Subclinical and Clinical Mastitis in Heifers Following the Use of a Teat Sealant Precalving

Is AMR in Dairy Products a Threat to Human Health? An Updated Review on the Origin, Prevention, Treatment, and Economic Impacts of Subclinical Mastitis

Background

Bovine mastitis is the most frequent and costly illness impacting dairy herds worldwide. The presence of subclinical mastitis in dairy cows has an impact on the decreased output of milk and milk quality, culling of affected cows, mortality rate, as well as mastitis-related treatment expenses, generating significant financial loss to the dairy industry. The pathogenic bacteria invade through the mammary gland, which then multiply in the milk-producing tissues causing infection, and the presence of pathogenic bacteria in milk is concerning, jeopardizes human health, and also has public health consequences. Intervention to promote herd health is essential to protect public health and the economy.

Results

This review attempts to provide an overview of subclinical mastitis, including mastitis in different species, the effect of mastitis on human health and its pathogenic mechanism, the prevalence and incidence of subclinical mastitis, and current preventive, diagnostic, and treatment methods for subclinical mastitis. It also elaborates on the management practices that should be followed by the farms to improve herd immunity and health.

Conclusion

This review brings the importance of the threat of antimicrobial resistance organisms to the dairy industry. Furthermore, this review gives a glimpse of the economic consequences faced by the farmers and a futuristic mastitis market analysis in the dairy industry.

Bayesian latent class models to determine diagnostic sensitivities and specificities of two point of care rapid tests (Selma plus, Dipslide) for the detection of Streptococcus uberis associated with mastitis in dairy cows

Introduction

Development and validations of accurate mastitis diagnostics are crucial to make timely and evidence-based decisions on mastitis therapy in order to reduce its impact on productivity, animal welfare and practicing the prudent use of antimicrobials on dairy farms.

Methods

The objectives of this study were to assess the agreement between test results from reference laboratory and two point of care tests (Selma plus, Dipslide) and to estimate the test accuracies with Bayesian latent class models (BLCMs). In total of 509 single quarter milk samples from cows with mastitis were included in the study.

Results

Among all analyzed mastitis pathogens, Streptococcus spp. was detected in up to one third of all analyzed samples and for Selma all Streptococcus samples were considered as Streptococcus uberis. The agreement (κ) when comparing two tests varied greatly depending on the bacteria, ranging from no agreement to good agreement (κ = negative to 0.86) depending on the prevalence of identified pathogens. Based on BLCMs to assess diagnostic test accuracies for the pathogen Streptococcus uberis, posterior sensitivities of 76, 71, and 64% for Selma plus, Dipslide and laboratory standard culture and specificities of 93%, 98% for Selma and Dipslide, respectively, were obtained.

Discussion

The two point of care rapid culture systems Dipslide and Selma plus plate can provide important preliminary pathogen identification for targeted mastitis therapy, especially when general information about growth and a rough classification of the bacteria into groups have an impact on treatment strategy. The two evaluated rapid culture systems, Dipslide and Selma plus plate, show good test accuracies for Streptococcus uberis at least at genus level. Therefore, using these tests may contribute to prudent use of antibiotics.

The Impact of Selective Dry Cow Therapy Adopted in a Brazilian Farm on Bacterial Diversity and the Abundance of Quarter Milk

Simple Summary

The current study sought to assess the impact of selective dry cow therapy (SDCT) (protocol 1: antibiotics combined with internal teat sealant (ITS); vs. protocol 2: ITS alone) on bacterial diversity and the abundance of quarter milk. Based on the results of bacteriological culturing, the quarters (n = 313) were categorized as healthy, cured, persistent, and new intramammary infection. The bacterial diversity was similar when comparing both healthy and cured quarters submitted to both drying-off protocols. Although healthy cows that were treated at drying-off using only teat sealant showed no alteration in the alpha and beta diversity of bacteria, they showed a higher abundance of bacterial groups that may be beneficial to or commensals of the mammary gland, which implies that antibiotic therapy should be reserved for mammary quarters with a history of mastitis.

Abstract

We aimed to evaluate the impact of selective dry cow therapy (SDCT) (protocol 1: antimicrobial combined with internal teat sealant (ITS); vs. protocol 2: ITS alone) on bacterial diversity and the abundance of quarter milk. Eighty high production cows (parity ≤ 3 and an average milk yield of 36.5 kg/cow/day) from the largest Brazilian dairy herd available were randomly selected; milk quarter samples were collected for microbiological culture (MC) on the day of drying-off (n = 313) and on day 7 post-calving (n = 313). Based on the results of the MC before and after calving, 240 quarters out of 313 were considered healthy, 38 were cured, 29 showed new infections and 6 had persistent infections. Mammary quarters were randomly selected based on intramammary information status and SDCT protocols for bacterial diversity analyses. The bacterial diversity was similar when comparing both healthy and cured quarters submitted to both drying-off protocols. Despite healthy cows that were treated at dry-off using only teat sealant showing no alteration in the alpha and beta bacterial diversity, they did show a higher abundance of bacterial groups that may be beneficial to or commensals of the mammary gland, which implies that antibiotic therapy should be reserved for mammary quarters with a history of mastitis.

