The effect of recurrent episodes of clinical mastitis caused by gram-positive and gram-negative bacteria and other organisms on mortality and culling in Holstein dairy cows

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.

In vitro antimicrobial resistance of Escherichia coli, Serratia marcescens, Klebsiella oxytoca and Klebsiella pneumoniae on Bavarian dairy farms between 2014-2022

The objective of this study was to describe the prevalence of antimicrobial resistance of E. coli, K. oxytoca, K. pneumoniae, and S. marcescens from quarter milk samples submitted to the udder health laboratory of the Bavarian Animal Health Services (TGD) in Southern Germany between 2014 and 2022. All samples were tested with the California Mastitis Test and analyzed with a standard microbroth dilution to determine the minimum inhibitory concentrations (MIC). The antimicrobials tested were amoxicillin/clavulanate, cefazoline, kanamycin/cefalexin, cefoperazone, cefquinome, and marbofloxacin. Breakpoints were chosen in accordance with CLSI. Over the study period, E. coli, K. oxytoca, and K. pneumoniae showed only few resistances to all antimicrobials tested. For those pathogens MIC 50 and MIC 90 were below breakpoint for all antimicrobials except cefoperazone over the 9 years. A decrease in MIC could be seen for E. coli and K. oxytoca for all of the antimicrobials. While the MIC for K. pneumoniae stayed more stagnant, the prevalence of resistance still decreased overall. S. marcescens isolates were proven intrinsically resistant to amoxicillin/clavulanate and cefazolin and while in vitro resistances were low for all other antimicrobials tested, S. marcescens tended toward higher MIC for most of the antimicrobials over the years. Over time, there was also an overall increase in the number of isolates for all 4 pathogens per year. Starting 2018 there was steep increase in the number of isolates particularly from clinical cases. This jump in numbers coincided with a change of the regulation for veterinary drug prescriptions in Germany in 2018 that required, among other things, antimicrobial resistance testing before a change of antibiotics in the course of treatment and the use of critically important antimicrobials. Overall, while the pathogens increased in numbers, the prevalence of their antimicrobial resistance remained low.

Prevalence and Molecular Characteristics of Enterococci Isolated from Clinical Bovine Mastitis Cases in Ningxia

Purpose

This study aimed to investigate the prevalence and genetic characterization of enterococcal isolates (Enterococcus faecalis, Enterococcus faecium and Enterococcus hirae) isolated from clinical bovine mastitis cases in Ningxia, China.

Patients and Methods

The enterococci were identified by 16S rRNA amplification and sequencing. Antimicrobial resistance was determined by disc diffusion method. Virulence and antimicrobial resistance genes were detected by PCR assays.

Results

Overall, 198 enterococcal isolates were identified from 2897 mastitis samples, including 137 (4.7%) E. faecalis, 50 (1.7%) E. faecium and 11 (0.4%) E. hirae. E. faecalis, E. faecium and E. hirae isolates showed high resistance to tetracycline (92.7%, 68.0%, 90.9%), followed by erythromycin (86.9%, 76.0%, 72.7%). The multidrug-resistant strains of E. faecalis and E. faecium were 29 (21.2%) and 13 (26.0%), respectively. The resistance of E. faecalis, E. faecium and E. hirae isolates to tetracycline is mainly attributed to the presence of tetL (alone or combined with tetM and/or tetK), the erythromycin resistance to ermB (alone or combined with ermC and/or ermA). Moreover, cpd (94.2%), gelE (77.4%), efaAfs (93.4%), and esp (79.6%) were the most common virulence genes in E. faecalis. In E. faecium, except for the gene efaAfs (82.0%), other virulence genes are rarely found. Only two strains of E. hirae carrying asa1 gene were detected.

Conclusion

The results of this study can provide a reference for the prevention and treatment of bovine mastitis caused by enterococci.

Global losses due to dairy cattle diseases: A comorbidity-adjusted economic analysis

An economic simulation was carried out over 183 milk-producing countries to estimate the global economic impacts of 12 dairy cattle diseases and health conditions: mastitis (subclinical and clinical), lameness, paratuberculosis (Johne's disease), displaced abomasum, dystocia, metritis, milk fever, ovarian cysts, retained placenta, and ketosis (subclinical and clinical). Estimates of disease impacts on milk yield, fertility, and culling were collected from the literature, standardized, meta-analyzed using a variety of methods ranging from simple averaging to random-effects models, and adjusted for comorbidities to prevent overestimation. These comorbidity-adjusted disease impacts were then combined with a set of country-level lactational incidence and/or prevalence estimates, herd characteristics, and price estimates within a series of Monte Carlo simulations that estimated and valued the economic losses due to these diseases. It was estimated that total annual global losses are USD 65 billion (B). Subclinical ketosis, clinical mastitis, and subclinical mastitis were the costliest diseases modeled, resulting in mean annual global losses of approximately USD 18B, USD 13B, and USD 9B, respectively. Estimated global annual losses due to clinical ketosis, displaced abomasum, dystocia, lameness, metritis, milk fever, ovarian cysts, paratuberculosis, and retained placenta were estimated to be USD 0.2B, 0.6B, 0.6B, 6B, 5B, 0.6B, 4B, 4B, and 3B, respectively. Without adjustment for comorbidities, when statistical associations between diseases were disregarded, mean aggregate global losses would have been overestimated by 45%. Although annual losses were greatest in India (USD 12B), the USA (USD 8B), and China (USD 5B), depending on the measure of losses used (losses as a percent of GDP, losses per capita, losses as a percent of gross milk revenue), the relative economic burden of these dairy cattle diseases across countries varied markedly.

The Influence of Milk Leakage, Udder Pressure and Further Risk Factors on the Development of New Intramammary Infections during the Dry Period of Dairy Cows

Prevention of new intramammary infection (NIMI) during the dry period (DP) is essential to prevent the development of mastitis in dairy cows. To investigate risk factors for NIMI, 212 cows, comprising a total of 848 udder quarters, were examined in this study. Quarter milk samples were taken on the day of drying off and 7 ± 3 days after calving. Cow- and quarter-level associated risk factors were assessed at the beginning of the DP and after calving. In total, 7.1% of the udder quarters developed an NIMI between the samplings. Non-aureus staphylococci (40.4%) and Gram-negative pathogens (22.8%) were most frequently the cause of NIMI. The observed milk leakage prevalence was 16.7%, with a peak 24 h after drying off. Simultaneously, the udder pressure peaked 24 h after drying off. A significant correlation between milk yield on the day before drying off and milk leakage could be proven. Cows with quarters leaking milk produced an average milk yield of 28.32 kg on the day before drying off. Generalised linear mixed models and odds ratios were calculated to determine the significant risk factors for NIMI during the DP and early lactation. Quarters leaking milk had 3.4 higher odds for NIMI between the samplings compared to quarters without milk leakage. Quarters from cows with dirty udders had 3.1 higher odds of developing an NIMI between the samplings compared to quarters from cows with clean udders. The results of this study demonstrate the importance of dry cow management before drying off and during the critical period of active involution of the udder tissue.

Genetic parameters and genome-wide association studies for mozzarella and milk production traits, lactation length, and lactation persistency in Murrah buffaloes

Genetic and genomic analyses of longitudinal traits related to milk production efficiency are paramount for optimizing water buffaloes breeding schemes. Therefore, this study aimed to (1) compare single-trait random regression models under a single-step genomic BLUP setting based on alternative covariance functions (i.e., Wood, Wilmink, and Ali and Schaeffer) to describe milk (MY), fat (FY), protein (PY), and mozzarella (MZY) yields, fat-to-protein ratio (FPR), somatic cell score (SCS), lactation length (LL), and lactation persistency (LP) in Murrah dairy buffaloes (Bubalus bubalis); (2) combine the best functions for each trait under a multiple-trait framework; (3) estimate time-dependent SNP effects for all the studied longitudinal traits; and (4) identify the most likely candidate genes associated with the traits. A total of 323,140 test-day records from the first lactation of 4,588 Murrah buffaloes were made available for the study. The model included the average curve of the population nested within herd-year-season of calving, systematic effects of number of milkings per day, and age at first calving as linear and quadratic covariates, and additive genetic, permanent environment, and residual as random effects. The Wood model had the best goodness of fit based on the deviance information criterion and posterior model probabilities for all traits. Moderate heritabilities were estimated over time for most traits (0.30 ± 0.02 for MY; 0.26 ± 0.03 for FY; 0.45 ± 0.04 for PY; 0.28 ± 0.05 for MZY; 0.13 ± 0.02 for FPR; and 0.15 ± 0.03 for SCS). The heritability estimates for LP ranged from 0.38 ± 0.02 to 0.65 ± 0.03 depending on the trait definition used. Similarly, heritabilities estimated for LL ranged from 0.10 ± 0.01 to 0.14 ± 0.03. The genetic correlation estimates across days in milk (DIM) for all traits ranged from -0.06 (186-215 DIM for MY-SCS) to 0.78 (66-95 DIM for PY-MZY). The SNP effects calculated for the random regression model coefficients were used to estimate the SNP effects throughout the lactation curve (from 5 to 305 d). Numerous relevant genomic regions and candidate genes were identified for all traits, confirming their polygenic nature. The candidate genes identified contribute to a better understanding of the genetic background of milk-related traits in Murrah buffaloes and reinforce the value of incorporating genomic information in their breeding programs.

