In vitro growth inhibition of major mastitis pathogens by Staphylococcus chromogenes originating from teat apices of dairy heifers

Earlier field observations suggest that teat apex colonization by Staphylococcus chromogenes pre-partum in dairy heifers protects udder quarters against elevated somatic cell counts early post-partum. To explain these findings, the in vitro inhibitory capability of S. chromogenes from teat apices of heifers towards some major mastitis pathogens was tested using a modified cross-streaking method. Two out of 10 S. chromogenes isolates, both originating from two different teats from the same heifer, consistently inhibited growth of all Staphylococcus aureus, Streptococcus dysgalactiae, and Streptococcus uberis strains, but none of the Escherichia coli strains. The present study, therefore, supports the protective effect of teat apex colonization by S. chromogenes by in vitro production of inhibitory substances.     

Effect of prepartum intramammary treatment with pirlimycin hydrochloride on prevalence of early first-lactation mastitis in dairy heifers

OBJECTIVE: To determine whether prepartum intramammary treatment of dairy heifers with pirlimycin hydrochloride would reduce the prevalence of intramammary infection (IMI) and lower the somatic cell count (SCC) during early lactation or improve 305-day mature equivalent milk production. DESIGN: Prospective clinical trial. ANIMALS: 183 Holstein-Friesian heifers (663 quarters) from 2 dairy farms. PROCEDURE: Heifers were assigned to treatment and control groups. Treated heifers received a single 50-mg dose of pirlimycin in each mammary quarter approximately 10 to 14 days prior to parturition. Prepartum mammary gland secretions and postpartum milk samples were collected for bacterial culture. Postpartum milk samples were also collected for determination of SCC or California mastitis testing and were tested for pirlimycin residues. Mature equivalent 305-day milk production data were recorded. RESULTS: Treated heifers in herd A had a higher overall cure rate, higher cure rates for IMI caused by coagulase-negative staphylococci (CNS) and Staphylococcus aureus, lower SCC, and lower prevalence of chronic IMI, compared with control heifers. Treated heifers in herd B had a higher overall cure rate and cure rate for IMI caused by CNS, compared with control heifers, but postpartum California mastitis test scores and prevalence of chronic IMI did not differ between groups. Mature equivalent 305-day milk production did not differ between herds or treatment groups. No pirlimycin residues were detected in postpartum milk samples. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that prepartum treatment of dairy heifers with pirlimycin may reduce the prevalence of early lactation IMI, particularly IMI caused by CNS, without causing pirlimycin residues in milk.     

Control of heifer mastitis: antimicrobial treatment-an overview

Initial studies in Louisiana, USA to determine the prevalence of mastitis in breeding age dairy heifers demonstrated that intramammary infections (IMIs) were present in 97% of heifers and 75% of quarters. Most common isolates were Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus chromogenes; somatic cell counts (SCCs) ranged from 12.4 to 17.3 x 10(6)ml(-1). Histologic examination of Staph. aureus-infected quarters demonstrated significant reductions in alveolar epithelial and luminal areas, and increases in connective tissue and leukocytosis, illustrating limited secretory development and marked inflammation. A one-time infusion of various nonlactating cow antibiotic preparations into infected quarters during different stages of gestation but >45 days prepartum resulted in cure rates for Staph. aureus IMI of 67-100%. Mean SCC was 50% lower at calving for treated heifers, and milk yield over the first 2 months of lactation was 10% greater than that of untreated controls. Subsequent multiple herd studies, however, revealed that use of nonlactating cow therapy was beneficial only in herds exhibiting a high prevalence of heifer mastitis and not in low prevalence herds. Results of lactating cow antibiotic therapy infused 1-2 weeks prepartum demonstrated cure rates of 59-76% vs. 26-31.7% in untreated controls. In some studies, milk production during the first lactation in treated heifers was approximately 10% higher than untreated controls, and SCC were significantly lower; however, in other studies, prepartum treatment was successful in reducing prevalence of infection but had no effect on SCC or milk yield during the subsequent lactation. Thus, treatment of heifers is advantageous because the cure rate is much higher than during lactation, there is no milk loss, and risk of antibiotic residues minimal; however, successful therapy may not necessarily result in lowered SCC and increased milk production in all herds.     

