New Perspectives in Udder Health Management

Risk Categorization in On-Farm Welfare in Different-Sized Dairy Sheep Flocks

The objective of the present work was to categorize the risks in the on-farm welfare of dairy sheep in semi-extensive systems in order to highlight if risks in welfare vary according to the farm size. To the best of our knowledge, this study constitutes one of the few categorizations of the risks in the welfare of dairy sheep reared semi-extensively. The survey was conducted on 12 semi-extensive dairy sheep farms in Tuscany (Central Italy), which were classified according to flock size: <500, from 500 to 1000, and >1000. The results showed an adequate rating for all the farms included in the study. The most critical issues concerned the ratio between the number of stockpersons and the number of animals within the farms, the small decubitus areas, the lack of udder cleaning procedures during milking operations, and, in terms of biosecurity, the lack of prevention, control, and eradication plans for the most important infectious ovine diseases. The results show that different items in the five areas evaluated, including the assessments of management of the flock, the number of daily inspections, and the hygiene of the water supplies are associated with the farm size. In large farms, the assessment of management of the flock was better, but the number of daily inspections and the hygiene of the water supplies were worse.

Is Galleria mellonella model a good alternative to study virulence in Staphylococcus aureus from bovine mastitis?

Staphylococcus aureus is one of the agents of bovine mastitis of hardest control due to a complex pathogenesis comprising a variety of virulence factors, which ensures its persistence in the mammary gland, causing significant health and economic losses. Therefore, understanding the pathogenesis of this agent is imperative. Galleria mellonella has stood out as an invertebrate animal model for the study of infectious diseases that affect several hosts. This work aimed to evaluate G. mellonella larvae as an experimental model for the study of virulence phenotypes in an S. aureus population isolated from bovine mastitis. Thirty genetically divergent S. aureus strains were chosen based on PFGE analysis. After experimental infection, larvae survival rates, bacterial growth in hemolymph, melanization intensity of the dorsal vessel, and histological characteristics of the infected tissues were evaluated. The G. mellonella model showed a clear diversity in the S. aureus pathogenicity pattern, allowing the differentiation of strains with virulence phenotypes ranging from high to low degrees. Histological analysis confirmed that the strains tested were capable of inducing the formation of nodules and melanization spots in the dorsal vessels of the larvae in different magnitudes. The strains 16S-717, 19C-828, and 31S-1443 presented the highest virulence intensity among the bacteria tested and will be used further for the generation of S. aureus mutant populations to prospect genetic targets aimed to develop control strategies of bovine mastitis. Altogether, our results suggest that G. mellonella is an attractive and low-cost animal model for characterizing virulence phenotypes of large S. aureus populations.

Randomized noninferiority field trial evaluating a postmilking teat dip for the prevention of naturally occurring intramammary infections

The aim of this study was to perform a positive-controlled field study under natural exposure conditions to test the efficacy of a newly developed chlorine dioxide-based postmilking teat disinfectant (experimental product, EX) for noninferiority compared with an already established chlorine dioxide-based teat disinfectant (positive control product, PC). After blocking by parity, approximately 200 Holstein cows in early to mid-lactation stages from a dairy farm near Padua, Italy, were randomly assigned to one of 2 groups. Over a 13-wk period between September and December 2021, the teats of cows were dipped with the EX or the PC after each milking. Milk samples were collected from individual quarters of enrolled cows for 13 wk to determine infection status. Teat condition was assessed at wk 1, 5, and 9. Mixed logistic regression was used to analyze the effect of treatment on the incidence of new intramammary infections. For the noninferiority analysis, the upper limit of the 95% confidence interval for the difference in new intramammary infection (NIMI) rate between the 2 treatments (EX - PC) had to be to the left of the critical value d (0.035) to conclude that EX was noninferior to PC in terms of the risk of NIMI. The results showed that the incidence of new infections in the quarters treated with EX (3.1%) was not different from that in the udder quarters treated with PC (2.6%). No overall difference was found between the treatments in terms of teat condition. As the upper limit of the 95% confidence interval of the NIMI rate difference was smaller than the predefined noninferiority limit, we concluded that the EX was noninferior compared with the PC.

Flagella are an important virulence factor in the subclinical persistence of Escherichia coli in bovine mammary gland

We compared the virulence profile and REP-PCR genotypes of Escherichia coli strains isolated from subclinical and clinical mastitis cases and dairy farm environments in Minas Gerais State, Brazil, to determine virulence factors and genotypes potentially associated with subclinical persistence in the udder. The virulence profile was obtained by the search for three virulence genes: lpfA (long polar fimbriae), fliC (flagella), and escN (type III secretion system). Subclinical isolates exhibited mainly the fliC gene (33.33%) and fliC + escN genes (30.30%). Clinical isolates exhibited mainly fliC + escN genes (50%) and environmental isolates the lpfA + escN genes (58.04%). Strains isolated from subclinical mastitis showed 6.75 times more positivity to fliC than environmental isolates. Thirty-four genotypes were observed in the REP-PCR analysis, and clinical mastitis isolates indicated more genetic proximity to dairy farm environment isolates than subclinical mastitis isolates. In conclusion, the results suggested that flagella may be an important virulence factor for mammary persistent E. coli infection in cattle, however, none of the E. coli REP-PCR genotypes were associated with subclinical infection.

Udder Hygiene and Mastitis Indicators in Contrasting Environmental Conditions during Half-Time Confinement in Pasture-Based Dairy Systems

This study aimed to compare the association between two types of housing, compost barns (CB) vs. outdoor soil-bedded yard (OD), and udder hygiene and mastitis indicators in Holstein dairy cows calving in autumn (n = 31) and spring (n = 27). After calving, cows were transferred to a pasture-based system with half-time confinement in one of two treatments: CB or OD. The udder hygiene score (UHS) was evaluated monthly and on days after rainfall over the entire lactation period. Individual somatic cell count (SCC) was determined throughout lactation, and the prevalence of intramammary infection (IMI) was estimated. Cows confined in OD presented higher UHS compared to cows in CB (p < 0.05) in both calving seasons. After rains, autumn-calving cows in OD were dirtier than on days without previous rain (OR = 1.85, CI 95%: 1.1-3.1; p < 0.02). However, no differences in IMI and clinical mastitis were found between OD and CB cows in either calving season.

Association between Mastitis Occurrence in Dairy Cows and Bedding Characteristics of Compost-Bedded Pack Barns

Compost-bedded pack barns (CB) are receiving increasing attention as a housing system that can potentially improve the welfare of dairy cows. This study characterized the frequency and profile of pathogens isolated from clinical (CM) and subclinical (SCM) mastitis in dairy cows housed in CB. It evaluated the association between mastitis occurrence and bedding characteristics in CB systems. Over six months, seven dairy herds were visited monthly for milk and bedding sample collections. Milk samples from mastitis cases were submitted to microbiological identification by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF MS). Bedding samples were submitted to physical-chemical (pH, organic matter, moisture, and carbon to nitrogen ratio) and microbiological counting (total bacterial counts, coliforms, streptococci, and staphylococci) analyses. Regression analysis was used to determine the association between mastitis occurrence and CB characteristics. Our results showed that Escherichia coli and environmental streptococci were the most frequently isolated pathogens from CM cases, while Staphylococcus chromogenes and contagious pathogens (Staphylococcus aureus and Streptococcus agalactiae) were the most commonly isolated from SCM cases. Bedding moisture content was positively associated with the incidence of CM. The bedding carbon to nitrogen ratio was negatively associated with the incidence of SCM, and the bedding total bacteria counts tended to be associated with the incidence of SCM. Bedding counts of coliforms positively associated with the prevalence of SCM. Our results can support decision-makers in the dairy industry seeking strategies for bedding management and mastitis control.

Antimicrobial susceptibility of bovine clinical mastitis pathogens in Japan and development of a simplified agar disk diffusion method for clinical practice

This study aimed to examine the antimicrobial susceptibility of bovine mastitis pathogens in Japan and develop criteria for testing antimicrobial susceptibility using the simplified agar disk diffusion (ADD) method that is currently being used in clinical practice. Milk samples from 1,349 dairy cows with clinical mastitis were collected and cultured. The minimum inhibitory concentrations (MICs) of the antimicrobials were determined for 504 strains of 28 bacteria. Of the gram-positive bacteria, most Staphylococcus spp. were susceptible to penicillin G (PCG), kanamycin (KM), oxytetracycline (OTC), cefazolin (CEZ), pirlimycin, enrofloxacin, and marbofloxacin. Streptococcus spp. and Trueperella pyogenes showed resistance to OTC and KM. Most gram-negative bacteria were resistant to OTC and CEZ and particularly susceptible to fluoroquinolones. To develop the criteria for a disk diffusion test of the simplified ADD method, the relationships between MICs and diameters of inhibition zones (DIZs) were analyzed and compared with the conventional method. The susceptibility breakpoints of several antimicrobials were lower for both gram-positive and gram-negative bacteria. Particularly for gram-positive bacteria, the application of the new criteria lowers the breakpoint for PCG, suggesting that the use of PCG instead of CEZ may increase. The results suggest that use of these criteria for the simplified ADD method may lead to appropriate antimicrobial choice and consequently the appropriate use of antimicrobials in clinical practice.

