunion is presented. This ununited fracture of the scaphoid was successfully grafted eight years later with a satisfactory outcome.

Confocal microscopy and three-dimensional reconstruction of electrophysiologically identified neurons in thick brain slices

Three-dimensional morphology and electrophysiology were correlated from individual neurons in a thick brain slice preparation. The hippocampal formation from immature and adult rats was cut transverse to the longitudinal axis into 500 microns-thick slices which were maintained under physiologic conditions. Individual neurons were impaled and physiologically characterized using microelectrodes. Recordings were made from the soma and in some cases from a dendrite. The impaled neurons were filled through the microelectrode with the fluorescent dye lucifer yellow and imaged by confocal scanning laser microscopy using an analog preprocessor. As many as 180 optical sections were recorded as a function of depth through the slices. Images are presented as a series of optical sections, stereo pairs, or three-dimensional reconstructions. Both stereo contouring and volume rendering methods were employed, and the reconstructions were viewed from any arbitrary perspective. Dendritic and axonal fields were separated from each other and displayed separately or as different pseudocolors. The three-dimensional reconstructions provided perspectives that were difficult or impossible to appreciate by viewing the optical sections or conventionally formed stereo pairs.

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.

Calcium modulation of the N-methyl-D-aspartate (NMDA) response and electrographic seizures in immature hippocampus

Recordings from the CA3 region of hippocampal slices indicate a developmental change in the divalent cation sensitivity of the response elicited by N-methyl-D-aspartate (NMDA) application. In parallel experiments a developmental difference is demonstrated in the capacity of extracellular calcium to modulate electrographic seizure generation. Calcium modulation of the NMDA-elicited response may contribute to the pronounced capacity of immature hippocampus to generate electrographic seizures. Under these conditions activity dependent changes in extracellular calcium could have a greater influence on ion flow produced by activation of the NMDA receptor. The possibility that changes in the receptor isoform may occur during development would have widespread implications for normal cognitive functions and dysfunctions during brain maturation.

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.

Gram-negative bacterial infections of the mammary gland in cows

Naturally acquired gram-negative bacterial intramammary infections (n = 160) were studied in 99 cows over a 2-year period. Escherichia coli, Klebsiella spp, Serratia spp, Enterobacter spp, and unidentified gram-negative bacteria were isolated from 28.8, 39.4, 9.4, 5.0, and 11.2%, respectively, of infected mammary glands. A majority (61%) of intramammary infections were first detected during the nonlactating period. Gram-negative bacteria isolated during the first half of the nonlactating period were predominantly Klebsiella spp, Serratia spp, and Enterobacter spp. Onset of E coli intramammary infections was more prevalent during the second half of the nonlactating period and during the first 7 days of lactation. The majority (59%) of infections were less than 28 days in duration, but Klebsiella spp and Serratia spp infections were of significantly (P less than 0.05) greater duration than infections with E coli. The greatest percentage (47%) of gram-negative bacterial intramammary infections were first detected during the summer.

Parameters affecting imaging of the horseradish-peroxidase-diaminobenzidine reaction product in the confocal scanning laser microscope

Neurons intracellularly filled with biocytin and labelled with nickel-intensified diaminobenzidine (DAB/Ni) can be imaged on the confocal scanning laser microscope in order to obtain three-dimensional and optical section images of neurons. Intensification of the DAB reaction product with nickel was found to be crucial for obtaining a workable signal level. On the other hand, the high absorption of light by the reaction product severely attenuated the detection of structures lying directly underneath, and the intensity of the unattenuated laser used for imaging faded or damaged DAB/Ni reaction product. We have determined that reduction of the laser intensity combined with the use of proper objective lenses and non-laser-based imaging for preliminary adjustments of the specimen all work to reduce or eliminate damage, and also improve the image. These items must be kept in mind when imaging and analysing DAB-labelled structures in the laser-based confocal microscope.

Hemagglutination and hemolysis by Escherichia coli isolated from bovine intramammary infections

Seventy-six Escherichia coli isolated from bovine intramammary infections were tested for hemagglutination and hemolysis of erythrocytes. Fifty-seven percent of isolates were hemagglutination-positive for bovine erythrocytes compared with 46% that agglutinated guinea pig erythrocytes. Twenty-eight percent of isolates were hemagglutination-positive for erythrocytes from both species. Only 14.5 and 2.6% of isolates were mannose-resistant, hemagglutination-positive for bovine and guinea pig erythrocytes, respectively. Neither duration nor severity of infection from which isolates were obtained differed between isolates that were hemagglutination-positive and hemagglutination-negative. Percentage distribution of hemagglutination-positive isolates did not differ among isolates from infections that originated at calving, during lactation, or the first half of the dry period. Hemagglutination reactions were also not related to in vitro growth in cell-free dry cow secretion. Percent of isolates that caused hemolysis of washed bovine erythrocytes was 2.6% compared to 3.9% for sheep erythrocytes. Hemolysis was not related to hemagglutination. Hemagglutination and hemolysis of erythrocytes did not appear to be virulence factors for E. coli isolated from bovine intramammary infections.

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.