Pathogen group specific risk factors at herd, heifer and quarter levels for intramammary infections in early lactating dairy heifers

Risk factors for intramammary infections caused by coagulase-negative staphylococci, contagious major pathogens and environmental major pathogens in early lactating heifers were evaluated at the herd, heifer and quarter levels. In total, 764 quarters of 191 dairy heifers in 20 randomly selected farms in Flanders (Belgium) were sampled. Quarter milk samples were collected between 1 and 4 days in milk and between 5 and 8 days in milk for bacteriological culture. Data were analyzed using multivariable, multilevel logistic regression analysis. Higher average herd milk somatic cell count (>200,000 cells/mL), not having an effective fly control strategy, contact with lactating cows prior to calving and moderate to severe udder edema prior to calving increased the odds of intramammary infections caused by contagious major pathogens. Poor heifer hygiene and lack of mineral/vitamin supplementation prior to calving were risk factors for intramammary infection caused by environmental major pathogens. Teat apex colonization with coagulase-negative staphylococci prior to calving seemed to protect quarters against intramammary infections caused by major pathogens. Poor heifer hygiene before calving, a non-clipped udder and not practicing of teat dipping prior to calving increased the odds of intramammary infection with coagulase-negative staphylococci. Although management is important in the prevention and control of intramammary infections in early lactating heifers, most variation in the prevalence of intramammary infections resided at the heifer and quarter levels, indicating that the susceptibility for intramammary infections around calving is mainly determined by heifer and quarter characteristics.     

A review of prevention and control of heifer mastitis via non-antibiotic strategies

Clinical and subclinical mastitis is a significant problem in primiparous dairy cattle (heifers) with a higher prevalence and incidence in heifers than cows, especially early in lactation. Differences in management (e.g. nutrition, pasturing, no use of dry cow therapy) as well as differences in physiological status (e.g. continuing growth in heifers) are likely contribute to the observed differences between heifers and cows. These differences may result in the requirement for different approaches for mastitis management in heifers than for cows. Mastitis is a multifactorial disease, hence control requires an understanding of the risk factors before effective interventions can be defined. Control strategies are aimed at reducing the incidence of new intramammary infections and eliminating existing infections. Potential strategies can include improved environmental and animal hygiene, application of internal and external teat sealants, prepartum application of teat antiseptics, prepartum milking and control of horn fly in environments where it acts as vector. Other less well-proven strategies to control heifer mastitis include management of heifers as a physically separate group from older cows and not feeding mastitic milk to calves. It is concluded that several well-proven strategies are available to manage heifer mastitis. However, further research is likely to improve understanding of heifer mastitis and lead to novel managerial approaches to mastitis control in this age group.     

Coagulase-negative staphylococci-emerging mastitis pathogens

Coagulase-negative staphylococci (CNS) have become the most common bovine mastitis isolate in many countries and could therefore be described as emerging mastitis pathogens. The prevalence of CNS mastitis is higher in primiparous cows than in older cows. CNS are not as pathogenic as the other principal mastitis pathogens and infection mostly remains subclinical. However, CNS can cause persistent infections, which result in increased milk somatic cell count (SCC) and decreased milk quality. CNS infection can damage udder tissue and lead to decreased milk production. Staphylococcus simulans and Staphylococcus chromogenes are currently the predominant CNS species in bovine mastitis. S. chromogenes is the major CNS species affecting nulliparous and primiparous cows whereas S. simulans has been isolated more frequently from older cows. Multiparous cows generally become infected with CNS during later lactation whereas primiparous cows develop infection before or shortly after calving. CNS mastitis is not a therapeutic problem as cure rates after antimicrobial treatment are usually high. Based on current knowledge, it is difficult to determine whether CNS species behave as contagious or environmental pathogens. Control measures against contagious mastitis pathogens, such as post-milking teat disinfection, reduce CNS infections in the herd. Phenotypic methods for identification of CNS are not sufficiently reliable, and molecular methods may soon replace them. Knowledge of the CNS species involved in bovine mastitis is limited. The dairy industry would benefit from more research on the epidemiology of CNS mastitis and more reliable methods for species identification.     

