Retrospective evaluation of udder recovery of cows with subclinical mastitis following treatment with acoustic pulse technology (APT) on commercial dairy farms and its economic impact.

Retrospective evaluation of udder recovery following treatment of the inflamed quarter with acoustic pulse technology (APT) of cows with subclinical mastitis was done on 4 Israeli commercial dairy farms. Here, we evaluated the APT treatment as a tool to manage subclinical mastitis and its economic consequences in commercial farms. Recovery of the infected glands following APT treatment was compared to the customary no-treatment (NT) for cows with subclinical mastitis. Over 2 years, 467 cows with subclinical mastitis were identified. Subclinical mastitis was defined by elevated somatic cell count (SCC; >1 × 106 cells/mL) in the monthly test-day milk sample; 222 cows were treated with APT and 245 cows were not treated and served as control. Differences between treatment groups in culling, milk quality, milk yield and bacterial elimination were analyzed. After treatment, cure from bacteria was calculated only for cows with pre-isolated bacteria. The percentage of sampled cows determined as cured (no bacterial finding) in the NT group was 32.7% (35/107) (30.9% Gram negative; 32.4% Gram positive) and in the APT-treated group, 83.9% (42/55) (89.4% Gram negative; 80.6% Gram positive). Culling rate due to mastitis was significantly lower (>90%) in the APT-treated vs. NT group. Recovery was 66.0% in the APT group compared to 11.5% in the NT group at 90 d post-treatment. Average milk volume per cow in the APT-treated group was 16.1% higher compared to NT cows. Based on the study, savings incurred by using APT to treat only subclinical cows per 100-cow herd can total $15,106/y, or $309 per treated subclinically infected cow.

[Investigations of a controlled, decision tree based procedure for Selective Dry Cow Treatment in Bavarian dairy farms]. / Untersuchungen zu einem kontrollierten, entscheidungsbaumbasierten Verfahren des Selektiven Trockenstellens in Bayerischen Milchviehbetrieben.

OBJECTIVE: Four parameters of a decision tree for Selective Dry Cow Treatment (SDCT), examined in a previous study, were analyzed regarding their efficacy in detecting cows for dry cow treatment (DCT, use of intramammary antimicrobials). This study set out to review wether all parameters (somatic cell count [SCC≥ 200 000 SC/ml 3 months' milk yield recordings prior dry off (DO)], clinical mastitis history during lactation [≥1 CM], culturing [14d prior DO, detection of major pathogens] and California-Mastitis-Test [CMT, > rate 1/+ at DO]) are necessary for accurate decision making, whether there are possible alternatives to replace culturing, and whether a simplified model could replace the decision tree. MATERIAL AND METHODS: Records of 18 Bavarian dairy farms from June 2015 to August 2017 were processed. Data analysis was carried out by means of descriptive statistics, as well as employing a binary cost sensitive classification tree and logit-models. For statistical analyses the outcomes of the full 4-parameter decision tree were taken as ground truth. RESULTS: 848 drying off procedures in 739 dairy cows (CDO) were included. SCC and CMT selected 88.1%, in combination with CM 95.6% of the cows that received DCT (n=494). Without culturing, 22 (4.4%) with major pathogens (8x Staphylococcus [S.] aureus) infected CDO would have been misclassified as not needing DCT. The average of geometric mean SCC (within 100 d prior DO) for CDO with negative results in culturing was<100 000 SC/ml milk, 100 000-150 000 SC/ml for CDO infected with minor pathogens, and ≥ 150 000 SC/ml for CDO infected with major pathogens (excluding S.aureus). Using SCC during lactation (at least 1x > 200 000 SC/ml) and positive CMT to select CDO for DCT, contrary to the decision tree, 37 CDO (4.4%) would have been treated "incorrectly without" and 43 CDO (5.1%) "unnecessarily with" DCT. Modifications were identified, such as SCC<131 000 SC/ml within 100 d prior to DO for detecting CDO with no growth or minor pathogens in culturing. The best model for grading CDO for or against DCT (CDO without CM and SCC<200 000 SC/ml [last 3 months prior DO]) had metrics of AUC=0.74, Accuracy=0.778, balanced Accuracy=0.63, Sensitivity=0.92 and Specificity=0.33. CONCLUSIONS: Combining the decision tree's parameters SCC, CMT and CM renders suitable selection criteria under the conditions of this study. When omitting culturing, lower thresholds for SCC should be considered for each farm individually to select CDO for DCT. Nonetheless, the most accurate model could not replace the full decision tree.

