The economic impact of mastitis-control procedures used in Scottish dairy herds with high bulk-tank somatic-cell counts.

We used multiple-regression analysis of field data to quantify the marginal impacts of various mastitis-control procedures on bulk-tank somatic-cell count (BTSCC). Estimates of milk-yield depression and the probability of herds paying a BTSCC penalty due to the presence of subclinical mastitis were made. An assessment of the economic efficiency of mastitis control by high BTSCC producers was also made using a loss-expenditure frontier. Significant interactions were detected between premilking udder-preparation methods (UP) and post-milking teat disinfection (PMTD), and also between the milking system of the herds and both the use of dry-cow therapy (DCT) and a regular milking-machine test (MMT). Udder preparation involving washing was associated with a higher SCC and had a detrimental effect on the efficacy of PMTD. Amongst herds facing a high-BTSCC problem (BTSCC >400,000 cells/ml), herds using PMTD without UP (regardless of the type of milking system), those using DCT (in parlour systems), and those with a parlour system having their milking machines tested obtained returns of Pound Sterling 1.4, Pound Sterling 3.9 and Pound Sterling 1.1, respectively, per Pound Sterling 1 investment in each of these procedures as a result of reductions in milk-yield losses and BTSCC penalties. The minimum total cost of disease within these herds was Pound Sterling 65.50/cow/year (due to Pound Sterling 41.40 revenue losses plus Pound Sterling 24.10 mastitis-control expenditure) attained by herds which had a parlour system and used DCT, MMT and PMTD (without UP). However, the average cost of subclinical mastitis for all high-BTSCC farms was Pound Sterling 100/cow/yr; hence, the difference (pound Sterling 34.50) could be saved by the more-efficient application of mastitis-control procedures.     

Association of herd productivity and bulk-tank somatic cell counts in US dairy herds in 1996

OBJECTIVE: To assess the association of bulk-tank somatic cell counts (BTSCC) and the value of herd productivity (milk produced, calves born, and net costs for cow replacements) in US dairy herds in 1996. DESIGN: Randomized stratified national survey of dairy producers. SAMPLE POPULATION: Records from 1,219 dairy herds in the top 20 dairy states. PROCEDURE: Responses for 1,178 herds had complete information for economic analysis. Per-cow value of production was determined for each herd. Data for herds with high (> or = 400,000 cells/ml) and medium (200,000 to 399,999 cells/ml) BTSCC were compared with values for herds with low BTSCC (< 200,000 cells/ml), using a multivariable regression model. RESULTS: In 1996, milk was priced at $0.287/kg ($13/cwt). Herds with low BTSCC annually generated $103.90/cow more in herd productivity than herds with medium BTSCC and $292.39/cow more than herds with high BTSCC. CONCLUSIONS AND CLINICAL RELEVANCE: Increased BTSCC (> 200,000 cells/ml) were associated with a reduced value of productivity per cow. Thus, dairy producers have a financial incentive to seek out and implement cost-effective management practices that will enable them to decrease their BTSCC to < 200,000 cells/ml and maximize herd productivity.     

Mycoplasma mastitis in dairy cattle

The most important characteristics of Mycoplasma mastitis on dairy farms are described, based on two case studies. Clinical symptoms, diagnostics, epidemiology, and a plan of action are presented. In the herds investigated, Mycoplasma mastitis was characterized by multiple affected quarters unresponsive to treatment with antibiotic and/or anti-inflammatory agents. Most striking were a sandy sediment, brown colouring, and rice-like structure of the milk of affected animals. Clinical symptoms differed in the two affected herds. Diagnosis was based on bacteriological investigation of samples of milk and synovial fluid taken from infected cows. Affected animals were culled immediately, and the herds were monitored by repeated testing of bulk milk samples. It was concluded that a consequence of the increasing size of cattle herds in the Netherlands is that subclinical/clinical Mycoplasma mastitis may be diagnosed more frequently than in the past. In the case of Mycoplasma mastitis, farmers and veterinary practitioners are advised to draw up a plan of action together, incorporating aspects such as diagnostics at cow level, direct culling of affected animals, hygiene during milking, including post-milking teat disinfection, and routine monitoring of bulk milk. Unpasteurized milk should not be given to calves.     