Characteristics of mammary secretions collected from infected and uninfected primigravid dairy heifer mammary glands

Intramammary infections (IMI) in primigravid dairy heifers can affect mammary growth and development, which can reduce first-lactation milk yield. Detection of IMI in heifers most often involves the use of culture-based methods that are not often used in production dairy settings given their labor- and time-consuming nature. The objective of this study was to determine whether mammary secretion somatic cell count (SCC) and viscosity were associated with the infection status of primigravid heifer mammary glands. A total of 270 heifers from a single farm were used, selected based on the farmer's willingness to participate. The study was conducted from June to October 2020. Mammary secretion samples were aseptically collected from a randomly selected quarter of each heifer at 75 d prepartum (75PP), and another quarter of each heifer was sampled at 35 d prepartum (35PP). The remaining 2 quarters of each heifer were not examined. Mammary secretion samples underwent bacteriological examination to determine IMI status and quantitative SCC measurement and were also assessed for secretion viscosity based on visual observation. Prevalence of IMI was 26% (69/270) and 28% (71/255) at 75 and 35 d prepartum, respectively. Uninfected secretion samples had 133.2 [95% confidence interval (CI): 16.8 to >999.9] times greater odds to be thick compared with samples infected with a major pathogen, and 14.4 (95% CI: 8.5 to 24.1) times greater odds to be thick compared with samples infected with non-aureus staphylococci (NAS). The mean secretion SCC of uninfected quarters (6.04 ± 0.03 log₁₀ cells/mL) was significantly lower than that of secretions collected from quarters infected with Staphylococcus chromogenes (6.34 ± 0.04 log₁₀ cells/mL), other NAS species (6.28 ± 0.10 log₁₀ cells/mL), or a major pathogen (6.73 ± 0.08 log₁₀ cells/mL). These results indicate that mammary secretion viscosity and SCC measurement may be useful tools in identifying primigravid heifer quarters with IMI. The ability to evaluate viscosity at time of sampling may be a useful strategy that could be incorporated into interventions designed to diminish the negative effects of prepartum IMI on lactational performance.

Alternative Practices in Organic Dairy Production and Effects on Animal Behavior, Health, and Welfare

The number of organic dairy farms has increased because of the increased growth of the organic market, higher organic milk price, and because some consumers prefer to purchase products from less intensive production systems. Best management practices are expected from organic dairy farms to ensure animal health and milk production. Organic dairy producers typically transition from conventional systems to avoid chemicals and pesticides, enhance economic viability, improve the environment, and increase soil fertility. Organic dairy producers respect and promote a natural environment for their animals, is also an important component of animal welfare. Organic producers have few options to mitigate pain in dairy calves. In the United States, therapies to mitigate pain for disbudded organic dairy calves are regulated by the US National Organic Program. Organic producers regularly use naturally derived alternatives for the treatment of health disorders of dairy calves, heifers, and cows. Alternative natural products may provide an option to mitigate pain in organic dairy calves. Despite the reluctance to implement pain alleviation methods, some organic farmers have expressed interest in or currently implement plant-based alternatives. Efficacy studies of alternative remedies for organic livestock are needed to verify that their use improves animal welfare. Non-effective practices represent a major challenge for organic dairy animal welfare. The relationship between humans and animals may be jeopardized during milking because first-lactation cows may exhibit adverse behaviors during the milking process, such as kicking and stomping. The periparturient period is particularly challenging for first-lactation cows. Adverse behaviors may jeopardize animal welfare and reduce safety for humans because stressed heifers may kick off the milking unit, kick at milkers, and display other unwanted behaviors in the milking parlor. This may reduce milking efficiency, overall production, and ultimately reduce the profitability of the dairy farm. Positive animal welfare is a challenging balancing act between the three overlapping ethic concerns. Identifying animal welfare deficits in organic livestock production is the first step in capitalizing on these opportunities to improve welfare.

A retrospective on claims regarding clinical mastitis in the subsequent lactation, after use of an internal teat sealant in the dry period

Infusion of an internal teat sealant into the mammary gland of the dairy cow at drying off has been claimed to reduce the incidence of clinical mastitis over many months in the subsequent lactation, despite the absence of any ingredient of the sealant remaining for that long. However, these claims have been poorly substantiated, often by lack of identification on when the infection occurred in the period from calving to disease, if the infection was present at post calving sampling and if the pathogen causing the disease was that causing an earlier infection. Moreover, no hypothesis on how any effect on clinical mastitis might occur has been advanced in any of the publications claiming the effect. That the effect might occur is only reported in a minority of publications, and the possibility that this is relatively specific to Gram-negative pathogens is reviewed.