Resistance mechanisms of the bovine udder: new implications for mastitis control at the teat end

Investigations on bovine teat-end defenses and their role in mastitis control were reviewed. Alteration of teat canal keratin by method of intramammary drug infusion through the teat canal influenced the number of new infections. At the beginning of the nonlactating period, 2 methods of administering antibiotic were studied: full insertion of treatment syringe cannulas into teat cisterns and expelling contents and partial insertion of cannulas into the distal 2 to 3 mm of teat canals and slowly infusing contents. Partial cannula insertion reduced new infections by 50% and is an easily adopted management tool to reduce prevalence of mastitis. Intramammary devices used during lactation and the nonlactating period increased leukocyte concentrations in mammary secretions. An abraded polyethylene coil device reduced clinical mastitis and increased milk yield. Staphylococci colonize teat canal keratin and lacteal secretions of dairy heifers as early as 9 months of age, leading to intramammary infection at time of calving and persisting into lactation. Subsequent somatic cell counts are associated with milk production losses. Previously, such infections were shown to be associated only with older, mature animals.     

Short- and longterm results after surgical treatment of teat stenosis in the region of Fürstenberg's rosette using theloresectoscopy: 15 cases (1999-2000)]

Teat obstructions cause considerable financial loss in dairy industry. Recently, progress in teat surgery was made by the use of minimal invasive surgical instrumentation. The technique of theloresectoscopy as well as short- and long-term results of this surgical intervention are presented in this study. The clinical reports of 15 dairy cows with distal teat obstructions operated with the theloresectoscope between May 1999 and January 2000 at the clinic for ruminants, Department of clinical veterinary medicine, University of Berne were reviewed. Data collected by telephone conversation with the owners included: somatic cell count and milk flow at machine milking during the lactation of surgery (lactation 1), as well as during the lactation following surgery (lactation 2). Eighty-seven percent of the owners reported normal milk flow during lactation 1 and 93% during lactation 2. Considering the fact that only 46.7% of the cows showed negative results in the California mastitis test (CMT) during lactation 1, many owners reported a high somatic cell count being a disadvantage of this surgical technique. Normal (negative) CMT results during lactation 2, however, were reported by 80% of the owners. Isolation of Staphylococcus aureus explained the high somatic cell count in 2 of 15 cases. In conclusion, theloresectoscopy is a valuable minimal invasive surgical technique that can be fully recommended for treatment of distal teat obstructions in dairy cows.     

Effect of precalving intramammary treatment with pirlimycin in nulliparous Holstein heifers

A clinical trial was conducted to determine whether prepartum intramammary pirlimycin reduces the proportion of nulliparous heifers with intramammary infection (IMI) during early lactation and improves milk production. Quarter milk samples were collected from 428 heifers, systematically allocated to treatment and control groups, 6 to 12 d before the expected calving date and 2 to 8 d after calving. At the prepartum visit, heifers in the treatment group (n = 219) received an infusion of pirlimycin hydrochloride in all 4 quarters; the control heifers (n = 209) received no infusions. Intramammary infection was detected in 69% of the heifers and 33% of the quarters before calving. After calving, the proportion of treated heifers with IMI was significantly lower than the proportion of control heifers (31% versus 45%). Staphylococcus aureus was isolated from 10% of the heifers and 3% of the quarters before calving. After calving, the proportion of IMIs due to S. aureus was significantly lower in the treated heifers than in the control heifers (5.6% versus 10%). Antibiotic treatment increased the percentage of cures and prevented new IMIs caused by gram-positive bacteria after calving. The incidence of new IMIs caused by gram-negative bacteria and yeast was higher among treated heifers than among control heifers. There was no overall effect of treatment on milk production, but there was a significant interaction effect of treatment and the interval between treatment and calving. An increase of 302 kg of milk was observed when antibiotic treatment was applied more than 1 wk before calving. Treatment did not affect the milk somatic cell count on the 1st 3 test days after calving.     