Management factors associated with the incidence of clinical mastitis over the non-lactation period and bulk tank somatic cell count during the subsequent lactation

Aim: To evaluate associations between management decisions related to the control of mastitis, including the infusion of antibiotics at the end of lactation (dry-cow therapy; DCT), on the incidence of clinical mastitis over the non-lactating period and the bulk tank somatic cell count (BTSCC) in the subsequent lactation. Methods: Dairy herd owners (n=158) provided information via a retrospective survey about (a) the proportion of their herds treated with DCT; (b) DCT management, including: number of occasions on which cows were dried off; manipulation of feed and water intake around drying off; infusion technique (partial vs full depth insertion of cannula); and hygiene before and after DCT infusion; (c) occurrence of mastitis and frequency of occurrence following drying off and in the subsequent lactation; (d) number of cows culled for mastitis-related conditions; (e) reasons for culling; (f) incidence of clinical mastitis; and (g) stock purchase policy with regard to mastitis. The BTSCC for each vat of milk supplied for the 1999/2000 and 2000/2001 seasons, and records of antibiotic purchases were collated for each herd. The probability that >2% of cows within a herd were diagnosed with clinical mastitis over the dry period was initially examined using univariate analysis (i.e. chi2 or logistic regression) and associated factors (p<0.2) were offered to a reverse stepwise logistic regression model. Factors hypothesised as being associated with the average lactation log10 BTSCC for the 2000/2001 season were initially examined using univariate analysis (i.e. ANOVA or linear regression analysis) and associated factors (p<0.2) were then tested using a forward manual model-building approach. Results: Increasing the percentage of the herd treated with DCT at the end of lactation was associated with reduced probability that >2% of a herd would be diagnosed with clinical mastitis over the non-lactating period and with a lower BTSCC in the subsequent lactation (p<0.01). A lower BTSCC was associated with small herds (<150 cows; p<0.05), not reducing feed intake around drying off (p<0.05), checking for clinical mastitis over the dry period in the milking parlour rather than at pasture (p<0.05), partial insertion of the DCT cannula (p<0.01), and use of 'change in udder shape' during lactation as a diagnostic criterion for mastitis (p<0.05). The incidence of clinical mastitis over the dry period was positively associated with reduced feeding around drying off (p=0.05) and the estimated volume of milk being produced at the time of drying off (p=0.014). Conclusions: Use of dry cow therapy was associated with fewer cases of clinical mastitis over the non-lactating period and reduced BTSCC over the subsequent lactation. Reduced BTSCC was also associated with smaller herds, use of partial (compared with full depth) insertion of the DCT cannula, not reducing feed intake at the time of drying off, checking for clinical mastitis over the dry (non-lactation) period in the milking parlour, and use of udder shape for diagnosis during lactation. Control of clinical mastitis and BTSCC involves a range of management practices that need to be used in conjunction with DCT. Keywords: Dairy cows, mastitis, dry-cow therapy, somatic cell count, management practices.     

National intervention study of mastitis control in dairy herds in England and Wales

An intervention study was carried out on 52 dairy farms in England and Wales to determine whether the implementation of a well-specified mastitis control plan in herds with an incidence of clinical mastitis of more than 35 cases per 100 cows per year would reduce the incidence of clinical mastitis, and also reduce the incidence of increases in the somatic cell counts of individual cows. A clearly defined plan for the diagnosis and control of mastitis was developed by two veterinary specialists from the research literature. The herds were randomly allocated to receive the plan either at the start of the study (intervention herds) or after one year (control herds). Data on mastitis management and the farm environment were collected during farm visits. After one year there was a significant 22 per cent reduction in the proportion of cows affected with clinical mastitis on the intervention farms compared with the control farms. There were also significant reductions of approximately 20 per cent in the incidence of clinical mastitis and in the occurrence of increases in the somatic cell counts of individual cows from below, to above 200,000 cells/ml.     

Progress in controlling mastitis in England and Wales

Mastitis in England and Wales has been controlled over the past 20 years while the average size of dairy herds has doubled to 65 cows. The incidence of clinical mastitis has been reduced from approximately 120 to 150 cases per 100 cows to less than 50 cases. The limited data on the prevalence of subclinical mastitis indicate that it has been reduced from over 50 per cent of cows infected to less than half this level. The application of the major mastitis control measures on the farm has doubled over the period 1973 to 1983 and had reached 66 to 90 per cent for individual measures by 1983. The national mean cell count in milk has been reduced from 573,000 to 352,000 cells/ml between 1971 and 1986, and the proportion of herds having annual mean cell counts below 300,000 cells/ml has increased from 15.7 per cent to 40.7 per cent in the last eight years.     