Long-term experience with a totally implanted catheter system in cancer patients

Long-term experience with totally implanted catheter systems (TICS) is limited. We retrospectively evaluated the performance and long-term complications of TICS for intravenous infusion in cancer patients; 134 systems were implanted in 128 patients. The median duration of implantation was 144 weeks with 49 systems implanted for more than one year. Complications related to surgical factors included malposition of reservoir (2%), skin perforation or wound dehiscence (1.5%) and pneumothorax (less than 1%). Complications not related to surgical factors included: drug extravasation (1.5%), mechanical malfunction (1.5%), vein thrombosis (less than 1%), clotting of the reservoir or catheter (2%), skin infection (1.5%), and sepsis (less than 1%). The total complication rate was 13%. Most complications resolved spontaneously or with medical treatment and only 6 patients (4.6%) required re-implantation of a second system. We conclude that with long-term usage of TICS, the complication rate remains low, making it a safe and viable alternative for patients requiring long-term intravenous therapy.

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.

Confocal scanning laser microscope images of hippocampal neurons intracellularly labeled with biocytin

We have assessed the properties and usefulness of confocal scanning laser microscopy in the reflection mode for the study of neuronal morphology. In this mode, the confocal microscope detects the light reflected off the specimen as opposed to the light emitted by a fluorescent label. Neurons in slices of rat hippocampus were filled with biocytin and reacted sequentially with avidin-horseradish peroxidase and nickel-intensified diaminobenzidine (DAB/Ni). In all parts of the neuron the DAB/Ni reaction product produced a strong reflection signal in the confocal microscope. The stereo images revealed aspects of three-dimensional hippocampal cell morphology such as the conical shape of the dendritic fields and a characteristic branching pattern of the axon. Labelling neurons intracellularly is an established technique for identifying physiologically-characterized neurons. Recently, confocal microscopy has become a powerful method for examining the three-dimensional morphology of biological specimens. The resulting images in this paper show that reflection-mode confocal microscopy provides an excellent representation of the filled neurons in three dimensions and presents an opportunity for correlative electrophysiological and morphological studies and extension to the electron-microscopic level.

Bacterial counts associated with recycled newspaper bedding

Bacterial counts associated with recycled newspaper, wood shavings, and pelleted corn cobs used as bedding for lactating dairy cows were compared. Chopped newspaper and pelleted corn cobs had similar gram-negative bacterial, coliform, and streptococcal bedding counts. Staphylococcal counts in pelleted corn cobs were greater than in chopped newspaper. Conversely, gram-negative bacterial, coliform, and staphylococcal counts in chopped newspaper were greater than in wood shavings. Coliform and streptococcal counts did not differ between chopped newspaper and wood shavings bedding materials. Teat swab counts from cows bedded on pelleted corn cobs were greater than those from cows bedded on chopped newspaper for gram-negative bacterial, coliform, Klebsiella species, and staphylococci. Streptococcal teat swab counts did not differ between cows bedded on chopped newspaper and pelleted corn cobs. Cows bedded on chopped newspaper and wood shavings had similar gram-negative bacterial, coliform, and Klebsiella species teat swab counts. Streptococcal and staphylococcal teat swab counts were greater from cows bedded on chopped newspaper than those from cows bedded on wood shavings. Teat swab and bedding counts were correlated. In general, bacterial counts in bedding suggest no advantage in using chopped newspaper over pelleted corn cobs or wood shavings in reducing exposure of teats to environmental mastitis pathogens.

Intramammary challenge of the bovine mammary gland with coliform bacteria during early involution

Isolates of Escherichia coli (n = 12), Klebsiella pneumoniae (n = 20), and Klebsiella oxytoca (n = 10) were used to challenge involuting mammary glands at 7 d of the dry period. Bacteria were selected for challenge on the basis of their ability to grow in a pooled source of dry cow secretion obtained at 21 d of involution. Challenge bacteria were classified as highly adapted (in vitro growth greater than 7 cfu log10/ml) or poorly adapted (growth less than 2 cfu log10/ml) for growth in dry cow secretion. Intramammary infusion of Escherichia coli, K. pneumoniae, and K. oxytoca resulted in 0, 40, and 30%, respectively, of quarters infected. Isolates highly adapted for growth in dry cow secretion caused 75% of K. pneumoniae and 67% of K. oxytoca experimental intramammary infections. Results indicated that the ability to overcome inhibitory properties of dry cow secretion was related to the establishment of K. pneumoniae and K. oxytoca intramammary infections in the dry gland. There was no evidence that growth of E. coli in dry cow secretion related to pathogenicity in the dry gland. Experimental challenge using multiple isolates did confirm the resistance of the involuting mammary gland to E. coli infection.

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.

Growth of gram-negative bacteria in dry cow secretion

Gram-negative bacteria (n = 192) isolated from infected bovine mammary glands were tested for growth in a pooled source of dry cow secretion. Growth of Klebsiella pneumoniae in dry cow secretion was greater than growth of Escherichia coli and Klebsiella oxytoca. Escherichia coli originating during the early dry period exhibited greater growth in dry cow secretion than those originating around calving or during lactation. Klebsiella pneumoniae growth did not differ with time of origin of intramammary infection. Escherichia coli, K. oxytoca, and K. pneumoniae growth in a synthetic medium was reduced by apolactoferrin plus Ig. Growth reduction was greatest for E. coli. Citrate reversed growth inhibition. The inhibitory properties of dry cow secretion for E. coli may contribute to the low number of naturally occurring intramammary infections originating during the early part of the dry period. Inhibitory properties of dry cow secretion are partially explained by lactoferrin acting in conjunction with antibody to prevent iron acquisition by many gram-negative bacteria.

