Sensitivity and specificity of a hand-held milk electrical conductivity meter compared to the California mastitis test for mastitis in dairy cattle

Cow-level risk factors associated with the increase in somatic cell count and the occurrence of subclinical mastitis in Brazilian Holstein and Jersey dairy cows

Mastitis, a multifactorial disease influenced by both cow and herd-level factors, results in significant losses throughout the dairy chain. We aimed to evaluate the relationship between milking frequency (MF), parity order (PO), days in milk (DIM), and milk yield (MY) on somatic cell count (SCC) and the odds of a cow having subclinical mastitis (SCM) in Brazilian Holstein and Jersey dairy cows. Our dataset consisted of 747,520 test-day records from 52,954 cows, including 49,089 Holstein cows and 3865 Jersey cows and 498 herds. The SCC was evaluated using a generalized linear mixed model, whereas SCM occurrence was evaluated using a logistic regression model. A case of SCM was defined when a cow had >200×103 cells/mL. Our results indicated that the SCC increases with higher PO and DIM and decreases in cows milked three times a day and those with higher MY in both breeds (>40 and >25 L/d for Holstein and Jersey, respectively). Increasing MF from two to three times a day reduced the chances of a Holstein and Jersey cow having SCM by 10 and 20 %, respectively. For Holstein and Jersey cows, those with ≥quadriparous had 3.9 times and 2.2 times higher chances, respectively, of having SCM compared to primiparous cows. Cows with >305 DIM had 2.0 times greater chances of having SCM for both, Holstein and Jersey cows, compared to cows with ≤105 DIM. Holstein cows yielding ≥40 L/d had a 75 % lower chance of having SCM compared to those yielding <20 L/d, while Jersey cows with ≥25 L/d had a 60 % lower chance compared to those yielding <15 L/d. In conclusion, higher PO and DIM pose risks, whereas a MF of three times a day and higher MY are protective factors against increases in SCC and SCM occurrence in Brazilian Holstein and Jersey cows.

Conductivity of mammary gland secretions is a sensitive and specific predictor of parturition in mares

BACKGROUND

Accurate prediction of parturition is paramount to ensuring monitoring of delivery and preventing complications. Assessing the pH and electrolytes of the mammary gland secretions (MGS) helps detect impending parturition. As conductivity is related to electrolyte concentrations and pH, it could be a useful alternative for predicting impending parturition; however, this hypothesis warrants a critical assessment.

OBJECTIVES

To assess the ability of conductivity, pH, and Brix in the MGS to predict parturition and to investigate their associations.

STUDY DESIGN

Field study.

METHODS

The MGS of periparturient mares (n = 241) was assessed daily for conductivity, pH, and Brix index from 320d until parturition. Receiving operating curve cut-off values for conductivity (≤4.8 mS/cm), pH (≤6.4), and Brix index (>23.6%) were used to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for predicting parturition in ≤24 h.

RESULTS

Impending parturition was associated with a reduction in conductivity and pH (p < 0.05), and conductivity was strongly correlated with pH (r = 0.88) and Brix (r = -0.80) (p < 0.05). Sensitivity, specificity, PPV, and NPV for parturition in ≤24 h for conductivity (82%, 91%, 77%, and 92%, respectively), pH (79%, 84%, 81%, and 71%, respectively), and Brix (72%, 79%, 66%, and 83%, respectively) were determined separated and pairwise. Of interest, the sensitivity, specificity, PPV, and NPV, of combining conductivity and pH, were 80%, 95%, 90%, and 88%, respectively. Conductivity (≤4.8 mS/cm) presented the greatest odds ratio for predicting parturition in ≤24 h, and coupling it with pH (≤6.4 pH units) doubled its odds ratio (i.e., 25.4-62.3).

MAIN LIMITATIONS

Field study.

CONCLUSION

The conductivity of MGS is a sensitive and specific method to predict parturition. This is the first large-scale study showing that a combination of conductivity and pH is useful for predicting parturition in mares. The methods employed can likely apply to other settings with similar results.