Factors affecting N-acetyl-ß-D-glucosaminidase as an indicator for mastitis detection in dairy sheep.

The study of new indirect methods for mastitis detection is of great relevance both at the economic level of the farm and dairies, and in terms of consumer health, and animal welfare. These methods help us to monitor the disease and speed up the decision-making process on treatment of the affected animal and the destination of the milk. The main aim of this work was to study the effect of intramammary infection and other non-infectious factors on the activity of the enzyme N-acetyl-ß-D-glucosaminidase (NAGase) in milk, in order to evaluate its use as an indicator for the early diagnosis of mastitis in sheep that could be less expensive, easier to measure and a better marker of inflammation or complementary to existing methods such as somatic cell count (SCC). Seven biweekly samplings were carried out, in which NAGase activity, SCC and milk were analyzed. Glands were classified according to their sanitary status based on the results of the SCC and bacteriological analysis. Non-infectious factors such as lactation stage, parity number and milking session had a statistically significant effect on NAGase values, finding the highest NAGase values at the onset and end of the study, in infectious mastitic glands of multiparous females and at morning milking. However, among the NAGase variation factors studied, the health status of the gland was the factor that caused the highest variation in enzyme levels, with infectious mastitic glands showing higher values than healthy glands. The predictive ability of NAGase was also studied by means of several logistic regression models, with the one that included NAGase together with lactation stage and parity obtaining the best results if sensitivity is to be prioritized, or the model that included NAGase, lactation stage, parity, milking and production if specificity is to be prioritized. From the results obtained, it can be concluded that the use of NAGase as an intramammary infection detection method in sheep can be useful when non-infectious factors that cause changes in the concentration of the enzyme are also considered.

Economic losses caused by mastitis and the influence of climate variation on the occurrence of the disease in a dairy cattle farm in southern Brazil.

This study evaluated the economic impacts caused by mastitis in a small dairy farm with similar characteristics and production to most dairy farms in southern Brazil and investigated if climatic variations influenced mastitis occurrence in the region. A farm with, on average, 45 lactating Holstein cattle was monitored from November 2021 to October 2022, and data on mastitis cases, bulk tank milk somatic cell count, animal treatment costs, milk production, animal disposal costs, and production losses were collected. Monthly averages of temperature, relative humidity (RH), and rainfall in the region were obtained. The greatest loss was related to the drop in milk production, resulting in 63.8% of total losses, followed by animal disposal (29.5%), milk disposal (4.6%), and treating animals with mastitis (2.0%), totaling a 10.6% reduction in the annual gross income. There were negative correlations between the clinical mastitis rate and monthly RH and between subclinical mastitis and temperature; the occurrence of subclinical mastitis and average RH were positively correlated. Our findings showed that mastitis negatively impacted the economy and that climate influenced mastitis occurrence.

Economic impact of subclinical mastitis treatment in early lactation using intramammary nisin.

Treatment of subclinical mastitis (SCM) during lactation is rarely recommended due to concerns related to both antimicrobial usage and the costs associated with milk discard. Nisin is a naturally produced antimicrobial peptide with a gram-positive spectrum that, when given to dairy cows, does not require milk discard. We evaluated the economic impact of the treatment of SCM during early lactation using a nisin-based intramammary treatment under different scenarios that included various treatment costs, milk prices, and cure rates. We stochastically simulated the dynamics of SCM detected during the first week of lactation. The net economic impact was expressed in US dollars per case. The probabilities of an event and their related costs were estimated using a model that was based on pathogen-specific assumptions selected from peer-reviewed articles. Nisin cure rates were based on results of pivotal studies included in the US Food and Drug Administration (FDA) approval submission. Based on our model, the average cost of a case of intramammary infection (i.e., only true-positive cases) in early lactation was $170 (90% = $148-$187), whereas the cost of a clinical mastitis case was $521 (90% range = $435-$581). Both estimates varied with etiology, parity, and stage of lactation. When comparing the net cost of SCM cases (i.e., CMT-positive tests) detected during the first week of lactation, nisin treatment generated an average positive economic impact of $19 per CMT-positive case. The use of nisin to treat SCM was beneficial 93% of the time. Based on the sensitivity analysis, treatment would result in an economically beneficial outcome for 95% and 73% of multiparous and primiparous cows, respectively. At the herd level, use of intramammary nisin to treat SCM in cows in early lactation was economically beneficial in most tested scenarios. However, the economic impact was highly influenced by factors such as rate of bacteriological cure, cost of treatment, and parity of the affected animal. These factors should be considered when deciding to use nisin as a treatment for SCM.