Udder Health Monitoring for Prevention of Bovine Mastitis and Improvement of Milk Quality

To maximize milk production, efficiency, and profits, modern dairy cows are genetically selected and bred to produce more and more milk and are fed copious quantities of high-energy feed to support ever-increasing milk volumes. As demands for increased milk yield and milking efficiency continue to rise to provide for the growing world population, more significant stress is placed on the dairy cow's productive capacity. In this climate, which is becoming increasingly hotter, millions of people depend on the capacity of cattle to respond to new environments and to cope with temperature shocks as well as additional stress factors such as solar radiation, animal crowding, insect pests, and poor ventilation, which are often associated with an increased risk of mastitis, resulting in lower milk quality and reduced production. This article reviews the impact of heat stress on milk production and quality and emphasizes the importance of udder health monitoring, with a focus on the use of emergent methods for monitoring udder health, such as infrared thermography, biosensors, and lab-on-chip devices, which may promote animal health and welfare, as well as the quality and safety of dairy products, without hindering the technological flow, while providing significant benefits to farmers, manufacturers, and consumers.

Prevalence and risk factors of coliform-associated mastitis and antibiotic resistance of coliforms from lactating dairy cows in North West Cameroon

Background

Coliform bacteria are major causative agents of bovine mastitis, a disease that has devastating effect on dairy animal health and milk production. This cross-sectional study, carried out in the North West region of Cameroon, sought to determine the prevalence of bovine mastitis, coliforms associated with bovine mastitis, risk factors for infection and the antibiotic resistance pattern of coliform bacterial isolates.

Materials and methods

A total of 1608 udder quarters were sampled from 411 cows using a questionnaire, clinical examination, California Mastitis Test and milk culture. Primary isolation of coliform bacteria was done on MacConkey agar while identification of coliforms employed Gram-staining and biochemical testing. Each coliform bacterial isolate was challenged with 11 antibiotics using the Kirby-Bauer disc diffusion method.

Results

The prevalence of mastitis was 53.0% (218/411) and 33.1% (532/1608) at the cow- and quarter-levels respectively. Overall, 21.9% (90/411) cows and 8.2% (132/1608) udder quarters showed coliform mastitis. Escherichia coli was isolated in 7.0% of mastitis milk, and other coliforms isolated were Enterobacter cloacae (12.6%), Klebsiella pneumoniae (2.4%), Enterobacter sakazakii (1.1%), Klebsiella oxytoca (0.8%), Citrobacter freudii (0.4%), Serratia ficaria (0.4%) and Serratia liquefaciens (0.2%). Lactation stage, breed, history of mastitis and moist/muddy faeces contaminated environment were significantly associated (P-value < 0.05) with coliform mastitis. Coliform isolates (99.0%; 203/205) were resistant to at least one antibiotic tested. Amoxicillin had the highest resistance (88.8%) while norfloxacin had the least resistance (3.4%). Multidrug resistance was exhibited by 52.7% (108/205) of the isolates in a proportion of 27.8% Enterobacter cloacae, 10.7% E. coli, 6.3% Klebsiella pneumoniae, 2.9% Enterobacter sakazakii, 2.0% Klebsiella oxytoca, 1.0% Citrobacter freundii, 1.0% Serratia ficaria, 0.5% Serratia liquefaciens and 0.5% Serratia odorifera.

Conclusion

Results indicate a need to educate these dairy farmers about mastitis (particularly subclinical), proper hygiene methods in milking and the public health implications of consuming contaminated raw milk.

Antimicrobial Selection for the Treatment of Clinical Mastitis and the Efficacy of Penicillin Treatment Protocols in Large Estonian Dairy Herds

Clinical mastitis (CM) is the most common microbial disease treated in dairy cows. We analyzed the antimicrobial usage in cows with CM (n = 11,420) in large dairy herds (n = 43) in Estonia. CM treatment data were collected during a 12-month study period. The antimicrobial usage was observed during the 21 days from the initiation of treatment, and the incidence of antimicrobial-treated CM was calculated for each study herd. The effect of intramammary (IMM), systemic, and combined (systemic and IMM) penicillin treatment of CM on the post-treatment somatic cell count (SCC) was analyzed using the treatment records of 2222 cows from 24 herds with a mixed multivariable linear regression model. The median incidence of antimicrobial-treated CM was 35.8 per 100 cow-years. Procaine benzylpenicillin and marbofloxacin were used in 6103 (35.5%, 95% CI 34.8-36.2) and 2839 (16.5%, 95% CI 16.0-17.1) CM treatments, respectively. Post-treatment SCC was higher after IMM penicillin therapy compared to systemic or combination therapy. Treatment of CM usually included first-choice antimicrobials, but different antimicrobial combinations were also widely used. The effect of procaine benzylpenicillin to post-treatment SCC was dependent on the administration route, cow parity, and days in milk. Further studies should evaluate the factors affecting veterinarians' choice of antimicrobial used in the treatment of CM.

Randomized controlled trial of pegbovigrastim as an adjunct therapy for naturally occurring severe clinical mastitis cases in dairy cows

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Treatment with pegbovigrastim increased survival after a case of severe clinical mastitis.

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Treatment with pegbovigrastim had no effect on subsequent bacteriological cure.

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Treatment with pegbovigrastim had no effect on subsequent milk production.

The main objective of this study was to quantify the effect of pegbovigrastim (PEG) as an adjunct therapy for naturally occurring severe mastitis cases on survival, intramammary bacteriological cure, and subsequent milk production. A double-blinded, randomized controlled trial was conducted on a single commercial dairy farm. During the study period, all cows having a case of severe clinical mastitis, defined as the presence of abnormal milk and inflammation in one quarter or more combined with the presence of systemic signs (pyrexia, dehydration, or recumbency), were enrolled in the study. In addition to a standardized therapy combining systemic and intramammary antimicrobials as well as systemic anti-inflammatory drugs, cows received a subcutaneous injection of either 2.7 mL of 0.9% sterile saline (control group; CON) or 2.7 mL of PEG (PEG group). A milk sample for bacteriological analysis was taken before treatment was administered and a second sample was taken 14 d after enrollment. Survival (30 d post-treatment) and bacteriological cure (14 d post-treatment) were analyzed by survival analysis and chi-squared tests, respectively, whereas daily milk production was treated as a repeated measure in mixed regression models. The 77 cows enrolled in the study were of parity 2 to 4 (mean = 3) and between 3 and 302 d in milk (mean = 154). The bacteria identified in milk at enrollment were Klebsiella spp. (n = 48; 62%), Escherichia coli (n = 16; 21%), Enterobacter spp. (n = 10; 13%), or no growth (n = 3; 4%). The probability of survival during the first 30 d after treatment was higher in the PEG group (84%) than in the control group (46%). Daily milk production over the 30-d period following treatment and bacteriological cure 14 d post-treatment did not differ between groups. Overall, cows treated with PEG as an adjunct therapy for naturally occurring cases of severe clinical mastitis had a better survival than cows treated with saline.

Whole-genome sequencing reveals high genetic diversity of Streptococcus uberis isolated from cows with mastitis

Background

Bovine mastitis is an important cause of economic loss in dairy farms. Streptococcus uberis is among the most frequently isolated bacterial species isolated from cows with mastitis. The aim of this study was to perform an in-depth genetic assessment of S. uberis strains isolated from bovine clinical mastitis (CM) and to perform a phylogenetic analysis to represent the evolutionary relationship among S. uberis sequences.

Results

A total of 159 isolates was genetically characterized using whole genome sequencing. According to the virulence determinants, all strains harbored the hasC, leuS, perR, purH, and purN virulence genes. Thirty-four resistance genes were identified in at least one strain. In terms of acquired genes, we observed that 152 (95.6 %) strains had a resistance gene to lincosamine (lnuD), 48 (30.2 %) to tetracycline (tetM), 4 (2.51 %) to tobramicine (ant6), and 1 to lincosamide (lsa(E)). MLST detected the Sequence Type (ST)797 (n = 23), while 85.5 % of the strains did not match to known STs.

