Diagnosis Of Subclinical Mastitis Research Articles

Relation between electrical conductivity, dielectric constant, somatic cell count and some other milk quality parameters in diagnosis of subclinical mastitis in Murrah buffaloes

The study was conducted to determine the relation between electrical conductivity (EC), dielectric constant (DC), somatic cell count (SCC) and some other milk quality parameters in Murrah Buffaloes and their effectiveness for diagnosis of subclinical (SCM) and clinical mastitis (CM). A total of 536 samples collected from Murrah buffaloes were examined for mastitis. Buffaloes having milk SCC below 2×10 5 per ml were categorised as healthy buffaloes, those with SCC lying in the range 2×10 5 - 5×10 5 per ml were considered to be subclinical and with SCC more than 5×10 5 per ml were placed in clinical mastitis category. The values of milk EC, DC and SCC were significantly (P<0.01) higher in SCM and CM Murrah buffaloes. Milk pH ranged 6.48 to 6.62 in healthy and subclinical cases, whereas, 7.03 in clinical mastitis cases. Milk temperature values varied between 33.15 o C in healthy, 33.48 o C in subclinical cases and 35.77 o C in clinical mastitis cases. There was a significant positive correlation (P <0.01) between EC, DC, pH, SCC and milk temperature. The multiple linear regression equation was developed for the experimental data to determine the relation between the somatic cell counts with milk quality parameters. The equation best described the data with 4.91 % RMS between experimental and predicted values, indicating that this relationship could be used an indicator for diagnosis of subclinical mastitis.

Electrical conductivity of milk and bacteriological findings in cows with subclinical mastitis

Intramammary infections change the composition of milk and increase electrical conductivity of milk and decrease milk electrical resistance. Electrical conductivity has been used to detect mastitis during last four decades. The aim of this research was to examine the reliability of the milk electrical conductivity measuring in detection of subclinical mastitis. The experiment was conducted on a dairy farm of Holstein-Friesian breed. A total of 113 quarter milk samples were examined, 55 samples from cows in first stage of lactation and 58 from cows in third stage of lactation. Electrical conductivity (EC) of milk samples was detected by Hand-held EC meter (Draminski mastitis detector). Quarter milk samples for bacteriological analysis were taken aseptically during the morning milking in sterile test tubes. Bacteria growth was not detected in 60 quarter milk samples (53.1%), while in the other 53 samples bacteria was found (46.9%). The most common isolated bacteria in first and third stage of lactation was Corynebacterium spp. (38.9%) and coagulase - negative staphylococci (3.54%). High quality and healthy milk with Draminski mastitis detector was observed in 59.29% of the samples (67/113). Cows with mastitis may not always show an increased EC of milk from the infected quarter. Electrical conductivity of milk can give useful informations about udder health status, but hand-held EC meters, such as Draminski mastitis detector, cannot be used alone in diagnosis of subclinical mastitis.

Different screening tests and milk somatic cell count for the prevalence of subclinical bovine mastitis in Bangladesh.