Coagulase-negative staphylococci and mammary gland infections in cows

Coagulase-negative staphylococci (CNS) are the most frequently isolated bacteria from bovine mammary gland milk samples. The objective of this study was to determine the type of inflammation evoked by CNS in the mammary gland of cows during their first lactation. Twenty-four Israeli-Holstein heifers in their first lactation were tested for bacteriological status, somatic cell count (SCC) and differential leucocyte count in milk 60-120 days postparturition and every 50-60 days after until drying off. Following the first testing, the 96 quarters of the 24 heifers were classified as follows: 69.8% as no bacterial growth (NBG), 27.1% infected with CNS and 3.1% infected with Staphylococcus aureus. During lactation, 84.5% quarters had no change in their classification, 6.2% were newly infected with other pathogens, 3.1% were classified as self-cured and in 6.2% sporadic bacteria were isolated. Among the CNS, S. intermedius, S. chromogenes and S. haemolyticus were the most frequently isolated. Milk from CNS-infected quarters had significantly higher SCC than milk from NBG quarters. An analysis of the leucocyte pattern in milk from CNS vs. NBG quarters revealed a significant increase in polymorphonuclears and a significant decrease in the percentage of total lymphocytes and lymphocytes bearing CD4+ or CD8+. The high percentage of CNS-infected quarters that remained unchanged in their bacterial status during the first lactation, indicates that those CNS have the ability to elude the immune system and persist in the mammary gland for a long time. The persisting infection, resulting to some extent from an increase of SCC by some CNS strains, suggests that in the near future control steps will have to be taken into consideration, in order to enhance the improvement of milk quality.     

Prevalence of staphylococcal species in four dairy herds

The prevalence of staphylococcal species isolated from bovine mammary glands was determined in four dairy herds. Staphylococcus aureus and S hyicus were the predominant organisms isolated from cows in a herd with a bulk milk somatic cell count (SCC) greater than 900 X 10(3). One herd with a bulk milk SCC of 565 X 10(3) had a high incidence of S aureus while the predominant coagulase-negative species were S epidermidis and S hyicus. S hyicus predominated in two herds with bulk milk SCC less than 200 X 10(3); prevalence of S aureus was low. The impact of herd management practices such as post-milking teat antisepsis on distribution of staphylococcal species is discussed.     

The prevalence of mastitis in primiparous heifers in eleven Waikato dairy herds

The objective of the study was to determine the prevalence of mastitis among primiparous heifers at calving and at drying off in 11 Waikato dairy herds during the 1993-94 dairy production season. Duplicate quarter milk samples were collected aseptically from 458 heifers within 5 days after calving for bacteriological analysis. Mastitis was diagnosed in at least one quarter in 35.6% of these heifers. Coagulase-negative staphylococci were isolated from 21.8% of the heifers. The prevalence of coagulase-negative staphylococci varied between herds from 4.3% to 44.8%. Environmental streptococci caused mastitis in 12.2% of heifers, ranging from 5.6% to 24.1% between herds. Streptococcus uberus was the pathogen identified most frequently at calving and accounted for more than 90% of the streptococcal isolates. Staphylococcus aureus and coliforms were isolated from less than 1% of samples. Clinical mastitis was observed in 8.1% of heifers at calving; environmental streptococci were isolated from 67.6% of these clinical clinical cases. Only 2.8% of heifers developed clinical mastitis during lactation and environmental streptococci were isolated from 38.5% of these cases. The prevalence of mastitis among 428 of the heifers at drying off was 64.7%; a 1.8 fold increase during lactation. Corynebactetium bovis was isolated from 43% of heifers at drying off even though it was not isolated from any heifers at calving. During the season, the prevalence of Staphylococcus aureus mastitis increased to 2.8% while mastitis caused by environmental streptococci declined to 2.8%. The prevalence of environmental mastitis pathogens decreased during lactation while contagious pathogens increased in each of the 11 herds. Ineffective post-milking teat sanitation probably contributed to the increase in mastitis caused by contagious pathogens. Specific factors were not determined that affected the variation in prevalence between herds.     

Dynamics of Staphylococcus aureus infections during vaccination with an autogenous bacterin in dairy cattle