Conclusions

Then, eleven distinct ST were identified after we submitted the new alleles to assign new STs. The other prevalent STs observed were ST1215 (n = 58), ST1219 (n = 35), and ST1213 (n = 15). And it was not possible to identify the MLST of four strains. Phylogenetic lineages indicated a high genomic diversity of S. uberis in our collection, confirming that most strains isolated from bovine mastitis have different reservoirs, typical of environmental pathogens.

Association between antimicrobial use and antimicrobial resistance of Streptococcus uberis causing clinical mastitis

It is unknown whether overuse of antimicrobials against clinical mastitis (CM) from Streptococcus uberis is associated with increased antimicrobial resistance (AMR). Therefore, the aim of this study was to evaluate the association between antimicrobial use (AMU) and AMR in relation to the Strep. uberis causing CM in dairy herds. A total of 83 Strep. uberis isolates were selected from a collection created during a previous study evaluating the epidemiology of CM in dairy herds (n = 17) of southeastern Brazil. For each case of CM identified on farm, the following information was recorded: cow's identification number, affected mammary quarter, date of CM diagnosis, antimicrobial commercial names, number of administrations, and descriptions of protocol changes during the treatment. Streptococcus uberis isolates were confirmed by conventional culture, MALDI-TOF mass spectrometry, and quantitative multiplex PCR analyses. Thus, a total of 8 antimicrobials commonly used for CM treatment were evaluated for antimicrobial activity against Strep. uberis isolates. The minimum inhibitory levels of antimicrobials were determined at the lowest concentrations able to inhibit 50 and 90%, respectively, of Strep. uberis isolates. Data related to the antibiotics used for treatment of CM was used to calculate the frequency of administered antimicrobials as the number of defined daily doses (DDD). The highest frequencies of resistant Strep. uberis were observed for erythromycin (80.7% resistant, R), tetracycline (R = 59%), and penicillin G (R = 57.8%), whereas against ceftiofur only 10.8% of Strep. uberis isolates were resistant, and only 1.2% of the Strep. uberis isolates were resistant to enrofloxacin. Regarding the evaluation of resistance for antimicrobial classes, the highest frequency was observed for macrolides (R = 80.7%; 19.3% susceptible, S). Additionally, a frequency of 18.7% of Strep. uberis isolates were resistant to cephalosporins (S = 81.3%), respectively. Further, 94% of Strep. uberis isolates were multiresistant; all these isolates presented resistance to at least 3 different antimicrobial classes. The overall monthly average of antimicrobial treatment incidence (ATI) among the 17 herds enrolled in the study was 23.7 DDD per 1,000 lactating dairy cows [standard deviation (SD) = 13.9], ranging from 5.0 to 55.4 DDD per 1,000 cows in lactation-day. Cephalosporins and penicillins were the most commonly used antimicrobial classes among the evaluated herds (n = 16; 94.1%), followed by tetracyclines (n = 15 herds; 88.2%), fluoroquinolones (n = 14; 82.3%), and sulfonamides (n = 14; 82.3%). The tetracycline class had the highest ATI mean (5.0 DDD per 1,000 lactating cow-days, SD = 5.8), followed by fluoroquinolones (4.7 DDD per 1,000 lactating cow-days, SD = 6.0) and cephalosporins (3.8 DDD per 1,000 lactating cow-days, SD = 6.0). The overall use of antimicrobials was associated with the resistance of Strep. uberis to the antimicrobial tetracycline.

Novel ways to use sensor data to improve mastitis management

Current sensor systems are used to detect cows with clinical mastitis. Although, the systems perform well enough to not negatively affect the adoption of automatic milking systems, the performance is far from perfect. An important advantage of sensor systems is the availability of multiple measurements per day. By clearly defining the need for detection of subclinical mastitis (SCM) and clinical mastitis (CM) from the farmers' management perspective, detection and management of SCM and CM may be improved. Sensor systems may also be used for other aspects of mastitis management. In this paper we have defined 4 mastitis situations that could be managed with the support of sensor systems. Because of differences in the associated management and the epidemiology of these specific mastitis situations, the required demands for performance of the sensor systems do differ. The 4 defined mastitis situations with the requirements of performance are the following: (1) Cows with severe CM needing immediate attention. Sensor systems should have a very high sensitivity (>95% and preferably close to 100%) and specificity (>99%) within a narrow time window (maximum 12 h) to ensure that close to all cows with true cases of severe CM are detected quickly. Although never studied, it is expected that because of the effects of severe CM, such a high detection performance is feasible. (2) Cows with mastitis that do not need immediate attention. Although these cows have a risk of progressing into severe CM or chronic mastitis, they should get the chance to cure spontaneously under close monitoring. Sensor alerts should have a reasonable sensitivity (>80%) and a high specificity (>99.5%). The time window may be around 7 d. (3) Cows needing attention at drying off. For selective dry cow treatment, the absence or presence of an intramammary infection at dry-off needs to be known. To avoid both false-positive and false-negative alerts, sensitivity and specificity can be equally high (>95%). (4) Herd-level udder health. By combining sensor readings from all cows in the herd, novel herd-level key performance indicators can be developed to monitor udder health status and development over time and raise alerts at significant deviances from predefined thresholds; sensitivity should be reasonably high, >80%, and because of the costs for further analysis of false-positive alerts, the specificity should be >99%. The development and validation of sensor-based algorithms specifically for these 4 mastitis situations will encourage situation-specific farmer interventions and operational udder health management.

Genetic parameters of differential somatic cell count, milk composition, and cheese-making traits measured and predicted using spectral data in Holstein cows

Mastitis is one of the most prevalent diseases in dairy cattle and is the cause of considerable economic losses. Alongside somatic cell count (SCC), differential somatic cell count (DSCC) has been recently introduced as a new indicator of intramammary infection. The DSCC is expressed as a count or a proportion (%) of polymorphonuclear neutrophils plus lymphocytes (PMN-LYM) in milk somatic cells. These numbers are complemented to total somatic cell count or to 100 by macrophages (MAC). The aim of this study was to investigate the genetic variation and heritability of DSCC, and its correlation with milk composition, udder health indicators, milk composition, and technological traits in Holstein cattle. Data used in the analysis consisted in single test-day records from 2,488 Holstein cows reared in 36 herds located in northern Italy. Fourier-transform infrared (FTIR) spectroscopy was used to predict missing information for some milk coagulation and cheese-making traits, to increase sample size and improve estimation of the genetic parameters. Bayesian animal models were implemented via Gibbs sampling. Marginal posterior means of the heritability estimates were 0.13 for somatic cell score (SCS); 0.11 for DSCC, MAC proportion, and MAC count; and 0.10 for PMN-LYM count. Posterior means of additive genetic correlations between SCS and milk composition and udder health were low to moderate and unfavorable. All the relevant genetic correlations between the SCC traits considered and the milk traits (composition, coagulation, cheese yield and nutrients recovery) were unfavorable. The SCS showed genetic correlations of -0.30 with the milk protein proportion, -0.56 with the lactose proportion and -0.52 with the casein index. In the case of milk technological traits, SCS showed genetic correlations of 0.38 with curd firming rate (k₂₀), 0.45 with rennet coagulation time estimated using the curd firming over time equation (RCT_eq), -0.39 with asymptotic potential curd firmness, -0.26 with maximum curd firmness (CF_max), and of -0.31 with protein recovery in the curd. Differential somatic cell count expressed as proportion was correlated with SCS (0.60) but had only 2 moderate genetic correlations with milk traits: with lactose (-0.32) and CF_max (-0.33). The SCS was highly correlated with the log PMN-LYM count (0.79) and with the log MAC count (0.69). The 2 latter traits were correlated with several milk traits: fat (-0.38 and -0.43 with PMN-LYM and MAC counts, respectively), lactose percentage (-0.40 and -0.46), RCT_eq (0.53 and 0.41), t_max (0.38 and 0.48). Log MAC count was correlated with k₂₀ (+0.34), and log PMN-LYM count was correlated with CF_max (-0.26) and weight of water curd as percentage of weight of milk processed (-0.26). The results obtained offer new insights into the relationships between the indicators of udder health and the milk technological traits in Holstein cows.