Identification of cows with subclinical mastitis (SCM) is an important tool for sustainable dairying and implementing effective mastitis control strategies. A total of 892 quarters milk samples from 228 lactating cows were screened by California mastitis test (CMT), White side test (WST), Surf field mastitis test (SFMT), and somatic cell count (SCC) to study the prevalence of bovine SCM in some selected areas of Bangladesh. Out of 228 cows, 148 (64.9%), 138 (60.5%), 132 (57.9%), and 164 (71.9%) were found positive for SCM by CMT, WST, SFMT, and SCC, respectively. The prevalence of bovine SCM was diagnosed 45.7, 40.2, 36.6, and 29.6% in Chittagong, Sirajgonj, Mymensingh, and Gazipur districts, respectively, based on a combination of all tests. The overall quarter-wise prevalence of SCM was 45.7, 43.5, 41.2, and 55.0% for CMT, WST, SFMT, and SCC. Single quarters and left front quarters were more prone to SCM (P < 0.05). Friesian crossbred cows (56.4%), BCS 2.0-2.5 (55.4%), and parity 4-6 (52.4%), the late lactation stage (5-8 months; 64.7%) and high yielding cows (16-20 L/day; 65.3%) were more susceptible to SCM (P < 0.05). The sensitivity of the CMT, WST, SFMT, and SCC was 65.8, 57.9, 51.0, and 82.5%; specificity 76.2, 72.4, 69.5, and 89.4%; percentage accuracy 70.0, 64.8, 59.9, and 85.2%; positive predictive value 75.2, 69.8, 64.9, and 92.7%, respectively. The categories of CMT reactions were strongly correlated with SCC (P < 0.05). Kappa value of SCC was higher than that of other tests (SCC>CMT>WST>SFMT). Thus, CMT was concluded to be the most accurate (r = 0.782) field diagnostic test after laboratory test like SCC (r = 0.924). However, the use of any single test may not be reliable in diagnosing SCM, while the result of CMT supported by SCC might be used effectively to pinpoint diagnosis of SCM in dairy animals than alone.

Identification of Diagnostic Protein Markers of Subclinical Mastitis in Bovine Whey Using Comparative Proteomics

Abstract The proteomics of inflammatory response in whey from cows with subclinical mastitis were analysed. Whey protein lysates were separated on 24 cm dry IPG strips (pH 3-10 linear) and 24 cm dry IPG strips (pH 4-7) using two-dimensional electrophoresis. The results indicated that the whey proteins in milk from cows with subclinical mastitis are different from those in milk from healthy cows. All protein spots were found to have biologically relevant changes in relative abundance during subclinical mastitis using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry analysis, including ß-1,4 galactosyltransferase, ß-2 microglobulin, complement 3, a-1-acid glycoprotein, ß-lactoglobulin A, a-S1 casein precursor, ß-casein B, and serotransferrin precursor. The mRNA expression of these genes was verified by quantitative real-time PCR. These proteins are involved in signal transduction, binding, transport, and immune defence activity. The results suggest that the markers may be used for the diagnosis of subclinical mastitis.

Süt Sığırlarında Somatik Hücre Sayısı, Önemi ve Etki Eden Faktörler

The somatic cell count (SCC) is commonly used as a measure of udder health and milk quality. Thus, to determine the milk quality standards in many countries, it legally determined as an indicator of somatic cell count raw milk and determines the level of payments to milk producers. The present study investigated that the somatic cell count is an indicator of udder health status, diagnosis of subclinical mastitis, health and quality of milk and milk products, its importance and effect factors on it.

Prevalence of sub-clinical mastitis in high yielding crossbred cows using Draminski mastitis detector

The subclinical mastitis (SCM) causes great economical loss in dairy farms due to reduction in milk production. The objectives of the study were to know the prevalence of subclinical mastitis in lactating cows using Draminski mastitis detector and to evaluate the efficacy of intramammary infusion against SCM in lactating dairy cows. The study was conducted in crossbred dairy cattle in peri-urban dairy production system within seven kilometers around the artificial insemination Centre, Bangladesh Agricultural University, Mymensingh during April, 2011 to May, 2012. The overall prevalence of SCM in lactating cows was 55.1%. The highest prevalence of SCM was 84.4% in more than 7 years old cows. The prevalence of SCM was significantly (p&lt;0.001) increasing with the advancement of the age. The prevalence of SCM was significantly (p&lt;0.05) higher (73.7%) in cows producing more than 15 liters of milk. Cows with 75% Holstein Friesian genotype experienced more SCM (63.0%) than other genotypes. An increased prevalence of SCM with increased number of parity in cows was also observed. The prevalence of SCM was significantly (p&lt;0.001) higher in cows with parity more than five. The highest prevalence of SCM was recorded in left hind quarter (32.3%) but the difference was not significant (p&gt;0.05) statistically. The efficacy of Neomastipra-JR5® as intra mammary infusion against SCM in lactating cows was 78.2%. Draminski mastitis detector could be a potential candidate for the diagnosis of SCM in dairy animals in Bangladesh context. But before introducing this machine in the field it should be validated either by comparing with a gold standard test like somatic cell counter or by using latent class evaluation in a multi-test approach. DOI: http://dx.doi.org/10.3329/bjvm.v11i1.17731 Bangl. J. Vet. Med. (2013). 11 (1): 37-41