Neural networks and synaptic transmission in immature hippocampus

The results reviewed in this chapter indicate that local circuit synaptic interactions are surprisingly well-developed in the rat hippocampal CA3 subfield during the second postnatal week. Intracellular recordings reveal large spontaneous epsps and ipsps. Synchronized bursts of synaptic potentials are observed in most paired intracellular recordings. Antidromic and orthodromic electrical stimulation evokes synaptic responses that are reminiscent of recordings from mature hippocampus. However, following brief trains of electrical stimuli and during bath application of a GABAA receptor antagonist, large prolonged depolarizations are recorded. These are suppressed by excitatory amino acid antagonists. In comparison, slices from mature rats do not produce these events under the same conditions. Thus, a hypothesis has been presented that the degree of recurrent synaptic interaction between pyramidal cells may be enhanced during this critical period in hippocampal development. An analysis of recurrent epsps using dual intracellular recordings is consistent with this contention. The degree of excitatory synaptic interaction between CA3 neurons appears to be at least equal to and likely in excess of that reported in mature hippocampus. One possible explanation for this is that the number of recurrent excitatory synapses may increase transiently during hippocampal development, only later to regress to numbers found in the adult. Recent studies of others suggest that activation of NMDA receptors may play a key role in the maintenance of synapses during development (Cline et al., 1987; Kleinschmidt et al., 1987). In this regard it is interesting that the characteristic of the NMDA receptor-ion channel complex on immature and mature rat CA3 hippocampal pyramidal cells appear to be quite different. These differences may play a role in synapse formation and maintenance. The role of NMDA receptors in LTP and learning (for review see Cotman et al., 1989; Lynch, 1986) are widely discussed. In other circles recurrent excitatory neuronal networks are thought to be substrates for memory (Lynch, 1986; Haberly and Bower, 1989). Both NMDA receptors and recurrent excitation are well represented in the CA3 subfield of immature hippocampus. One challenging area for future study will be the clarification of the interrelations between synaptogenesis and synaptic plasticity within neural networks of the developing hippocampus.

Effects of oral base therapy on serum ionized calcium, phosphorus and parathyroid hormone in chronic hemodialysis patients

The purpose of this study was to evaluate the effects of oral base therapy on selected chemical parameters in chronic hemodialysis patients. Oral base supplements were administered to 20 acidotic chronic hemodialysis patients for one month. Serum bicarbonate levels rose from 18.6 +/- 2.9 to 22.5 +/- 4.0 mEq/L (p less than 0.0005) and pH rose from 7.35 +/- 0.03 to 7.39 +/- 0.04 (p less than 0.0005). Serum ionized calcium levels fell from 5.03 +/- 0.37 to 4.83 +/- 0.34 mg/dL (1.25 +/- 0.09 to 1.21 +/- 0.08 mmol/L) (p less than 0.01), while intact parathyroid hormone (PTH) levels rose from 547 +/- 697 to 619 +/- 776 pg/mL (p less than 0.05). Base therapy did not result in significant changes in serum levels of total calcium, phosphorus, alkaline phosphatase, urea nitrogen, creatinine, total protein, albumin or potassium. If empiric therapy with exogenous base is given to dialysis patients, ionized calcium levels should be closely monitored since changes in calcium supplement or vitamin D therapy may be required to maintain ionized calcium and parathyroid hormone values at the pre-treatment levels.

Serum susceptibility of coliforms isolated from bovine intramammary infections

A total of 35 coliforms isolated from bovine intramammary infections were tested for serum susceptibility. Growth responses of Klebsiella pneumoniae isolated from intramammary infections originating during the dry period were inhibited more than were growth responses of Klebsiella pneumoniae isolated from infections originating during lactation. Escherichia coli growth responses did not differ between isolates originating from dry period and lactational intramammary infections. Mean growth responses to serum did not differ between Klebsiella pneumoniae and Escherichia coli. Bactericidal properties of serum were due to complement activity. The classical pathway of complement appeared to be the principal source of bactericidal activity of serum toward Klebsiella pneumoniae. Alternative and classical pathways of complement were both important for bactericidal effects of serum on Escherichia coli. Iron saturation of serum did not affect growth responses of either Klebsiella pneumoniae or Escherichia coli. These data illustrate that coliforms isolated from intramammary infection originating during the dry period were not more resistant to the bactericidal activity of bovine serum than were coliforms isolated from intramammary infection occurring during lactation.