Multi-criteria decision analysis for supporting the selection of subclinical mastitis screening tests to use in large- and small-scale dairy farms in Türkiye

The production of high-quality and safe milk is closely associated with the udder health of dairy cows. While there are many mastitis diagnostic tests/methods available, choosing the most appropriate diagnostic test for a sustainable udder health control program could be a challenge. This study was aimed at selecting tests for the screening of subclinical mastitis on small- and large-scale dairy farms in Türkiye, using multi-criteria decision-making methods. An integrated approach employing the analytical hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS) together was used to select subclinical mastitis screening tests for on-farm use. While the AHP determines the weights of the evaluation criteria, the TOPSIS provides a final ranking. Nine different subclinical mastitis screening (SCM) methods (DeLaval somatic cell counter, PortaSCC test, California mastitis test (CMT), rapid culture, portable/hand-held electrical conductivity meter, infrared thermography, leukocyte esterase strip test, milk pH, UdderCheck test) were analyzed on the basis of five selection criteria (the market availability of the test, the diagnostic accuracy of the test, the cost of the test, the cow-side use of the test, and the practicality of the test). The selection criteria were determined based on literature review and stakeholder input. The weighting of the criteria with the AHP was based on the pairwise comparison of the criteria by stakeholders. The criteria were weighted from 1 to 9 according to their relative importance as follows: "1: equally important," "3: moderately important," "5: strongly important," "7: very strongly important," "9: extremely important," and "2, 4, 6, 8: intermediate values." Final ranking of SCM tests with the TOPSIS was based on the stakeholder evaluations of fulfillment of the criteria by the alternatives. The most appropriate screening test for both large- and small-scale dairy farms was determined to be the CMT. The CMT is a very useful, easy to perform, and low-cost tool for detecting subclinical mastitis. Being a major element of udder health control programs, the CMT, if regularly used on dairy farms in Türkiye, would enable the culling of chronically infected animals and the reduction of mastitis-associated economic losses. Furthermore, regular CMTs would contribute to reducing milk SCC and improving milk quality. In conclusion, multi-criteria decision-making methods not only provide a systematic approach that may assist both veterinarians and farmers in deciding on the best choice among the different tests available for the screening of subclinical mastitis but also offer potential benefits to policymakers, researchers, and other industry stakeholders.

Electrical conductivity and total dissolved solid of raw milk for the detection of bovine subclinical mastitis

Background and Aim

Bovine subclinical mastitis (SCM) is highly prevalent among dairy cattle. A cross-sectional study was conducted in Bangladesh to evaluate the performance of electric conductivity (EC) and total dissolved solids (TDS) tests for the detection of SCM.

Materials and Methods

We randomly selected 108 milk samples from cows of different breeds in the primary milk-producing region of Pabna and Sirajgonj districts of Bangladesh. Samples were subjected to the California mastitis test (CMT), white side test (WST), electric conductivity (EC), TDS, and culture. A cow was considered positive for SCM if it tested positive in CMT, WST, and culture, whereas a cow was considered negative for SCM if it tested negative in all three methods. These gold standards have been used to evaluate the performance of the EC and TDS tests. The optimal EC and TDS cutoff values for the detection of SCM were determined using the "optimal cutoff" function in R version 4.3.1.

Results

The optimal EC cutoff value for SCM detection was found to be 6159 μS/cm or 6.16 mS/cm. A positive likelihood ratio (LR+) of 31.2 and an area under the curve (AUC) of 0.905 were obtained for this cutoff value. The optimal cutoff value for TDS was 3100 mg/L of milk, which resulted in a positive LR+ of 45.5 and an AUC of 0.924.

Conclusion

To the best of our knowledge, this is the first study to evaluate the performance of EC and TDS tests in detecting SCM in Bangladesh. These results suggest that EC and TDS tests, which are inexpensive, rapid, and easy to conduct, can effectively detect SCM at the farm level.

