Incidence of mastitis in beef cows after intramuscular administration of oxytetracycline

There is limited information on the value of antibiotic therapy for mastitis in beef cows. Effects of antibiotic treatment at weaning and the subsequent calving on calf weaning weight, milk somatic cell counts, milk components, and intramammary infection were studied in beef cows. Additionally, effects of number of infected mammary quarters, number of dry mammary quarters, type of intramammary pathogen, and parity on response variables were determined. Cows (n = 192) were randomly assigned to treatments in a 2 x 2 factorial arrangement; factors were time of treatment (weaning and after calving) and treatment (vehicle and vehicle plus antibiotic). Oxytetracycline (LA-200) or vehicle was administered intramuscularly following collection of quarter milk samples at weaning and calving. Percentage of infected cows and quarters averaged 43.4 and 16.4%, respectively, at calving and increased (P < 0.05) to 53.7 and 29.7% at weaning. Calves from cows with one or two dry quarters weighed 12.7 kg less (P < 0.05) at 90 d after calving and 18.7% less (P < 0.05) at 212 d after calving than calves from cows with no dry quarters. Calves from cows with three or four infected quarters weighed 17.5 kg less (P < 0.05) at 90 d and 25.5 kg less (P < 0.05) at weaning than calves from cows with two or fewer infected quarters. Infections by Staphylococcus aureus and coagulase-negative staphylococci were the most common and accounted for 67 and 78% of the infections. Percentages of infected cows and quarters, infections caused by S. aureus, and dry quarters increased (P < 0.05) with parity. No differences were found among antibiotic treatments for any of the response variables studied. Intramuscular oxytetracycline was not effective in the control of mastitis in beef cows under the conditions of the study.     

Effects of dry cow treatment of beef cows on pathogenic organisms, milk somatic cell counts, and calf growth during the subsequent lactation

Spring calving Angus and Angus x Hereford multiparous cows were utilized to determine the effects of intramammary treatment with penicillin G procaine (200,000 IU) and novobiocin (400 mg) at the time of weaning on udder health and calf growth after the subsequent calving. Cows were stratified by age and breed and assigned randomly to receive intramammary treatment (n = 99) at weaning or as untreated controls (n = 97). Quarter milk samples were collected at weaning and at 8 to 14 d after calving. Milk samples were analyzed for somatic cell counts (SCC) and mastitis-causing bacteria. Dry cow treatment decreased (P = 0.005) the number of cows infected after calving. Treatment decreased (P = 0.04) the number of cows that developed new infections and reduced (P = 0.03) the number of quarters with mastitis-causing bacteria after calving that were infected at weaning. Somatic cell counts after calving were greatest (P = 0.008) for cows infected with Staphylococcus aureus. Treatment did not alter (P = 0.19) SCC of quarters after calving that were infected with S. aureus at weaning but reduced (P = 0.002) SCC after calving of quarters that were infected with coagulase-negative staphylococci at weaning. Body weight of calves during early lactation was increased (P = 0.006) if cows with intramammary infection were treated at weaning. Treatment of noninfected cows at weaning increased (P = 0.008) adjusted 205-d weaning weights of calves after the subsequent lactation when compared with untreated noninfected cows. We conclude that treatment of beef cows at weaning with intramammary antibiotics decreased intramammary infections after calving, improved udder health during the subsequent lactation, and increased BW gain of the calves.     

Prevalence and effects of intramammary infection in beef cows

Prevalence and effects of intramammary infection in 322 beef cows was determined during three calving intervals. Intramammary infection was confirmed in 37% of cows and 18.1% of quarters. Coagulase-positive staphylococci accounted for 17.9% of infections with Staphylococcus aureus isolated from 7.1% of cows. Coagulase-negative staphylococci and micrococci accounted for the remainder of infectious organisms. Butterfat and total protein levels were reduced 27.3 (P less than .05) and 25.5% (P less than .01), respectively, in milk from quarters infected with S. aureus. Somatic cell counts were elevated (P less than .001) with 3,827 X 10(3) cells/ml for S. aureus-infected quarters as compared with 555 X 10(3) cells/ml for uninfected quarters. Somatic cell counts were negatively correlated with 210-d calf weaning weights. Staphylococcus aureus-infected cows weaned calves weighing 19.1 kg less (P less than .01) than uninfected cows. At a present market value of $1.65/kg, economic losses were placed at $31.43/calf from cows infected with S. aureus in one or more quarters.     