Monitoring the Transition Period in Dairy Cows through 1H NMR-Based Untargeted Metabolomics

The metabolic alterations associated with the increase in milk production make the transition period critical to the health of dairy cows, usually leading to a higher incidence of disease in periparturient animals. In this manuscript, we describe the use of NMR-based untargeted metabolomics to follow how these changes impact the serum metabolome in a group of 28 transition dairy cows with no initial clinical diseases. Principal component analysis (PCA) of serum 1H NMR data from four weeks before calving to 8 weeks after parturition allowed us to clearly identify four stages during the transition period. Pairwise comparisons using orthogonal partial least square discriminant analysis (OPLS-DA) and univariate data analysis led to the identification of 18 metabolites that varied significantly through these stages. Species such as acetate, betaine, and creatine are observed early after calving, while other markers of metabolic stress, including acetone, β-hydroxybutyrate (BHB), and choline, accumulate significantly at the height of milk production. Furthermore, marked variations in the levels of lactate, allantoin, alanine, and other amino acids reveal the activation of different gluconeogenic pathways following parturition. Concomitant with a return to homeostasis, a gradual normalization of the serum metabolome occurs 8 weeks after calving. Correlations of metabolite levels with dietary and metabolic adaptations based on animal parity could also be identified. Overall, these results show that NMR-based chemometric methods are ideally suited to monitor manifestations of metabolic diseases throughout the transition period and to assess the impact of nutritional management schemes on the metabolism of dairy cows.

Will Fly Repellency Using Deltamethrin Reduce Intramammary Infections, Stress and Fatigue Indicators of Dairy Ewes under Intensive Management?

Intramammary infections (IMIs) caused by various pathogens may lead to clinical or subclinical mastitis, challenging the health and welfare status of infected animals and decreasing the quantity and quality of the produced milk. Additionally, the zoonotic potential of some of the pathogens isolated from IMI cases, the emergence of antibiotic resistance due to the extensive antibiotic use for IMI treatment, and the accumulation of antibiotic residues in milk and meat represent significant concerns for public health. Therefore, the investigation of IMI risk factors and the proposal of efficient measures to mitigate their effects on animal health and welfare is crucial. Although fly infestation is considered to play a significant role in the transmission of IMI pathogens, its adverse effects on udder health and the overall comfort status of dairy ewes have not been quantified and assessed on an evidential basis. Hence, the objectives of this study were to assess, for the first time, the fly repellent effect of deltamethrin and link it to: (i) the occurrence of common bacterial IMI; (ii) the somatic cell counts in milk; and (iii) the serum cortisol and creatine kinase levels (stress and fatigue indicators). The study was carried out in an intensive dairy sheep farm in northern Greece, during peak fly season. Deltamethrin treatment was associated with a reduced (i) number of flies (mostly Musca domestica) landing on treated ewes, compared to untreated ones (p < 0.05); (ii) colony-forming units in the case of Non-aureus Staphylococci IMIs (p < 0.05); and (iii) number of somatic cells in the milk (p < 0.001). Finally, serum cortisol and creatine kinase levels were significantly lower in deltamethrin-treated ewes (p < 0.001), indicating a less stressful environment for them.

Efficacy of a Lactobacillus-Based Teat Spray on Udder Health in Lactating Dairy Cows

Teat disinfection is a common pre- and post-milking mastitis prevention practice that is part of a mastitis control program in dairy herds. Commercially available teat disinfectants are generally chemical-based products. The use of these products has occasionally raised concerns about the risk of chemical residues in milk. An alternative treatment or prevention strategy based on probiotics has the potential to circumvent this risk. Two treatments were compared in a cross-over clinical trial in a single herd: a lactobacillus-based, post-milking teat spray (LACT), and a commercial iodine-based post-milking teat disinfectant product as (positive control, PC). The effect of the two treatments on cow somatic cell counts was quantified using a multivariate mixed-effects linear regression model with cow fitted as a random effect. The odds of teat end scores increasing from a low to a high score tended to be lower (OR = 0.74, 95% CI 0.54-1.01, P = 0.06) for cows receiving LACT treatment. On average, there was also a tendency for a lower somatic cell counts in the LACT treated cows (antilog of coefficient = 0.91, 95% CI 0.80-1.03, P = 0.13) compared with the PC treated cows. The application of the lactobacillus-based product to teats could reduce the rate of teat end scores progression from low to higher scores, and potentially improve teat end sphincter functions and udder health. Further, larger scale validation work is required to support the findings of the current study.

Implementation of a targeted mastitis therapy concept using an on-farm rapid test: antimicrobial consumption, cure rates and compliance

BACKGROUND

Aim of the present study was to investigate the implementation of a targeted therapy (tLCT) concept under real-life circumstances, taking both pathogen-related and animal-related factors into account. The reduction of antibiotics without negative effects on cure rates was evaluated as well as the compliance by the farmers.

METHODS

After analysing the existing conventional therapy (CT) concepts of five farms, the tLCT concept and a novel on-farm test were introduced. Three treatment groups were compared with respect to bacteriological cure (BC), cytological cure (CYC), full cure (FC), new infection rate (NIR), relapse rate and the treatment approach per mastitis case: the CT group, the tLCT group including all clinical mastitis (CM) cases treated according to the concept, and the modified tLCT group (tLCTmod), including the CM cases in which farmers deviated from the concept.

RESULTS

Even so farmers deviated from the treatment concept in 506 out of 909 cases; belonging to one of the three treatment groups had no significant impact on BC, CYC, FC, NIR or relapse rate. The antibiotic usage in the tLCT as well as in the tLCTmod group was significantly lower in comparison to the CT group.

CONCLUSION

From this, it can be deduced that farmers will reduce antibiotic doses by implementing a tLCT concept.

Serum amyloid A as an marker of cow֨ s mastitis caused by Streptococcus sp

The aim of the study was to evaluate the concentrations of amyloid A in serum (SAA) and in milk (MAA) of cows with mastitis caused by Streptococcus agalactiae, Streptococcus dysgalactiae and Streptococcus uberis and healthy cows. The blood and milk samples were obtained from Holstein-Friesian cows with clinical signs of mastitis from two tie-stall housing systems herds in the Lublin region in Poland. A total of 80 milk and serum samples from 30 cows with mastitis and 10 healthy cows were selected for study. In the quarter milk samples from cows with mastitis Streptococcus strains were isolated: Strep. agalactiae (7 cows), Strep. dysgalactiae (9 cows) and Strep. uberis (14 cows). The present study indicates that amyloid A concentration was significantly higher in milk of cows with mastitis compared to control cows (1134.25 ng/mL and 324.50 ng/mL, P < 0.001). The highest concentration of amyloid A was found in milk of cows with mastitis caused by Strep. agalactiae and Strep. uberis whereas lowest in the milk of cows with mastitis caused by Strep. dysgalactiae (3882.50 ng/mL, 2587.75 ng/mL and 812.00 ng/mL, respectively). No statistically significant difference in amyloid A concentration in serum was revealed between all unhealthy cows and control group (2140.00 ng/mL and 2510.00 ng/mL, P > 0.05). There was also no statistically significant difference between the level of amyloid A in serum and in milk of cows with mastitis caused by Strep. agalactiae and Strep. uberis. Whereas, in the case of Strep. dysgalactiae, like in the group of healthy cows, the level of amyloid A was significantly higher in serum compared to this in milk (2100 ng/mL and 812.00 ng/mL, P < 0.001; 2510.00 ng/mL and 324.50 ng/mL, P < 0.001; respectively).

Dynamics of the within-herd prevalence of Mycoplasma bovis intramammary infection in endemically infected dairy herds

We aimed to identify the dynamics of the within-herd prevalence of Mycoplasma (M.) bovis intramammary infection (IMI) in four dairy herds, estimate prevalence of M. bovis in colostrum and clinical mastitis cases and compare M. bovis strains from calves' respiratory and cow clinical mastitis samples. Within a six-month study period, cow composite milk samples (CMS) were collected three times during routine milk recording, first milking colostrum samples from all calving cows and udder quarter milk samples from clinical mastitis cases. Calf respiratory samples were collected from calves with respiratory disease. Pooled milk samples were analysed for M. bovis with the Mastitis 4B polymerase chain reaction (PCR) test kit (DNA Diagnostic A/S). Prevalence estimates were calculated with Bayesian framework in R statistical programme. cg-MLST was used for M. bovis genotyping. In Herd I and II first testing M. bovis IMI within-herd prevalence (95 % credibility interval (CI)) was 4.7 % (2.9; 6.8) and 3.4 % (2.3; 4.6), changing to 1.0 % (0.1; 1.7) and 0.8 % (0.1; 1.4) in Herd I and 0.4 % (0.0; 0.7) in Herd II at the next samplings. In Herd III and IV first testing M. bovis IMI within-herd prevalence was 12.3 % (9.7; 15.2) and 7.8 % (6.2; 9.5), changing to 4.6 % (3.0; 6.4) and 3.2 % (1.9; 4.8) in Herd III and to 2.8 % (1.9; 3.8) and 4.9 % (3.6; 6.4) in Herd IV at the next samplings. The estimated prevalence of M. bovis in colostrum ranged between 1.7 % (0.2; 2.8) and 4.7 % (2.7; 7.1) and in clinical mastitis cases between 3.7 % (1.7; 6.4) and 11.0 % (7.5; 15.2) in the study herds. M. bovis strains isolated from cows and calves clustered within herds indicating possible transmission of M. bovis between dairy cows and calves. Prevalence of M. bovis in colostrum and clinical mastitis cases as well as the within-herd prevalence of M. bovis IMI was low in endemically infected dairy herds.