Escherichia coli Mastitis in Dairy Cattle: Etiology, Diagnosis, and Treatment Challenges

Bovine mastitis is an inflammation of the udder tissue parenchyma that causes pathological changes in the glandular tissue and abnormalities in milk leading to significant economic losses to the dairy industry across the world. Mammary pathogenic Escherichia (E.) coli (MPEC) is one of the main etiologic agents of acute clinical mastitis in dairy cattle. MPEC strains have virulence attributes to resist the host innate defenses and thrive in the mammary gland environment. The association between specific virulence factors of MPEC with the severity of mastitis in cattle is not fully understood. Furthermore, the indiscriminate use of antibiotics to treat mastitis has resulted in antimicrobial resistance to all major antibiotic classes in MPEC. A thorough understanding of MPEC’s pathogenesis and antimicrobial susceptibility pattern is required to develop better interventions to reduce mastitis incidence and prevalence in cattle and the environment. This review compiles important information on mastitis caused by MPEC (e.g., types of mastitis, host immune response, diagnosis, treatment, and control of the disease) as well as the current knowledge on MPEC virulence factors, antimicrobial resistance, and the dilemma of MPEC as a new pathotype. The information provided in this review is critical to identifying gaps in knowledge that will guide future studies to better design diagnostic, prevent, and develop therapeutic interventions for this significant dairy disease.

Prevalence and Risk Factors of Staphylococcal Subclinical Mastitis in Dairy Animals of Chitwan, Nepal

Subclinical mastitis (SCM), the asymptomatic inflammation of breast tissue, is the most common form of mastitis in livestock. SCM prevalence and risk factors in dairy animals in Western Chitwan, Bagmati Province, Nepal, were the primary objectives of this study. Out of 243 dairy animals, 104 representing 42.8% were positive for SCM in the California mastitis test (CMT) in the study area. At the quarter level, out of 972 active quarters tested for SCM, 188 (19.3%) were positive to CMT test. The prevalence of Staphylococcal SCM was 39.92% (97/243) and 18.21% (177/972) at animal level and quarter level, respectively. Coagulase Negative Staphylococcus (CNS) (46.33%) was the most prevalent Staphylococcus to cause SCM at quarter level. While at animal level, SCM due to occurrence of both S. aureus and CNS (36.08%) in an individual was more common. High susceptibility towards Amikacin, Ceftriaxone and Gentamicin was seen against both isolates. Low resistance against Amikacin and Ceftriaxone was seen against both isolates. Ciprofloxacin (41.2% vs 27.4%) and Gentamicin (37.8% vs 23.2%) were more resistance towards CNS whereas Enrofloxacin (41.1% vs 25.2%) and Tetracycline (36.8% vs 15.1%) were more resistant towards S. aureus. Older aged, multiparous and late lactating animals had the highest prevalence of staphylococcal SCM i.e., 58.1%, 56% and 52.6%, respectively. The study concludes that there is a high prevalence of Staphylococcal SCM in Western Chitwan, Nepal. CNS is the most common mastitis pathogen. Increased antimicrobial resistance to S. aureus and CNS could be the result of the indiscriminate use of antibiotic drugs without an antibiotic susceptibility test (AST). This study emphasizes the importance of ongoing antibiotic surveillance, excellent farm and animal hygiene, and suitable housing and feeding management.

Postmortem Electrical Conductivity Changes of Dicentrarchus labrax Skeletal Muscle: Root Mean Square (RMS) Parameter in Estimating Time since Death

Simple Summary

The estimation of postmortem interval (PMI) still poses a major challenge for pathologists worldwide, making the search for new and more accurate technologies to assist in PMI estimation worthy of growing scientific interest. This study aimed to explore for the first time the use of an oscilloscope coupled with a signal generator, as innovative technology, to evaluate changes in the electrical conductivity of skeletal muscle of sea bass specimens during the early postmortem interval, to find an accurate, quantitative parameter useful in PMI estimation. The use of the oscilloscope, especially for the RMS measured parameter, has been shown here as a promising technology for studying dielectric muscle properties during the early postmortem interval, with the advantage of being a rapid, non-destructive, and inexpensive method.