Udder health in beef cows and its association with calf growth

Background

Studies outside the Nordic countries have indicated that subclinical mastitis (measured by milk somatic cell count or the California Mastitis Test), intramammary infections (IMI), or blind quarters in beef cows may have negative effects on beef calf growth. Knowledge on prevalence of such udder health problems in Swedish beef cows is scarce. Therefore, the main aim of this study was to investigate subclinical mastitis, IMI and udder conformation in a number of beef cow herds. Production of β-lactamase in staphylococci was also investigated. Associations between certain cow factors and subclinical mastitis and IMI, and associations between cow and calf factors and 200 day calf weaning weight were also studied. The herds were visited once within a month after calving and once at weaning. Udder examination and quarter milk sampling, for somatic cell count and bacteriology, were performed in 8 to 12 cows per herd and occasion.

Results

Approximately 50%, 40% and 10% of the cows had subclinical mastitis, IMI, and at least one blind quarter, respectively, but the prevalence varied markedly between herds. Intramammary infections (mainly due to staphylococci) were identified in 13-16% of the milk samples. Less than 5% of the staphylococcal isolates produced β-lactamase. Approximately 11% of the cows sampled twice had the same IMI (mostly Staphylococcus aureus) at both samplings. Cow factors of importance for subclinical mastitis and/or IMI were teat and udder shape, breed, parity, presence of blind quarters, and cow hygiene. No significant associations were found between udder health parameters studied and calf weaning weights.

Conclusions

Subclinical mastitis and IMI, but not blind quarters, were common in beef cows, but the prevalence varied markedly between herds. Most IMI were caused by staphylococci and more than 95% of those were sensitive to penicillin. Cows with large funnel-shaped teats or pendulous udder after calving, and cows with blind quarters were at risk of having subclinical mastitis and/or IMI. Poor hygiene was also a risk factor for udder health problems. No significant associations were found between udder health and calf weaning weight. More studies on risk factors are warranted to improve advisory services on awareness and prevention of mastitis in beef cows.     

Efficacy of intramuscular treatment of beef cows with oxytetracycline to reduce mastitis and to increase calf growth

Spring-calving multiparous Angus x Hereford cows were used to determine the efficacy of intramuscular treatment with oxytetracycline to reduce the incidence of mastitis-causing bacteria, decrease milk somatic cell counts (SCC), and increase calf growth. During 2 yr, milk samples were collected from each quarter from a total of 319 cows at 8 to 14 d after calving and at weaning, to determine the presence of bacteria and SCC. A California mastitis test (CMT) was performed on milk from each quarter of each cow at the initial sample collection. Cows with a CMT score of 1, 2, or 3 in at least one quarter, were randomly assigned to receive either an intramuscular injection of oxytetracycline (n = 63) or the control vehicle (n = 60), and cows with a CMT score of 0 or trace in all four quarters were not treated (n = 196). Calf weights were determined at birth, early lactation, and weaning. The number of somatic cells in milk and the percentage of quarters that were infected increased as CMT score increased (P < 0.01). The presence of mastitis-causing bacteria at calving increased (P < 0.05) the incidence of infection at weaning. The presence of mastitis-causing bacteria at weaning was associated with increased SCC for quarters and average SCC for cows (P < 0.01). Average SCC per cow at weaning increased (P < 0.05) as the number of infected quarters per cow increased. Treatment did not alter (P > 0.10) the percentage of cows or quarters infected with mastitis-causing bacteria or SCC of cows or quarters at weaning. Average SCC per cow was negatively correlated (P < 0.05) with calf weights at early lactation, but not with weaning weights of calves. Treatment did not influence (P > 0.10) calf weights at early lactation or at weaning. Cows with one or more dry quarters after calving had calves that weighed less at early lactation and weaning than cows with four functional quarters (P < 0.01). Intramuscular oxytetracycline treatment of beef cows that had CMT scores of 1 or greater after calving did not reduce intramammary infection rates or increase calf weights at weaning.     