The Assessment of Housing Conditions, Management, Animal-Based Measure of Dairy Goats’ Welfare and Its Association with Productive and Reproductive Traits

Simple Summary

Small ruminant production systems are generally perceived by consumers to be associated with a high standard of welfare, notably in relation to aspects of traditional breeding. However, their performances have reached the same levels of the dairy cow sector, with similar negative externalities. We aimed to evaluate the welfare of dairy goats of 32 farms located in Northwestern Italy by the application of an on-farm assessment protocol. The farms were classified as ‘intensive’ or ‘semi-intensive’ according to the access to pasture. Overall, we observed an adequate level of animal wellbeing both in intensive and semi-intensive farming systems. This is possible thanks to the increased knowledge on goat breeding characteristics, and to the fact that veterinarians and farmers understood the importance of welfare protection to achieve a better health, although some challenges remain, such as the farmers’ approach toward animals. The importance of the farmer’s role is highlighted by the positive association between the milk yield and the presence of the owner on the farm.

Abstract

The aim of the study was to evaluate the welfare of dairy goats of 32 farms located in Northwestern Italy, applying an on-farm assessment protocol, centered on animal-, resources- and management-based measures. The farms were classified as ‘intensive’ or ‘semi-intensive’ according to access to pasture. During each on-farm visit, a checklist was compiled, based on specific scores for housing and management conditions, and animals’ nutritional status, health, and behavior. Finally, the possible association between welfare measures and productive and reproductive traits was assessed. Overall, we observed an adequate level of animal wellbeing both in intensive and semi-intensive farming systems. This is possible thanks to the increased knowledge on goat breeding characteristics, and to the fact that veterinarians and farmers understood the importance of welfare protection to achieve a better health. Higher milk production was associated to some management practices (presence of the owner on the farm, high frequency of bedding change), and to seasonal breeding (which was mainly performed in the intensive farming). Moreover, it was associated to a quantity of urea in the milk comprised between 33 and 44 mg/dL. In intensive farms, the prevalence of caseous lymphadenitis was significantly higher compared to non-intensive farms. The semi-intensive breeding system positively influences the animals’ behavior.

Genotyping and antimicrobial resistance of Streptococcus uberis isolated from bovine clinical mastitis

A genotypic characterization of Streptococcus uberis isolated from clinical mastitis (CM) in dairy cows, and the association of Strep. uberis genotypes and antimicrobial susceptibility (AMS) was performed. A total of 89 isolates identified as Strep. uberis from 86 dairy cows with CM in 17 dairy herds of Southeastern Brazil were genotyped using random amplified polymorphic DNA (RAPD) analysis. After genotyping, two clusters (I and II) were created according to RAPD types. A commercial broth microdilution test was used to determine the susceptibility of Strep. uberis isolates to 8 antimicrobials (ampicillin, ceftiofur, cephalothin, erythromycin, penicillin, penicillin+novobiocin, pirlimycin and tetracycline). For each antimicrobial, we determined the minimal inhibitory concentrations that inhibit 50% (MIC₅₀) and 90% (MIC₉₀) of Strep. uberis strains. Differences in AMS among genotypic clusters were evaluated using mixed regression models. Overall, a great polymorphism (56 RAPD-types) was found among Strep. uberis isolates, although a higher genetic similarity (based on the PCR bands features) was observed within herds after genotypic clustering. No differences in AMS were observed among clusters. Strep. uberis isolated from bovine CM were resistant to most antimicrobials, with the exception of cephalothin and penicillin+novobiocin.

Screening commercial teat disinfectants against bacteria isolated from bovine milk using disk diffusion

Background and Aim:

Teat disinfection is an important tool in reducing the incidence of bovine mastitis. Identifying the potential mastitis-causing bacterial species in milk can be the first step in choosing the correct teat disinfectant product. The objective of this study was to screen commercial teat disinfectants for inhibition against mastitis-associated bacteria isolated from various types of milk samples.

Materials and Methods:

Twelve commercially available teat disinfectant products were tested, against 12 mastitis-associated bacteria strains isolated from bulk tank milk samples and bacterial strains isolated from clinical (n=2) and subclinical (n=3) quarter foremilk samples using the disk diffusion method.

Results:

There was a significant variation (7-30 mm) in bacterial inhibition between teat disinfection products, with products containing a lactic acid combination (with chlorhexidine or salicylic acid) resulting in the greatest levels of bacterial inhibition against all tested bacteria (p<0.05).

Conclusion:

In this study, combined ingredients in teat disinfection products had greater levels of bacterial inhibition than when the ingredients were used individually. The disk diffusion assay is a suitable screening method to effectively differentiate the bacterial inhibition of different teat disinfectant products.

Molecular epidemiology of coagulase-negative Staphylococcus species isolated at different lactation stages from dairy cattle in the United States

Background

Coagulase negative Staphylococcus (CNS) species are currently the most prevalent intra-mammary pathogens causing subclinical mastitis and occasional clinical mastitis or persistent infection in lactating dairy cattle. More than 10 CNS species have been identified, but they are generally managed as one group on most dairies in the United States. However, improved management decisions and treatment outcomes may be achieved with better understanding of the prevalent species, pathogenicity and strain diversity within and across dairies.

Methodology

A total of 604 CNS isolates were cultured from milk samples collected during a dry-cow treatment clinical trial conducted on 6 dairy herds in 4 states in the US. All the study cows were randomized to receive 1 of the 3 different intra-mammary antimicrobial infusions (Quatermaster, Spectramast DC or ToMorrow Dry Cow) at dry-off. Milk samples were collected at dry-off, calving (0–6 days in milk, DIM), post-calving (7–13 DIM) and at mastitis events within the first 100 DIM. The CNS isolates were identified to species level by partial sequencing of the rpoβ gene, and genetic relatedness within species was investigated by phylogenetic analysis of the pulse-field gel electrophoresis profiles of the isolates.

Results

The major CNS species identified were S. chromogenes (48.3%), S. haemolyticus (17.9%), S. simulans and S. epidermidis (each at 6.5%). Other CNS species identified at lower frequencies included S. hominis, S. auricularis, S. sciuri, S. spp KS-SP, S. capitis, S. cohnii, S. warneri, S. pasteuri, S. xylosus, S. hyicus, S. equorum, S. microti, S. rostri, S. gallinarum, S. saprophyticus and S. succinus. Phylogenetic analyses of the major species types demonstrated an association between genetic relatedness and epidemiological distributions of S. chromogenes, S. simulans, S. haemolyticus and S. auricularis. Additionally, identical strains of S. chromogenes and S. simulans were isolated from the same udder quarter of several cows at consecutive sample stages. The rest of the minor species had no deducible genetic-epidemiological link.

Discussion

The observed association between genetic and epidemiological distributions indicated animal-adapted nature of four CNS species, suggesting possible host-adapted and environmental transmission of these species. Multi-stage isolation of the same udder quarter strain was evidence for chronic intra-mammary infection.

Conclusion

The different CNS species and strains circulating on US dairy herds were genetically diverse. Four species identified were likely udder-adapted pathogens, 2 of which caused persistent infection. Our findings are important in guiding the design of effective mastitis control strategies.