Causative organisms and somatic cell counts in subclinical intramammary infections in milking goats in the UK

The bacterial causes of subclinical mastitis were determined in samples of milk taken from one half of the udders of 159 goats in three different herds. The mean prevalence of subclinical infection was 33 percent, with prevalences of 26 percent, 39 percent and 42 percent in the three herds. Staphylococcus aureus was isolated from seven (13 percent) of the 53 infected halves, coagulase-negative staphylococci accounted for 47 percent, Corynebacterium species for 31 percent and alpha-haemolytic streptococci for 6 percent of the infected samples. The mean somatic cell count of the uninfected milk samples was 428,000 cells/ml, and 93 percent of uninfected samples had counts less than 1,000,000 cells/ml; the mean cell count of the infected samples was 2,785,000 cells/ml.     

A large scale mastitis control programme in Somerset.

The results of a mastitis control programme operated in south west England for three years are given. Farmers participating in the full mastitis control group agreed to treat each cow at drying off with 500 mg benzathine cloxacillin in each quarter, to have their milking machines tested and to correct any faults, and to practise teat dipping. Data covering cell counts, milk production, milk quality and clinical mastitis, were assessed from herds taking part in the programme. Cell counts were analysed from all 507 herds taking part in the programme. Milk production records for the full mastitis control group (188 herds) over a three year period are discussed, and these results compared with milk production figures from Milk Marketing Board records from herds in the south west of England which were carrying out no specific mastitis control programme. The milk quality data compare the findings in 159 herds in the full mastitis control programme with those in 247 herds in the partial and no mastitis control groups. Cases of clinical mastitis during the three year period were recorded in 73 herds in the full mastitis control group. The problems of applying the control routines are presented with observations on clinical mastitis, bulk milk cell count, milk production and milk quality. After three years, herds in the programme had on average increased milk production by 75 gallons a cow, achieved a 14.6 per cent reduction in the incidence of clinical mastitis, and improved the milk total solids percentage by one milk quality payment class.     

A HACCP-based approach to mastitis control in dairy herds. Part 1: Development

Hazard Analysis and Critical Control Points (HACCP) systems are a risk based preventive approach developed to increase levels of food safety assurance. This is part 1 of a pilot study on the development, implementation and evaluation of a HACCP-based approach for the control of good udder health in dairy cows. The paper describes the use of a novel approach based on a deconstruction of the infectious process in mastitis to identify Critical Control Points (CCPs) and develop a HACCP-based system to prevent and control mastitis in dairy herds. The approach involved the creation of an Infectious Process Flow Diagram, which was then cross-referenced to two production process flow diagrams of the milking process and cow management cycle. The HACCP plan developed, may be suitable for customisation and implementation on dairy farms. This is a logical, systematic approach to the development of a mastitis control programme that could be used as a template for the development of control programmes for other infectious diseases in the dairy herd.     

Epidemiological analyses of the associations between bovine udder health and housing

Data from a mastitis control programme involving 158 herds in northern Norway are presented. The association between housing factors and indoor climate variables, and the prevalence of subclinical mastitis and herd cell count was calculated from a least squares model by a backward elimination procedure. Ten to 23% of the herd udder health variation at the start of the programme was associated with environmental variables. The following variables were found to be of significance: herd size, hoof trimming, lactation age, stall floor surface, type of stall, stall width, stall length, presence or absence of a grating over dung channel, single-/double-glazed windows and ambient humidity.     

Studies on the incidence of clinical mastitis and blood levels of vitamin E and selenium in dairy herds in England

In a trial conducted in the south of England in January to February 1989, blood samples were obtained from nine dairy herds with more than 30 cases of clinical mastitis/100 cows and from nine herds with less than 30 cases/100 cows during the previous 12 months. Whole blood glutathione peroxidase (GSHPx) activity and plasma vitamin E concentration were determined for 12 cows in each herd. The mean (+/-sd) values for the herds with the lower incidence of mastitis were 7.57 +/- 1.86 micrograms/ml plasma vitamin E and 23.8 +/- 22.8 U/ml rbc GSHPx activity, compared with 7.74 +/- 1.69 micrograms/ml plasma vitamin E and 20.61 +/- 8.8 U/ml rbc GSHPx activity for the herds with the higher incidence of the disease. These values indicate that the vitamin E levels were generally adequate but that some animals and herds had low GSHPx activities, suggesting that their diets may have contained inadequate selenium. The activities of GSHPx and the vitamin E levels in plasma were not significantly different in the two groups of herds, and no relationship was found between the two nutrients and the incidence of clinical mastitis. However, there was a significant negative correlation between the activity of GSHPx and the bulk milk cell counts in the herds with a low incidence of mastitis suggesting that there was an association between the incidence of subclinical mastitis or inflammation and the selenium status of these herds.     