Economic impact of treatment of subclinical mastitis 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 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 treatment of SCM during early lactation using a nisin-based intramammary treatment under different scenarios which 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 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 (90th percentage range = $148 to $187), while the cost of a clinical mastitis case was $521 (90th percentage range = $435 to $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. 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, economic impact was highly influenced by factors such as rate of bacteriological cure, cost of treatment, and parity of affected animal. These factors should be considered when deciding to use nisin as a treatment for SCM.

Exploring the Milk Microbiota of Healthy and Mastitic Nili Ravi Buffalo Using 16S rRNA Gene Base Metagenomic Analysis

The Nili Ravi, a buffalo breed from Pakistan, significantly contributes to the dairy industry. Mastitis is one of the major challenges affecting milk production in this breed. The objective of the current study was to identify the bacterial communities and diversity in healthy and mastitic milk of this breed. Milk samples (n = 14) were collected from Nili Ravi buffaloes with different udder health statuses, i.e., healthy (5), subclinical mastitis (4), and clinical mastitis (5). The DNAs were extracted, subjected to partial amplification of 16S rDNA (V3 and V4 regions), and sequenced using the Illumina platform. The results revealed variations in the bacterial communities in the milk of animals with different udder health statuses. Proteobacteria was the predominant phylum in the healthy group, while clinical and subclinical mastitis milk had a higher abundance of Firmicutes. Dominant bacterial genera in the healthy group were Streptococcus (11.60%), Herbaspirillum (7.65%), and Staphylococcus (4.70%), whereas the clinical mastitis group was dominated by Streptococcus (33.96%), Staphylococcus (7.87%), and Corynebacterium (2.68%), and the subclinical mastitis group was dominated by Bacillus (15.70%), Corynebacterium (6.70%), and Staphylococcus (6.58%). Assignment of operational taxonomic units at the species level resulted in most species being assigned to uncultured or unknown bacteria or remaining unassigned. Alpha diversity indices indicated lower microbial diversity in the clinical mastitis group, while beta diversity indices showed a scattered pattern of sample clustering in PCA plots among different groups. It is concluded that bacterial diversity in the milk of Nili Ravi buffaloes suffering from clinical mastitis is lower compared to healthy and subclinical mastitis cases. It is concluded that the variations in the microbiota of healthy and mastitic milk may be further investigated and exploited as signature microbes associated with the udder health status of Nili Ravi buffalo.

Incidence rate, risk factors, and bacterial causes of clinical mastitis on dairy farms in Hawassa City, southern Ethiopia

Mastitis is the most common disease of dairy cattle worldwide, causing economic losses due to reduced yield and poor quality of milk. It is of particular concern in Ethiopia, where effective prevention and control practices are lacking. The objective of the present prospective longitudinal study was to estimate the incidence rate of clinical mastitis (CM), identify the risk factors, isolate the bacterial agents, and determine the risk of recurrence. For this purpose, a total of 217 lactating cows were followed up every two weeks from calving to drying off or the end of the study period. Of these, 79 (36.41%) developed CM, of which 23% had recurrent infections in the same or a different quarter. The overall incidence rate of CM was 83.72 (95% CI: 63.2-98.2) cases per 100 cow-years at risk. In the multivariable Cox regression model, the risk of CM was found to be significantly higher in multiparous cows (HR = 1.96; p = 0.03), in cows with a history of mastitis (HR = 2.04; p = 0.030), in cows that had severely keratinized teat end condition (HR = 7.72; p < 0.001) and in cows kept in poorly cleaned barns (HR = 1.89; p = 0.007). The pathogenic bacteria isolated from mastitis-positive cows were Staphylococcus aureus (28.1%), E. coli (21.1%), Bacillus spp. (14%), Streptococcus spp. (14%), coagulase-negative staphylococci (12.3%), non aureus staphylococci (5.3%), Enterobacter spp. (3.5%), Klebsiella spp. (1.8%), Corynebacterium spp. (1.8%), and Proteus spp. (1.8%). The high incidence rate of CM in the present study shows that the disease spreads rapidly and can be responsible for a significant economic loss to milk producers in the study area. Therefore, raising awareness among dairy farmers, early detection and treatment of cases, post-milking teat disinfection, improvement of the hygienic status of cows and barns, use of dry cow therapy, and culling of chronic cases are recommended as viable measures to prevent and control clinical mastitis in the study area.

Culling and mortality of dairy cows: why it happens and how it can be mitigated

The United Nations estimates that the global population will total 9.7 billion in 2050. Rapid population growth pose a significant obstacle to achieving the Sustainable Development Goals, particularly eradicating hunger and poverty. In view of the expanding population growth, food production ideally should triple to prevent massive food shortages. Sustainable food and nutrition security is the focal point of the dairy industry. Dairy production plays a pivotal role in addressing and advancing global food and nutrition security. It serves as a major source of protein, calcium, and phosphorus in many families in developing countries with a fast-growing population. Consequently, the dairy industry is expected to grow by approximately 26% in the next 10 years and produce an estimated 1077 million tonnes of milk by 2050. However, the growth and distribution of the dairy industry is limited by many factors such as culling and mortality of dairy cows. Several studies highlight reproduction failures, old age, poor milk yield, diseases (mastitis, lameness, and dystocia), and heat stress as some reasons for culling of dairy cows. Hence, this review highlights the factors influencing culling and mortality in dairy production farms, and discusses mitigating measures to limit culling.

Culling and mortality of dairy cows: why it happens and how it can be mitigated

The United Nations estimates that the global population will total 9.7 billion in 2050. Rapid population growth pose a significant obstacle to achieving the Sustainable Development Goals, particularly eradicating hunger and poverty. In view of the expanding population growth, food production ideally should triple to prevent massive food shortages. Sustainable food and nutrition security is the focal point of the dairy industry. Dairy production plays a pivotal role in addressing and advancing global food and nutrition security. It serves as a major source of protein, calcium, and phosphorus in many families in developing countries with a fast-growing population. Consequently, the dairy industry is expected to grow by approximately 26% in the next 10 years and produce an estimated 1077 million tonnes of milk by 2050. However, the growth and distribution of the dairy industry is limited by many factors such as culling and mortality of dairy cows. Several studies highlight reproduction failures, old age, poor milk yield, diseases (mastitis, lameness, and dystocia), and heat stress as some reasons for culling of dairy cows. Hence, this review highlights the factors influencing culling and mortality in dairy production farms, and discusses mitigating measures to limit culling.

NIR-triggered photocatalytic and photothermal performance for sterilization based on copper sulfide nanoparticles anchored on Ti3C2Tx MXene

Harmful bacterial flourish with the increase in environmental pollution and pose a great threat to human health. Thus, developing new and efficient antibacterial materials is imperative to reduce the pollution caused by traditional sterilization materials and improve sterilization efficiency. In this study, a new photocatalytic antibacterial material was developed to achieve an efficient antibacterial effect. Ti₃C₂T_x@CuS composites were synthesized by simple hydrothermal method, by which copper sulfide (CuS) nanoparticles were anchored on the surface of Ti₃C₂T_x to sharply improve the photocatalytic its antibacterial ability. Ti₃C₂T_x@CuS exhibits excellent antibacterial activity against Escherichia coli and Staphylococcus aureus with bactericidal rates of 99.6% and 99.1%, respectively. Photoluminescence spectroscopy (PL), decay time PL, photocurrent test, electrochemical impedance spectroscopy and finite element method showed that the formation of Ti₃C₂T_x@CuS heterojunction promoted the separation of electrons and holes, improved the electron transport efficiency, and elevated the generation of reactive oxygen species. Moreover, Ti₃C₂T_x@CuS has a stronger photothermal effect and causes more heat release than CuS to improve antibacterial performance. The Ti₃C₂T_x@CuS heterojunction has a broad application prospect in the disinfection and antibacterial fields.