Administration of internal teat sealant in primigravid dairy heifers at different times of gestation to prevent intramammary infections at calving

Intramammary infections (IMI) are common in primigravid dairy heifers and can negatively affect future milk production. Bismuth subnitrate-based internal teat sealants (ITS) have been used to prevent prepartum IMI in dairy heifers by creating a physical barrier within the teat, preventing pathogens from entering the gland, though determination of when to administer ITS in heifers has yet to be investigated. The objectives of this study were to determine if administration of ITS in primigravid heifers reduced the odds of IMI at calving and if administration of ITS at different stages of gestation (75 vs. 35 d prepartum) affected the odds of IMI at calving. A total of 270 heifers were used at a single farm. One quarter of each heifer was randomly chosen to be aseptically sampled and administered ITS 75 d prepartum (ITS75), another quarter of each heifer was sampled and received ITS 35 d prepartum (ITS35), whereas the remaining 2 quarters of each heifer served as control quarters (CON) and were not sampled before calving. Within 12 h of calving, aseptic colostrum samples were collected from all quarters to determine quarter infection status. When an IMI was caused by mastitis pathogens other than non-aureus staphylococci (NAS), CON quarters were 3 times [95% confidence interval (CI): 1.4-6.3] and 2.5 times (95% CI: 1.2-4.9) more likely to be infected at calving than ITS75 and ITS35 quarters, respectively. For IMI with NAS, CON quarters were 5.8 (95% CI: 3.2-10.5) and 6.4 (95% CI: 3.4-12.0) times more likely to be infected than ITS75 and ITS35 quarters, respectively. Odds of IMI at calving was similar between ITS75 and ITS35 quarters for both NAS (odds ratio = 0.9) and other pathogens (odds ratio = 1.2). Results indicate that ITS administration at either 75 and 35 d prepartum reduced IMI prevalence at calving in primigravid dairy heifers. Farm specific factors may influence prevalence and timing of heifer IMI and earlier administration of ITS provides an extended period of protection for the developing gland.

Prevalence of bovine mastitis and main risk factors in Tunisia

Tunisian milk chain is in danger with a dramatical reduction of milk production over the last years. Improving the quality of milk seems mandatory to improve farmers' income, but for the moment, there is only scarce data on milk quality management in Tunisia. In this context, the aims of our study were first to describe the prevalence of bovine mastitis in 267 cows from 71 representative small dairy farms in the North (43.7%) and Center (56.3%) regions of Tunisia, using mastitis detection by California Mastitis Test (CMT) on milk quarter and clinical signs, and second, to assess possible risk factors for mastitis from animal, environment, and breeding management. In parallel, cow and bulk milk somatic cell count (SCC) were analyzed. Our results demonstrated that 60.3% of cows showed mastitis as determined by CMT and clinical examinations. Increased stage of lactation, parity, udder depth, and type of milking were significantly (P < 0.05) associated with increased odds of mastitis prevalence. The mean of individual cow SCC (ISCC) and bulk milk SCC (BMSCC) was very high (1083 × 10³ cells/mL and 698 × 10³ cells/mL, respectively), all ranks and stages of lactations combined. These high values confirm the infectious origin of mastitis that we found caused mainly by Staphylococcus aureus and coagulase-negative Staphylococci. In conclusion, control of the identified risks factors and improved biosecurity measures must be encouraged to restore udder health and milk quality and thus productivity and durability of Tunisian milk chain.

Advances in therapeutic and managemental approaches of bovine mastitis: a comprehensive review

Mastitis (intramammary inflammation) caused by infectious pathogens is still considered a devastating condition of dairy animals affecting animal welfare as well as economically incurring huge losses to the dairy industry by means of decreased production performance and increased culling rates. Bovine mastitis is the inflammation of the mammary glands/udder of bovines, caused by bacterial pathogens, in most cases. Routine diagnosis is based on clinical and subclinical forms of the disease. This underlines the significance of early and rapid identification/detection of etiological agents at the farm level, for which several diagnostic techniques have been developed. Therapeutic regimens such as antibiotics, immunotherapy, bacteriocins, bacteriophages, antimicrobial peptides, probiotics, stem cell therapy, native secretory factors, nutritional, dry cow and lactation therapy, genetic selection, herbs, and nanoparticle technology-based therapy have been evaluated for their efficacy in the treatment of mastitis. Even though several strategies have been developed over the years for the purpose of managing both clinical and subclinical forms of mastitis, all of them lacked the efficacy to eliminate the associated etiological agent when used as a monotherapy. Further, research has to be directed towards the development of new therapeutic agents/techniques that can both replace conventional techniques and also solve the problem of emerging antibiotic resistance. The objective of the present review is to describe the etiological agents, pathogenesis, and diagnosis in brief along with an extensive discussion on the advances in the treatment and management of mastitis, which would help safeguard the health of dairy animals.