The epidemiology of Staphylococcus aureus infections from subclinical mastitis in dairy cows during a control programme

The objective was to investigate the spread of S. aureus in seven dairy herds. Milk samples were taken to determine mastitis pathogens and somatic cell count. An approved hygiene programme was established to control the spread of S. aureus from quarter to quarter. S. aureus isolates were differentiated by geno- and phenotyping to trace their spread within a herd.In two herds S. aureus showed a high prevalence, but were eliminated from the herds by the control programme. In these herds and a third herd typing results identified a particular type that was found much more frequently than all other types. The frequent types were repeatedly detectable during the study. In three other herds with a lower S. aureus prevalence and also in one herd with a long history of S. aureus and high prevalence subclinical mastitis was caused by several distinguishable S. aureus types. These types occurred simultaneously in the particular herd and showed little or no tendency to spread from quarter to quarter. They seemed to circumvent the control procedures resulting in a relatively high rate of new infected animals and therefore were hardly eliminated. The typing results and the clinical observations indicated that strains differed in their tendency to spread and their ability to infect udder quarters. In three herds typing methods identified a predominant type with the common epidemiological features of a contagious mastitis pathogen, while in the other herds the S. aureus type patterns were similar to that of environmental pathogens.     

THE NEW SOUTH WALES MASTITIS CONTROL PROGRAM

SUMMARY A mastitis control program based on teat dipping and dry cow therapy was evaluated in 35 herds over a 3 year period. The incidence of subclinical mastitis as detected by the Rapid Mastitis Test (RMT) fell from 34% to 12% quarters positive, a reduction of 65%. Clinical mastitis was reduced from 37 clinical cases per 100 cows in the first 3 month period to 12 clinical cases per 100 cows in the last 3 month period, a reduction of 68%. Variations in response to the program in the reduction of subclinical and clinical mastitis are discussed and the results compared with similar trials conducted overseas. The Modified Whiteside Test was used on bulk milk samples from the control herds and these results were significantly correlated with the prevalence of subclinical mastitis assessed by RMT individual quarters.     

Risk Indicators Associated with Subclinical Mastitis in Smallholder Dairy Cows in Tanzania

Smallholder dairy farmers in Tanzania appear to be unaware of the subclinical mastitis situation in their cows. A cross-sectional study was carried out between June and September 2002 on smallholder dairy herds in the Dar es Salaam region. The study objectives were to establish the prevalence of subclinical mastitis and related risk indicators, and to assess their contribution to the occurrence of subclinical mastitis. Three field procedures based on the principles of herd health and production management were followed: clinical, farm and data inspection. The California mastitis test (CMT) was carried out on quarter milk samples to determine the prevalence of subclinical mastitis. A total of 182 lactating cows from 62 herds were investigated. Clinical inspection indicated that 3.8% of the lactating cows had clinical mastitis. Subclinical mastitis was detected in 90.3% of lactating cows screened. Farm inspection revealed that water scarcity, barn size, residual suckling, single udder-towel and dairy labourers as the most substantial (p < 0.05) risk indicators. Although most of the risk indicators studied were not found to be statistically significantly associated with the occurrence of subclinical mastitis, possibly owing to sample size and the presence of confounders, the epidemiological need to address such risk indicators cannot be overemphasized.     

The potential use of cell count linear scores in veterinary herd health and production control on dairy farms. A preliminary report

Subclinical mastitis is a major problem in udder health control. Reduction of this infection is hard to achieve because subclinical mastitis is not obvious to the farmer. This study examined the value to the farmer of regularly supplying somatic cell counts from individual cows for the control of subclinical mastitis. The use of linear scores, i.e. logarithmic transformations of cell counts, appeared to be appropriate when combined with other relevant information on udder health and included in a herd health computer programme.     

An outbreak of Streptococcus canis mastitis in a dairy herd in Israel

CASE HISTORY: An increase in the bulk somatic cell count (BSCC) of up to 1,000 x 103 cells/ml occurred in a dairy herd in Israel at the end of 2001 and beginning of 2002. CLINICAL FINDINGS: Bacteriological examination of milk from 69 cows revealed a high prevalence of Streptococcus group G bacteria, identified as S. canis, affecting 38% of cows and 20% of all quarters. Isolates were sensitive to cephalothin and moderately sensitive to penicillin G. Infected cows were separated from the herd, treated with intramammary antibiotics, milked last, and strict hygiene practices were introduced to the milking routine. The pathogen was cleared from the herd and BSCC decreased to 250-350 x 103 cells/ml after 6 months. DIAGNOSIS: Streptococcus canis mastitis. CLINICAL RELEVANCE: Streptococcus canis infection may cause subclinical mastitis and high bulk SCC in dairy herds and be resolved by treatment with intramammary antibiotics and the introduction of strict hygiene practices.     