Metformin Inhibits Lipoteichoic Acid-Induced Oxidative Stress and Inflammation Through AMPK/NRF2/NF-κB Signaling Pathway in Bovine Mammary Epithelial Cells

The objective of this research was to explore the effect of metformin on the lipoteichoic acid (LTA)–induced mastitis model using isolated primary bovine mammary epithelial cells (PBMECs). The PBMECs were exposed to either 3 mM metformin for 12 h as a metformin group (MET) or 100 μg/mL LTA for 6 h as LTA group (LTA). Cells pretreated with 3 mM metformin for 12 h followed by washing and 100 μg/mL LTA exposure for 6 h served as the MET + LTA group. Phosphate-buffered saline was added to cells as the control group. PBMECs pretreated with different metformin doses were analyzed by a flow cytometry (annexin V–fluorescein isothiocyanate assay) to detect the cell apoptotic rate. We performed quantitative reverse transcriptase–polymerase chain reaction and Western blot analysis to evaluate the inflammatory and oxidative responses to metformin and LTA by measuring cellular cytotoxicity, mRNA expression, and protein expression. Immunofluorescence was used to evaluate nuclear localization. The results showed that the gene expression of COX2, IL-1β, and IL-6 significantly increased in the cells challenged with LTA doses compared to control cells. In inflammatory PBMECs, metformin attenuated LTA-induced expression of inflammatory genes nuclear factor κB (NF-κB) p65, tumor necrosis factor α, cyclooxygenase 2, and interleukin 1β, as well as the nuclear localization and phosphorylation of NF-κBp65 protein, but increased the transcription of nuclear factor erythroid 2–related factor 2 (Nrf2) and Nrf2-targeted antioxidative genes heme oxygenase-1 (HO-1) and Gpx1, as well as the nuclear localization of HO-1 protein. Importantly, metformin-induced activation of Nrf2 is AMP-activated protein kinase (AMPK)–dependent; as metformin-pretreated PBMECs activated AMPK signaling via the upregulation of phosphorylated AMPK levels, cell pretreatment with metformin also reversed the translocation of Nrf2 that was LTA inhibited. This convergence between AMPK and Nrf2 pathways is essential for the anti-inflammatory effect of metformin in LTA-stimulated PBMECs. Altogether, our results indicate that metformin exerts anti-inflammation and oxidative stress through regulation of AMPK/Nrf2/NF-κB signaling pathway, which highlights the role of AMPK as a potential therapeutic strategy for treatment of bovine mastitis.

Researching 100 t cows: An innovative approach to identify intrinsic cows factors associated with a high lifetime milk production

Longevity is an important trait both from an economic and social perspective. Modern dairy cows are criticized for their short productive lifespan: only a minority of animals survives to a fourth lactation, implying that most cows are culled before reaching their maximal potential. In contrast, the population of 100 t cows (HT), reaching the threshold of 100,000 kg lifetime milk yield, is growing rapidly. As these cows combine a long lifespan with high functionality, a better understanding of their intrinsic characteristics might help us to improve the overall lifespan and lifetime production in dairy cows. The aim of the present research was to compare HT with their less-producing herd mates in order to identify intrinsic cow factors associated with longevity and high lifetime production. Therefore, we matched 26,248 HT with 691,597 herd mates, born in the same year in the same herd. Data were provided by Coöperatie rundveeverbetering (CRV) and contained birth dates, calving dates, milk yield and dam information. In addition, scores for conformation traits based on classifications in the first lactation and breeding values (for milk yield, fertility, udder health and claw health) were provided. Multivariable conditional logistic regression models were built to identify factors associated with reaching a lifetime milk yield of 100,000 kg. Results revealed cows born in September and born out of heifers to have the highest odds to become a HT. When cows received a score ≥ 83 (population average 80) for udder and feet & legs conformation, they had higher odds of reaching the 100,000 kg threshold. While a greater body condition and larger rump angle increased the odds of becoming a HT, this was decreased in cows with a large body depth. Finally, breeding values for milk yield, fertility, udder health and claw health were positively associated with the likelihood of reaching a lifetime milk yield of 100,000 kg. In conclusion, to increase lifetime milk yield in dairy herds, farmers should select heifers with high scores for conformation traits like udder and feet & legs and high breeding values for milk yield, fertility and udder health. Furthermore, our data suggest that being born in September out of a heifer potentially contributes to reaching a high lifetime milk yield.

Description of the Characteristics of Five Bedding Materials and Association With Bulk Tank Milk Quality on Five New York Dairy Herds

Environmental mastitis represents a major challenge on dairy farms where contagious pathogens are controlled by improved milking procedures. Therefore, research focused on the environment is important to improve udder health programs. The objectives of this prospective and descriptive study were to (1) describe bedding bacterial counts, pH, and dry matter (DM) of five different bedding types (organic: manure solids, straw, paper fiber; inorganic: sand, recycled sand) and (2) explore the association between bedding bacterial counts with bulk tank milk quality. This study took place within five conveniently selected commercial dairy herds, each with a predominant bedding material in lactating pens. Bedding samples (used n = 237; fresh n = 53) were collected monthly from July 2018 to July 2019 following a standard operating procedure (SOP) to minimize sampling variability. Additionally, a bulk tank (BT) milk sample (n = 40) was collected on the same day unless milk had been picked up prior to arrival. Both BT and bedding samples were submitted to the laboratory for culture and bacterial identification and quantification of Streptococcus spp, coliforms, and non-coliforms as well as detection of several pathogens of mastitis importance. Somatic cell count was evaluated in BT samples. Within bedding type, the correlation between bedding characteristics and bacterial counts in bedding was evaluated using Pearson correlation. Within bedding type, the correlation between bacterial counts in bedding samples and bacterial counts in BT were determined. The Kruskal–Wallis test was used to evaluate the bacterial count by bedding type and to evaluate BT somatic cell count differences based on bedding type. In fresh bedding, bacterial counts were generally higher for manure solids for all bacterial groups compared with other materials. In used samples, organic materials had the highest levels of all bacterial groups. The proportion of samples with detectable organisms of mastitis importance varied within and among herds in both bedding and BT samples throughout the study period. In bedding samples, a higher DM content had the lowest levels of bacterial growth compared with those with lower DM content. Most bedding samples were on the alkaline side within a pH range of 8–11. No relationship between bacterial counts and pH was observed. No associations between BT bacteria counts and bedding bacterial counts were observed. No association between bulk tank somatic cell counts based on bedding type were observed. Despite using an SOP for bedding sampling in an effort to consistently collect samples, we still observed a large amount of variability both within and among bedding samples. This variability may have obscured any potential association between BT milk quality and bedding type.

Heat stress and cow factors affect bacteria shedding pattern from naturally infected mammary gland quarters in dairy cattle

Mastitis-causing pathogens are shed from infected mammary gland quarters and thus contribute to an increased risk of new intramammary infections. The objective of the current study was to investigate the shedding characteristics of various mastitis-causing pathogens and associated animal-specific (somatic cell score and parity) and environmental (heat stress) factors. In a longitudinal study, infected udder quarters were sampled consecutively on 5 dairy farms in Germany. To capture climatic factors, temperature-humidity index (THI) was calculated. In the laboratory analysis, the pathogens and their counts in the milk samples were determined. A generalized linear mixed model with gamma link was used to evaluate the factors influencing pathogen-shedding characteristics. The variables somatic cell count, pathogen, parity, and THI had significant influence on pathogen shedding. Staphylococci were shed in lower values than streptococci. The pathogen shedding from mammary gland quarters with intramammary infections was higher in the first and second lactation than in higher lactations. Exceeding the THI threshold 60 resulted in higher pathogen counts on the same day. This was only caused by the pathogens yeasts and Streptococcus uberis. Possible mechanisms causing differences in pathogen shedding are changes in the counts due to influenced milk quantities, better growth conditions at higher temperatures, or altered immunological reactions. The mechanisms often remain speculative and require further investigation. The study underlines the contribution of cows with high somatic cell counts regarding the transmission of mastitis pathogens within a herd. Furthermore, it becomes clear that heat stress in Germany influences udder health and that prevention measures are useful.