Effects of Pre-Parturient Iodine Teat Dip Applications on Modulating Aversive Behaviors and Mastitis in Primiparous Cows

Heifers and their human handlers are at risk for decreased welfare during the early lactation period. This experiment investigated pre-parturient teat dipping and parlor acclimation to reduce mastitis and aversive behaviors in early lactation heifers. Three weeks prior to calving, heifers were randomly assigned to receive either: (1) a weekly 1.0% iodine-based teat dip in the parlor (trained; n = 37) or (2) no treatment (control; n = 30). For the first 3 days of lactation, heifers were milked twice daily, and treatment-blinded handlers assessed behaviors and clinical mastitis. Aseptic quarter milk samples were collected within 36 h of calving and analyzed for pathogens. Control heifers had (OR ± SE) 2.2 ± 0.6 times greater (p < 0.01) odds of kicking during milking. Trained heifers had (OR ± SE) 1.7 ± 0.4 times greater (p = 0.02) odds of being very calm during milking, while control heifers had 2.2 ± 0.8 and 3.8 ± 2.1 times greater (p < 0.04) odds of being restless and very restless or hostile during milking, respectively. Quarters of control heifers had (OR ± SE) 5.4 ± 3.4 greater (p < 0.01) odds of intramammary Staphylococcus aureus infection, yet clinical mastitis was similar among treatments. The results indicate that teat dipping in the parlor weekly for 3 weeks before calving may alleviate some aversive milking behaviors and protect against early lactation S. aureus intramammary infections.

Genetic analysis of pathogen-specific intramammary infections in dairy cows

Mastitis is one of the most common diseases in dairy cattle, causing severe economic losses to dairy farmers. Mastitis usually occurs due to intramammary infection (IMI) caused by a variety of pathogenic bacteria. Although good progress has been made in understanding genetics of pathogen-specific clinical mastitis, studies involving genetic analysis of pathogen-specific IMI are scarce. The overall objective of this study was, therefore, to assess genetic variation of overall and pathogen-specific IMI in nonclinical primiparous and multiparous cows using bacterial culture. Data and milk samples were collected over a 2-yr interval as part of the Canadian Bovine Mastitis Research Network. The final data set contained records of 46,900 quarter milk samples from 3,382 clinically healthy primiparous and multiparous Holstein cows from 84 dairy herds. For the genetic analysis, we considered the following 7 traits: overall IMI, non-aureus staphylococci (NAS) IMI, contagious pathogen IMI, environmental pathogen IMI, major pathogen IMI, minor pathogen IMI and somatic cell score (SCS). Data were analyzed at the quarter level using a threshold-probit model via Gibbs sampling in BLUPF90. Prevalence of IMI traits at the quarter level in multiparous cow from 0 to 400 DIM ranged from 6.8 to 45.5%. Posterior mean of quarter heritability estimates (on the underlying scale, posterior SD in brackets) of overall IMI and pathogen-specific IMI traits ranged from 0.017 to 0.073 (±0.009 to 0.030). Weak to strong genetic correlations [ranging from 0.18 to 0.97 (±0.01 to 0.29)] among pathogen-specific IMI traits and with overall IMI indicated that not all of these traits were genetically similar. Weak to moderate Spearman rank correlations between estimated breeding values for overall IMI and pathogen-specific IMI traits (from 0.31 to 0.87) indicated possible substantial reranking of sires. The percentage of daughters with IMI caused by various pathogen groups ranged from 13 to 80% and from 38 to 94% for the best (10% decile) and worst sires (90% decile) according to their IMI trait-specific estimated breeding values, respectively. Pathogen-specific IMI traits and overall IMI had weak to moderate positive genetic correlations [ranging from 0.11 to 0.81 (±0.11 to 0.22)] with SCS. Therefore, selection for lower SCS will improve resistance to IMI. However, based on the observed weak to moderate rank correlations (0.04 to 0.47) between pathogen-specific IMI traits and SCS, selection for lower SCC will not improve resistance to IMI from every pathogen-specific IMI group in the same manner. Therefore, despite low heritability estimates, there was sizeable genetic variation for pathogen-specific IMI traits, indicating that long-term direct genetic selection for pathogen-specific IMI can improve pathogen-specific IMI resistance.

Randomized equivalence study comparing the efficacy of 2 commercial internal teat sealants in dairy cows

The use of an internal teat sealant (ITS) at dry-off has been repeatedly shown to improve udder health in the subsequent lactation. However, almost all ITS research conducted in North America has evaluated one product (Orbeseal, Zoetis, Parsippany, NJ). The objective of this study was to evaluate a new ITS product (Lockout, Boehringer-Ingelheim Animal Health, Duluth, GA), by comparing it directly to Orbeseal in a multi-site, randomized, positively controlled equivalence trial for health indicators during the dry period [quarter-level new intramammary infection (IMI) risk, IMI cure risk, and IMI risk at 1 to 13 d in milk, DIM] and during the first 100 DIM [clinical mastitis and culling or death risk and test-day milk somatic cell count (SCC) and milk yield]. At dry-off, cows were randomly allocated to be treated with Orbeseal or Lockout after blanket administration of a cloxacillin dry cow therapy product. Cows were then followed from dry-off until 100 DIM. Intramammary infection status at enrollment and at 1 to 13 DIM was determined using standard bacteriological methods, allowing for the measurement of IMI dynamics during the dry period (i.e., IMI cures and new IMI). The effect of ITS group on dry period IMI cure, dry period new IMI, and IMI risk at 1 to 13 DIM was determined using generalized linear mixed models (logistic). Marginal standardization was used to derive risk difference estimates. An equivalence hypothesis test was conducted to compare ITS groups for dry period new IMI risk (margin of equivalence was ±5% units). The effect of ITS group on clinical mastitis and culling or death was determined using Cox proportional hazards regression. The effect of ITS group on test-day SCC and milk yield was determined using linear mixed models. Final models indicated that measures of quarter-level IMI dynamics were similar between ITS groups (i.e., risk difference estimates and 95% confidence intervals all close to zero). Furthermore, Lockout was found to be equivalent to Orbeseal for dry period new IMI risk using an equivalence hypothesis test. Hazard ratio estimates for clinical mastitis and culling or death were close to 1 and differences in SCC and milk yield between ITS groups were close to 0, indicating negligible effects of ITS group on test-day SCC and milk yield. In most cases, these effect estimates were relatively precise (i.e., narrow 95% confidence intervals). We conclude that producers using blanket dry cow therapy could consider including Orbeseal or Lockout treatment in their programs.