Prevalence of subclinical mastitis and isolated udder pathogens in dairy cows in Southern Vietnam

Dairy production is not traditional in Vietnam. The farmers have little practical knowledge and udder health control is generally lacking. In order to give the farmers appropriate advice, knowledge about the distribution of udder pathogens is crucial. The aim of the study was to investigate the prevalence of sub-clinical mastitis and to identify udder pathogens isolated from smallholder dairy herds in Southern Vietnam. Twenty farms with a herd somatic cell count (SCC) ranging from low (≤400?×?10³?cells/mL) to high (>400?×?10³?cells/mL) were randomly selected. Milk samples were collected from 458 quarters of 115 clinically healthy cows. SCC was analyzed on farm by a portable cell counter. Bacteriological samples were taken using Mastistrip^© cassettes and sent to Sweden for examination. For all herds the mean herd SCC was 632?×?10³/mL milk. The prevalence of subclinical mastitis at quarter SCC basis was 63.2 % and at cow basis 88.6 %. Only 40 % of all cows were bacteriologically negative in all quarters. Streptococcus agalactiae was the most commonly found bacteria species, isolated from 96 of the 458 quarter samples, in 13 of the 20 farms. The results indicate pronounced subclinical mastitis problems among the dairy cows in this region mainly due to infections with S. agalactiae. The high prevalence of this highly contagious pathogen is probably attributable to the generally poor milking hygiene and low awareness of proper measures to prevent occurrence and spread of udder infections. A strict, targeted action program for the herds in this area is required in order to lower the prevalence of subclinical mastitis.     

Indicators of inflammation in the diagnosis of mastitis

Mastitis affects the quality of milk and is a potential health risk for the other cows. In a well managed dairy herd, in addition to clinical mastitis, subclinical mastitis should be efficiently detected. Bacteriological sampling is not feasible as a routine test to identify subclinical mastitis, and indirect tests of mastitis are more suitable for selecting cows with intramammary infections for subsequent bacteriological sampling. Mastitis affects the composition of milk, and the degree of changes depends on the infecting agent and the inflammatory response. Indicators of inflammation in the milk which can be determined using rapid, reliable and easy routine techniques, can be used for the early detection of mastitis. The measuring of the somatic cell count in milk is the standard method, but the analysis technique is problematic for routine use in herds. The most promising parameters for monitoring subclinical mastitis are milk N-acetyl-beta-D-glucosaminidase activity, lactose, and electrical conductivity along with some other indicators such as optical and milk flow measurements, preferably with an inter-quarter evaluation included in the test. Acute phase proteins, haptoglobin and serum amyloid A, are also potential candidates for mastitis monitoring. New mastitis detection systems which can be adapted into on-line use are urgently needed, since dairy units are growing bigger and automatic milking systems are being taken into use.     

Effects of adjuvants on the immune response of staphylococcal alpha toxin and capsular polysaccharide (CPS) in rabbit

This study was performed to isolate a vaccine strain of S. aureus from clinical or subclinical mastitis and to choose the most optimal adjuvant for immune response of alpha toxin and capsular polysaccharide (CPS) of field strain. Of thirty strains of S. aureus isolated from milk of clinical or subclinical mastitis, V112 strain isolated from milk of gangrenous mastitis was used in this vaccine. Twenty one of rabbits were allocated into 5 groups based on adjuvants and immunized twice every 2 weeks for 8 weeks. This vaccine was composed of alpha toxin (10 hemolytic units) and formalinized whole cells (1 x 10(11) cells/ml. Five rabbits received PBS solution as a control group. The highest antibody titers against alpha toxin and CPS were observed in dextran sulfate- and aluminium hydroxide-adjuvant group at 8 weeks after immunization, respectively. These results of the study showed that one adjuvant could not induce strong and long-term immune response of alpha toxin and CPS antigens. Therefore, the use of combined adjuvants in subunit vaccine may be useful and feasible.     

Epidemiological Analyses of the Associations between bovine udder health and milking machine and milking management

This paper presents data from 158 dairy herds in northern Norway. The influence of the milking machine and milking management on the prevalence of subclinical mastitis and herd cell counts was calculated from a least squares model by a backward elimination procedure. It was shown that 16–45% of the herd udder health variation found at the start of the programme could be associated with milking machine and milking management variables. The following variables were found to be of significance: number of clusters in the herd, vaccum, function and vaccum regulator, undulation of pipeline, limping of pulsator, rate of pulsator, type of claw-piece, hygienic/-technical condition of liner, preparation time, air admission during application of teat cups, overmilking and machine-on time.