Effects of Peptidoglycan, Lipoteichoic Acid and Lipopolysaccharide on Inflammation, Proliferation and Milk Fat Synthesis in Bovine Mammary Epithelial Cells

The mammary gland of the cow is particularly susceptible to infections of a wide range of pathogenic bacteria, including both Gram-positive and Gram-negative bacteria. The endotoxins of these pathogenic bacteria include peptidoglycan (PGN), lipoteichoic acid (LTA) and lipopolysaccharide (LPS), and they are the pathogen-associated molecular patterns (PAMPs) to induce mastitis. LPS can directly inhibit proliferation and milk fat synthesis of bovine mammary epithelial cells (BMECs) while inducing mastitis, but it is unclear whether PGN and LTA also have such effects. Furthermore, since the three PAMPs usually appear simultaneously in the udder of cows with mastitis, their synergistic effects on proliferation and milk fat synthesis of BMECs are worth investigating. The immortalized BMECs (MAC-T cells) were stimulated for 24 h using various concentrations of PGN, LTA and LPS, respectively, to determine the doses that could effectively cause inflammatory responses. Next, the cells were stimulated for 24 h with no endotoxins (CON), PGN, LTA, LPS, PGN + LTA, and PGN + LTA + LPS, respectively, with the predetermined doses to analyze their effects on proliferation and milk fat synthesis of BMECs. PGN, LTA and LPS successfully induced inflammatory responses of BMECs with doses of 30, 30 and 0.1 μg/mL, respectively. Although the proliferation of BMECs was significantly inhibited in the following order: LTA < PGN + LTA < PGN + LTA + LPS, there was no change in cell morphology and cell death. LTA significantly promoted the expression of fatty acid synthesis-related genes but did not change the content of intracellular triglyceride (TG), compared with the CON group. The mRNA expression of fatty acid synthesis-related genes in the LPS group was the lowest among all the groups. Meanwhile, LPS significantly decreased the content of intracellular non-esterified fatty acids (NEFAs) and TG, compared with the CON group. PGN had no effects on milk fat synthesis. Co-stimulation with PGN, LTA and LPS significantly increased the expression of fat acid synthesis-related genes and the intracellular NEFAs, but decreased intracellular TG, compared with sole LPS stimulation. Collectively, PGN, LTA and LPS showed an additive effect on inhibiting proliferation of BMECs. The promoting role of LTA in fatty acid synthesis might offset the negative effects of LPS in this regard, but co-stimulation with PGN, LTA and LPS significantly decreased intracellular TG content.

The Synergism of PGN, LTA and LPS in Inducing Transcriptome Changes, Inflammatory Responses and a Decrease in Lactation as Well as the Associated Epigenetic Mechanisms in Bovine Mammary Epithelial Cells

Mastitis is usually caused by a variety of pathogenic bacteria that include both Gram-positive and Gram-negative bacteria. Lipopolysaccharide (LPS) is the pathogen-associated molecular pattern (PAMP) of Gram-negative bacteria, and peptidoglycan (PGN) and lipoteichoic acid (LTA) are those of Gram-positive bacteria. The effects of LPS, PGN and/or LTA on inflammatory response and lactation in bovine mammary epithelial cells (BMECs) are well studied, but the epigenetic mechanisms of their effects received less attention. Furthermore, since the three PAMPs are often simultaneously present in the udder of cows with mastitis, it has implications in practice to study their additive effects. The results show that co-stimulation of bovine mammary epithelial cells with PGN, LTA, and LPS induced a higher number of differentially expressed genes (DEGs) and greater expressions of inflammatory factors including interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α (TNF-α), chemokine (C-X-C motif) ligand (CXCL)1, and CXCL6. In addition, co-stimulation further increased DNA hypomethylation compared with sole LPS stimulation. Co-stimulation greatly decreased casein expression but did not further decrease histone acetylation levels and affect the activity of histone acetyltransferase (HAT) and histone deacetylase (HDAC), compared with sole LPS stimulation. Collectively, this study demonstrated that PGN, LTA, and LPS had an additive effect on inducing transcriptome changes and inflammatory responses in BMECs, probably through inducing a greater decrease in DNA methylation. Co-stimulation with PGN, LTA, and LPS decreased casein expression to a greater degree, but it might not be linked to histone acetylation and HAT and HDAC activity.

Prediction of quarter level subclinical mastitis by combining in-line and on-animal sensor data

We investigated the potential for automatic detection of subclinical mastitis (SCM) in pasture-based automatic milking systems. The objective of the study was to determine the ability of electrical conductivity (EC), together with relative changes in daily activity (activity) and daily rumination (rumination) recorded using heat and rumination–long-distance tags, to predict quarter-level SCM. Activity (arbitrary unit/day) and rumination (min/day) data were determined across 21 days using heat and rumination–long-distance tags for 170 cows. Cows were allocated into the following three groups: SCM (n = 32, EC ≥ 7.5 millisiemens/cm (mS/cm) in one or more quarters and a positive bacteriological culture in the corresponding quarter(s)); true-negative (TN, n = 9, EC ≥ 7.5 mS/cm and a negative culture in all four quarters); and apparently healthy (n = 129, no culture test and EC &lt; 7.5 mS/cm). Group mean differences in activity and rumination were compared using Welch’s t-tests. Logistic mixed models were used to predict SCM by EC, activity and rumination changes before mastitis detection, including parity information between SCM and TN groups. Cow- and quarter-specific information were included as random effects, followed by model assessment by producing receiver operating-characteristic curve and area under the curve (AUC) value. In total, 287 quarters were used in the prediction model, including 143 quarters with a positive culture (Gram-positive; n = 131, Gram-negative; n = 6, mixed; n = 6) and 144 quarters with a negative culture. On average, SCM group had 4.65% greater (P &lt; 0.01) activity and 9.89% greater (P &lt; 0.001) rumination than did the TN group and 11.70% greater (P &lt; 0.001) activity than did the apparently healthy group. A combined model with terms for EC, activity changes, rumination changes prior to detect SCM and parity had a better SCM prediction (AUC = 0.92) ability than did any of them separately (all AUC &lt; 0.8). Hence, we conclude that EC in combination with activity and rumination information can improve the accuracy of prediction of quarter-level SCM.

Combined effect of mastitis and parity on pregnancy loss in lactating Holstein cows

The main objective of this study was to examine the combined effect of mastitis and parity on pregnancy loss (PL) in lactating Holstein cows. A secondary objective was to estimate the cost of mastitis including that of PL attributable to mastitis. A total of 1,774 lactation periods from 1,047 Holstein cows with different parities from one dairy farm were included in a matched case-control study. All study cows were diagnosed pregnant by transrectal ultrasonography on day 33 after timed artificial insemination (TAI). Case cows (n = 222 lactations) were those later diagnosed non-pregnant by transrectal palpation on day 47 or 75 after TAI. Control cows (n = 1,552 lactations) were those confirmed pregnant by transrectal palpation on day 75 after TAI. Case cows were matched with eligible controls according to year of calving and calving-to-conception interval (CCI) ± 3 days. Cows with different parities were classified as exposed to subclinical mastitis (somatic cell score (SCS) > 4.5 in at least one Dairy Herd Improvement Association (DHIA) test day) or clinical mastitis (with or without evidence of subclinical mastitis) during two exposure periods: 1-42 days before breeding or 1-75 days during gestation (1 to PL diagnosis day in case cows, or 1-75 day in control cows). Conditional logistic regression was used to model the odds of PL as a function of previous exposure to mastitis in different parities. Cost of PL attributable to mastitis ($/case) among cows with mastitis was estimated based on attributable risk calculated in the epidemiologic analysis. We observed a higher than expected combined effect between exposure to mastitis (subclinical or clinical) before breeding and parity 3 or ≥ 4, and during gestation and parity ≥ 4 on PL. The cost of PL attributable to mastitis was highest ($196/case) in cows in parity ≥ 4 affected with clinical mastitis during gestation. Overall, study results indicate the impact of mastitis on PL is higher in older cows (parity ≥ 3). Dairy farmers and attending veterinarians can consider the combined effect of mastitis and parity when evaluating causes for PL and strategies for optimizing reproductive performance in dairy cows.