Field survey of clinical mastitis in low somatic cell count herds

Nine commercial dairy herds, each with low herd milk somatic cell counts, were monitored for 1 yr to determine prevalence of intramammary infections and rates of clinical mastitis. Staphylococcus species was the bacterial group most frequently isolated from quarters at calving and at drying off. Environmental streptococci and coliform intramammary infections totaled less than 6% of quarters at both calving and at drying off. Staphylococcus aureus were isolated from less than 1% of quarters and Streptococcus agalactiae from 0% of quarters at both calving and drying off. A total of 646 clinical cases of mastitis were diagnosed in 548 quarters of 406 cows. Mean rate of clinical mastitis among herds was .457 clinical cases/305 cow-days. Rates of clinical mastitis ranged among herds from .273 to .748 clinical cases/305 cow-days. Coliforms and bacteriologically negative and environmental streptococci accounted for 82.3% of clinical cases. Rates of clinical mastitis and severity of clinical signs differed among herds, seasons of the year, parity groups, and stages of lactation. Rates of clinical mastitis were highest during summer, in first lactation cows, and during the first 7 d of lactation.

A slow NMDA-mediated synaptic potential underlies seizures originating from midbrain

After bath-perfusion with gamma-aminobutyric acid antagonists, slices of the rat's inferior colliculus were studied electrophysiologically. Synchronized epileptiform events were found to occur. The most prominent intracellular event was a sustained 30 mV depolarization which was pharmacologically and electrophysiologically characterized as an N-methyl-D-aspartate-mediated event. We propose that elicitation of this slow synaptic potential is the a priori basis of seizures arising in this midbrain nucleus.

Inhibition of erythropoiesis by a soluble factor in murine malaria

To study the cellular mechanisms involved in the ineffective erythropoiesis associated with malaria, an in vitro proliferative assay was used to measure the response to erythropoietin (Epo) of erythroid progenitor cells from malaria-infected mice. In this assay, spleen (SP) cells from phenylhydrazine (PHZ)-treated mice (PHZ-SP), enriched for erythroid progenitor cells, respond to Epo in a dose-dependent manner. Despite a similar degree of anemia, SP and bone marrow (BM) cells from Plasmodium berghei- or P. vinckei-infected mice did not show a significant response to Epo in this assay. When SP or BM cells from malaria-infected mice were added to cultures of SP or BM cells from PHZ-treated mice the response to Epo of these cells was significantly inhibited. Removal of parasitized red blood cells (pRBC) from SP cells of P. berghei-infected mice had no effect on the ability of the cells to inhibit the response to Epo. Adherent SP cells and SP cells positive for the Mac-1 antigen, from malaria-infected mice, were shown to be enriched for cells that could inhibit the response to Epo. Cell-free conditioned media (CM) prepared from SP cells of P. berghei- or P. vinckei-infected mice or from normal SP cells incubated with pRBC were also able to inhibit the response to Epo of SP cells from PHZ-treated mice. These investigations have shown that during the course of malaria infection, cells appear in the SP and BM capable of inhibiting, via soluble mediators, the response to Epo of erythroid progenitor cells. The cells responsible are probably macrophages. The nature of the factor(s) and its mechanism of action are not known. Through the ability to inhibit erythropoiesis, soluble factors may, in part, mediate the anemia associated with malaria.

Prolonged in vitro exposure of Staphylococcus aureus to germicidal teat dips

Eight strains of Staphylococcus aureus were tested to determine if prolonged exposure to commercial teat dips could enhance bacterial tolerance to teat dips in vitro. All strains of S. aureus were serially plated 15 times on chemically defined agar medium containing sublethal concentrations of linear dodecyl benzene sulfonic acid, chlorhexidine, sodium hypochlorite, and iodophor teat dips. Growth responses of S. aureus to chlorhexidine, sodium hypochlorite, and iodophor were not affected by prolonged exposure to these teat dips. Isolates subcultured on agar containing .1% linear dodecyl benzene sulfonic acid teat dip subsequently had a greater mean growth response to .1% solution of the germicide than did controls subcultured on basal medium. Hemolytic patterns, tube coagulase, clumping factor, and protein A reactions of S. aureus were not altered by exposure to any of the teat dips tested. In general, prolonged exposure to commercial teat dips did not alter germicidal susceptibility of S. aureus.

Bacterial counts in bedding materials used on nine commercial dairies

Bacterial counts were monitored for 1 yr in bedding materials used on nine commercial dairies. Organic materials used to bed lactating cows had significantly higher moisture content and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts than did inorganic materials. Klebsiella species counts were higher in sawdust than in chopped straw. Streptococcal counts were higher in chopped straw than sawdust. Bacterial counts did not differ between sand and crushed limestone. Gram-negative bacterial and coliform counts were higher during summer and fall than in winter and spring months. Streptococcal counts did not differ among seasons of the year. Linear relationships were significant between total rates of clinical mastitis during lactation and both gram-negative bacterial and Klebsiella species counts in lactating cow bedding. These data indicate that bacterial populations differed between both types of bedding and among seasons of the year. Rates of clinical mastitis were related to bacterial counts in bedding.

Bacterial and Somatic Cell Counts in Bulk Tank Milk from Nine Well Managed Herds1

Factors associated with bulk tank milk bacterial and somatic cell counts were investigated for one year on nine well managed dairies. Geometric mean total bacterial count among dairies was 4.4 × 10³ colony cfu/ml. Geometric mean bulk tank milk somatic cell counts among herds was 265 × 10³ml. Bacterial counts in bulk tank milk were correlated with rates of coliform and environmental streptococcal clinical mastitis cases. Rates of total clinical cases were also correlated with bulk tank milk somatic cell counts. Correlations were measured among bulk tank milk bacterial counts and gram-negative bacterial, coliform, Klebsiella species, and streptococcal counts in materials used to bed lactating cows. Total bacterial and staphylococcal bulk tank milk counts increased when synthetic rubber liners were used greater than 800 quarter milkings. Correlations measured indicated that monitoring bulk tank milk may be an effective means of detecting management changes in herds with low bacterial and milk somatic cell counts.