Staphylococcus aureus and Streptococcus agalactiae: prevalence, resistance to antimicrobials, and their relationship with the milk quality of dairy cattle herds in Minas Gerais state, Brazil

ABSTRACT: Bovine mastitis is the most frequent disease worldwide in dairy herds, causing high economic losses to producers and industry, as well as having implications for public health due to the zoonotic potential of some agents involved in its etiology and the increased risk of antimicrobial residues in milk and its derivatives. Considering the multifactorial aspect of this disease, knowledge of the agents involved in its etiology and their antimicrobial susceptibility profiles is very important. This study was conducted with 306 dairy herds from the Campo das Vertentes region, located in the south of Minas Gerais state, whose owners were milk suppliers to a dairy in the same region. The study involved approximately 34,000 dairy cows and covered an area of approximately 12,564 km2. In these herds, prevalence rates of Staphylococcus aureus and Streptococcus agalactiae and their relationship with bulk milk somatic cell counts (BMSCC), total bacterial counts (TBC), and daily production were evaluated. In addition, analyses of resistance of these pathogens to the antimicrobials most commonly used in the treatment of mastitis in dairy herds were performed. Microbiological analyses of milk samples from collect from bulk milk tanks were performed aiming to evaluate the prevalence of S. aureus and S. agalactiae. For these proposes, the modified Baird-Parker Agar medium was used for detection of S. aureus and the modified Edwards Agar medium, enriched with 5% defibrinated sheep blood, was used for detection of S. agalactiae. The disc diffusion technique was applied to evaluate antimicrobial resistance. Results show high prevalence rates of S. aureus (70.3%) and S. agalactiae (67.0%) in the dairy farms studied, with 47.71% of the herds showing both pathogens. Associations between BMSCC and the presence of pathogens S. aureus and S. agalactiae and between TBC and the presence of S. agalactiae were observed, demonstrating the influence of these pathogens in milk quality. No variation was observed in the distribution of S. aureus and S. agalactiae in the different strata of daily production. High levels of resistance and multi-resistance were observed among the pathogens S. aureus and S. agalactiae. The results indicate the need for more effective control measures for mastitis caused by S. aureus and S. agalactiae in the dairy herds of the region studied and more judicious use of antimicrobials in order to reduce the problem of resistance to them.

Fly repellency using deltamethrin may reduce intramammary infections of dairy cows under intensive management

The aim of this study was to assess the possible effect of the fly repellent deltamethrin on the full microbiological profile of the intramammary infections as well as on the somatic cell count in one Greek dairy cattle farm under intensive management, during peak fly season. Fifty five multiparous cows, stabled in the same farm, were randomly divided in three groups; cows of Group A were dressed on their back with deltamethrin, cows of Group B remained untreated within the same pen and cows of Group C remained untreated in a separate pen. Clinical records of the herd showed a history of clinical and subclinical mastitis (especially during spring and early summer) and fly infestation. Deltamethrin reduced fly population, landing on the cows of Group A, facilitating a significant decrease of S. aureus, coagulase negative staplylococci, E. coli intramammary infections and somatic cell count, throughout the study period. Consequently, there is a relationship between fly abundance and transmission of bacteria resulting in intramammary infections and mastitis in dairy cows. The use of the pyrethroid deltamethrin reduced fly abundance and therefore, the possibility of transmitting pathogenic bacteria in the mammary gland.

Genetic diversity and antimicrobial resistance in Staphylococcus aureus and coagulase-negative Staphylococcus isolates from bovine mastitis in Minas Gerais, Brazil

The aims of this study were to determine the antimicrobial susceptibility profile and genetic diversity of Staphylococcus spp. isolated from dairy cows in Minas Gerais, Brazil, and to assess the relationship among the isolates’ susceptibility profiles and pulsed‐field gel electrophoresis (PFGE) genotypes. Seventy‐nine isolates were used, including S. aureus (n = 71) and coagulase‐negative staphylococci (CoNS) (n = 8). Susceptibility to 12 antimicrobial agents was performed. All Staphylococcus spp. were subjected to PFGE. Staphylococcus aureus and CoNS isolates exhibited full susceptibility only to cephalothin. The greatest percentages of resistance among Staphylococcus spp. were observed to penicillins, folate pathway inhibitors, and tetracyclines. Twelve S. aureus and four CoNS were classified as multidrug resistance strains. Percentage of MRSA was also higher among CoNS (75%), compared to S. aureus isolates (2.81%). Adopting 100% of similarity, 34 different genotypes were identified. Association of minimum‐spanning tree (MST) analysis with data from municipalities, herds, methicillin‐resistant S. aureus (MRSA), and resistance patterns for all isolates did not show any clustering. However, a clustering pattern of bacterial species was observed. Results from this study indicate a high frequency of antimicrobial resistance, especially among CoNS, and a high genetic diversity among Staphylococcus spp. isolated from dairy cows with mastitis in Minas Gerais, Brazil.

Development of a Teat Bio-sealant and Evaluation of its Technological and Functional Properties

A teat bio-sealant was developed using Weissella cibaria, and the bio-sealant's technological and functional properties were assessed. The development included four experimental phases that were analyzed using independent experimental designs. Initially, sterilized or pasteurized Aloe vera gels were used, and the effect of heat treatment was investigated. In the second phase, the effects of time, storage temperature, and addition of cryopreservatives on the viability of the probiotic were observed. The third phase consisted of evaluating the synergistic effects of the cryopreservatives. The fourth phase involved selecting a material that would provide viscosity to the teat sealant. Technological and functional properties were measured in terms of viability of W. cibaria, and antimicrobial activity against Staphylococcus aureus and Streptococcus agalactiae was also analyzed. A mixture of milk powder and glycerol preserved this antimicrobial activity. Pullulan provided greater viscosity and maintained the technological and functional properties of the bio-sealant for 29 days. This teat bio-sealant can be used as an alternative for the prevention of bovine mastitis.

Within-herd prevalence of intramammary infection caused by Mycoplasma bovis and associations between cow udder health, milk yield, and composition

Subclinical mastitis is one of the major health problems in dairy herds due to decreased milk production and reduced milk quality. The aim of this study was to examine the within-herd prevalence of subclinical intramammary infection caused by Mycoplasma bovis and to evaluate associations between M. bovis and cow daily milk yield, udder health, and milk composition. Individual cow composite milk samples (n = 522) were collected from all lactating dairy cows in 1 Estonian dairy farm in November 2014. Daily milk yield, days in milk, and parity were recorded. Collected milk samples were analyzed for somatic cell count, milk protein, fat, and urea content. The presence of M. bovis, Staphylococcus aureus, Streptococcus agalactiae, and Streptococcus uberis in the milk samples was confirmed by quantitative PCR analysis. The within-herd prevalence of M. bovis was 17.2% in the study herd. No association was observed between days in milk and parity to the presence of M. bovis in milk. According to linear regression analysis, the daily milk yield from cows positive for M. bovis was on average 3.0 kg lower compared with cows negative for M. bovis. In addition, the presence of M. bovis in milk samples was significantly associated with higher somatic cell count and lower fat and urea content compared with milk samples negative for M. bovis. In conclusion, subclinical M. bovis intramammary infection is associated with decreased milk yield and lower milk quality.

Bacteriological etiology and treatment of mastitis in Finnish dairy herds

Background

The Finnish dairy herd recording system maintains production and health records of cows and herds. Veterinarians and farmers register veterinary treatments in the system. Milk samples for microbiological analysis are routinely taken from mastitic cows. The laboratory of the largest dairy company in Finland, Valio Ltd., analyzes most samples using real-time PCR. This study addressed pathogen-specific microbiological data and treatment and culling records, in combination with cow and herd characteristics, from the Finnish dairy herd recording system during 2010–2012.

Results

The data derived from 240,067 quarter milk samples from 93,529 dairy cows with mastitis; 238,235 cows from the same herds served as the control group. No target pathogen DNA was detected in 12% of the samples. In 49% of the positive samples, only one target species and in 19%, two species with one dominant species were present. The most common species in the samples with a single species only were coagulase-negative staphylococci (CNS) (43%), followed by Staphylococcus aureus (21%), Streptococcus uberis (9%), Streptococcus dysgalactiae (8%), Corynebacterium bovis (7%), and Escherichia coli (5%). On average, 36% of the study cows and 6% of the control cows had recorded mastitis treatments during lactation. The corresponding proportions were 16 and 6% at drying-off. For more than 75% of the treatments during lactation, diagnosis was acute clinical mastitis. In the milk samples from cows with a recorded mastitis treatment during lactation, CNS and S. aureus were most common, followed by streptococci. Altogether, 48% of the cows were culled during the study. Mastitis was reported as the most common reason to cull; 49% of study cows and 18% of control cows were culled because of mastitis. Culling was most likely if S. aureus was detected in the milk sample submitted during the culling year.

Conclusions

The PCR test has proven to be an applicable method also for large-scale use in bacterial diagnostics. In the present study, microbiological diagnosis was unequivocal in the great majority of samples where a single species or two species with one dominating were detected. Coagulase-negative staphylococci and S. aureus were the most common species. S. aureus was also the most common pathogen among the culled cows, which emphasizes the importance of preventive measures.