The effect of an autogenous vaccine against Staphylococcus aureus on S. aureus prevalence and mastitis, as well as on somatic cell count (SCC), was studied in a dairy herd with a high prevalence of S. aureus. The vaccination group (n = 35; 22 cows and 13 heifers) and the control group (n = 36; 23 cows and 13 heifers) received the vaccine or a placebo, respectively, according to the following protocol: all animals: basic immunization (twice, 3 weeks apart); cows: booster dose at the time of drying off, 5 and 2 weeks before calculated calving date; heifers: booster dose 2 and 5 weeks before calculated calving date. The vaccine or the placebo was administered subcutaneously in the area of the supramammary lymph nodes. Quarter milk samples were collected monthly and subjected to SCC and bacteriological evaluation. At this time, the animals were also checked for signs of clinical mastitis. Non-clinical S. aureus mastitis diagnoses were based on udder quarter SCC and a positive S. aureus culture. In order to compare the SCC in individual whole milk samples, records from the monthly milk quality testing were evaluated. Cow and udder quarter prevalence of S. aureus intramammary infections calculated for the experimental animals and quarters, respectively, did not differ between groups. However, during the lactation period following the boostcr dose, the prevalence of S. aureus increased in both groups (P < 0.05). The cumulative incidence of various mastitis diagnoses (clinical, subclinical, latent infection) due to S. aureus on an animal basis did not differ between groups. On an udder quarter basis, the cumulative incidence of subclinical mastitis was higher in vaccinated animals than in control animals (33.8 versus 26.0%; P < 0.05). This was mainly due to a higher cumulative incidence of subclinical mastitis in vaccinated than control heifers. The SCC in composite milk samples did not differ between groups, but increased as lactation progressed. The herd prevalence of S. aureus differed considerably throughout the study period, but declined consistently to below 10% at the end of the study period. Recent herd checks revealed a prevalence of S aureus infections of < 5%. It is concluded that the autogenous bacterin tested in this study did not have the desired effect on the prevalence of S. aureus infections and mastitis or SCC. The decline in S. aureus prevalence was very probably due to other factors than specific immunization against S. aureus.     

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.     

Bacteriological survey of mammary secretions from prepartum heifers in a dairy herd with a high prevalence of Staphylococcus aureus infection

This study was performed to examine the bacteriological findings in 58 mammary secretions from 15 heifers at 4-5 weeks before parturition, and to evaluate whether a high prevalence of S. aureus infection in lactating cows affects the occurrence of S. aureus infection in prepartum heifers in the dairy herd. A total of 86.7%(13/15) of the heifers and 60.3%(35/58) of quarter milk samples from the heifers were bacteriologically positive. No S. aureus isolate was detected in mammary secretions from the heifers. Coagulase-negative staphylococcus (CNS) species were predominantly detected in 54.3%(19/35) and Streptococci other than Streptococcus agalactiae were isolated from 22.9%(8/35) of the quarters. A high S. aureus prevalence in the herd may not necessarily be a decisive factor for S. aureus infection in heifers.     

Observations on intramammary infections in first calf heifers in early lactation

Intramammary infections and mastitis were monitored on four occasions at three-week intervals in 61 first calf heifers in five dairy herds during the first ten weeks of lactation. Of 940 quarter milk samples examined 65% were classed as negative, 10.4% as positive for mastitis (mainly subclinical), 1.8% as group 3 (infection present but no elevation in somatic cell count) and 22.8% as group 4 (elevated somatic cell count). Seventy-seven percent of the infections detected and identified were those due to coagulase-negative staphylococci, the main species being S. hyicus, S. epidermidis, S. simulans and S. hominis. Other infections detected with Corynebacterium pyogenes (three samples), Escherichia coli (one sample), Micrococcus spp. (one sample), S. aureus (two samples) and Streptococci (non-agalactiae) (seven samples).The geometric mean somatic cell count for 23 quarters infected with coagulase-negative staphylococci was 311 x 10(3) cells / mL compared to 134 x 10(3) cells / mL in noninfected adjacent contralateral quarters. The respective figures for% cell volume in Channel 8 (mainly neutrophils) were 10.6% and 3.5%. There was a highly significant association between herd and the proportion of quarter milk samples in the four mastitis categories.     

Raised herd somatic cell count due to Staphylococcus aureus following the failure of an automatic teat spraying system

This study describes the failure of a single jet exit race automatic teat spray (ATS) system resulting in the spread of Staphylococcus aureus infection in a 135-cow dairy herd, which showed an increased herd somatic cell count from 91,000/ml to 554,000/ml over a nine-month period. S aureus was isolated from 34 of 46 high cell count cows. The milking procedures were modified and manual teat spraying was restarted. Bacteriology was used to identify S aureus positive high cell count cows, and first and second lactation cows were treated during lactation. If their cell counts were not reduced, these were then culled. High cell count S aureus cows in lactation three or above were culled. The three-month geometric mean cell count fell to below 150,000/ml within five months. As all replacements were home-bred, S aureus infection must have spread from within the herd itself. All other causes have been eliminated, and this spread is attributed to the failure of the ATS to carry out effective postmilking teat disinfection. The advantages and disadvantages of ATS systems are discussed, especially in relation to robotic or voluntary milking systems.     