Mastitis in beef cows and its effects on calf weight gain.

Quarter milk samples from 51 purebred (Angus, Polled Hereford, and Simmental) and 69 crossbred (Angus x Simmental x Charolais three-way cross) beef cows were collected aseptically at three times during lactation to determine the prevalence of intramammary infection, milk somatic cell counts (SCC), and effects of infection on calf weight gain. Quarter infection prevalence was 13.1, 14.9, and 27.5% in early, mid, and late lactation; corresponding cow infection prevalence was 25.8, 29.2, and 54.4%. Staphylococcus aureus was isolated from 2.9, 2.7, and 3.2% of quarters in early, mid, and late lactation, respectively. Corynebacterium bovis, generally regarded as a minor pathogen, was isolated from 4.0, 7.6, and 18.2% of quarters at the three respective times. Geometric SCC means (10(3) cells/ml) were 1,522, 344, and 509 for S. aureus-infected quarters; 344, 899, and 221 for Staphylococcus hyicus-infected quarters; 65, 36, and 86 for C. bovis-infected quarters; and 20, 17, and 18 for uninfected quarters in early, mid, and late lactation, respectively. Adjusted 205-d weight gain for calves with S. aureus-infected dams was 9.6 kg less (P less than .05) than for calves with uninfected dams. Adjusted 205-d weight gain for calves with dams infected with any mastitis pathogen did not differ significantly from that of calves with uninfected dams. At weaning half of the infected cows and half of the uninfected cows were given an intramammary infusion product containing 300 mg of cephapirin benzathine in each quarter; the remaining cows were untreated controls. Quarter samples were collected aseptically from all cows 14 to 28 d after subsequent calving. Quarter prevalence of infection after calving was lower (P less than .05) in treated (8.2%) than in control (22.4%) cows. Significantly more infections present at weaning were eliminated in treated than in control cows, but the new infection rate during the dry period and early lactation did not differ between the two groups.     

The effect of polyethylene intramammary devices on the somatic cell count and milk production of dairy cows

SUMMARY Polyethylene intramammary devices (IMO) were inserted into all 4 quarters of 15 multiparous dairy cows. Fifteen cows, matched for parity and production, were controls. The insertion of IMD's was easily achieved and produced no adverse effects. Throughout the 150-day test period, the mean somatic cell count of cows with IMD's in situ was 216,000 cells per ml, compared with 119,000 cells per ml in controls (P<0.01). Total production of milk, butterfat and protein was not significantly different between the 2 groups. The new infection rate was too low to allow assessment of the value of the IMD for mastitis prevention.     

Milk leucocyte population patterns in bovine udder infection of different aetiology

This study compared the different leucocyte populations in milk from udders infected with different mastitic pathogens and in different stages of infection. Milk samples were collected from quarters free of intramammary infection, acutely infected with Escherichia coli or Staphylococcus aureus and chronically infected with S. aureus, coagulase-negative staphylococci (CNS) or Streptococcus dysgalactiae. Udder bacteriological status was confirmed after three consecutive bacteriological examinations from weekly quarter milk samples. At the time of the trial, milk samples were tested for somatic cell count (SCC) and differential cell count by both light microscopy (LM) and flow cytometry. Monoclonal antibody (mAb) CD11a/CD18 was used in order to differentiate between leucocytes and epithelial cells when tested by flow cytometry. Udder quarters free of intramammary infection had a mean SCC lower than 107 x 10(3) cells/ml in which the epithelial cells were the main cell type followed by polymorphonuclear cells (PMNs), while macrophages and lymphocytes had a lower concentration. Only 56% of the cells were labelled with the mAb anti-CD11a/CD18. In either acute E. coli- or S. aureus-infected quarters, SCC were significantly higher (P < 0.0001) than in samples from the time of inoculation, with over 90% of the cells labelled with the mAb anti-CD11a/CD18. The main cell type was neutrophils. In chronically infected cows, differences in SCC and in leucocyte patterns were found between infecting pathogens as well as between quarters harbouring the same pathogen. In all the chronically infected quarters, SCC was significantly higher (P < 0.05) than in uninfected ones. The distribution of the leucocyte patterns in the quarters infected with S. dysgalactiae did not differ from that in quarters with acute infection with both E. coli and S. aureus. In the cows chronically infected with S. aureus or CNS, the proportion of PMN was higher but not significantly different from quarters free of intramammary infection, while epithelial cells were significantly lower (P < 0.05). The T lymphocytes bearing CD4+ or CD8+ were significantly higher in quarters chronically infected with S. aureus than in quarters free of intramammary infection and in quarters acutely infected with either E. coli or S. aureus. In all samples B cells were negligible.     