Abstract

Electric impedance spectroscopy techniques have been widely employed to study basic biological processes, and recently explored to estimate postmortem interval (PMI). However, the most-relevant parameter to approximate PMI has not been recognized so far. This study investigated electrical conductivity changes in muscle of 18 sea bass specimens, maintained at different room temperatures (15.0 °C; 20.0 °C; 25.0 °C), during a 24 h postmortem period using an oscilloscope coupled with a signal generator, as innovative technology. The root mean square (RMS) was selected among all measured parameters, and recorded every 15 min for 24 h after death. The RMS(t) time series for each animal were collected and statistically analyzed using MATLAB^®. A similar trend in RMS values was observed in all animals over the 24 h study period. After a short period, during which the RMS signal decreased, an increasing trend of the signal was recorded for all fish until it reached a peak. Subsequently, the RMS value gradually decreased over time. A strong linear correlation was observed among the time series, confirming that the above time-behaviour holds for all animals. The time at which maximum value is reached strongly depended on the room temperature during the experiments, ranging from 6 h in fish kept at 25.0 °C to 14 h in animals kept at 15.0 °C. The use of the oscilloscope has proven to be a promising technology in the study of electrical muscle properties during the early postmortem interval, with the advantage of being a fast, non-destructive, and inexpensive method, although more studies will be needed to validate this technology before moving to real-time field investigations.

Prevalence and antimicrobial drug resistance of Staphylococcus aureus isolated from cow milk samples

Background and Aim:

Staphylococcus aureus infections and antimicrobial resistance (AMR) in mastitis cases are both of clinical and economic importance. This study investigated the prevalence and AMR patterns of S. aureus isolated from composite milk samples of dairy cows submitted to the Onderstepoort Milk Laboratory for routine diagnosis.

Materials and Methods:

A total of 2862 cow milk samples randomly selected from submitted samples were tested for the presence of S. aureus using microbiological and biochemical tests. Confirmation of isolates was done using the analytical profile index. Antimicrobial susceptibility of S. aureus isolates against 12 antimicrobial agents was determined using the disk diffusion method.

Results:

S. aureus was isolated from 1.7% (50/2862) of the samples tested. All (100%) S. aureus isolates were resistant to at least one antimicrobial, while 62% (31/50) were resistant to three or more categories of antimicrobials (multidrug-resistant [MDR]). Most S. aureus isolates were resistant to erythromycin (62%; 31/50) and ampicillin (62%; 31/50). Almost half of S. aureus isolates were resistant to oxacillin (46%; 23/50) and only 8% (4/50) were resistant to cefoxitin.

Conclusion:

Although the prevalence of S. aureus among mastitis cases in this study was low, isolates exhibited high resistance to aminoglycosides, macrolides, and penicillins, all of which are important drugs in human medicine. The high prevalence of MDR S. aureus and the presence of methicillin resistance among S. aureus observed in this study are of both clinical and public health concerns.

Intramammary antibiotics with complementary acupuncture decreases milk serum N-acetyl-beta-D-glucosaminidase concentrations in dairy cattle with subclinical mastitis

The objective of this research is to determine whether intramammary antibiotics with complementary acupuncture can reduce bovine mammary inflammation due to subclinical mastitis. Lactating cows were selected based on milk with a somatic cell count (SCC) greater than 500,000 cells/ml. Pre- and post-treatment milk samples were collected to determine SCC, aerobic bacterial content, milk ion conductivity, total protein, lactate dehydrogenase (LDH) and N-acetyl-beta-D-glucosaminidase (NAGase) concentrations. Milk serum was prepared from milk samples by double centrifugation. Concentrations of LDH and NAGase were determined using commercial enzyme-linked immunosorbent assays. Cows being treated with intramammary antibiotics were separated by random assignment to the acupuncture group (n = 10) and a no-acupuncture (control) group (n = 9). Both the acupuncture and control group were restrained for 30 min in a head catch 12 hr apart for a total of four times. For front quarters affected by subclinical mastitis, the acupuncture points used were spleen (SP) 12, SP 17, SP 18, SP 21, stomach (ST) 18 and conception vessel (CV) 12. For rear quarters affected by subclinical mastitis, the acupuncture points used were bladder (BL) 30, BL 30-1, BL 49, kidney (KI) 10, conception vessel (CV) 2 and CV 3. All parameters were compared using a Student t test. Significance was defined as p < .05. Compared to control cows, complementary acupuncture treatment reduced NAGase enzymatic activity in quarters of cows with subclinical mastitis. The reduction in NAGase suggests that complementary acupuncture treatment may be associated with healing of the damaged mammary epithelial cells, which are the primary source of NAGase activity in milk serum.