Effect of bismuth subnitrate on in vitro growth of major mastitis pathogens

The mode of action of bismuth subnitrate in teat sealant formulations as a preventative for intramammary infections during the dry period is unknown. Although previous studies proposed an action mechanism-creating a physical barrier in the teat canal to prevent bacterial invasion-it has not been proven experimentally. We hypothesized that bismuth subnitrate has an inhibitory effect on bacterial growth, in addition to its barrier effect. The objective of this study was to assess the effect of bismuth subnitrate on bacterial growth of major mastitis-causing agents. A strain of Streptococcus uberis (SR115), 2 strains of Staphylococcus aureus (SA3971/59 and SA1), and a strain of Escherichia coli (P17.14291) were tested in vitro for their ability to grow in the presence or absence of bismuth subnitrate. Disk diffusion testing, impedance measurement, and evaluation of bacterial growth in shaking conditions were the methods used to test this hypothesis. A reduction of growth in the presence of bismuth subnitrate occurred for all the strains tested. However, we observed strain and species variations in the extent of growth inhibition. These results suggest that an inhibitory effect on bacterial growth by bismuth subnitrate could partially explain the efficacy of bismuth-based formulations for preventing intramammary infections over the dry period. Further research is required to test the effect of teat sealant formulations on bacterial growth.

Prevention of Intramammary Infections by Prepartum External Application of a Teat Dip Containing Lactic Acid Bacteria with Antimicrobial Properties in Dairy Heifers

The aim of the current study was to investigate the effects of the prepartum external treatment of teats with a combination of four lactic acid bacteria strains viz. Lactobacillus (Lb.) rhamnosus ATCC 7469, Lactococcus lactis subsp. lactis ATCC 11454, Lb. paracasei 78/37 (DSM 26911), and Lb. plantarum 118/37 (DSM 26912) on the postcalving udder health of dairy heifers. The study used a split-udder design. Two weeks before the expected calving date, one of two contralateral teats of a teat pair was dipped with an aqueous suspension of lactic acid bacteria (final bacterial counts 8.40–8.47 log₁₀-transformed CFU/mL) once in a week until calving; the other teat of the pair was not treated. After calving, quarter foremilk samples were taken and investigated cyto-microbiologically. In total, 629 teat pairs of 319 heifers were included. There was an association between the treatment and intramammary infections caused by the major udder-pathogenic bacteria Staphylococcus aureus, Streptococcus dysgalactiae, and enterococci, as well as clinical mastitis in the first 100 days after calving. The present study indicates that intramammary infections with major pathogens and clinical mastitis may be prevented by regular prepartum external application of lactic acid bacteria in dairy heifers.

Investigation of the association between the interval from internal teat sealant administration to calving and early lactation clinical mastitis in New Zealand dairy heifers

AIMS

To examine the association between the interval from internal teat sealant (ITS) administration to calving and the incidence of farmer-recorded clinical mastitis in the first 30 days of lactation in pasture-based dairy heifers.

METHODS

Heifers that were administered an ITS by a single veterinary business in the South Island of New Zealand over the winter of 2014 were enrolled in a cross-sectional observational study. ITS was administered to all heifers on each participating farm on a single calendar day. The dates of calving and farmer-diagnosed clinical mastitis were recorded by farm staff. The interval from ITS administration to calving was categorised into four approximately evenly sized groups: <35, 35-48, 49-69 and >69 days. The quartile of the farm's calving period in which each heifer calved was also investigated as a potential confounding variable. A hierarchical logistic regression model was constructed to determine the association between the interval from ITS administration to calving with the odds of clinical mastitis in the first 30 days of lactation.