Microbiologic investigation of an epizootic of mastitis caused by Serratia marcescens in a dairy herd.

An epizootic of subclinical and clinical mastitis caused by Serratia marcescens was investigated in a 1,000-cow dairy farm in California. Serratia marcescens was isolated from 13 to 18% of composite milk samples obtained from lactating dairy cows. During monthly milk sampling performed during a 4-month period, S marcescens was isolated from 38.8 to 62.3% of composite milk samples obtained from cows from which S marcescens was previously isolated. Few cows infected with S marcescens had evidence of clinical mastitis. Somatic cell count value was associated with isolation of S marcescens. Cows with somatic cell counts greater than 500,000 were 5.48 times as likely to have intramammary infections with S marcescens, compared with cows with somatic cell count less than or equal to 500,000. Lactation number also was associated with S marcescens intramammary infection. After adjusting for the effect of lactation number, cows with high somatic cell count values were 2.98 times as likely to have intramammary infection with S marcescens, compared with cows with low somatic cell counts. Infection with S marcescens was independent of days in lactation, production string, and daily milk production. Eleven months after the beginning of the epizootic, S marcescens was isolated from organic bedding samples obtained from the dairy. Despite numerous attempts, other sources of S marcescens could not be identified on this dairy.     

Effects of autogenous toxoid-bacterin in lactating cows with Staphylococcus aureus subclinical mastitis

To evaluate clinical effects of autogenous toxoid-bacterin treatment for Staphylococcus aureus subclinical mastitis in lactating cows, 22 cows which had at least one S. aureus infected quarter were selected from among cows at a S. aureus prevalent dairy farm. Eleven cows were injected with their own autogenous toxoid-bacterin and the others were maintained as non-injected control. In the toxoid-bacterin injected group, 27% of infected quarters were cured during the 12-week trial, compared to 5% in the control group. New intramammary infections with S. aureus were only detected in 3 quarters of the control group. Mean IgG antibody titer against S. aureus somatic antigens and alpha-toxin in serum and milk were significantly increased in the toxoid-bacterin injected group (p<0.05) and remained higher than those of the control group which showed no significant changes (p<0.05). In contrast to the control group, from 3 weeks after the second injection of the toxoid-bacterin injected group, mean S. aureus cfu/ml in milk samples from injected quarters with S. aureus was significantly decreased until the end of the study (p<0.05). In the toxoid-bacterin injected group, significant decreases of mean SCC were detected from milk samples from infected quarters with S. aureus from week 7 to week 10 (p<0.05). These data show that autogenous toxoid-bacterin treatment against S. aureus subclinical mastitis in lactating cows may increase the cure rate of the infections, reduce the severity of the infections and also prevent occurrence of the new infections.     