Phenotypic and genotypic assessment of iron acquisition in diverse bovine-associated non-aureus staphylococcal strains.

Although the role of iron in bacterial infections has been well described for Staphylococcus (S.) aureus, iron acquisition in (bovine-associated) non-aureus staphylococci and mammaliicocci (NASM) remains insufficiently mapped. This study aimed at elucidating differences between four diverse bovine NASM field strains from two species, namely S. chromogenes and S. equorum, in regards to iron uptake (with ferritin and lactoferrin as an iron source) and siderophore production (staphyloferrin A and staphyloferrin B) by investigating the relationship between the genetic basis of iron acquisition through whole genome sequencing (WGS) with their observed phenotypic behavior. The four field strains were isolated in a previous study from composite cow milk (CCM) and bulk tank milk (BTM) in a Flemish dairy herd. Additionally, two well-studied S. chromogenes isolates originating from a persistent intramammary infection and from a teat apex were included for comparative purpose in all assays. Significant differences between species and strains were identified. In our phenotypical iron acquisition assay, while lactoferrin had no effect on growth recovery for all strains in iron deficient media, we found that ferritin served as an effective source for growth recovery in iron-deficient media for S. chromogenes CCM and BTM strains. This finding was further corroborated by analyzing potential ferritin iron acquisition genes using whole-genome sequencing data, which showed that all S. chromogenes strains contained hits for all three proposed ferritin reductive pathway genes. Furthermore, a qualitative assay indicated siderophore production by all strains, except for S. equorum. This lack of siderophore production in S. equorum was supported by a quantitative assay, which revealed significantly lower or negligible siderophore amounts compared to S. aureus and S. chromogenes. The WGS analysis showed that all tested strains, except for S. equorum, possessed complete staphyloferrin A (SA)-synthesis and export operons, which likely explains the phenotypic absence of siderophore production in S. equorum strains. While analyzing the staphyloferrin A and staphyloferrin B operon landscapes for all strains, we noticed some differences in the proteins responsible for iron acquisition between different species. However, within strains of the same species, the siderophore-related proteins remained conserved. Our findings contribute valuable insights into the genetic elements associated with bovine NASM pathogenesis.

Seasonal assessment of mastitis using thermogram analysis in Sahiwal cows.

"India is the world's leading producer of milk" and demands a non-invasive diagnostic tool like infrared thermography (IRT) to identify the costliest production disease, mastitis. It can form the basis of precision dairy farming. Therefore, the present study focuses on thermal imaging of the udder and teat quarters of Sahiwal cows during different seasons to identify subclinical (SCM) and clinical mastitis (CM) cases using the Darvi DTL007 camera. A total of 24-69 lactating Sahiwal cows were screened out using IRT regularly throughout the year. The intramammary infection status was further assessed using the CMT. The receiver operating characteristic analysis was carried out to develop the current study's cut-off for various thermographic parameters. The incidence for SCM and CM ranged from 26.47 to 38.75% and 17.83-22.79%, respectively during different seasons in Sahiwal udder quarters. The thermogram analysis revealed a significant difference (p < 0.01) in the mean values of the udder and teat surface temperature of Sahiwal cows between healthy, SCM, and CM during different seasons. The mean values of udder skin surface temperature (USST) during different seasons ranged between 29.07 and 36.91 °C, 31.51 to 37.88 °C and 32.42 to 38.79 °C among healthy, SCM, and CM-affected quarters, and correspondingly, the mean values of teat skin surface temperature (TSST) were 28.28 to 36.77 °C, 30.68 to 37.88 °C and 31.70 to 38.73 °C, respectively. Further results revealed an increase (p < 0.01) in the mean values of USST during winter, summer, rainy, and autumn as 2.44, 3.35; 0.97, 1.88; 1.06, 1.83; 1.29, 2.39 °C and TSST as 2.4, 3.42; 1.11, 1.96; 1.21, 2.19, 1.3, 2.4 °C of SCM, CM-affected quarters to healthy quarters, respectively, in Sahiwal cows. Thermograms showed a strong positive correlation with the CMT scores of SCM, CM cases, and healthy samples. Henceforth, irrespective of the seasons studied in the present work, IRT is an efficient, supportive tool for the early identification of subclinical mastitis.