Estimating the impact of clinical mastitis in dairy cows on greenhouse gas emissions using a dynamic stochastic simulation model: a case study

The increasing attention for global warming is likely to contribute to the introduction of policies or other incentives to reduce greenhouse gas (GHG) emissions related to livestock production, including dairy. The dairy sector is an important contributor to GHG emissions. Clinical mastitis (CM), an intramammary infection, results in reduced milk production and fertility, increases culling and mortality of cows and, therefore, has a negative impact on the efficiency (output/input) of milk production. This may increase GHG emissions per unit of product. Our objective was to estimate the impact of CM in dairy cows on GHG emissions of milk production for the Dutch situation. A dynamic stochastic simulation model was developed to simulate the dynamics and losses of CM for individual lactations. Cows receive a parity (1 to 5+), a milk production and a calving interval (CI). Based on the parity, cows have a risk of CM, with a maximum of three cases in a lactation. Pathogens causing CM were classified as gram-positive bacteria, gram-negative bacteria, or other. Based on the parity and pathogen combinations, cows had a reduced milk production, discarded milk, prolonged CI and a risk of removal (culling and mortality) that reduce productivity of dairy cows and therefore increase GHG emissions per unit of product. Using life cycle assessment, emissions of GHGs were estimated from cradle to farm gate for processes along the milk production chain that are affected by CM. Processes included were feed production, enteric fermentation, and manure management. Emissions of GHGs were expressed as kg CO2 equivalents per ton of fat-and-protein-corrected milk (kg CO2e/t FPCM). Emissions of cows with CM increased on average by 57.5 (6.2%) kg CO2e/t FPCM compared with cows without CM. This increase was caused by removal (39%), discarded milk (38%), reduced milk production (17%) and prolonged CI (6%). The GHG emissions increased by 48 kg CO2e/t FPCM for cows with one case of CM, by 69 kg CO2e/t FPCM for cows with two cases of CM and by 92 kg CO2e/t FPCM for cows with three cases of CM compared with cows without CM. Preventing CM can be an effective strategy for farmers to reduce GHG emissions and can contribute to sustainable development of the dairy sector, because this also can improve the income of farmers and the welfare of cows. The impact of CM on GHG emissions, however, will vary between farms due to environmental conditions and management practices.

[Einfluss eines komplementärmedizinischen telefonischen Beratungssystems auf den Antibiotikaeinsatz bei Nutztieren in der Schweiz]

Hintergrund: Der Antibiotikaeinsatz bei Nutztieren fördert die Entwicklung antibiotikaresistenter Bakterien. Die Komplementärmedizin könnte einen Beitrag zur Reduktion von Antibiotika leisten, wird bisher jedoch nicht flächendeckend angeboten. Das Beratungsprogramm "Kometian" unter-stützt teilnehmende Landwirte darin, ihre Tiere komplementärmedizinisch zu behandeln. Methoden und Resultate: 128 von 223 teilnehmenden Betrieben nutzten in den ersten 3 Projektjahren die telefonische Beratung von Kometian. Die Mehrheit der Landwirte hielt Milchkühe. Frühestens 1 Woche nach der Kometianberatung wurde eine telefonische Nachfrage beim Tierbesitzer hinsichtlich des Gesundheitszustandes des Tieres durchgeführt. Es konnten so 661 Beratungsfälle recherchiert werden. In 486 Fällen erfolgte keine weitere schulmedizinische Behandlung, in 373 Fällen gab der Landwirt einen Behandlungserfolg an. Von 188 angefragten und seit mindestens einem Jahr an Kometian teilnehmenden Betrieben stellten 46 ihre Behandlungsjournale zur Verfügung. Die betriebliche antibiotische Behandlungsinzidenz sank signifikant (p < 0,001) von 27 vor Beitritt auf 18 Behandlungen pro 100 Tiere im ersten Jahr. Schlussfolgerung: Es scheint, dass Kometian einen Beitrag dazu leisten konnte, den Antibiotikaeinsatz auf Betriebsebene zu reduzieren.

BACKGROUND

A regular use of antibiotics in farm animals is assumed to induce antibiotic-resistant bacteria. Complementary and alternative medicine (CAM) may contribute to a reduction of antibiotic use but it is not extensively offered by Swiss veterinarians. The advisory program “Kometian” supports farmers in treating their animals with CAM.

METHODS AND RESULTS

128 out of 223 participating farmers used the telephone consultations of Kometian in the first 3 years of the project. The majority of the farmers kept dairy cattle. No sooner than 1 week after such a consultation, the famer was questioned by phone about the health progress of the animal. Thus, the development of health could be verified in 661 cases (of 714). 486 cases were not treated further by conventional medicine; in 373 cases the farmer reported a positive treatment effect. Of 188 examined farms, which had participated in the advisory program for at least 1 year, 46 made their treatment records available. The incidence of antibiotic treatment decreased significantly (p < 0.001) from 27 before entering the program to 18 treatments per 100 animals in the first year.

CONCLUSION

It seems that the advisory program Kometian could contribute to reduce the use of antibiotics on the farm level.

Photoperiodic Effects on Diurnal Rhythms in Cell Numbers of Peripheral Leukocytes in Domestic Pigs

The photoperiod is known to modulate immune cell number and function and is regarded essential for seasonal disease susceptibility. In addition, diurnal variations in the immune system are regarded important for immune competence. Whereas few studies investigated the influence of season, none investigated the specific effect of the photoperiod on these diurnal immune rhythms until now. Therefore, the present study compared diurnal rhythms in cell numbers of peripheral leukocyte types in domestic pigs held either under long day conditions (LD) or short day conditions (SD). Cosinor analyses of cell numbers of various peripheral leukocyte subtypes investigated over periods of 50 h revealed distinct photoperiodic differences in diurnal immune rhythms. Relative amplitudes of cell numbers of total leukocytes, NK cells, T cells, and monocytes in blood were higher under SD than LD. In addition, cell counts of total leukocytes, NK cells, T cells including various T cell subtypes, and eosinophils peaked earlier relative to the time of lights-on under SD than LD. In contrast, diurnal rhythms of neutrophil counts did not show photoperiodic differences. Mesor values did not differ in any leukocyte type. Generalized linear mixed model analyses revealed associations of leukocyte counts with plasma cortisol concentration and activity behavior in most investigated cell types. Moreover, the present study demonstrated photoperiodic effects on diurnal rhythms in plasma cortisol concentrations and activity behavior, which is in agreement with human and primate studies. The results of the present study imply stronger rhythmicity in leukocyte counts in general under SD. Common intrinsic mechanisms seem to regulate photoperiodic effects on diurnal rhythms in leukocyte counts, except for neutrophils, in domestic pigs. Our results reveal considerable insights into the regulation of immune rhythms in diurnally active species.

Symposium review: Intramammary infections-Major pathogens and strain-associated complexity

Intramammary infection (IMI) is one of the most costly diseases to the dairy industry. It is primarily due to bacterial infection and the major intramammary pathogens include Escherichia coli, Streptococcus uberis, and Staphylococcus aureus. The severity and outcome of IMI is dependent on several host factors including innate host resistance, energy balance, immune status, parity, and stage of lactation. Additionally, the infecting organism can influence the host immune response and progression of disease. It is increasingly recognized that not only the infecting pathogen species, but also the strain, can affect the transmission, severity, and outcome of IMI. For each of 3 major IMI-associated pathogens, S. aureus, Strep. uberis, and E. coli, specific strains have been identified that are adapted to the intramammary environment. Strain-dependent variation in the host immune response to infection has also been reported. The diversity of strains associated with IMI must be considered if vaccines effective against the full repertoire of mammary pathogenic strains are to be developed. Although important advances have been made recently in understanding the molecular mechanism underpinning strain-specific virulence, further research is required to fully elucidate the cellular and molecular pathogenesis of mammary adapted strains and the role of the strain in influencing the pathophysiology of infection. Improved understanding of molecular pathogenesis of strains associated with bovine IMI will contribute to the development of new control strategies, therapies, and vaccines. The development of enabling technologies such as pathogenomics, transcriptomics, and proteomics can facilitate system-level studies of strain-specific molecular pathogenesis and the identification of key mediators of host-pathogen interactions.

Impact of intramammary inoculation of inactivated Lactobacillus rhamnosus and antibiotics on the milk microbiota of water buffalo with subclinical mastitis

Water buffalo mastitis represents a major issue in terms of animal health, cost of therapy, premature culling and decreased milk yeld. The emergence of antibiotic resistance has led to investigate strategies to avoid or reduce antibiotics' based therapies, in particular during subclinical mastitis. The use of Generally Regarded As Safe bacteria (GRAS) such as Lactobacillus rhamnosus to restore the unbalance in mammary gland microbiota could provide potential corrective measures. The aim of this study was to investigate the changes in milk microbiota after the intramammary treatment with inactivated cultures of Lactobacillus rhamnosus of mammary gland quarters naturally affected by subclinical mastitis as compared to antibiotic therapy.A number of 43 quarters affected by subclinical mastitis with no signs of clinical inflammation and aerobic culture positive for pathogens were included in the study. The experimental design was as follows: 11 quarters were treated with antibiotics, 15 with inactivated cultures of Lactobacillus rhmnosus and 17 with PBS as negative control, by means of intrammary injection. Samples were collected at eight time points, pre- (T-29, T-21, T-15, T-7, T0 days) and post- treatment (T1, T2, and T6 days). Microbiological culture and Somatic Cell Count (SCC) were perfomed on all the samples, and microbiota was determined on milk samples collected at T0 and T6 by amplifying the V4 region of 16S rRNA gene by PCR and sequencing using next generation sequencing technique. Treatment with Lactobacillus rhamnosus elicited a strong chemotactic response, as determined by a significant increase of leukocytes in milk, but did not change the microbiological culture results of the treated quarters. For what concerns the analysis of the microbiota, the treatment with Lactobacillus rhamnosus induced the modification in relative abundance of some genera such as Pseudomonas and 5-7N15. As expected, antibiotic treatment caused major changes in microbiota structure with an increase of Methylobacterium relative abundance. No changes were detected after PBS treatment. In conclusion, the present findings demonstrated that the in vivo intrammmary treatment with Lactobacillus rhamnosus has a transient pro-inflammatory activity by increasing SCC and is capable to modify the microbiota of milk after six days from inoculation, albeit slightly, even when the bacterial cultures were heat inactivated. Further studies are necessary to assess the potential use of this GRAS as supportive therapy against mastitis.