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

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

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

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

Effects of systematic influences and intramammary infection on differential and total somatic cell counts in quarter milk samples from dairy cows

Effects of bacteriological status, stage of lactation, parity and season of sampling on differential and total somatic cell counts were estimated in quarter milk samples taken from 39 dairy cows. Log somatic cell count was affected by the bacteriological status of the quarter, as well as by the bacteriological status of adjacent quarters. Differential cell counts were affected by presence or absence of pathogens in the quarters themselves, but not by the bacteriological status of the adjacent quarters. Log somatic cell count was clearly affected by stage of lactation, due mainly to physiological variation, but possibly also accentuated by variation in infection rates throughout lactation. With the exception of early lactation, little physiological variation throughout lactation was detected for differential cell counts. Presence of infections seemed to have some indirect effect on trends throughout lactation as regards percentages of granulocytes and monocytes. Variation in somatic cell counts due to parity could be explained by variation in infection rates, rather than being physiologically determined.     

Fungi isolated from bovine udders , and their possible sources

AIM: To identify fungi isolated from infections of the bovine mammary gland, and establish their possible sources. METHODS: From a herd of 420 cows, milk samples were collected from all quarters at calving and cultured to detect causative organisms. Quarters identified as infected with fungi were further sampled during early lactation. Samples from feedstuffs, the feed pad and ends of teats were also collected and analysed for the presence of fungi. RESULTS: Eleven of 420 cows were diagnosed with intramammary infections (IMI) caused by yeasts (nine cows, 10 quarters) and moulds (two cows, three quarters). Six of the yeast species had previously been reported as being responsible for mastitis. Elevated somatic cell counts (SCC) were observed in many quarters, but most infections were eliminated spontaneously. Two of the fungi isolated from milk samples were also isolated from feedstuffs and teat swabs, and seven other fungi isolated from milk samples were not isolated from feed, the feed pad or cows' teats. CONCLUSIONS: Isolation of fungi from the udder is rarely reported in dairy cows in New Zealand. In this herd, contamination of the end of the teat originating from feedstuffs and possibly exacerbated by the use of a feed pad may have led to the establishment of IMI caused by fungi. CLINICAL RELEVENCE: Fungi are infrequently if ever reported in mastitis trial data or surveys in New Zealand and are probably of little clinical significance. KEY WORDS: Fungi, yeast, mould, bovine, intramammary infection, somatic cell count, mastitis.     

Efficacy of extended pirlimycin hydrochloride therapy for treatment of environmental Streptococcus spp and Staphylococcus aureus intramammary infections in lactating dairy cows

Fifty-one chronically infected lactating dairy cows were used to evaluate the efficacy of extended pirlimycin therapy regimens for treatment of intramammary infections by environmental Streptococcus spp and Staphylococcus aureus. Cows (n = 47) with one or more infected mammary quarters were blocked by parity and randomly allocated to one of three groups for treatment with pirlimycin (50 mg/mammary quarter) as follows: one treatment per day for 2 days (n = 36 infected mammary quarters); one treatment per day for 5 days (n = 36 infected mammary quarters); and one treatment per day for 8 days (n = 20 infected mammary quarters). Four cows with nine infected mammary quarters were included as untreated controls. Milk samples from each mammary quarter were collected 7 days before treatment, immediately before treatment, and weekly for 4 weeks after the final treatment for microbiological evaluation. A bacteriologic cure was defined as a treated, infected quarter that was bacteriologically negative for the presence of previously identified bacteria at weekly intervals after treatment. Efficacy of pirlimycin therapy against intramammary infections caused by environmental Streptococcus spp and S. aureus was 44.4%, 61.1%, and 95.0% for the 2-, 5-, and 8-day treatment regimens, respectively. None of the infections in the untreated control quarters was cured. Significant differences in efficacy were detected between all pirlimycin groups and the untreated control group, between the 8- and 2-day treatment regimens, and between the 8-day and 5-day treatment regimens (P < or = .05). Results of this study indicate that extended pirlimycin therapy was effective in eliminating intramammary infections caused by environmental streptococci and S. aureus in lactating dairy cows.     