Diagnosis of clinical or subclinical mastitis in ewes

Objectives of this paper are to review (i) diagnostic methods and procedures available for clinical or subclinical mastitis in ewes and (ii) applications of these procedures in the diagnosis of mastitis. Early and correct diagnosis of the disease is important for identification of affected animals. The following diagnostic procedures can be used: clinical examination, imaging techniques (ultrasonography, endoscopy), bacteriological examination of milk samples, immunological tests, identification of biomarkers (cytological examination of milk and measurement of milk electroconductivity). In most cases, diagnosis of clinical mastitis is straightforward, based on the findings of clinical examination. The differential diagnosis includes primarily (i) bacterial mastitis (usually sporadic occurrence in a flock, usually unilateral, isolation of bacteria from milk samples), (ii) mycoplasmal mastitis [usually epidemic occurrence in a flock, usually bilateral accompanied by other signs (e.g., arthritis), isolation of Mycoplasma spp. from milk samples] and (iii) infection by Small Ruminant Lentivirus [usually epidemic occurrence in a flock, usually bilateral accompanied by various signs (e.g., respiratory or neurological signs) in the same or other animals of the flock, detection of antibodies to the virus, pro-viral DNA or viral RNA in blood samples]. Subclinical mastitis should be always suspected as one of the primary causes in cases of decreased milk production in dairy flocks; it should also be considered as a possible factor in cases of suboptimal growth rate of lambs in mutton-type production flocks. Diagnosis of subclinical mastitis is based on detection of infection (i.e., isolation of microorganisms from milk samples) and/or inflammatory reaction in the mammary gland. The best method for detection of the inflammatory reaction remains the demonstration of increased cellular content in milk, although various other methods, have been proposed. For individual animals, values <0.5×106cellsmL−1 indicate a healthy mammary gland and values >1.0×106cellsmL−1 indicate a mammary gland with clinical or subclinical mastitis, with no need to perform a simultaneous bacteriological examination of milk samples to confirm the problem; values between 0.5×106 and 1.0×106cellsmL−1 indicate ‘suspected disease’, hence there is a need for performing bacteriological examination in milk. Two consecutive measurements increase accuracy of results. In bulk milk samples, counts of 0.65×106cellsmL−1 indicate approximately 15% prevalence of subclinical mastitis in the flock. In the differential diagnosis of cases of reduced milk yield in ewes, other possible causes of the problem should be taken into account (e.g., parasitic infections, chronic wasting diseases, suboptimal level of nutrition); in cases of suboptimal growth rate of lambs, other factors may be responsible (e.g., protozoan or parasitic infections, energy or micronutrient deficiency, viral disease).