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.

Genomic analysis and assessment of pathogenic (toxicogenic) potential of Staphylococcus haemolyticus and Bacillus paranthracis consortia isolated from bovine mastitis in Russia.

Three stable microbial consortia, each composed of Bacillus paranthracis and Staphylococcus haemolyticus strains, were isolated from milk of cows diagnosed with mastitis in three geographically remote regions of Russia. The composition of these consortia remained stable following multiple passages on culture media. Apparently, this stability is due to the structure of the microbial biofilms formed by the communities. The virulence of the consortia depended on the B. paranthracis strains. It seems plausible that the ability of the consortia to cause mastitis in cattle was affected by mutations of the cytK gene of B. paranthracis.

Assessment of antibiotic use patterns in bovine mastitis treatment in the dairy sector in Serbia.

The dairy sector is essential for the world's food systems, playing a vital role in agricultural production. Yet, mastitis, an inflammation of the mammary gland, affects a considerable portion of the dairy cow population annually, leading to reduced productivity and sustainability. Insight into therapeutic protocols is essential for a better understanding of the situation on farms with the aim of developing new or harmonizing existing protocols in the mastitis treatment. This study conducted on dairy farm in Serbia aimed to explore the most commonly used antibiotics during bovine mastitis treatment and their association with daily milk yield. Data from 100 lactating cows, including therapeutic protocols, lactation numbers, mastitis episodes, milk yield, and antibiotic usage, were obtained from a computerized database and statistically analysed. The results demonstrated a high prevalence of narrow-spectrum antibiotics usage, with the majority of cows treated with combination therapy. The route of antibiotic application did not significantly impact daily milk yield, while treatment duration had no discernible effect. Nonetheless, specific antibiotics were associated with milk yield variations, suggesting the need for careful antibiotic selection and management in mastitis therapy. These findings emphasize the importance of prudent antibiotic use to safeguard animal health and long-term milk production sustainability.

Association between management practices and estimated mastitis incidence and milk losses on robotic dairy farms.

This study aims to describe the relation between farm-level management factors and estimated farm-level mastitis incidence and milk loss traits (MIMLT) at dairy farms with automated milking systems. In this observational study, 43 commercial dairy farms in Belgium and the Netherlands were included and 148 'management and udder health related variables' were obtained during a farm visit through a farm audit and survey. The MIMLT were estimated from milk yield data. Quarter-level milk yield perturbations that were caused by presumable mastitis cases (PMC) were selected based on quarter-level milk yield and electrical conductivity. On average, 57.6 ± 5.4% of the identified milk yield perturbations complied with our criteria. From these PMC, 3 farm-level MIMLT were calculated over a one-year period around the farm visit date: (1) the 'average number of PMC per cow per year', (2) the 'absolute milk loss per cow per day', calculated as the farm-level sum of all milk losses during PMC in one year, divided by the average number of lactating cows and the number of days, and (3) the 'relative milk loss', calculated as the farm-level sum of milk losses during PMC in one year, divided by the estimated total production in the absence of PMC. The 'average number of PMC per cow per year' was on average 1.81 ± 0.47. The PMC caused an average milk loss of 0.77 ± 0.26 kg per lactating cow per day, which corresponded to an average production loss of 2.38 ± 0.82% of the expected production in the absence of PMC. We performed a principal component regression (PCR) analysis to link the 3 MIMLT to the 'management and udder health related variables', whilst reducing the multicollinearity and the number of dimensions. The first principal component was mainly related to 'milking system brand, maintenance and settings'. The second component mainly linked to average productivity and somatic cell counts, whereas the third component mainly contained variables linked with mastitis management, treatment, and biosecurity. The 3 PCR models had R² ranging from 0.46 (for absolute milk loss per cow per day) to 0.57 (for relative milk loss). For all models, the second PC had the largest effect size. This analysis raises awareness of the impact of management factors on a factual basis and provides handles to take management actions to improve udder health.