Prevalence of clinical mastitis in 38 Waikato dairy herds in early lactation

AIM: To determine the prevalence of clinical mastitis in spring-calving dairy herds in the Waikato Region of New Zealand and to identify factors associated with variation in the prevalence of clinical mastitis between herds. METHOD: A total of 799 quarters from 595 dairy cows from 38 dairy herds were diagnosed by herd owners as having clinical mastitis between 8 July and 21 August 1997. Quarters diagnosed with clinical mastitis were sampled for bacterial culture and somatic cell count, and the presence of clots in the milk and the presence of udder oedema were assessed by a technician or veterinarian. RESULTS: Clinical mastitis was diagnosed in an average (+/-s.e.m.) of 9.9% (+/-0.8%, range 0.9-21.4%) of calved cows within the herds. Bacteria were not cultured from an average of 12.4 % (+/- 2.0%, range 0.0-45.5%) of cows and 22.3% (+/- 2.4%, range 0.0-54.0%) of quarters diagnosed as having clinical mastitis. There were significant differences between herds in the proportion of cows diagnosed with mastitis and in the proportion of clinical mastitis cases from which bacteria were not cultured. A decreased prevalence of clinical mastitis (p<0.001) was associated with an increased percentage of the herd treated with dry cow antibiotics. An increased prevalence of clinical mastitis (p<0.0001) was associated with both an increased percentage of cows treated in the previous season with lactating cow antibiotics and an increased percentage of heifers in the herd. Herds that were fed supplements before or during lactation had a higher prevalence of clinical mastitis than herds that were not fed supplements (p<0.001). An increased proportion of quarters diagnosed with clinical mastitis that did not culture bacteria was associated with an increased prevalence of clinical mastitis (p<0.001). The proportion of quarters that the technician or veterinarian found with evidence of clinical mastitis (i.e. a somatic cell count >500,000 cells/ml and the presence of either clots or udder oedema) within a herd was inversely related to the proportion of quarters within a herd from which no bacteria were isolated. CONCLUSION: There was a large variation in the prevalence of clinical mastitis and in the proportion of clinical quarters from which no bacteria were grown between herds. Management factors such as the use of dry cow therapy, feeding regimes and heifer replacement rates all affected the prevalence of clinical mastitis. Herd owners appear to differ in the sensitivity and specificity of their diagnosis of clinical mastitis, with bacteria not isolated from up to 50% of quarters diagnosed with clinical mastitis in some herds. Improvements in the specificity of herd owner diagnosis of clinical mastitis may reduce the use of antibiotics for mastitis during lactation and hence may reduce the risk of antibiotic contamination of milk supplied for human consumption.     

Prevalence and herd-level risk factors for intramammary infection with coagulase-negative staphylococci in Dutch dairy herds

In this study, the prevalence of intramammary infection (IMI) with coagulase-negative staphylococci (CNS) in The Netherlands was estimated on 49 randomly selected herds with at least 40 lactating cows. In total, 4220 quarter milk samples were collected. The prevalence of CNS IMI in The Netherlands was estimated at 10.8% at quarter level and 34.4% at cow level, making it the most frequently isolated group of pathogens. Fourteen species of CNS were identified; the most frequently isolated species was Staphylococcus chromogenes (30.3%) followed by Staphylococcus epidermidis (12.9%) and Staphylococcus capitis (11.0%). Prevalence of CNS IMI was higher in heifers compared to older cows. Geometric mean quarter SCC of CNS-positive quarters was 109,000 cells/ml, which was approximately twice as high as culture-negative quarters. Quarters infected with S. chromogenes, S. capitis and Staphylococcus xylosus had a higher SCC (P<0.05) than culture-negative quarters, while quarters that were culture-positive for S. epidermidis and Staphylococcus hyicus tended to have a higher SCC than culture-negative quarters. An increased prevalence of CNS IMI was associated with the herd-level variables source of drinking water not being tap water, housing of dry cows in one group instead of multiple groups, measurement of cow SCC every month, udder health monitoring by the veterinarian, pasturing during outdoor season, percentage of stalls contaminated with milk, and BMSCC>250,000 cells/ml. Although a causal relation between these factors and prevalence of CNS is not proven and for some factors not even likely, knowledge of the associations found may be helpful when approaching CNS problems on dairy farms.     

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

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