Anatomical characteristics of teats and premilking bacterial counts of teat skin swabs of primiparous cows exposed to different types of bedding

Bacterial populations of teat skin are associated with risk of intramammary infection and may be influenced by anatomical characteristics of teats. The objective of this study was to evaluate associations of selected anatomical characteristics of teats with bacterial counts of teat skin of cows exposed to different types of bedding. Primarily primiparous Holstein cows (n = 128) were randomly allocated to 4 pens within a single barn. Each pen contained 1 type of bedding [new sand (NES), recycled sand (RS), deep-bedded manure solids (DBMS), and shallow-bedded manure solids over foam core mattresses (SBMS)]. During a single farm visit udders (n = 112) were scored for hygiene and 1 front (n = 112) and 1 rear teat (n = 111) of each enrolled cow were scored for hyperkeratosis (HK). Teat length, teat barrel diameter, and teat apex diameter were measured and teat skin swabs were systematically collected for microbiological analysis. Linear type evaluation data for udders of each cow were retrieved for each cow. Teat position (front or rear) was associated with occurrence of clinical mastitis during the 12 mo before the farm visit and more cases occurred in front quarters. The proportion of udders that were classified as clean (score 1 or 2) was 68, 82, 54, and 95% for cows housed in pens containing NES, RS, SBMS, and DBMS, respectively. No association was found between HK score and teat position and no association was found between HK score and teat skin bacterial count. Bacterial counts of teat skin swabs from front teats of cows in pens containing RS and SBMS were significantly less than those of rear teats of cows in pens containing DBMS or NES. Teat skin bacterial counts were significantly greater for swabs obtained from teats of cows with udder hygiene scores of 3 and 4 as compared with swabs obtained from cows with cleaner udders. Of all udder conformation traits evaluated, only narrower rear teat placement was positively associated with bacterial counts on teat skin.

Prevalence of bovine milk pathogens in Azorean pastures: mobile versus fixed milking machines

The aims of the present study were (1) to evaluate the influence of using mobile (n=47) or fixed (n=45) milking machines in Azorean herds on the apparent prevalence of several milk pathogens in bulk tank milk (BTM) and (2) to determine whether separated subclinical mastitic cows can serve, in real time, as predictors of milk pathogen prevalence for the remaining animals at the herd level. The use of a mobile or fixed milking machine influenced (P≤0.05) the prevalence of Staphylococcus aureus (72.3 per cent; n=34 v 51.1 per cent; n=23, respectively) and Klebsiella species (46.8 per cent; n=22 v 26.7 per cent; n=12, respectively). S aureus (95 per cent CI OR 1.1 to 6.0) and Klebsiella species (95 per cent CI OR 1.0 to 5.8) were 2.5 times more likely to increase in the BTM of herds using mobile milking machines. The prevalence of coagulase-negative staphylococci (100 per cent; n=92), Escherichia coli (75.0 per cent), Corynebacterium bovis (57.6 per cent), Enterococcus species (55.4 per cent), Streptococcus dysgalactiae (51.1 per cent), Streptococcus uberis (41.3 per cent), Actinomyces pyogenes or Peptostreptococcus indolicus (41.3 per cent) and Streptococcus agalactiae (32.6 per cent) in BTM remained similar among the herds. κ coefficients were always <0.70, indicating intra-herd disagreement of the prevalence of milk pathogens between BTM and separated milking cows. Milking hygiene should be improved in pastures, focusing specifically on herds that use a mobile milking machine. The segregated cows at milking time are not good predictors of milk pathogens in BTM.

Antimicrobial Susceptibility Patterns of Environmental Streptococci Recovered from Bovine Milk Samples in the Maritime Provinces of Canada

Determination of antimicrobial susceptibility of bovine mastitis pathogens is important for guiding antimicrobial treatment decisions and for the detection of emerging resistance. Environmental streptococci are ubiquitous in the farm environment and are a frequent cause of mastitis in dairy cows. The aim of the study was to determine patterns of antimicrobial susceptibility among species of environmental streptococci isolated from dairy cows in the Maritime Provinces of Canada. The collection consisted of 192 isolates identified in milk samples collected from 177 cows originating from 18 dairy herds. Results were aggregated into: (1) Streptococcus uberis (n = 70), (2) Streptococcus dysgalactiae (n = 28), (3) other Streptococci spp. (n = 35), (4), Lactococcus spp. (n = 32), and (5) Enterococcus spp. (n = 27). Minimum inhibitory concentrations (MICs) were determined using the Sensititre microdilution system and mastitis plate format. Multilevel logistic regression models were used to analyze the data, with antimicrobial susceptibility as the outcome. The proportion of susceptible S. uberis ranged from 23% (for penicillin) to 99% (for penicillin/novobiocin), with a median of 82%. All S. dysgalactiae were susceptible to all antimicrobials except for penicillin (93% susceptible) and tetracycline (18% susceptible). The range of susceptibility for other Streptococcus spp. was 43% (for tetracycline) to 100%, with a median percent susceptibility of 92%. Lactococcus spp. isolates displayed percent susceptibilities ranging from 0% (for penicillin) to 97% (for erythromycin), median 75%. For the antimicrobials tested, the minimum inhibitory concentrations were higher for Enterococcus spp. than for the other species. According to the multilevel models, there was a significant interaction between antimicrobial and bacterial species, indicating that susceptibility against a particular antimicrobial varied among the species of environmental streptococci and vice versa. Generally, susceptibility decreased with increasing within-herd average somatic cell count, isolates recovered in mid-lactation were more susceptible than isolates recovered in early lactation, and isolates recovered in samples collected post-clinical mastitis were more susceptible than isolates recovered from non-clinical lactating quarters. The results of this research support continued susceptibility of environmental streptococci to beta-lactam antimicrobials. A departure from the expected susceptibility to beta-lactams was the apparent reduced susceptibility of S. uberis to penicillin.

Short communication: Efficacy of glycolic acid-based and iodine-based postmilking barrier teat disinfectants for prevention of new intramammary infections in dairy cattle

A positive-control, natural exposure noninferiority field study was conducted to test the efficacy of a novel glycolic acid-based postmilking barrier teat disinfectant compared with a commercial iodine-based postmilking barrier teat disinfectant (positive control). Cows from 2 pens from a California Central Valley dairy farm were dipped after milking either with the positive-control product (PC) or the experimental product (EX) over 12 wk. New intramammary infections (NIMI) were determined by biweekly sampling of all quarters of study cows and classified as a NIMI based on somatic cell count and milk bacteriological culture results. The mean quarter-level incidence risks during a 2 wk study period were 3.50% (EX) and 4.28% (PC). The majority of NIMI were caused by coagulase-negative staphylococci, followed by non-agalactiae streptococci. The study results indicated that EX was noninferior to PC, with a 17% relative efficacy (improvement) in reducing NIMI compared with the PC group. Also, quarter somatic cell count was not affected by the postmilking teat disinfectant used. Finally, the EX product was safe in terms of teat conditioning: teat condition scores were not different between study groups. The study concluded that the glycolic acid-based experimental post-dip barrier was noninferior to the control, and could be considered a safe and effective postmilking teat disinfectant.

Incidence rate of pathogen-specific clinical mastitis on conventional and organic Canadian dairy farms

Mastitis is a common and costly production disease on dairy farms. In Canada, the incidence rate of clinical mastitis (IRCM) has been determined for conventionally managed dairy farms; however, no studies to date have assessed rates in organically managed systems. The objectives of this observational study were (1) to determine the producer-reported IRCM and predominant pathogen types on conventional and organic dairy farms in Southern Ontario, Canada, and (2) to evaluate the association of both mean overall IRCM and pathogen-specific IRCM with management system, housing type, and pasture access. Data from 59 dairy farms in Southern Ontario, Canada, distributed across conventional (n=41) and organic management (n=18) systems, were collected from April 2011 to May 2012. In addition to management system, farms were categorized by housing method (loose or tie-stall) and pasture access for lactating cows. Participating producers identified and collected samples from 936 cases of clinical mastitis. The most frequently isolated mastitis pathogens were coagulase-negative staphylococci, Bacillus spp., Streptococcus spp., Staphylococcus aureus, and Escherichia coli. The IRCM was higher on conventional farms than organic (23.7 vs. 13.2 cases per 100 cow-years) and was not associated with housing type (loose or tie-stall), pasture access, or herd-average milk yield. Bulk tank somatic cell count tended to be lower on conventional farms than organic (222,000 vs. 272,000 cells/mL). Pathogen-specific IRCM attributed to Staph. aureus, Bacillus spp., and E. coli was greater on conventional than organic farms, but was not associated with housing or any other factors. In conclusion, organic management was associated with reduced overall and pathogen-specific IRCM.