The contribution of mammary infections by coagulase-negative staphylococci to the herd bulk milk somatic cell count

Quarter foremilk samples were taken at 2–3 weekly intervals for several years in a experimental herd comprising about 45 cows. The samples were submitted to bacteriological analysis and somatic cell counting. The most prevalent quarter infections from 1982 to 1988 were by coagulase-negative staphylococci (15–20% of all the quarters sampled). Most of these (75.6%) persisted until drying-off Dry cow therapy eliminated 86.5% of these infections. Comparison of udder quarters within cows, involving 775 samples from pairs of non-infected quarters and quarters infected by coagulase-negative staphylococci, yielded geometric means of somatic cell counts of 210 000 and 420 000 cells/ml, respectively. The correlation (r=0.87) between the herd bulk milk somatic cell count (SCC) and its estimation from the quarter milk somatic cell count performed on the same day allowed us to evaluate the contribution of the different categories of quarters, according to their infection status, to the herd bulk milk SCC. Quarters infected by a major pathogen (8.5% of samples) gave rise to 46.6% of the total number of cells, while quarters infected by coagulase-negative staphylococci (17.8% of samples) gave rise to 18.1%. Although coagulase-negative staphylococci represented only a secondary source of somatic cells as compared to major pathogens, they were not a negligible source considering the threshold of 300 000 somatic cells advocated for herd milk of good quality.     

Persistent Experimental Salmonella dublin Intramammary Infection in Dairy Cows

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

Herd benefit-to-cost ratio and effects of a bovine mastitis control program that includes blitz treatment of Streptococcus agalactiae

Twelve dairy herds that had participated in the Pennsylvania Dairy Herd Improvement Association (DHIA) program for at least 12 months, that had a 12-month mean DHIA somatic cell count greater than 700,000 cells/ml, and that had greater than 25% of lactating cows infected with Streptococcus agalactiae participated in a herd blitz treatment program. Initially, quarter milk samples for bacteriologic culturing were collected from all lactating cows. Subsequently, all cows identified as infected with Str agalactiae were treated, using a commercial penicillin-novobiocin intramammary infusion product. In addition, a herd mastitis management program of postmilking teat dipping and treatment of all cows at the start of the nonlactating period was instituted. Thirty days after the initial herd visit, samples from all lactating cows were again cultured, and cows infected at that time were treated. Twelve months after the initial herd visit, samples from all lactating cows were again cultured. Mean prevalence of infection with Str agalactiae decreased (P less than 0.05) from 23.0% of quarters and 41.6% of cows initially to 3.4% of quarters and 9.3% of cows at 30 days and 1.6% of quarters and 4.2% of cows at 1 year. Mean herd DHIA somatic cell count decreased (P less than 0.05) from 918,000 cells/ml initially to 439,000 cells/ml at 30 days and 268,000 cells/ml at 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bacterial cure and somatic cell count response of dairy cows with a positive California Mastitis Test at calving to therapy with cephapirin sodium

Cows without signs of clinical mastitis were evaluated by the California Mastitis Test at calving (Day 0). Milk samples from 117 of 184 quarters (64 cows) were positive by this test for mastitis and were submitted for bacterial culture and determination of somatic cell counts. Cows with infected quarters were randomly allocated to treatment with cephapirin sodium by intramammary infusion or to be untreated as controls. Two and 4 weeks following calving, milk was again sampled from the infected quarters and tested. By the 4-week evaluation, the quarters treated with cephapirin sodium had significantly (P < or = .05) fewer positive bacterial cultures and somatic cell counts were significantly (P < or =.05) reduced compared with untreated control quarters.     

Detection of capsular polysaccharide in milk of cows with natural intramammary infection caused by Staphylococcus aureus

Detection of capsular polysaccharide (CP) in milk of cows with natural intramammary infection caused by Staphylococcus aureus was attempted. Five quarters of 5 cows harboring S aureus strains that produce type-8 CP were selected. Using an ELISA with a monoclonal antibody, type-8 CP was not detected in extracts prepared from fresh milk collected aseptically. By contrast, CP was easily detectable after incubation of infected milk at 38 C for 20 hours. Quantitation of CP in extracts from incubated milk samples by use of ELISA indicated a great variation of CP expression by strains. Although an incubation step was necessary to detect CP, results of the study indicate that CP may be expressed in vivo during intramammary infection caused by S aureus.