Efficacy of vaccination with a Klebsiella pneumoniae siderophore receptor protein vaccine for reduction of Klebsiella mastitis in lactating cattle

Clinical mastitis caused by Klebsiella spp. is an emerging problem in the US dairy industry and results in a high degree of financial losses to dairy workers. This study was conducted as a randomized, blinded, and placebo-controlled efficacy study of a Klebsiella pneumoniae siderophore receptor protein (SRP) vaccine (Kleb-SRP), with a total of 569 cows and heifers enrolled. The study was designed to look at vaccine effect on Klebsiella mastitis; however, the SRP in Klebsiella are highly conserved across coliform bacteria, which means that the vaccine has potential for cross-protection against all coliforms. Cows were paired based on parity, days in milk at enrollment, and somatic cell count. Within pairs, individuals were randomized to receive either Kleb-SRP or a placebo formulation. Following vaccination, the incidence of Klebsiella spp. and total coliform mastitis from natural exposure were compared to determine the efficacy of the vaccine. When analyzing all cows, the reduction of mastitis risk was not significant, though milk production increased 0.31 kg/d and somatic cell counts were reduced by 20.1%. When administered before calving, the vaccine reduced the risk of Klebsiella and total coliform mastitis by 76.9 and 47.5% respectively; however, we observed no significant effect when administered after calving. The vaccine, when administered before calving, also increased milk production by an average of 1.74 kg/d and reduced somatic cell counts by 64.8%. When administered after calving, we noted a slight decrease in daily milk production (0.39 kg) but no significant effect on somatic cell counts. All cows in the study (including vaccinates and placebo) received multiple doses of a commercially available licensed Escherichia coli bacterin. It should be noted that this herd was chosen because of the high number of clinical Klebsiella clinical mastitis cases this herd experienced before the trial and the extreme environmental challenge that was present from bedding with dried manure solids. The data from this study demonstrate efficacy of the Kleb-SRP vaccine against Klebsiella mastitis alone and coliform mastitis in general (including all coliforms) when administered before the initiation of a lactation cycle.

Epidemiologic and economic analyses of pregnancy loss attributable to mastitis in primiparous Holstein cows

The main objective of the study reported here was to examine the association between pregnancy loss (PL) and previous exposure to clinical or subclinical mastitis before breeding or during gestation in primiparous Holstein cows. A secondary objective was to estimate the cost of clinical mastitis during gestation, including that of PL attributable to mastitis in study cows. A total of 687 primiparous Holstein cows from 1 dairy farm were included in a matched case-control study. Study cows were declared pregnant via ultrasound on d 33 after timed artificial insemination (TAI). Case cows (n = 78) were those diagnosed as nonpregnant by rectal palpation on d 47 or 75 after TAI. Control cows were those confirmed as pregnant by rectal palpation on d 47 and 75 after TAI. Case cows were matched with eligible controls according to year of calving and calving-to-conception interval ±3 d. Cows were assigned to 1 of 3 groups: (1) cows not affected with clinical or subclinical mastitis; (2) cows affected with subclinical mastitis (Dairy Herd Improvement Association somatic cell score >4.5); and (3) cows affected with clinical mastitis during 2 exposure periods, 1 to 42 d before breeding or during gestation (1 to PL diagnosis day for case cows, and 1 to 75 d for control cows). Conditional logistic regression was used to model the odds of PL as a function of previous exposure to mastitis in study cows. Mastitis before breeding was not associated with PL. The odds of PL were 2.21 times greater in cows affected with clinical mastitis during gestation (95% confidence interval = 1.01, 4.83), compared with cows without mastitis, after controlling for breeding type and lameness. The cost of clinical mastitis during gestation was $149, which includes the cost ($27) of PL attributable to mastitis. In conclusion, this study provides evidence that clinical mastitis during gestation can cause PL in primiparous dairy cows leading to economic losses.

Associations of the first occurrence of pathogen-specific clinical mastitis with milk yield and milk composition in dairy cows

The aim of this study was to estimate the associations of the first occurrence of pathogen-specific clinical mastitis (CM) with milk yield and milk composition (somatic cell count (SCC), lactose, fat, protein content in milk and milk urea nitrogen (MUN)). We studied 3149 dairy cows in 31 Hokkaido dairy farms in Japan. Five pathogen groups were studied: Streptococcus spp.; Staphylococcus aureus (S. aureus); coagulase-negative staphylococci (CNS); coliforms; and fungi. Test-day milk data and clinical records were collected from June 2011 until February 2014. Mixed models with an autoregressive correlation structure were fitted to quantify the effects of CM and several other control variables (herd, calving season, parity, week of lactation, and other diseases). Primipara (first lactation) and multipara (second and later lactations) were analysed separately. All pathogens, particularly S. aureus and fungi, were associated with significant milk losses in multipara. In this study, S. aureus and CNS infections were not associated with significant milk loss in primipara. All pathogens, in particular S. aureus and fungi, significantly increased SCC in both parity groups. All pathogens, especially CNS (in primipara) and S. aureus (in multipara), decreased lactose content. All pathogen groups except for fungi were associated with significant changes in fat, protein and MUN. Some pathogens such as Streptococcus spp. and coliforms seemed to be associated with long-term fat, protein and MUN changes. These findings provide estimates that could be used to calculate precise costs of CM, and also provide better indicators of pathogen-specific mastitis.

On-farm deaths of dairy cows are associated with features of freestall barns

On-farm death (OFD) of a dairy cow is always a financial loss for a farmer, and potentially a welfare issue that has to be addressed within the dairy industry. The aim of this study was to explore the associations between OFD of dairy cows, housing, and herd management in freestall barns. To achieve the goal, we followed 10,837 cows calving in 2011 in 82 herds. Data were gathered with observations and a structured interview during farm visits and from a national dairy herd improvement database. The hazard of OFD was modeled with a shared frailty survival model, with SAS 9.3 PHREG procedure (SAS Institute Inc., Cary, NC). The study population was 58% Ayrshire and 42% Holstein cows. The median herd size and mean milk yield in the study herds were 116 cows and 9,151 kg of milk per cow per year. The overall probability of OFD was 6.0%; 1.8% of the cows died unassisted and 4.2% were euthanized. Variation in OFD percentage between individual herds was large, from 0 to 16%, accounting for 0 to 58% of all removals in the herds. Keeping close-up dry cows in their own group was associated with higher hazard of OFD [hazard ratio (HR) = 1.37] compared with keeping them in the same pen with far-off dry cows. Higher hazard on OFD was observed when barns had only one kind of calving pen; single (HR = 2.09) or group pens (HR = 1.72), compared with having both of those types. The hazard of OFD was lower if the whole herd was housed in barns or pens that had only 1 type of feed barrier at the feed bunk, namely post-and-rail (HR = 0.51) or a type with barriers between the cow's heads (HR = 0.49), compared with having 2 types. Lower OFD hazard was observed with wider than 340 cm of walking alley next to the feeding table (HR = 0.75), and with housing a whole herd in pens with only 1 type of walking alley surface, specifically slatted (HR = 0.53) or solid (HR = 0.48), compared with having both types. The hazard of OFD was higher with stalls wider than 120 cm (HR = 1.38) compared with narrower stalls. The hazard of OFD was also associated with breed, parity, and calving season. This study identified many factors that contribute to the incidence of OFD of dairy cows. The solutions for reducing on-farm mortality include housing, management, and breeding choices that are most probably herd specific.