Use of milk amyloid A in the diagnosis of subclinical mastitis in dairy ewes

Subclinical mastitis (SM) is one of the most important diseases affecting dairy ewes worldwide, with negative impact on the animal health, farm income and public health. Animals with SM often remain untreated because the disease may not be revealed. Increase in somatic cell count (SCC) and positive bacteriology for mastitis pathogens in milk samples are indicative of SM but the evidence of only one of these alterations must suggest an uncertain SM (UM). UM is defined when positive bacteriological examination (Latent-SM) or SCC>500000cells/ml (non-specific-SM) are detected in milk. Nevertheless, SCC and bacteriological examination are expensive, time consuming and are not yet in use at the farm level in dairy ewes. Recently, a sensitive acute phase protein, amyloid A, displaying multiple isoforms in plasma and different body fluids including mammary secretion (milk amyloid A-MAA), has been investigated as a marker of mastitis in cows and, in a few studies, in sheep. The aim of this trial was to compare the concentration of MAA of single udder-halves in ewes with healthy udder-halves (HU-control group) and naturally occurring subclinical mastitis, both confirmed (SM group) and uncertain (UM groups: Latent-SM and non-specific-SM), for monitoring udder health. The reliability of a specific ELISA kit for the measurement of MAA was also tested. During a 3-month trial period, 153 udder halves were assigned to the experimental groups based on their health status: 25 with SM, 40 with UM (11 with latent-SM and 29 with non-specific-SM) and 88 HU. SCC and bacteriological analysis were performed to establish the control and subclinical mastitis groups. MAA concentrations in milk samples were measured using a specific commercially milk ELISA kit. The data were submitted to statistical analysis. Significant (P<0·05) differences among the groups SM, non-specific-SM and HU were detected with the SM having the highest level and HU the lowest. MAA concentration is affected by the udder health status and is a useful indicator of subclinical mastitis and increased SCC in sheep.

Prevalence and risk factors of subclinical mastitis in lactating dairy cows in north and south regions of Bangladesh

The purpose of the study was to identify the potential risk factors for subclinical mastitis (SCM) in lactating dairy cows in Bangladesh. A cross-sectional study was carried out on randomly selected 212 smallholder dairy farms of Sadar upazilas of Rangpur, Mymensingh, and Satkhira districts of Bangladesh during January to October 2011. The direct interview using a structured questionnaire and physical examination of the cows were done to collect data on 15 variables. Milk samples collected from study cows were subjected to California Mastitis Test (CMT). The diagnosis of SCM was based on the results of CMT and physical examination of udder and milk. The bivariable followed by multivariable analysis was done using SPSS 17.0. Of the total cows examined, 20.2 % had subclinical mastitis. In bivariable analysis, eight risk factors were identified. However, in the final model of multivariable analysis, four potential risk factors were identified. These were history of previous clinical mastitis (odds ratio (OR) 10.51, p<0.001), pendulous type of udder (OR 2.26, p=0.008), no grass feeding (OR 1.84, p=0.039), and body condition score (BCS) 2.5 or less (OR 7.25, p=0.054). Four different factors were significantly associated with the occurrence of subclinical mastitis, which need to be considered in the control of the disease. However, particular emphasis should be given on grass feeding and BCS because these traits can be modified or improved to allow prevention of SCM.

Evaluation of Milk Trace Elements, Lactate Dehydrogenase, Alkaline Phosphatase and Aspartate Aminotransferase Activity of Subclinical Mastitis as and Indicator of Subclinical Mastitis in Riverine Buffalo (Bubalus bubalis).

Mastitis is a highly morbid disease that requires detection at the subclinical stage. Tropical countries like India mainly depend on milch buffaloes for milk. The present study was conducted to investigate whether the trace minerals viz. copper (Cu), iron (Fe), zinc (Zn), cobalt (Co) and manganese (Mn) and enzyme activity of lactate dehydrogenase (LDH), alkaline phosphatase (ALP) and aspartate aminotransferase (AST) in riverine buffalo milk can be used as an indicator of subclinical mastitis (SCM) with the aim of developing suitable diagnostic kit for SCM. Trace elements and enzyme activity in milk were estimated with Atomic absorption Spectrophotometer, GBC 932 plus and biochemical methods, respectively. Somatic cell count (SCC) was done microscopically. The cultural examination revealed Gram positive bacteria as the most prevalent etiological agent. A statistically significant (p<0.01) increase in SCC, Fe, Zn, Co and LDH occurred in SCM milk containing gram positive bacterial agents only. ALP was found to be elevated in milk infected by both gram positive and negative bacteria. The percent sensitivity, specificity and accuracy, predictive values and likelihood ratios were calculated taking bacterial culture examination and SCC≥2×105 cells/ml of milk as the benchmark. Only ALP and Zn, the former being superior, were found to be suitable for diagnosis of SCM irrespective of etiological agents. LDH, Co and Fe can be introduced in the screening programs where Gram positive bacteria are omnipresent. It is recommended that both ALP and Zn be measured together in milk to diagnose buffalo SCM, irrespective of etiology.