RESULTS

Analysis was performed on 7,126 eligible heifers from 31 farms, with ITS administered between 9 May and 11 July 2014. The mean interval from ITS administration to calving was 52.9 (SD 24.4, min 1, max 137) days. Clinical mastitis was diagnosed in 420/7,126 (5.9 (95% CI=5.4-6.5)%) heifers between calving and day 30 of lactation. In the final multivariable model, which included calving period quartile, interval from ITS administration to calving was not associated with the odds of clinical mastitis (p=0.516). Compared to an interval from ITS administration to calving of <35 days, the adjusted OR of clinical mastitis for intervals of 35-48, 49-69 and >69 days were 0.83 (95% CI=0.59-1.17), 0.71 (95% CI=0.45-1.11) and 0.68 (95% CI=0.36-1.29), respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Within the range of intervals from ITS administration to calving observed in this study, there was no association with the odds of clinical mastitis in the first 30 days of lactation in dairy heifers. This study suggests that veterinary clinics may be able to extend their ITS administration service and treat dairy heifers earlier than the current recommendation of approximately 4 weeks before the planned start of calving.

Antimicrobial Resistance in Streptococcus spp

The genus Streptococcus includes Gram-positive organisms shaped in cocci and organized in chains. They are commensals, pathogens, and opportunistic pathogens for humans and animals. Most Streptococcus species of veterinary relevance have a specific ecological niche, such as S. uberis, which is almost exclusively an environmental pathogen causing bovine mastitis. In contrast, S. suis can be considered as a true zoonotic pathogen, causing specific diseases in humans after contact with infected animals or derived food products. Finally, Streptococcus species such as S. agalactiae can be sporadically zoonotic, even though they are pathogens of both humans and animals independently. For clarification, a short taxonomical overview will be given here to highlight the diversity of streptococci that infect animals. Several families of antibiotics are used to treat animals for streptococcal infections. First-line treatments are penicillins (alone or in combination with aminoglycosides), macrolides and lincosamides, fluoroquinolones, and tetracyclines. Because of the selecting role of antibiotics, resistance phenotypes have been reported in streptococci isolated from animals worldwide. Globally, the dynamic of resistance acquisition in streptococci is slower than what is experienced in Enterobacteriaceae, probably due to the much more limited horizontal spread of resistance genes. Nonetheless, transposons or integrative and conjugative elements can disseminate resistance determinants among streptococci. Besides providing key elements on the prevalence of resistance in streptococci from animals, this article will also largely consider the mechanisms and molecular epidemiology of the major types of resistance to antimicrobials encountered in the most important streptococcal species in veterinary medicine.

Communications of Staphylococcus aureus and non-aureus Staphylococcus species from bovine intramammary infections and teat apex colonization

The role of non-aureus staphylococci (NAS) in the risk of acquisition of intramammary infections with Staphylococcus aureus is vague and still under debate. The objectives of this study were to (1) investigate the distribution patterns of NAS species from milk and teat skin in dairy herds with automatic milking systems, and (2) examine if the isolated NAS influences the expression of S. aureus virulence factors controlled by the accessory gene regulator (agr) quorum sensing system. In 8 herds, 14 to 20 cows with elevated somatic cell count were randomly selected for teat skin swabbing and aseptic quarter foremilk samples from right hind and left front quarters. Teat skin swabs were collected using the modified wet-dry method and milk samples were taken aseptically for bacterial culture. Colonies from quarters with suspicion of having NAS in milk or teat skin samples (or both) were subjected to MALDI-TOF assay for species identification. To investigate the interaction between S. aureus and NAS, 81 isolates NAS were subjected to a qualitative β-galactosidase reporter plate assay. In total, 373 NAS isolates were identified representing 105 from milk and 268 from teat skin of 284 quarters (= 142 cows). Sixteen different NAS species were identified, 15 species from teat skin and 10 species from milk. The most prevalent NAS species identified from milk were Staphylococcus epidermidis (50%), Staphylococcus haemolyticus (15%), and Staphylococcus chromogenes (11%), accounting for 76%. Meanwhile, the most prevalent NAS species from teat skin were Staphylococcus equorum (43%), S. haemolyticus (16%), and Staphylococcus cohnii (14%), accounting for 73%. Using reporter gene fusions monitoring transcriptional activity of key virulence factors and regulators, we found that out of 81 supernatants of NAS isolates, 77% reduced expression of hla, encoding a-hemolysin, 70% reduced expression of RNAIII, the key effector molecule of agr, and 61% reduced expression of spa encoding protein A of S. aureus, respectively. Our NAS isolates showed 3 main patterns: (1) downregulation effect such as S. chromogenes (milk) and Staphylococcus xylosus (milk and teat), (2) no effect such as Staphylococcus sciuri (teat) and S. vitulinus (teat), and the third pattern (c) variable effect such as S. epidermidis (milk and teat) and S. equorum (milk and teat). The pattern of cross-talk between NAS species and S. aureus virulence genes varied according to the involved NAS species, habitat type, and herd factors. The knowledge of how NAS influences S. aureus virulence factor expression could explain the varying protective effect of NAS on S. aureus intramammary infections.