Variation in partial direct costs of treating clinical mastitis among 37 Wisconsin dairy farms.

The objective of this observational study was to describe variations in partial direct costs of clinical mastitis (CM) treatments among 37 dairy herds using data obtained from herd management records. Animal health and drug purchase records were retrospectively collected from 37 Wisconsin dairy herds for a period of 1 yr. Each farm was visited to verify case definitions, recording accuracy, and detection criteria of CM cases. Descriptive statistics were used to summarize cost of drugs and milk discard. Differences in costs among protocols, intramammary (IMM) products, parities, days in milk, and recurrence were analyzed using ANOVA. Of 20,625 cases of CM, 31% did not receive antimicrobial treatment. The average cost of drugs and milk discard (including cases that were not treated) was $192.36 ± 8.90 (mean ± SE) per case and ranged among farms from $118.13 to $337.25. For CM cases treated only with IMM antimicrobials, milk discard accounted for 87% of total costs and was highly influenced by duration of therapy. Differences in costs were observed among parities, recurrence, and stage of lactation at case detection. Eight different treatment protocols were observed, but 64% of cases were treated using only IMM antimicrobials. Treatment costs varied among protocols; however, cases treated using both IMM and injectable antimicrobials as well as supportive therapy had the greatest costs as they were also treated for the longest duration. Ceftiofur was used for 82% of cases that received IMM antimicrobials while ampicillin was used for 51% of cases treated using injectable antimicrobials. With the exception of ceftiofur and pirlimycin IMM products, many IMM products were given for durations that exceeded the maximum labeled duration. For cases treated using only IMM therapy, as compared with observed costs, we estimated that partial direct costs could be reduced by $65.20 per case if the minimum labeled durations were used. Overall, partial direct costs per case varied among herds, cow factors, and treatment protocols and were highly influenced by the duration of therapy.

The costs of chronic mastitis: A simulation study of an automatic milking system farm.

Mastitis is a production disease in dairy farming that causes economic losses. Especially chronic mastitis (i.e., mastitis cases continuing longer than 28 days) can substantially affect the risk of transmission of intramammary infections (IMI) and total milk production losses. Insights into the impact of chronic mastitis on production and farm economics are needed to guide chronic mastitis decision-making. We aimed to estimate the costs of chronic mastitis with a Monte Carlo simulation model in which the costs of chronic mastitis were estimated as part of the total mastitis costs. The model simulated milk yields, IMI dynamics, somatic cell count (SCC), and pregnancy status on an average Dutch dairy farm with 100 cow places over 9 years. The model was parameterized using information from the literature and actual sensor data from automatic milking system (AMS) farms. The daily subclinical milk production losses were modeled using a generalized additive model and sensor data. Transmission of IMI was modeled as well. The model results indicated median total costs of mastitis of € 230 per generic IMI case (i.e., a weighted average of all pathogens). The most substantial cost factors were the extra mastitis cases due to transmission, culling, and milk production losses. Other significant costs originated from dry cow treatments and diverted milk. The model also indicated median total costs due to chronic mastitis of € 118 (51 % of the total mastitis costs). The share of chronic mastitis relative to the total mastitis costs was substantial. Transmission of contagious bacteria had the largest share among the chronic mastitis costs (51 % of the costs of chronic cases). The large share of chronic mastitis costs in the total mastitis costs indicates the economic importance of these mastitis cases. The results of the study point to the need for future research to focus on chronic mastitis and reducing its presence on the AMS dairy farm.

Economic losses associated with mastitis due to bovine leukemia virus infection.