Use of milk electrical conductivity for the differentiation of mastitis causing pathogens in Holstein cows

Mastitis is one of the most prevalent and costly diseases in dairy cattle. Key components for adequate mastitis control are the detection of early stages of infection, as well as the selection of appropriate management interventions and therapies based on the causal pathogens associated with the infection. The objective was to characterize the pattern of electrical conductivity (EC) in milk during intramammary infection, considering specific mastitis-causing pathogen groups involvement. Cows (n = 200) identified by an in-line mastitis detection system with a positive deviation ≥15% in the manufacturer's proprietary algorithm for EC (high electrical conductivity (HEC)) were considered cases and enrolled in the study at the subsequent milking. One control (CON) cow, within normal ranges for EC, was matched to each case. A composite milk sample was collected aseptically from each cow for bacteriological culture. Milk yield (MY) and EC were recorded for each milking during ±7 days relative to enrollment. Milk cultures were categorized into gram positive (GP), gram negative (GN), other (OTH) and no growth (NOG). Data were submitted for repeated-measures analysis with EC as the dependent variable and EC status at day -1, bacteriological culture category, parity number, stage of lactation and days relative to sampling as main independent variables. Average (± standard error (SE)) EC was greater in HEC than in CON cows (12.5 ± 0.5 v. 10.8 ± 0.5 mS/cm) on the day of identification (day -1). Milk yield on day -1 was greater in CON than in HEC (37.6 ± 5.1 v. 33.5 ± 5.2 kg). For practical management purposes, average EC on day -1 was similar for the different bacteriological culture categories: 11.4 ± 0.6, 11.7 ± 0.5, 12.3 ± 0.8 and 11.7 ± 0.5 mS/cm in GN, GP, OTH and NOG, respectively. Parity number was only associated with day -1 EC in HEC group, with the greatest EC values in parity 3 (12.3 ± 0.3 mS/cm), followed by parity 2 (11.9 ± 0.2 mS/cm), parity >3 (11.6 ± 0.5 mS/cm) and primiparous cows (11.2 ± 0.2 mS/cm). An effect on EC for the interaction of day relative to identification by pathogen gram category was observed. The same interaction effect was observed on daily MY. Overall, the level of variation for MY and EC between- and within-cows was substantial, and as indicated by the model diagnostic procedures, the magnitude of the variance in the cows in the CON group resulted in deviations from normality in the residuals. We concluded that characteristic temporal patterns in EC and MY in particular pathogen groups may provide indications for differentiation of groups of mastitis-causing pathogens. Further research to build detection models including EC, MY and cow-level factors is required for accurate differentiation.

Evaluation of hand-held sodium, potassium, calcium, and electrical conductivity meters for diagnosing subclinical mastitis and intramammary infection in dairy cattle

Background

Subclinical mastitis (SCM) and intramammary infection (IMI) increase the sodium (Na) concentration and electrical conductivity (EC) and decrease the potassium (K) and calcium (Ca) concentrations in glandular secretions of lactating dairy cattle.

Hypothesis

Low‐cost portable Na, K, Ca, and EC meters are clinically useful cow‐side tests for diagnosing SCM and IMI.

Animals

One hundred fifteen dairy cows at dry off and 92 cows within 4‐7 days postcalving.

Methods

Quarter foremilk samples were obtained and the somatic cell count (SCC) was measured using a DeLaval cell counter with SCM defined as SCC ≥ 200 000 cells/mL. Microbiological culture of foremilk samples was used to diagnose IMI. Cisternal milk Na, K, and Ca concentrations and EC were measured using portable ion‐selective meters. Logistic regression was used to determine the area under the receiver operating characteristic curve (AUC) and the optimal cut point was determined using Youden's index. Diagnostic test performance was evaluated by comparing the AUC and calculating the sensitivity, specificity, and positive likelihood ratio (+LR) at the optimal cut point for SCM and IMI.