Immunomodulation of in vitro antigen presentation by cations

The ability of various cations to alter an antigen-specific (ovalbumin) T cell activation system in vitro has been assessed. This in vitro system includes analysis of antigen capture, processing, and presentation by antigen presenting cells (APC) (splenocytes, B cells or macrophages) in a major histocompatibility complex (MHC) restricted fashion and the evaluation of the activation of a T-cell hybridoma, DO-11.10, which is specific for "processed" ovalbumin in association with I-Ad. Activation is determined by production of IL2 which is quantitated in a bioassay with HT-2 cells. Numerous metals (10 and 100 microM) were screened in the coculture assay (APC and DO-11.10 plus ovalbumin). Metals with inhibitory effects were Cd greater than Cu greater than Pb greater than Zn. Co and Cr had no modulatory effect and Ni had an enhancing effect (increased IL2 production). The effects of the modulatory metals were further assessed for influences on the individual cellular components of this system. Cd was toxic to all cell types whereas Cu was toxic only to irradiated splenocytes and Do-11.10. Pb was the only metal which was not toxic to any cell type but still inhibited antigen presentation. To prevent influences of metals on DO-11.10 or carryover into the bioassay, APC were preincubated with metals and then assessed for presentation capability. After preincubation, only Cd, Pb, and Cu were inhibitory. The inhibition by Cd was due to toxicity. Cu inhibited only irradiated splenocyte presentation and this effect was due to toxicity. Pb inhibition was due to a mechanism other than toxicity and its biochemical influences on APC are discussed.

Sensitivity and specificity of latex agglutination tests used to identify Streptococcus agalactiae and Staphylococcus aureus isolated from bulk tank milk

Comparisons were made among rapid latex agglutination tests and conventional biochemical tests used to identify Streptococcus agalactiae and Staphylococcus aureus. Ninety-eight streptococci and 149 staphylococci isolated from bulk tank milk were tested. Sensitivity and specificity for the latex agglutination test used for identification of Str agalactiae were 97.6 and 98.2%, respectively. Sensitivity and specificity for the latex agglutination test used for identification of S aureus were 90.2 and 67.5%, respectively. Of 25 staphylococci considered false-positive by the latex agglutination test, 14 (56%) were considered tube coagulase-positive. Fifteen staphylococci considered false-positive by latex agglutination test had biotypes representative of S hyicus of S xylosus.

Rate of environmental mastitis in quarters infected with Corynebacterium bovis and Staphylococcus species

Rates of environmental streptococcal and coliform intramammary infections were compared among quarters uninfected and infected with either Corynebacterium bovis or Staphylococcus species. Rate of environmental streptococcal intramammary infections was 3.9 times greater in C. bovis-infected quarters than in uninfected quarters. Rate of environmental streptococcal infections was 2.6 times greater in quarters infected with Staphylococcus species than in uninfected quarters. Rate of coliform intramammary infections did not differ among quarters with differing bacteriological infection statuses. Quarters infected with either C. bovis or Staphylococcus species had higher milk SCC than did uninfected quarters. Intramammary infection with either Corynebacterium bovis or Staphylococcus species did not protect quarters against coliform infection. Rate of environmental streptococcal infections was enhanced in quarters infected with either C. bovis or Staphylococcus species.

Growth responses of environmental mastitis pathogens to long-chain fatty acids

Streptococcus uberis, Streptococcus faecalis, Escherichia coli, and Klebsiella pneumoniae were tested for susceptibility to long-chain fatty acids predominant in teat canal keratin. Antibacterial activity of free fatty acids on each bacterial species was measured after 12 h in synthetic media. Growth responses of all three strains of Streptococcus uberis were completely inhibited by C18:3 and those of two of three strains by C18:2 at 1 micrograms/ml. None of the fatty acids tested were bactericidal to Streptococcus faecalis. Saturated fatty acids C14 and C16 were more bacteriostatic to Streptococcus faecalis than were polyene fatty acids. Growth responses of coliform species were not affected by long-chain fatty acids. In general, environmental mastitis pathogens were resistant to fatty acids predominant in teat canal keratin.