Bovine leukemia virus (BLV), which causes enzootic bovine leukosis and immunosuppression, is widely prevalent on Japanese dairy farms. However, in the absence of a national eradication scheme with compensation programs, it is important to estimate BLV-associated economic losses to raise farmers' awareness. Mastitis (includes both clinical and subclinical) is a common disease in the dairy industry and the most common reason for culling. We hypothesized that immunosuppression due to BLV predisposes subclinical mastitis. A retrospective cohort study was conducted to trace Holstein cows at 9 commercial dairy farms in the Nemuro and Kushiro regions of Hokkaido Prefecture, Japan, where monitoring of BLV proviral load is routine. Information regarding Dairy Herd Improvement data, parity number, and delivery day was collected at each farm. Cows with no confirmed infection with BLV during lactation were defined as non-infected. Low-proviral-load and high-proviral-load (H-PVL) cows were defined as those in which proviral load was below and over 2,465 copies/50 ng of DNA, respectively, or 56,765 copies/105 cells, respectively, throughout the lactation period. Survival analysis was performed using the frailty model to estimate the hazard ratio of subclinical mastitis for BLV infection status using data from 1,034 dairy cows after adjusting for parity number and delivery season as confounding factors. Kaplan-Meier survivor curves demonstrated that half of the H-PVL cows developed subclinical mastitis within 52 d after calving. The hazard ratio of subclinical mastitis for H-PVL cows was 2.61 times higher than that of non-infected cows. In 2017, there were 264,443 clinical mastitis cases in Hokkaido. Using field and published data, annual economic losses were estimated using Monte Carlo simulation. The economic loss due to mastitis associated with BLV infection per H-PVL cow was $418.59 (¥43,952), with the annual economic loss in Hokkaido Prefecture due to mastitis caused by BLV infection estimated at $6,097,225 (¥640,208,633). In summary, H-PVL cows were more susceptible to subclinical mastitis than non-infected and low-proviral-load cows, and mastitis due to BLV infection was projected to cause significant economic losses.

Udder health, veterinary costs, and antibiotic usage in free stall compared with tie stall dairy housing systems: An optimized matching approach in Switzerland.

Observational studies are important in livestock science. As treatment is not assigned randomly in such studies, selection bias can be a problem. This is often addressed by matching methods. However, if treatment and control groups differ considerably in their characteristics, it might be necessary to additionally prune observations that lack overlap in the opposite group. "Matching Frontier" method was developed because pruning observations manually often results in suboptimal solutions. The feasibility of the approach for animal health and welfare issues was tested in an observational study evaluating the effect of free stall housing and increased lying comfort on udder health, veterinary costs, and antibiotic usage in Swiss dairy farming. Data were collected in a survey with 1835 Swiss dairy farmers (response rate 28.3%). The treatment group (n = 179) comprised farmers participating in a voluntary animal welfare program that, in addition to free stall housing, required increased lying comfort. Farmers in the control group (n = 229) kept their cows in tie stalls. Using the Matching Frontier method, treated units were matched to control units based on five confounders. Subsequently, observations were pruned to achieve sufficient balance and overlap between the two groups. The effect of the program on the eight outcome variables was finally estimated using linear regression. Farmers in the treatment group had a lower incidence of clinical mastitis (-3.66 per 100 cow-years, -25%, p < 0.05), a lower incidence of culled cows due to udder health problems (-1.61 per 100 cow-years, -30%, p < 0.05), fewer veterinary costs (-42.44 per cow-year, -22%, p < 0.05), a lower incidence of total intramammary antibiotic treatments (-15.88 per 100 cow-years, -23%, p < 0.01), a lower incidence of intramammary antibiotic treatments for mastitis therapy (-7.83 per 100 cow-years, -32%, p < 0.01), and a lower incidence of intramammary antibiotic treatments for dry-cow therapy (-8.80 per 100 cow-years, -21%, p < 0.05). No differences were found for the average somatic cell count and the number of cows with a cell count above 150.000. The results suggest that free stall housing, in combination with increased lying comfort, can have a positive effect on udder health, animal welfare, and the economic situation of the farm. Additionally, fewer antibiotic treatments can be beneficial to public health. The Matching Frontier method has proven to be a helpful tool that may also have added value for future observational studies in livestock science.

Identification of bacterial species in milk by MALDI-TOF and assessment of some oxidant-antioxidant parameters in blood and milk from cows with different health status of the udder.