Invited review: Incidence, risk factors, and effects of clinical mastitis recurrence in dairy cows

Clinical mastitis (CM) is one of the most frequent and costly diseases in dairy cows. A frustrating aspect of CM is its recurrent nature. This review was conducted to synthesize knowledge on risk of repeated cases of CM, effects of recurrent CM cases, and risk factors for CM recurrence. A systematic review methodology was used to identify articles for this narrative review. Searches were performed to identify relevant scientific literature published after 1989 in English or French from 2 databases (PubMed and CAB Abstracts) and 1 search platform (Web of Science). Fifty-seven manuscripts were selected for qualitative synthesis according to the inclusion criteria. Among the 57 manuscripts selected in this review, a description of CM recurrence, its risk factors, and effects were investigated and reported in 33, 37, and 19 selected manuscripts, respectively. Meta-analysis and meta-regression analyses were used to compute risk ratio comparing risk of CM in cows that already had 1 CM event in the current lactation with risk of CM in healthy cows. For these analyses, 9 manuscripts that reported the total number of lactations followed and the number of lactations with ≤1 and ≤2 CM cases were used. When summarizing results from studies requiring ≥5 d between CM events to consider a CM event as a new case, we observed no significant change in CM susceptibility following a first CM case (risk ratio: 0.99; 95% confidence interval: 0.86-1.14). However, for studies using a more liberal CM recurrence definition (i.e., only 24 h between CM events to consider new CM cases), we observed a 1.54 times greater CM risk (95% confidence interval: 1.20-1.97) for cows that already had 1 CM event in the current lactation compared with healthy cows. The most important risk factors for CM recurrence were parity (i.e., higher risk in older cows), a higher milk production, pathogen species involved in the preceding case, and whether a bacteriological cure was observed following the preceding case. The most important effects of recurrent CM were the milk yield reduction following a recurrent CM case, which was reported to be similar to that of the first CM case, and the increased risk of culling and mortality, which were reported to surpass those of first CM cases.

The microbiota of water buffalo milk during mastitis

The aim of this study was to define the microbiota of water buffalo milk during sub-clinical and clinical mastitis, as compared to healthy status, by using high-throughput sequencing of the 16S rRNA gene. A total of 137 quarter samples were included in the experimental design: 27 samples derived from healthy, culture negative quarters, with a Somatic Cell Count (SCC) of less than 200,000 cells/ml; 27 samples from quarters with clinical mastitis; 83 samples were collected from quarters with subclinical mastitis, with a SCC number greater of 200,000 cells/ml and/or culture positive for udder pathogens, without clinical signs of mastitis. Bacterial DNA was purified and the 16S rRNA genes were individually amplified and sequenced. Significant differences were found in milk samples from healthy quarters and those with sub-clinical and clinical mastitis. The microbiota diversity of milk from healthy quarters was richer as compared to samples with sub-clinical mastitis, whose microbiota diversity was in turn richer as compared to those from clinical mastitis. The core microbiota of water buffalo milk, defined as the asset of microorganisms shared by all healthy milk samples, includes 15 genera, namely Micrococcus, Propionibacterium, 5-7N15, Solibacillus, Staphylococcus, Aerococcus, Facklamia, Trichococcus, Turicibacter, 02d06, SMB53, Clostridium, Acinetobacter, Psychrobacter and Pseudomonas. Only two genera (Acinetobacter and Pseudomonas) were present in all the samples from sub-clinical mastitis, and no genus was shared across all in clinical mastitis milk samples. The presence of mastitis was found to be related to the change in the relative abundance of genera, such as Psychrobacter, whose relative abundance decreased from 16.26% in the milk samples from healthy quarters to 3.2% in clinical mastitis. Other genera, such as SMB53 and Solibacillus, were decreased as well. Discriminant analysis presents the evidence that the microbial community of healthy and clinical mastitis could be discriminated on the background of their microbiota profiles.

Early detection of clinical mastitis from electrical conductivity data in an automatic milking system

Mastitis adversely affects profit and animal welfare in the Australian dairy industry. Electrical conductivity (EC) is increasingly used to detect mastitis, but with variable results. The aim of the present study was to develop and evaluate a range of indexes and algorithms created from quarter-level EC data for the early detection of clinical mastitis at four different time windows (7 days, 14 days, 21 days, 27 days). Historical longitudinal data collected (4-week period) for 33 infected and 139 healthy quarters was used to compare the sensitivity (Se; target >80%), specificity (Sp; target >99%), accuracy (target >90%) and timing of ‘alert’ by three different approaches. These approaches involved the use of EC thresholds (range 7.5– 10 mS/cm), testing of over 250 indexes (created ad hoc), and a statistical process-control method. The indexes were developed by combining factors (and levels within each factor), such as conditional rolling average increase, percentage of variation, mean absolute deviation, mean error %; infected to non-infected ratio, all relative to the rolling average (3–9 data points) of either the affected quarter or the average of the four quarters. Using EC thresholds resulted in Se, Sp and accuracy ranging between 47% and 92%, 39% and 92% and 51% and 82% respectively (threshold 7.5 mS/cm performed best). The six highest performing indexes achieved Se, Sp and accuracy ranging between 68% and 84%, 60% and 85% and 56% and 81% respectively. The statistical process-control approach did not generate accurate predictions for early detection of clinical mastitis on the basis of EC data. Improved Sp was achieved when the time window before treatment was reduced regardless of the test approach. We concluded that EC alone cannot provide the accuracy required to detect infected quarters. Incorporating other information (e.g. milk yield, milk flow, number of incomplete milking) may increase accuracy of detection and ability to determine early onset of mastitis.

Use of rumination and activity monitoring for the identification of dairy cows with health disorders: Part II. Mastitis

The objectives of this study were to evaluate (1) the performance of an automated health-monitoring system (AHMS) to identify cows with mastitis based on an alert system (health index score, HIS) that combines rumination time and physical activity; (2) the number of days between the first HIS alert and clinical diagnosis (CD) of mastitis by farm personnel; and (3) the daily rumination time, physical activity, and HIS patterns around CD. Holstein cows (n=1,121; 451 nulliparous and 670 multiparous) were fitted with a neck-mounted electronic rumination and activity monitoring tag (HR Tags, SCR Dairy, Netanya, Israel.) from at least -21 to 80 d in milk (DIM). Raw data collected in 2-h periods were summarized per 24 h as daily rumination and activity. An HIS (0 to 100 arbitrary units) was calculated daily for individual cows with an algorithm that used rumination and activity. A positive HIS outcome was defined as an HIS of <86 units during at least 1 d from -5 to 2 d after CD. Blood concentrations of nonesterified fatty acids, β-hydroxybutyrate, total calcium, and haptoglobin were also determined in a subgroup of cows (n=459) at -11±3, -4±3, 0, 3±1, 7±1, 14±1, and 28±1 DIM. The sensitivity of the HIS was 58% [95% confidence interval (CI): 49, 67] for all cases of clinical mastitis (n=123), and 55% (95% CI: 46, 64; n=114) and 89% (95% CI: 68, 100; n=9) for cases of mastitis alone or concurrent with other health disorders, respectively. Among clinical cases, sensitivity was 80.7% (95% CI: 67, 97) for cases caused by Escherichia coli (n=31) and ranged from 45 to 48% for cases caused by gram-positive bacteria (n=39; Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Streptococcus spp., Staphylococcus spp., and Trueperella pyogenes), Staphylococcus aureus (n=11), or cases with no bacterial growth (n=25). Days between the first HIS <86 and CD were -0.6 (95% CI: -1.1, -0.2) for all cases of mastitis. Cows diagnosed with mastitis had alterations of their rumination, activity, HIS patterns, and reduced milk production around CD depending on the type of mastitis case. Cows with mastitis also had some alterations of their calcium and haptoglobin concentrations around calving. The AHMS used in this study was effective for identifying cows with clinical cases of mastitis caused by E. coli and cows with another disease occurring during an event of mastitis, but it was less effective in identifying cows with mastitis not caused by E. coli.

Episodes of clinical mastitis and its relationship with duration of treatment and seasonality in crossbred cows maintained in organized dairy farm

Aim:

Present study aimed to evaluate the different episodes of clinical mastitis (CM) and influence of duration of treatment and seasonality on the occurrence of different episodes of CM in crossbred cows.

Materials and Methods:

A total of 1194 lactation data of crossbred CM cows were collected from mastitis treatment record from 2002 to 2012. Data of CM cows were classified into types of episodes (pattern of repeated or multiple episodes occurrence) and number of episodes (magnitude of multiple cases). Types of episodes were divided as single (clinical cure by a single episode of treatment), relapse (retreatment of the same cow within 21 days), recurrence (new CM at least 21 days after treatment), and both (relapse and recurrence). The season was classified as winter (December to March), summer (April to June), rainy (July to September), and autumn (October to November). The difference between incidences of different types of CM episodes and the association between number or type of CM episodes with duration of treatment and seasons of CM occurrence were analyzed by Chi-square test.