Isolation, Biochemical and Molecular Identification, and In-Vitro Antimicrobial Resistance Patterns of Bacteria Isolated from Bubaline Subclinical Mastitis in South India

Buffaloes are the second largest source of milk. Mastitis is a major impediment for milk production, but not much information is available about bubaline mastitis, especially subclinical mastitis. The aim of this study was to (a) investigate the application of various tests for the diagnosis of bubaline subclinical mastitis, (b) identify the major bacteria associated with it, and (c) evaluate the antibiotic resistance pattern of the bacteria. To this end, 190 quarter milk samples were collected from 57 domesticated dairy buffaloes from organized (64 samples) and unorganized (126 samples) sectors. Of these, 48.4%, 40.0%, 45.8%, 61.1%, and 61.6% were positive for subclinical mastitis by somatic cell count, electrical conductivity, California mastitis test, bromothymol blue test, and N-acetyl glucosaminidase test, respectively. As compared to the gold standard of somatic cell count, California mastitis test performed the best. However, a combination of the two methods was found to be the best option. Microbiological evaluation, both by biochemical methods as well as by monoplex and multiplex polymerase chain reaction, revealed that coagulase-negative staphylococci were the most predominant (64.8%) bacteria, followed by streptococci (18.1%), Escherichia coli (9.8%) and Staphylococcus aureus (7.3%). Most of the pathogens were resistant to multiple antibiotics, especially to β-lactam antibiotics. We propose that California mastitis test be combined with somatic cell count for diagnosis of subclinical mastitis in domestic dairy buffaloes. Further, our results reveal high resistance of the associated bacteria to the β-lactam class of antibiotics, and a possible major role of coagulase-negative staphylococci in causing the disease in India.

Relação da idade na presença de bactérias resistentes a antimicrobianos em rebanhos leiteiros no Rio Grande do Sul

A mastite bovina é uma doença importante na bovinocultura de leite, devido à sua alta incidência e perdas econômicas associadas principalmente com a produção de leite reduzida e aos custos do tratamento. O uso de antimicrobianos para o tratamento de casos clínicos e no período seco tem levantado preocupações quanto à seleção de cepas bacterianas resistentes. Isso também pode refletir na saúde pública, uma vez que bactérias resistentes, como o Staphylococcus aureus meticilina-resistente (MRSA), podem ser transmitidas aos seres humanos por contato direto com animais infectados ou produtos lácteos. A resistência das bactérias aos agentes antimicrobianos aumentou, em geral, devido a tratamentos ineficazes. Estudos realizados no Brasil com amostras não planejadas mostram aumento no padrão de resistência, principalmente em S. aureus. A exposição ao tratamento antimicrobiano repetido ao longo das lactações consecutivas de vacas pode ser um fator predisponente para o desenvolvimento da resistência antimicrobiana em bactérias que infectam o úbere. Assim, o objetivo deste estudo foi determinar a possível associação causal entre resistência antimicrobiana em bactérias isoladas a partir do leite bovino e dados como idade e período de lactação. As amostras de leite foram coletadas de 21 rebanhos leiteiros do Rio Grande do Sul, Brasil, selecionados aleatoriamente a partir da população-alvo de 1.656 explorações leiteiras semi-intensivas, estratificada por tamanho do rebanho. A bactéria foi considerada a unidade amostral, e para a estimativa de prevalência foram utilizados os seguintes parâmetros: uma frequência de 35% de Staphylococcus sp. resistentes à penicilina; um nível de confiança de 90%; e uma precisão absoluta de 12%. As bactérias foram isoladas de amostras de leite compostas de todos os quartos mamários de cada vaca após descartar os primeiros três ou quatro jatos de leite. Para acessar os potenciais fatores de risco, características dos animais foram obtidas através de uma entrevista com os produtores. Os exames laboratoriais foram realizados de acordo com as recomendações do National Mastitis Council. Um total de 242 isolados foi obtido de 195 vacas a partir da amostra do rebanho total (251 vacas). A prevalência de infecções foi descrita em grupos de acordo com o perfil epidemiológico: bactérias ambientais, contagiosas e outras. Estas perfizeram 57,3%, 26,3% e 11,2%, respectivamente, dos animais amostrados. Testes de suscetibilidade antimicrobiana contra 12 diferentes antimicrobianos foram realizados em 159 isolados. No total, 30% dos isolados testados mostraram resistência a pelo menos três grupos diferentes de antimicrobianos e foram classificados como multirresistentes. Foram observadas as freqüências mais elevadas de resistência contra a ampicilina para os estafilococos coagulase-negativo, seguida de eritromicina para estafilococos coagulase-positivo e tetraciclina para estreptococos. A análise de regressão logística mostrou uma relação significativa entre a idade das vacas e a presença de estafilococos coagulase-positivo multirresistentes e distribuição de classes diferentes de bactérias nos diferentes estratos etários, o que sugere uma concorrência dinâmica ao longo do tempo (p < 0,05). Animais com três a quatro anos tiveram 13,7 vezes mais chances (IC95% 1,4 - 130,2, p = 0,02) de ter estafilococos coagulase-positivo multirresistentes em comparação com aqueles com dois ou três anos. O tempo de exposição a agentes infecciosos e consequentes terapias sugere uma maior chance de colonização do úbere por patógenos resistentes devido à pressão de seleção repetida durante a vida.

Identification of coagulase-negative staphylococci from bovine intramammary infection by matrix-assisted laser desorption ionization-time of flight mass spectrometry

Coagulase-negative staphylococci (CoNS) are among the main pathogens causing bovine intramammary infection (IMI) in many countries. However, one of the limitations related to the specific diagnosis of CoNS is the lack of an accurate, rapid, and convenient method that can differentiate the bacterial species comprising this group. The aim of this study was to evaluate the ability of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) to accurately identify CoNS species in dairy cow IMI. In addition, the study aimed to determine the frequency of CoNS species causing bovine IMI. A total of 108 bacterial isolates were diagnosed as CoNS by microbiological cultures from two milk samples collected from 21 dairy herds; the first sample was collected at the cow level (i.e., 1,242 composite samples from all quarters), while the second sample was collected at the mammary quarter level (i.e., 1,140 mammary samples collected from 285 cows). After CoNS isolation was confirmed by microbiological culture for both samples, all CoNS isolates (n=108) were genotypically differentiated by PCR restriction fragment length polymorphism (RFLP) analysis of a partial groEL gene sequence and subjected to the MALDI-TOF MS identification procedure. MALDI-TOF MS correctly identified 103 (95.4%) of the CoNS isolates identified by PCR-RFLP at the species level. Eleven CoNS species isolated from bovine IMI were identified by PCR-RFLP, and the most prevalent species was Staphylococcus chromogenes (n=80; 74.1%). In conclusion, MALDI-TOF MS may be a reliable alternative method for differentiating CoNS species causing bovine IMI.

Nordic veterinarians' threshold for medical treatment of dairy cows, influence on disease recording and medicine use: mild clinical mastitis as an example

National databases for dairy cows in the four Nordic countries, Denmark, Finland, Norway and Sweden, have been found to capture varying proportions of disease events on farm. A variation in the thresholds of veterinarians to initiate medical treatment may be a reason for this. Studying these thresholds may increase the understanding of prudent use of antibiotics. The primary objective of this study was to investigate whether Nordic veterinarians, on a between country-level, vary in their intention to start medical treatment of a dairy cow with mild clinical mastitis, on the same day as making the diagnosis. The threshold for initiating treatment was quantified as an intention score. Secondary, underlying behavioural components of the intention score was studied within each country. A social psychology model, the Theory of Planned Behaviour (TPB), was used to design a questionnaire that was distributed to 1047 veterinarians in cattle practice in the four countries during autumn 2010. The response rate was around 50% in all the countries, and 543 observations were retained for analysis. The between-country differences in intention were tested with one-way analysis of variance. Multivariable linear regression was used to estimate the proportion of variability in intention explained by the three behavioural components, attitude, subjective norm and perceived behavioural control. The Spearman rank correlations between specific beliefs about the behaviour and intention scores were estimated to find beliefs of high influence on the decision to treat or not. Intention scores differed between all countries (p<0.05) except between NO and SE (p=0.06). The mean intention scores were 0.71, 0.42, 0.58 and 0.50 in DK, FI, NO and SE, respectively. As measured by the adjusted R(2) in linear regression models, the underlying behavioural components of the TPB explained 0.37, 0.41, 0.40 and 0.48 of the variation in intention scores in DK, FI, NO and SE, respectively. Attitude was the most important predictor in DK, NO and SE, but perceived behavioural control was most important in FI. In all countries the specific attitude belief of highest influence was that starting treatment the same day as diagnosing a case of mild clinical mastitis gives the best result, compared to delaying treatment. The varying intentions of veterinarians to initiate medical treatment are likely to influence centrally registered mastitis incidence. This study has given an improved understanding of this behaviour, which may be useful in intervention studies or campaigns aiming at prudent use of antibiotics on dairy farms.