This study aimed to identify bacterial pathogens in milk samples from dairy cows with subclinical and clinical mastitis as well as to assess the concentrations of oxidant-antioxidant parameters [malondialdehyde (MDA), reduced glutathione (GSH), and total GSH levels] in both blood and milk samples. From a total of 200 dairy cows in 8 farms, 800 quarter milk samples obtained from each udder were tested in the laboratory for the presence of udder pathogens. Cultivated bacteria causing intramammary infection from milk samples were identified by Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF). In addition, from tested animals 60 cows were selected including 20 healthy cows that were CMT negative, 20 cows with subclinical mastitis (SM), and 20 cows with clinical mastitis (CM) for detection of MDA, GSH, and total GSH levels in blood and milk samples. Three hundred and eighty (47.5%; 380/800), 300 (37.5%; 300/800), and 120 (15%; 120/800) of milk samples, respectively were CMT positive or SM and CM, and those positives were cows from different farms. We observed that 87.4% (332/380), 25.3% (76/300), and 34.2% (41/120) of cows with CMT positive, CMT negative, and CM had bacterial growth. The most predominantly identified bacteria were Staphylococcus chromogenes (18.7%) obtained mainly from SM and Staphylococcus aureus (16.7%) as the most frequent cause of CM. According to our results, dairy cows with CM had the highest MDA levels, the lowest GSH, and total GSH levels in both blood and milk samples however, high MDA levels and low GSH levels in milk samples with SM were observed. Based on our results, lipid oxidant MDA and antioxidant GSH could be excellent biomarkers of cow's milk for developing inflammation of the mammary gland. In addition, there was no link between nutrition and MDA and GSH levels.

Divergent Analyses of Genetic Relatedness and Evidence-Based Assessment of Therapeutics of Staphylococcus aureus from Semi-intensive Dairy Systems.

Use of antibiotics without following standard guidelines is routine practice in developing countries which is giving rise to genetic divergence and increased drug resistance. The current study analyzed genetic divergence and drug resistance by S. aureus and therapeutic efficacy of novel antibiotic combinations. The study revealed that 42.30% (minimum 20%-maximum 70%) of milk samples are positive for S. aureus. Study also revealed seven SNPs in the S. aureus nuc gene (c.53A>G, c.61A>G, c.73T>C, c.93C>A, c.217C>T, c.280T>C, and c.331T>A). Local isolates Staph-2 and Staph-3 were closely related to Bos taurus nuc gene (bovine S. aureus), while Staph-1 was closely related to Homo sapiens (human S. aureus) indicating shifting of host. Change of two amino acids and staphylococcal nuclease conserved domain was observed in all local isolates of S. aureus. The isoelectric points predicted by protParam of Staph-1, Staph-2, and Staph-3 proteins were 9.30, 9.20, and 9.20, respectively. The antibiotic susceptibility profile of S. aureus presented highest resistance against penicillin (46.67%) and glycopeptide (43.33%). When a single antibiotic regimen was adopted in a field trial, the highest efficacy was reported in the case of oxytetracycline (80%) while lowest was presented by azithromycin. Among antibiotics' combined regimen, the highest efficacy (80%) was presented by gentamicin with oxytetracycline: cefotaxime with vancomycin; and ciprofloxacin with vancomycin. The current study concluded rising percentages of S. aureus from dairy milk, proofs of genetic host shifts, and altered responses of in on field therapeutics.

Economics of reducing antibiotic usage for pathogen-specific clinical mastitis through genomic selection and disease management.

The recent introduction of the mastitis resistance trait into the US genomic selection index, Lifetime Net Merit 2018 (NM$), is expected to reduce the incidence of pathogen-specific clinical mastitis (PS-CM) incidence in U.S. dairy herds. To maximize the herd performance by reducing the PS-CM incidence, we compared the herd performance of 6 different replacement selection and PS-CM disease management strategies. We used an agent-based dairy simulation model in which the performance of individual animals was affected by the genetic traits included in the NM$. The genetic trends for the sires used affected the 15 yr herd performance. Each animal had a daily underlying base probability of contracting 5 different types of PS-CM (Staphylococcus aureus, Streptococcus dysgalactiae, Strep. uberis, Escherichia coli and Klebsiella) during lactation. On top of this base probability, the genetic and environmental components of the mastitis resistance trait (MAST) determined the actual incidence of PS-CM. Genomic estimated breeding values were simulated for each animal, based on which replacement selection decisions were made. The PS-CM associated milk loss, increased somatic cell count, decreased conception, and increased mortality and culling were accounted for in the simulated genomic estimated breeding values of different correlated production and reproduction traits included in NM$. The 6 different strategies illustrate the effects of replacement selection and PS-CM management decisions on PS-CM incidence, herd antibiotic use (ABU) and herd economics, over the course of 15 yr. Due to the genetic gain in the MAST, the incidence of PS-CM decreased on average by 10% points in 15 yr, which trickled down to overall reduction in herd ABU. Our PS-CM treatment and prevention strategies were assumed to be based on precise information about the 5 different PS-CM causative pathogens. Hence the corresponding ABU further decreased over the course of 15 years, when compared to blanket PS-CM therapies, which used antibiotics for all cases of CM. Our strategies illustrated the fact that herds combining genomic selection and following precise treatment and prevention strategies for PS-CM could reduce the 15-year cumulative ABU against PS-CM significantly. Capitalizing on the genetic gain in NM$ traits, the average profit per cow per year was higher on average by $1209 in year 15 when compared to year 0 for the 6 strategies simulated. We concluded that three decision strategies (genomic selection for NM$, selective therapy for PS-CM, and selective dry cow therapy for PS-CM prevention) when combined can reduce the incidence of PS-CM and the associated ABU, while increasing the profitability of the herd.