Prepartum application of internal teat sealant or intramammary amoxicillin on dairy heifers: Effect on udder health, survival, and performance

Intramammary infusion of antimicrobials (IA) and application of an internal teat sealant (ITS) at the end of the lactation is a common strategy to prevent and treat intramammary infections during the dry period. In heifers, precalving IA has been reported to improve udder health and milk quality; however, the effect of ITS in heifers housed in freestall barns is still unknown. The objective of this study was to investigate the effect of prepartum application of ITS or IA on udder health of dairy heifers. A total of 886 heifers were randomly allocated into 1 of 4 treatment groups when they were 245 ± 3 d pregnant. Control heifers (CON) did not receive any treatment. Heifers in the ITS group received the application of ITS containing 2.6 g of bismuth subnitrate. Animals in the IA group received intramammary administration of 62.5 mg of amoxicillin. Heifers in IA+ITS group received intramammary administration of amoxicillin followed by ITS application. The follow-up period was 270 d in milk (DIM). Clinical mastitis was diagnosed and treated by trained farm personnel throughout the study period. Composite milk somatic cell counts (SCC) were determined monthly for the first 9 mo of lactation by Dairy Herd Improvement Association. Subclinical mastitis was defined as a cow having a SCC >200,000 cells/mL for at least 1 test day and not diagnosed with clinical mastitis during the study period. At 7 ± 3 DIM, composite milk samples were collected for bacteriological analysis for a subset of the study animals. The presence of pathogens in milk at 7 ± 3 DIM was more frequently detected in the CON heifers compared with animals enrolled in the treatment groups. Heifers in IA+ITS group had a decreased incidence of clinical mastitis compared with CON heifers (12.9 vs. 21.4%). Additionally, the incidence of subclinical mastitis was decreased for IA+ITS heifers compared with CON counterparts (20.1 vs. 43.8%). During the first 9 mo of lactation, IA and IA+ITS heifers had lower SCC linear scores compared with ITS and CON counterparts. Although IA+ITS treatment successfully improved udder health, it did not result in better milk yield, fertility, and survivability. In conclusion, ITS alone was not effective in improving udder health; however, the combination of ITS and IA decreased the incidence of clinical and subclinical mastitis during the first 9 mo of lactation. Additionally, IA+ITS had a long-term effect on the SCC linear score throughout the study period.

Efficacy of an internal teat seal associated with a dry cow intramammary antibiotic for prevention of intramammary infections in dairy cows during the dry and early lactation periods

ABSTRACT: The present study aimed to evaluate the use of an internal dry period teat seal containing bismuth subnitrate (Teatseal®, Zoetis®, Florham Park, Nova Jersey, USA) associated with a long-acting cloxacilin preparation (Orbenin® Extra dry cow, Zoetis®, Florham Park, Nova Jersey, USA), in preventing new infections during the dry-off and early postpartum period. A total of 150 Holstein cows (average production of 9,000 kg of milk per lactation), with four functional udder quarters without clinical mastitis was included in the study. All animals were dried-off 60 days before the expected calving date. Two teats positioned diagonal-contralaterally received only dry cow antibiotic, control group C (n=300) and the other two teats, treatment group T (n=300) received dry cow antibiotic and infusion with an internal teat seal. Data from SCC variable were transformed by log base-10 transformation. Duncan’s test was used accepting 5% as the level of statistical significance. The occurrence of intramammary infection (IMI) and chronicity rate, and frequency of microorganisms isolated at drying and immediately postpartum in teats of group C and group T were evaluated using a non-parametric Chi-square Test, accepting 10% as the statistical significance level. There was a decrease in the occurrence of new infections in the early postpartum in cows which the sealant was used (C=19.6%, T=11.4%). In the postpartum period, Gram-negative bacteria were isolated from 16 teats in C and seven in T. The greatest reduction was observed for Escherichia coli (8 vs 1) in group T. There was no effect using the internal sealant on the frequency of isolation of environmental Streptococus. The use of sealant reduced the prevalence of subclinical mastitis cows between drying-off and the early postpartum period (C=51% versus T=42%) and resulted in a lower somatic cell count (SCC) in the treatment group when compared with the control group (T=1,073x103, C=1,793x103). The use of the internal teat seal combined with dry cow antibiotic is effective in the prevention of IMI during the dry period and early lactation and results in the reduction of SCC in immediate postpartum period. The treatment is effective in reducing infection between dry-off and the immediate postpartum caused by major and minor pathogens. However, no effect on infections caused by contagious pathogens was observed.