Relations between electrical conductivity, somatic cell count, California mastitis test and some quality parameters in the diagnosis of subclinical mastitis in dairy cows

This study was conducted to determine the effectiveness of the electrical conductivity (EC) method on the diagnosis of subclinical mastitis in dairy cows comparing with somatic cell count (SCC) and California mastitis test (CMT), and also to investigate the effect of these values on the amount of total viable bacteria, density, freezing point, and mineral substances. A total of 386 milk samples collected from quarters of 188 cows at 10 different farms were used as materials. Of the samples, 258 (66.85%) were CMT (+), 85 (22.02%) were CMT (++), and 43 (11.13%) were CMT (+++). The mean EC and SCC were 25.71, 28.02, and 29.63 mS and 249,453, 1,167,058, and 2,108,139, respectively, according to the CMT results. The total viable bacteria counts ranged from 3.4771 to 6.9395, from 3.4771 to 7.3617, and from 4.7782 to 7.5315 log CFU/mL, respectively. The average amounts of mineral substances were 0.65%, 0.70%, and 0.76%; the density values were 1.031, 1.0297, and 1.029; and the freezing points were -0.5281, -0.5285, and -0.5282, respectively. As a result, it has been concluded that EC showed similarity with the CMT and the SCC in the detection of subclinical mastitis; furthermore, its reliability would further increase when used together with the other diagnostic methods.

Rapid Diagnostic Device for Subclinical Mastitis Based on Electrochemical Detection of Superoxide Produced from Neutrophils in Fresh Milk

Electrochemical microdevices were fabricated to identify mastitic cows based on the increased number of neutrophils in raw milk. Because neutrophils produce superoxide (O2·-), the amount of O2·- can be used as an early indicator for subclinical mastitis. In the microdevices, O2·- was detected on a gold electrode using superoxide dismutase immobilized via a self-assembled monolayer of cysteine. In a preliminary test using xanthine oxidase to produce O2·-, one of the devices detected the production and rapid extinction of O2·-. When neutrophils obtained from a mastitic cow were concentrated by centrifugation and introduced into the device, a current increase distinctly different from the background was observed. Furthermore, a micropillar structure was fabricated on the gold electrode to trap and collect neutrophils, thereby facilitating the concentration of these cells around the electrode. The measured current clearly depended on the number of neutrophils in raw milk samples, demonstrating the applicability of the device for rapid diagnosis of subclinical mastitis.

VALORES DE HAPTOGLOBINA PLASMÁTICA EM VACAS COM DIFERENTES CONTAGENS DE CÉLULAS SOMÁTICAS EM AMOSTRAS DE LEITE

PLASMA HAPTOGLOBIN VALUES IN COWS WITH DIFFERENT MILK SOMATIC CELL COUNT This study investigates the relationship between plasma values for haptoglobin (Hp) and variations of milk somatic cell count (SCC) in dairy cows from Rio Grande do Sul. A total of 50 animals were divided into three groups according to SCC: cows with healthy mammary glands (SCC below 600.000 cells/mL), subclinical mastitis (SCC above 600.000 cells/mL), and clinical mastitis with signs of inflammatory conditions. Total bacterial count and concentrations of lactose, fat, protein and total solids were also determined. Blood samples were collected for fibrinogen, albumin, and Hp analysis. Results revealed that cows with mastitis had significantly lower concentrations of lactose, fat and total solids, whereas protein, fibrinogen, and Hp values were higher. These last two variables presented no differences in healthy and subclinical mastitis groups. The increase of plasma Hp serum level in cows with low milk SCC was probably due to factors other than an inflammatory condition. Significant positive correlation coefficients were found between milk SCC and plasma fibrinogen (r= 0,27) as well as plasma Hp (r= 0,36). Findings from this study were not able to show how Hp values may be useful in the diagnosis of subclinical mastitis in dairy cows.