Health and productivity of dairy cows fed polychlorinated biphenyls

Holstein cows were studied through a complete lactation, a nonlactating period, and 42 days of a subsequent lactation for overt and subtle responses to a commercial mixture of polychlorinated biphenyls. Dosed cows (n = 4) received consecutive 60-day periods of daily dosing with 10, 100, and 1000 mg of Aroclor 1254. Control cows (n = 6) received daily sham doses. The following were recorded: daily milk production, feed intake, and health observations; weekly body weight, temperature, heart and respiratory rates and rectal palpation; semi-monthly clinical chemistry determinations; and monthly milk fat, microbiological culture of quarter foremilk samples, and composite milk somatic cell counts. Mean daily milk production (22.4 +/- 1.1 vs 24.8 +/- 1.0 kg) and net energy of a complete lactation (1.46 +/- 0.05 vs 1.45 +/- 0.03 Mcal/kg dry matter intake) were not different (p = 0.85) for control and PCB-dosed cows. Milk production during the first 42 days of the subsequent lactation was also similar for control and dosed cows. Occurrences of injuries, dysfunctions, and general infections were not related to polychlorinated biphenyl exposure. Intramammary infections were detected for both lactations with 51 and 32 infections detected in microbiological cultures, respectively, for the control and dosed groups. Environmental pathogens were most frequently isolated from cases of clinically apparent mastitis. The majority of quarter infections detected were due to Corynebacterium bovis. Only one animal (dosed, necropsy revealed left oviduct obstructed) failed to conceive with three to six services required before conception for the other control and dosed cows. Exposure to polychlorinated biphenyls resulting in maximal residues in milk fat, near 100 micrograms/g, had no apparent effect on health and productivity.

Carbamazepine suppresses synchronized afterdischarging in disinhibited immature rat hippocampus in vitro

Bath application of therapeutic concentrations of the anticonvulsant carbamazepine suppressed penicillin-induced synchronized afterdischarging in immature rat CA3 hippocampal pyramidal cells. Afterdischarging was completely abolished in all preparations at a concentration of 30 microM (IC50 = 8.5 +/- 1.4 microM; mean +/- S.E.M.). The duration of the preceding epileptiform burst was not altered at this concentration and was diminished by only 24.4 +/- 1.2% at a supratherapeutic concentration of 100 microM. These results suggest that a carbamazepine-sensitive neurophysiological mechanism distinct from those responsible for epileptiform burst generation plays a key role in the generation of afterdischarges in developing hippocampus.

Extracellular K+ accumulation during penicillin-induced epileptogenesis in the CA3 region of immature rat hippocampus

Ion-selective microelectrode techniques were used to study extracellular K+ changes associated with penicillin-induced epileptogenesis in the CA3 region of hippocampal slices. Recordings were made in slices taken from rats 9-16 days of age, which have a pronounced capacity to undergo prolonged synchronized afterdischarges. Direct comparisons were made to slices from hippocampus from more mature rats, 30-35 days old, which are much less prone to seizure-like events. The amplitude and time course of the K+ transients varied across the CA3 laminae. K+ signals were largest close to stratum pyramidale in stratum oriens (the infrapyramidal zone). Recordings from this site showed extracellular K+ accumulation to be unusually large in immature hippocampus. The ceiling [K+]o level recorded during seizure-like events ranged from 14.4 to 20.2 mM and averaged 16.9 mM. The peak amplitude of extracellular K+ transients following an epileptiform burst in slices from immature rats averaged 4.31 mM while the mean of similar recordings from mature rats was 0.97 mM. Detailed laminar distribution studies in developing hippocampus revealed that the K+ signals were large in the proximal two-thirds of the basilar dendrites and proximal half of the apical dendrites. K+ accumulation in stratum pyramidale was comparatively small even though at its very edge in stratum oriens large K+ transients were always recorded. The latter was also true in recordings from mature hippocampus. Other dendritic signals in mature tissue were comparatively small. Laminar analysis was performed of the field potentials recorded by the reference barrel of the K+ electrodes. Negative field potential for the epileptiform burst and subsequent slow potential correlated in space with sites of K+ accumulation in both immature and mature hippocampal slices. Interictal and prolonged ictal-like discharges, recorded in developing hippocampus, arose from the same baseline [K+]o. However, since [K+]o is excessively high during the course of these epileptiform events it most likely has a role in the unusual propensity of immature hippocampus for seizures.

Lack of effect of Lactobacillus on gastrointestinal bacterial colonization in premature infants

Studies were carried out on premature infants in the neonatal intensive care unit to determine the effect of feeding of lactobacilli on colonization of the gastrointestinal tract by antibiotic-resistant gram-negative enteric organisms. Thirty premature infants were matched by birth weight and gestational age, randomized and fed double blind either lactobacilli-containing formula or non-lactobacilli-containing formula within 72 hours of delivery. The two study groups were screened weekly by culture for stool lactobacilli, for gram-negative bacteria and for antibiotic resistance of these bacteria. Lactobacilli were cultured from the stools of 13 of 15 patients receiving lactobacilli and from 3 of 15 patients not receiving lactobacilli (P less than 0.001). Gram-negative enteric organisms were isolated during 40 of the 86 weeks (47%) of hospitalization for patients receiving lactobacilli and during 28 of 57 weeks (49%) for patients not receiving lactobacilli. There was no significant difference between the study groups in the number of resistant organisms or in the proportion of resistant organisms per gram-negative enteric isolates (4 of 40 vs. 0 of 28). These results suggest that facultative gram-negative enteric bacterial colonization, with either total or aminoglycoside-resistant strains, is not decreased by oral feedings of Lactobacillus acidophilus in premature infants.