Efficacy Assessment of Phage Therapy in Treating Staphylococcus aureus-Induced Mastitis in Mice.

The primary aim of this study was to evaluate the efficacy of phage against mastitis induced by drug-resistant S. aureus in a mouse model. In this study, five S. aureus phages-4086-1, 4086-2, 4086-3, 4086-4, and 4086-6-were isolated from milk samples secreted by mastitis cows. Transmission electron microscopy showed that all the five phages had icosahedral heads and short non-contractile tails, which are typical characteristics of the family Podoviridae. All these phages were species-specific against S. aureus. The one-step growth curve showed a short latency period (10-20 min) and high burst size (up to 400 PFU/infected cell). To evaluate the effectiveness of the phage 4086-1 in the treatment against mastitis, a mouse model of mastitis was challenged with drug-resistant S. aureus. The results showed the proliferation of S. aureus in the mammary glands was significantly inhibited after treating by phage 4086-1. The concentrations of TNF-α and IL-6 decreased significantly, which demonstrated the phages could effectively alleviate the inflammatory responses. Furthermore, the histopathological analysis showed that inflammatory infiltration in the mammary glands was significantly reduced. These results demonstrate that phage may be a promising alternative therapy against mastitis caused by drug-resistant S. aureus.

A stochastic modelling approach to determine the effect of diverse Staphylococcus aureus strains on the economic and epidemiological outcomes of mastitis intervention strategies in dairy cattle.

Staphylococcus aureus (S. aureus) strains with considerable genetic and phenotypic differences have previously been identified. The economic and epidemiologic impact of S. aureus mastitis has been investigated, but none of these studies took differences between strains into account. Here we aimed to investigate how differences between S. aureus strains affect the economic and epidemiologic outcome of various intervention strategies against clinical and subclinical intramammary infections. Five S. aureus strains were modelled using a stochastic bio-economic model simulating a dairy herd of 200 cows using single-day time steps. The strain characteristics of the five simulated S. aureus strains (general, contagious, spill-over, clinical and persistent) were based on divergent phenotypes as described in literature. Outcomes of the model included incidence (both clinical and subclinical), number of antibiotic treatment days, number of culled cows, and net income. Intervention strategies against clinical and subclinical intramammary infections were based on (variations of) intramammary antibiotic treatment, testing, and culling. Both single and multiple pathogen (intramammary infection caused by S. aureus, Escherichia coli, and non-aureus staphylococci) scenarios were simulated to determine the effect of the five S. aureus strains on the impact of 19 different intervention strategies. The results showed that the incidence (both clinical and subclinical), number of treatment days, number of culled cows, and net income varied considerably for the different S. aureus strains. Comparison of the model outcomes within and between strains showed that for most intervention strategies the relative impact differed per strain. However, the intervention strategy with the best outcome for most variables and strains was the culling of cows with a recovery probability lower than 50%. This shows that the relative economic and epidemiologic impact of most of the modelled intervention strategies were strain-dependent, while some intervention strategies were not strain-dependent. From this, we conclude that, depending on the intervention strategy applied on a farm, it could be advantageous to type S. aureus to determine whether it would be economically and epidemiologically beneficial for the existing intervention strategy to be changed.