Subclinical Mastitis May Not Reduce Breastmilk Intake During Established Lactation

This study determined the effect of subclinical mastitis (SCM) on infant breastmilk intake. Participants (60 Ghanaian lactating mothers and their infants) were from periurban communities in the Manya Krobo district of Ghana in 2006-2007. Bilateral breastmilk samples were obtained once between months 3 and 6 postpartum and tested for SCM using the California mastitis test (CMT) and the sodium/potassium (Na/K) ratio. Infants' 12-hour breastmilk intake was assessed by test weighing. CMT scoring for SCM diagnosis was scaled as >or=1 = positive (n = 37) and <1 = negative (n = 23). SCM diagnosis was confirmed as a Na/K ratio of >1.0 (n = 14). Breastmilk intake was nonsignificantly lower among infants whose mothers had elevated Na/K ratios of >1.0 (-65.1 g; 95% confidence interval -141.3 g, 11.1 g). Infants whose mothers were positive for SCM with both CMT and Na/K ratio criteria had significantly lower breastmilk intake (-88.9 g; 95% confidence interval -171.1 g, -6.9 g) compared to those whose mothers tested either negative with both tests or positive on only one. Infant weight (p < 0.01) and frequency of feeding (p = 0.01) were independently associated with breastmilk intake. However, the effect of SCM on breastmilk intake disappeared when infant weight and feeding frequency were included in a multiple linear regression model. The results of this study did not show an effect of SCM on breastmilk intake among 3-6-month-old infants. A larger sample size with a longitudinal design will be needed in future studies.

Use of serum amyloid A and milk amyloid A in the diagnosis of subclinical mastitis in dairy cows

Mastitis is the most frequent and costly disease in dairy herds, as it negatively affects yield and milk quality. The presence of clinical mastitis is quite easy to asses, whereas the diagnosis of the subclinical form can be more difficult and requires laboratory assays. Somatic cell count (SCC) is widely used as a rapid and low-cost indicator of mastitis, even if is not useful in discriminating between the clinical and subclinical form. As amyloid A has been investigated as a marker of mastitis, the aim of this study was to assess the potential value of measuring amyloid A in serum and milk and the correlation with SCC in the diagnosis of subclinical mastitis. The reliability of two different ELISA kits for the measurement of amyloid A in milk was also tested. During a 1-month trial period, 21 cows were assigned to three experimental groups according to their health status: 6 cows with clinical mastitis (CM), 10 cows with subclinical mastitis (SM) and 5 healthy cows (HE). Amyloid A was measured both in serum (SAA) and in quarter milk samples (mAA) with a serum ELISA kit, and in quarter milk samples (MAA) with a milk ELISA kit. SCC, total microbial count (TMC) and bacterial examination of the milk were also carried out. After a log transformation, the data were submitted to ANOVA and linear regression. TMC was significantly higher in cows with clinical mastitis, while no differences were observed between the other two experimental groups. SCC and MAA levels were significantly different among the three groups. mAA concentrations were similar between cows with subclinical and clinical mastitis, and SAA was not affected by mastitis. A significant correlation between SCC and MAA or mAA was detected, while no correlation was recorded between SAA and mAA. A close relationship between MAA and mAA was noticeable even at low concentrations, suggesting MAA as a potential physiological marker of subclinical mastitis.