Fluorometric quantitation of cellular and nonprotein thiols

A microfluorometric assay for thiols has been developed using the thiol-specific fluorochrome N-[4-(7-diethylamino-4-methyl-3-coumarinyl)phenyl]maleimide (CPM). The technique may be used to quantitate either cellular or plasma thiols over a range of 0.01 to 3.0 nmol and may be used with as few as 1-3 X 10(5) cells giving highly proportional and reproducible results. Values for nonprotein thiols obtained with this assay agree well with previous reports on glutathione (GSH) levels for both lymphocytes and plasma. Readings are determined with the aid of an automated fluorescence microplate reader which allows up to 96 samples, including standards, to be read at the same time. Cellular thiols accessible after lysis were also quantitated before and after treatment of intact cells with various thiol-reactive chemicals. Interestingly, HgCl2, bromoethanesulfonic acid, and N-ethylmaleimide differentially modified protein and nonprotein thiol levels.

Evaluation of Summer Sausage Manufactured Using Mixed Lactobacillus and Leuconostoc Starter Culture 1

A 1:1 mixture of Leuconostoc and Lactobacillus plantarum and of L. plantarum alone were used as starter-cultures in making two batches of summer sausage. Sausage samples were evaluated for volatile flavor compounds and by sensory evaluation. Ethanol was the primary volatile flavor compound in the sausage from mixed culture while acetaldehyde predominated in the single culture sausage. Sensory evaluation indicated a significant difference (p≤0.01) between the two types of sausages with 66% of the panelists preferring sausage prepared with L. plantarum alone.

Health concerns of adolescents: impact of family status, sex, family size, and birth order

This paper reports results of a study of 149 early adolescents' self-perceptions of their health concerns, as related to certain familial characteristics. Of these adolescents (aged 12 to 15 yr.) those in single-parent families expressed fewer concerns than those in traditional homes. Girls in smaller families (less than 4.55 persons) were more concerned about physical appearance—skin, etc. Girls in larger families (more than 4.55 persons) expressed psychological worry about “tension.” In contrast, boys expressed no significant health concerns, regardless of family size. Finally, ordinal position in the family was important: boys who were oldest or youngest siblings were concerned about their muscles. Girls, in contrast, who were oldest siblings expressed concern about nervousness and being down in the dumps; girls who were youngest siblings noted facial appearance as a concern, along with worries about feeling good about themselves, their future, emotions, and feelings.

In vitro growth of mastitis-associated streptococci in bovine mammary secretions

Cell-free, fat-free mammary secretions were tested in vitro for ability to support growth of streptococci associated with mastitis. Secretions were obtained prior to drying off, during the dry period, at calving, and during lactation from four cow treatment groups. Treatment groups were dry cow therapy, dry cow therapy and mammary glands subjected to induced inflammation 7 d post-drying-off, no dry cow therapy and no induced inflammation, no dry cow therapy but mammary glands subjected to induced inflammation. Growth of Streptococcus uberis, Streptococcus faecalis, and Streptococcus agalactiae in secretions from nonlactating glands was unaffected by induced inflammation. Growth of Streptococcus bovis was significantly inhibited in secretion obtained 14 d after induced inflammation. Dry cow therapy had no effect on streptococcal growth in secretion obtained 7 d after therapy. Streptococcal growth was greatest in secretions from involuted glands, and there was little or no evidence for growth inhibitory factors in cell-free, fat-free secretions obtained during the dry period. Milk from lactating glands inhibited streptococcal growth, and the inhibitory factor was presumptively identified as lactoperoxidase. Apolactoferrin, immunoglobulin, or both had little effect on streptococcal growth.

Environmental mastitis: cause, prevalence, prevention

Rate of intramammary infection by coliform bacteria and species of streptococci other than Streptococcus agalactiae (environmental pathogens) was studied in a dairy herd in total confinement. Rate was higher during the dry period than during lactation and increased progressively as parity increased. Rate was maximal during summer and coincided with maximum exposure to coliforms in bedding. Streptococcal infections were longer than coliform. Approximately 59% of streptococcal infections and 69% of coliform infections were present for 30 lactation days or less. Percent quarters infected by day of year varied between .7 and 3.0% for coliform bacteria and between 1.6 and 4.7% for streptococci. Approximately 81% of coliform infections and 53% of streptococcal infections during lactation were clinical. Clinical cases were highest during the first 76 days of lactation and during summer. Only 6.7% of coliform infections resulted in acute coliform mastitis, and all acute cases were during summer or early lactation. Dry cow therapy reduced rate of streptococcal infection during the early dry period but was without effect during the prepartum period. There was no effect of dry cow therapy on coliform infection rate during the dry period. Problems associated with prevalence and control of environmental mastitis were discussed.

Environmental pathogens and intramammary infection during the dry period

Rate of coliform and streptococcal intramammary infection during the dry period was studied in 168 dry periods. Coliform infection rate was influenced by stage of dry period, parity, and season during which dry periods occurred. Effects of dry cow therapy, immunization, or induced inflammation on coliform infection rate were minimal. Coliform infections originating in the first 50% of the dry period and persisting to lactation were predominantly other than Escherichia coli, whereas the majority originating in the last 50% of the dry period and persisting to lactation were Escherichia coli. Duration of streptococcal infections was greater than coliform infections. Dry cow therapy reduced streptococcal infection rate, and the effect was exerted primarily during the first 25% of the dry period. Effects of parity and season were not significant and likely masked by the positive effects of dry cow therapy. Results support the contention that all quarters of all cows should be dry treated for maximum reduction of new streptococcal infection during the dry period. Results suggest that methods other than conventional dry cow therapy are required for control of coliform infection during the dry period and streptococcal infection during the latter half of the dry period.