Results

Diagnostic test performance was much better when the meters were used to diagnose SCM as compared to IMI. Cisternal milk Na concentration provided the most accurate method for identifying quarters with SCM or IMI. However, AUC was <0.90 and +LR was <10 for all diagnostic test evaluations.

Conclusions and Clinical Importance

Cisternal milk Na, K, and Ca concentrations and EC were not sufficiently predictive of SCM or IMI to be recommended as clinically useful diagnostic tests.

Evaluation of milk cathelicidin for detection of bovine mastitis

Mastitis due to intramammary infection is one of the most economically relevant diseases in dairy cows, causing reductions in milk quality and quantity. Currently, mastitis monitoring is based on somatic cell count (SCC) and bacteriologic culture (BC) of milk. Nevertheless, inflammation-specific protein markers might provide more sensitive and reliable assays, enabling immunoassay-based screening strategies. Cathelicidin is an inflammatory protein released in milk that has recently demonstrated fair reliability and diagnostic potential for ewe mastitis. To assess its performance in cows, 531 quarter milk samples from 2 herds were tested using cathelicidin ELISA, SCC, and BC. We found that 29.0% of samples were positive for cathelicidin, 18.8% had SCC >200,000 cells/mL, and 13.7% were BC-positive. Cathelicidin showed a strong positive correlation with SCC as demonstrated by receiver operating characteristics curve analysis and by the clustering of cathelicidin-negative and cathelicidin-positive samples in association with low and high SCC values, respectively. For evaluating the diagnostic performance of a novel test, BC cannot be considered a reliable gold standard for true disease status because of its known limitations. Therefore, we assessed the sensitivity (Se) and specificity (Sp) of the milk cathelicidin ELISA using a latent class analysis approach together with BC and SCC by considering different diagnostic thresholds to identify the preferred Se/Sp combination. We modeled conditional dependence of cathelicidin and SCC to account for their close association. The cathelicidin ELISA showed higher Se than SCC and BC for almost all threshold combinations. In fact, at the best-performing threshold combination, the Se of cathelicidin was 80.6%, 6.2 percentage points higher than that of SCC >200,000 cells/mL (74.4%) and similar to that of SCC >100,000 cells/mL (80.2%). Most importantly, this Se was obtained with a loss in Sp of only 1.4 percentage points compared with SCC >200,000 cells/mL (94.9% Sp for cathelicidin vs. 96.3% for SCC >200,000). The limited Se of BC (38.8%) was also confirmed in this study, and BC showed a slightly lower Sp than both cathelicidin and SCC for most of threshold combinations. This study confirmed that cathelicidin is released in the milk of cows with mastitis and that its presence is highly correlated with SCC. The measurement of cathelicidin by ELISA may hold significant potential for improving the sensitivity of mastitis detection in dairy cows while maintaining high specificity.

Hydration kinetics and physical properties of split chickpea as affected by soaking temperature and time

In this study, some physical properties (principal dimensions, mean diameters, sphericity, area, density and electrical conductivity) of split chickpea were measured as function of soaking time (up to 360 min) and temperature (25-65 °C). Initially, the water absorption rate was high and then it showed a progressive decrease at all temperatures, whereas solid loss exhibited a power function of temperature (P < 0.05). The Peleg model was predicted well the kinetic of split chickpea soaking. No significant difference (P < 0.05) was observed in Peleg rate constant (K1) and Peleg capacity constant (K2) at all temperatures except for K1 at 25 °C. The discrepancy for K1 was in relation to permeability characteristics of split chickpea at temperature of 25 °C. As temperature increased from 25 to 65 °C, the K1 value decreased from 0.04620 to 0.00945 g h(-1), whereas the K2 value increased from 0.08597 to 0.11320 g(-1). Plot for K1 exhibited a slope changes around 45 °C corresponding to gelatinization temperature of split chickpeas. The effect of temperature and time on physical properties of split chickpea during soaking was monitored by regression equations. It was concluded that physical properties of split chickpea affected by its water absorption especially at higher temperatures.