Results:

Among 1194 animals suffered with CM, 53, 16, and 18% had the single episode, relapse, and recurrence, respectively; while 13% suffered by both relapse and recurrence. We estimated the duration of treatment and found 80% of the cows treated 1-8 days, in which 65% treated for 1-4 days, while 35% cows were treated for 5-8 days. Further, 12% cows treated for 9-15 days and 7.5% cows treated >15 days. The relationship between duration of treatment and different episodes of CM revealed that 1-8 days treated cows were mostly cured by the single episode with less relapse and recurrence. In contrast, the incidences of recurrence and relapse episodes were higher in cows treated for more than 9 days. The highest incidence of relapse was noticed in winter (36%) than other seasons (10-28%), while the recurrence was less during autumn (9%) compared to other seasons (20-40%).

Conclusion:

Cows those suffered by both relapse and recurrence were more susceptible to CM, and they need to be culled from farm to control the transmission of infections. Although the influence of seasonality was difficult to understand, the higher magnitude of relapse and recurrence during winter suggested the adverse effects of cold stress on treatment outcome.

Evidence of no protection for a recurrent case of pathogen specific clinical mastitis from a previous case

The objective of this study was to determine whether the occurrence of a previous case of pathogen-specific clinical mastitis (CM) protects Holstein dairy cows against a recurrent case. Pathogens studied were Escherichia coli, Staphylococcus aureus, Staphylococcus spp., Streptococcus spp., Klebsiella spp., and Trueperella pyogenes. A total of 40 864 lactations (17,265 primiparous and 23,599 multiparous) from 19 835 cows from 5 large, high milk producing New York State dairy herds were analysed. We estimated the effects of parity, calving diseases, milk yield, current season and number of CM cases in the previous lactation on the risk of a first CM case using generalised linear mixed models with a log link and Poisson error distribution. The aforementioned risk factors and the occurrence of previous cases of pathogen-specific CM within the current lactation were evaluated as risks for second and third cases of pathogen-specific CM. Cows with more CM cases in the previous lactation were at greater risk of pathogen-specific CM in the current lactation. Multiparous cows were at greater risk of a second CM case if they had suffered from a first CM case that was caused by the same pathogen as the second case. In contrast, a second CM case generally put cows at greater risk of a third case, irrespective of whether the third case was caused by the same or a different pathogen. Our results showed that a previous case of pathogen specific CM does not generally protect against a recurrent case.

The cost of clinical mastitis in the first 30 days of lactation: An economic modeling tool

Clinical mastitis results in considerable economic losses for dairy producers and is most commonly diagnosed in early lactation. The objective of this research was to estimate the economic impact of clinical mastitis occurring during the first 30 days of lactation for a representative US dairy. A deterministic partial budget model was created to estimate direct and indirect costs per case of clinical mastitis occurring during the first 30 days of lactation. Model inputs were selected from the available literature, or when none were available, from herd data. The average case of clinical mastitis resulted in a total economic cost of $444, including $128 in direct costs and $316 in indirect costs. Direct costs included diagnostics ($10), therapeutics ($36), non-saleable milk ($25), veterinary service ($4), labor ($21), and death loss ($32). Indirect costs included future milk production loss ($125), premature culling and replacement loss ($182), and future reproductive loss ($9). Accurate decision making regarding mastitis control relies on understanding the economic impacts of clinical mastitis, especially the longer term indirect costs that represent 71% of the total cost per case of mastitis. Future milk production loss represents 28% of total cost, and future culling and replacement loss represents 41% of the total cost of a case of clinical mastitis. In contrast to older estimates, these values represent the current dairy economic climate, including milk price ($0.461/kg), feed price ($0.279/kg DM (dry matter)), and replacement costs ($2,094/head), along with the latest published estimates on the production and culling effects of clinical mastitis. This economic model is designed to be customized for specific dairy producers and their herd characteristics to better aid them in developing mastitis control strategies.

Survival analysis of clinical mastitis data using a nested frailty Cox model fit as a mixed-effects Poisson model

Mastitis is a complex disease affecting dairy cows and is considered to be the most costly disease of dairy herds. The hazard of mastitis is a function of many factors, both managerial and environmental, making its control a difficult issue to milk producers. Observational studies of clinical mastitis (CM) often generate datasets with a number of characteristics which influence the analysis of those data: the outcome of interest may be the time to occurrence of a case of mastitis, predictors may change over time (time-dependent predictors), the effects of factors may change over time (time-dependent effects), there are usually multiple hierarchical levels, and datasets may be very large. Analysis of such data often requires expansion of the data into the counting-process format - leading to larger datasets - thus complicating the analysis and requiring excessive computing time. In this study, a nested frailty Cox model with time-dependent predictors and effects was applied to Canadian Bovine Mastitis Research Network data in which 10,831 lactations of 8035 cows from 69 herds were followed through lactation until the first occurrence of CM. The model was fit to the data as a Poisson model with nested normally distributed random effects at the cow and herd levels. Risk factors associated with the hazard of CM during the lactation were identified, such as parity, calving season, herd somatic cell score, pasture access, fore-stripping, and proportion of treated cases of CM in a herd. The analysis showed that most of the predictors had a strong effect early in lactation and also demonstrated substantial variation in the baseline hazard among cows and between herds. A small simulation study for a setting similar to the real data was conducted to evaluate the Poisson maximum likelihood estimation approach with both Gaussian quadrature method and Laplace approximation. Further, the performance of the two methods was compared with the performance of a widely used estimation approach for frailty Cox models based on the penalized partial likelihood. The simulation study showed good performance for the Poisson maximum likelihood approach with Gaussian quadrature and biased variance component estimates for both the Poisson maximum likelihood with Laplace approximation and penalized partial likelihood approaches.

Progression to multi-scale models and the application to food system intervention strategies

The aim of this article is to discuss how the systems science approach can be used to optimize intervention strategies in food animal systems. It advocates the idea that the challenges of maintaining a safe food supply are best addressed by integrating modeling and mathematics with biological studies critical to formulation of public policy to address these challenges. Much information on the biology and epidemiology of food animal systems has been characterized through single-discipline methods, but until now this information has not been thoroughly utilized in a fully integrated manner. The examples are drawn from our current research. The first, explained in depth, uses clinical mastitis to introduce the concept of dynamic programming to optimize management decisions in dairy cows (also introducing the curse of dimensionality problem). In the second example, a compartmental epidemic model for Johne's disease with different intervention strategies is optimized. The goal of the optimization strategy depends on whether there is a relationship between Johne's and Crohn's disease. If so, optimization is based on eradication of infection; if not, it is based on the cow's performance only (i.e., economic optimization, similar to the mastitis example). The third example focuses on food safety to introduce risk assessment using Listeria monocytogenes and Salmonella Typhimurium. The last example, practical interventions to effectively manage antibiotic resistance in beef and dairy cattle systems, introduces meta-population modeling that accounts for bacterial growth not only in the host (cow), but also in the cow's feed, drinking water and the housing environment. Each example stresses the need to progress toward multi-scale modeling. The article ends with examples of multi-scale systems, from food supply systems to Johne's disease. Reducing the consequences of foodborne illnesses (i.e., minimizing disease occurrence and associated costs) can only occur through an understanding of the system as a whole, including all its complexities. Thus the goal of future research should be to merge disciplines such as molecular biology, applied mathematics and social sciences to gain a better understanding of complex systems such as the food supply chain.

Prevalence of sub-clinical mastitis in dairy farms

A total of 560 lactating cows belonging to Bangladesh Agricultural University dairy farm (n = 59): Local Zebu (L), Local × Friesian (L × F), Local × Jersey (L × J), Local × Red Chittagong Cattle (L × RCC), Local × Sahiwal (L × SL), Red Chittagong Cattle (RCC); and Central Cattle Breeding Station and Dairy Farm (n = 501): Local Zebu, L × F, SL × F, Sahiwal and Australian Friesian Sahiwal (AFS) were selected to measure prevalence of subclinical mastitis (SM). The California Mastitis Test was done and the prevalence of SM was 68% on cow basis and 57% on quarter basis. The prevalence rate was significantly higher in L × F (87%, P < 0.05), SL × F (88%, P < 0.05), L × J (100%, P < 0.01), AFS (89%, P< 0.05) and SL (100%, P < 0.01). The local Zebu (31%) and RCC (28%) were least susceptible to SM. SM was significantly higher in multiparous (P < 0.05) and older cows (P < 0.05). The front quarters were more prone to SM than the rear. Factors such as breed, age, parity and management may have been responsible for high prevalence of SM in both farms. DOI: http://dx.doi.org/10.3329/bvet.v30i2.18257 Bangl. vet. 2013. Vol. 30, No. 2, 70-77