Enteric viral infections of calves and passive immunity

At least eight viruses have been identified, four within the last 5 yr, that produce diarrhea and pathological intestinal lesions in experimentally inoculated calves. Coronavirus and rotavirus frequently are associated with the neonatal calf diarrhea syndrome, but the etiologic role of the newly identified viruses is undefined. All diarrheal viruses replicate within small intestinal epithelial cells, resulting in variable degrees of villous atrophy. Immunity against these viral infections, therefore, must be directed toward protection of the susceptible intestinal epithelial cells. Because most of these viral infections occur in calves less than 3 wk of age, passive lactogenic immunity within the gut lumen plays an important role in protection. This report reviews methods of boosting rotavirus antibody responses in bovine mammary secretions and analyses of passive and active immunity in calves supplemented with colostrum and challenged by rotavirus. Results indicate rotavirus immunoglobulin G1 antibodies in colostrum and milk were elevated after intramuscular and intramammary vaccination of pregnant cows with an Ohio Agricultural Research and Development Center rotavirus vaccine but not after intramuscular immunization with a commercial rota-coronavirus vaccine. Feeding colostrum from intramuscular plus intramammary immunized cows to newborn calves challenged by rotavirus prevented diarrhea and shedding of rotavirus.

Biochemical and antibacterial properties of bovine mammary secretion during mammary involution and at parturition

Mammary secretions from four Holstein Friesian cows were collected during late lactation, early involution, and early in subsequent lactation. Changes of pH, concentration of serum albumin, immunoglobulin G, citrate, lactoferrin, and number of leukocytes in secretions were typical of milk from glands undergoing these physiological transitions. Whey prepared from a cow's secretions was evaluated for its capacity to inhibit growth of Escherichia coli, 60-Lilly, and a coliform strain isolated from mammary secretions of that cow. Wheys from different glands of the same cow differed markedly in their capacity to inhibit growth of coliforms. Inhibition of both strains by the wheys increased significantly during the dry period and was maximal in wheys collected day 15 of the dry period and at parturition in the subsequent lactation. The coliform strain isolated from a specific cow was inhibited more than Escherichia coli, 60-Lilly, by whey from the specific cow. Inhibition of the cow-specific coliform strain by the day 15 whey was reduced significantly after addition of ferric iron or sodium citrate. Addition of excess ferric iron or citrate to wheys collected at parturition did not alter significantly their inhibitory capacity within cow. However, reduction of growth inhibition was significant when data from the four cows were pooled.

Effect of vitamin E and selenium supplementation on incidence of clinical mastitis and duration of clinical symptoms

Incidence of clinical mastitis and duration of clinical symptoms for complete lactations were evaluated for 80 cows randomly assigned to one of four groups: vitamin E supplemented- and selenium injected, selenium injected, vitamin E supplemented, and controls. Vitamin E supplementation and selenium injection were during the dry period. Log-linear analysis of incidence data revealed a significant 37% reduction of clinical mastitis by vitamin E. Incidence was not affected by selenium alone, nor was there any evidence for interaction of vitamin E with selenium on incidence. However, duration of clinical symptoms (calendar months clinical/quarter lactating) was reduced by 46% for the selenium group, 44% for the vitamin E group, and 62% for the vitamin E-selenium group as compared to controls. We conclude that dairy cow diets deficient of vitamin E may elevate incidence of clinical mastitis. Selenium deficiency may result in greater duration of clinical symptoms, and selenium may interact with vitamin E. Coliform bacteria and species of streptococcus other than Streptococcus agalactiae were isolated from 70% of the clinical cases.

Inhibition of mastitic bacteria by bovine milk apo-lactoferrin evaluated by in vitro microassay of bacterial growth

An in vitro microassay was developed to evaluate antimicrobial properties of bovine apo-lactoferrin. The growth of coliform, staphylococcal, and streptococcal bacterial strains in a defined synthetic medium was inhibited by bovine apo-lactoferrin (.5 to 30.0 mg/ml). Addition of iron-saturated lactoferrin to the synthetic medium did not inhibit growth of test strains. Inhibition by apo-lactoferrin was greater for coliform than Gram-positive strains for all concentrations of apo-lactoferrin evaluated. No concentration of apo-lactoferrin proved bactericidal for either coliform or Gram-positive strains. Inhibition of two coliform strains by apo-lactoferrin (10 mg/ml) was abolished by addition of ferric iron to the assay system, indicating an iron-dependent nature of apo-lactoferrin induced inhibition of bacteria. Bicarbonate supplementation of the growth system containing apo-lactoferrin (1 mg/ml) increased inhibition of three coliform strains by apo-lactoferrin. Addition of increasing concentrations of citrate (2.0 mg/ml) to an assay system containing apo-lactoferrin (5 mg/ml) resulted in a concomitant reduction of growth inhibition of three coliform strains. These data indicate a potential relationship between the molar ratio of citrate to lactoferrin of the lacteal secretion and its capacity to inhibit coliform strains associated with mastitis.