Diagnosis of Subclinical Mastitis in Goats

Diagnosis of Subclinical Mastitis in Goats

Haptoglobin and serum amyloid A in relation to the somatic cell count in quarter, cow composite and bulk tank milk samples

Milk somatic cell count (SCC) is the gold standard in diagnosis of subclinical mastitis, and is also an important parameter in quality programmes of dairy cooperatives. As routine SCC analysis is usually restricted to central laboratories, much effort has been invested in the search for alternative biomarkers of mastitis and milk quality, including the presence in the milk of the acute phase proteins (APP), haptoglobin (Hp) and serum amyloid A (SAA). The aim of this study was to investigate relationships between Hp, SAA and SCC in quarter, cow composite, and bulk tank milk samples. Cows (n=165), without any clinical signs of disease or abnormalities in the milk or udder, from three different dairy farms, were used. Cow composite milk samples from all cows delivering milk at the sampling occasion were taken once in each herd. In one of the farms, representative quarter milk samples (n=103) from 26 cows were also collected. In addition, bulk tank milk samples from 96 dairy farms were included in the study. Samples were analysed for Hp, SAA and SCC, and relationships between the parameters were evaluated at quarter, cow and tank milk levels using Chi-square analysis. Milk samples were categorized according to their SCC, and the presence, or no presence, of SAA and Hp, based on the detection limits of the screening methods (0.3 mg/l and 1.0 mg/l for SAA and Hp, respectively). Hp and SAA were found in milk at quarter, cow composite and bulk tank levels. A large proportion (53%) of the animals had detectable milk concentrations of APP, and SAA was detected more frequently, and at higher concentrations than Hp, regardless of sample type. SAA was detected in as many as 82% of the bulk tank milk samples. Significant relationships were found between Hp, SAA and SCC at quarter and cow composite milk levels, but only between SAA and SCC at bulk tank milk level. Detectable levels of APP were more common at high SCC.

The use of a hand-held conductivity meter for the diagnosis of subclinical mastitis in dairy cows during late lactation

AIM: To evaluate the accuracy of a hand-held electrical conductivity meter for the detection of subclinical mastitis in an Australian dairy herd in late lactation. METHODS: A hand-held conductivity meter was evaluated during late lactation in a herd of dairy cows that had a high prevalence of Streptococcus agalactiae and Staphylococcus aureus infection. The ability of the conductivity meter to accurately discriminate between uninfected quarters and those infected with major pathogens was assessed, using bacteriology as the definitive test for infection status. Milk samples for bacteriology, and electrical conductivity measurements, were collected from 233 quarters from 59 cows. The ability of the device to identify infected and uninfected cows was also assessed. Sensitivity and specificity were calculated for a range of threshold values, using absolute values, the range of quarter values within a cow and the ratio of quarter values within a cow. RESULTS: Electrical conductivity was higher in infected quarters than uninfected quarters, but the degree of overlap between the populations was substantial, even when quarters were assessed as case-control pairs from the same cow. Use of the device according to the manufacturer's recommendations for diagnostic criteria of mastitic quarters had a sensitivity of 51% and a specificity of 71%. The ability of the device to correctly diagnose the infection status of cows was dependent on both the analytical method and the threshold value used. Applying the manufacturer's recommended criteria to the diagnosis of the status of cows, the sensitivity of the test was 91% and the specificity 17%. CONCLUSION: The variability between individual quarters and between cows in this study was such that the use of this device to measure the conductivity of milk was not a reliable method by which to diagnose subclinical mastitis in cows in late lactation. CLINICAL RELEVANCE: Interpretation of results from handheld conductivity meters when used for the diagnosis of subclinical mastitis in dairy cows needs to be made with care. In some circumstances the results obtained do not accurately reflect the bacteriological status of either individual quarters, or cows.

The diagnosis of subclinical mastitis by redefinition of the interquarter ratio and definition of the interquarter variation using analysis of variance methods

A definition is proposed for the interquarter ratio of markers of inflammation in the bovine mammary gland which in contrast to present measurement procedures has well-defined distributional properties and thus facilitates statistical analysis. Our proposal of an interquarter ratio is equally applicable to evaluation of both single and multi-sample experiments. Finally, we define a new index for diagnosis of subclinical mastitis at the cow level, the interquarter variation, which assesses the degree of dispersion of the four quarter levels for values of any continuous inflammatory marker.