Cytological quality of milk of primiparous cows kept in cubicles bedded with separated manure

Abstract. A study was conducted on the effect of separated manure as bedding material on milk quality as manifested in the somatic cell count. Cows were maintained in a loose barn in cubicles bedded with fresh separated cattle manure (SCM) with 40 % solids content. Analyses were conducted on 242 primiparous Polish Black and White Holstein-Friesian cows in the course of a 305-day lactation. Mean milk yield in that period amounted to over 9000 kg per cow. Somatic cell counts, daily milk yields and chemical composition of milk were analysed. Data were obtained from analyses of 2324 milk samples. It was found that 93.3 % of samples contained less than 400 000 somatic cells per 1 mL milk. Approximately 4.3 % of milk samples contained the number of somatic cells indicating subclinical mastitis (200 000 cells mL−1), while in 2.4 % it was clinical mastitis (> 800 000 cells mL−1). The incidence rate for both forms of mastitis was similar in the beginning and at the end of lactation. Mean daily milk yield of cows producing milk classified according to quality (SCC) grades 1 (< 25 000 cells mL−1) and 2 (< 25 000; 50 000 > cells mL−1) was statistically significantly greater than the yields of other cows. For analysed milk constituents a relationship was found between SCC classes and contents of milk fat and solids. Conducted analyses showed that SCM as bedding in cow cubicles had no effect on somatic cell counts in milk of primiparous cows. The study was conducted in a single holding, in one lactation, on cows calving in 2014.

Use of internal teat sealant in heifers reduces mastitis and may affect milk production

Mastitis in heifers is costly, affecting milk quality and reducing milk production throughout the first lactation. Several studies have reported the beneficial effects of internal teat sealants (ITS) on mastitis in heifers, but there appear to be no reports on the subsequent effects on milk quality and production. The consequences of using ITS before calving were examined in a retrospective study in which two cohorts of primiparous heifers (n = 189), treated with an ITS precalving, were compared with four cohorts when ITS was not used (n = 287), using detailed bacteriology and herd-test production data in a DairyNZ research herd. In years when ITS was used, fewer (P < 0.001) heifers were detected with an intramammary infection at the first milking after calving, and fewer (P < 0.001) cases of clinical mastitis were detected in the first 30 days of lactation, than in years when ITS was not used. During the first 8 weeks of lactation, heifers treated with ITS had a lower (P < 0.0001) somatic cell count and produced 49 kg more milk (P < 0.05) and 5 kg more milksolids (P < 0.001) than did non-treated counterparts. These positive benefits associated with use of ITS provide sufficient evidence to justify further investigation in the form of a prospective controlled study.

Effect of management practices and animal age on incidence of mastitis in Nili Ravi buffaloes

Buffalo is an economically important dairy animal in South Asia but mostly ignored in research priorities. In this retrospective study, the effect of management practices and age of animal on the incidence of mastitis in Nili Ravi buffaloes was investigated. A total of 1,560 quarters of buffaloes (n = 390) were screened by visual examination of the udder and milk (clinical mastitis) and California mastitis test (subclinical mastitis). Household data was collected on a predesigned questionnaire and analyzed. The prevalence of subclinical mastitis, clinical mastitis, and blind quarters was 41.8, 13.6, and 9.7 %, respectively. The highest prevalence was noted in the hind quarters and left side as compared to that in the forequarters and right side. This data significantly (p < 0.05) supported the idea that larger herd size has more chances of mastitis, with the highest prevalence (40, 32, and 27 %) in the large, medium, and small herds, respectively. Stage of lactation was significantly (p < 0.01) involved in mastitis, and the highest incidence (43.3 %) was noted in early lactation. Milk production of lactating buffaloes that ranged 6-10 l/day showed a higher rate of mastitis occurrence (p < 0.05). The cleanliness condition of a farm also contributed significantly. Animal age significantly affected the incidence of mastitis. Results revealed that age of the animal has a positive correlation (R (2) = 0.772) with mastitis. This study concluded that some factors alone or in combination with other factors influence significantly the occurrence of mastitis, and to minimize the infection, these factors should be considered. The outcome of the study will be valuable for policy-making for positive management practices and implementation of preventive measures.

The effect of internal teat sealant products (Teatseal and Orbeseal) on intramammary infection, clinical mastitis, and somatic cell counts in lactating dairy cows: a meta-analysis

The objective of this study was to assess the efficacy of internal teat sealant products containing bismuth subnitrate (Teatseal and Orbeseal; Pfizer Animal Health, West Ryde, Australia) when used alone, or in the presence of antibiotic dry cow therapy (ADCT), before or at drying off on the incidence of new intramammary infections (IMI), clinical mastitis, and milk somatic cell count (SCC) during lactation. The literature search identified 18 English-language publications on the use of Teatseal in dairy cattle. A total of 12 studies with 17 subtrials or comparisons including 13 positive control subtrials (internal teat sealant and ADCT vs. ADCT) and 4 negative control subtrials (internal teat sealant vs. untreated) examining IMI were included in the analysis. Internal teat sealants, alone or in the presence of ADCT, reduced the risk of acquiring new IMI after calving by 25% [risk ratio (RR)=0.75; 95% confidence interval (CI): 0.67 to 0.83]. Internal teat sealants reduced the risk of IMI by 73% compared with untreated cows (RR=0.27; 95% CI: 0.13 to 0.55). The results of both meta-analyses of IMI, with positive and negative controls, were heterogeneous [I(2) (a statistic that describes the proportion of total variation in study effect estimates that is due to heterogeneity)=65.4 and 92.1%]. No farm or cow factors studied significantly contributed to the heterogeneity of the results. A total of 16 studies (21 subtrials), including 14 positive control subtrials and 7 negative control subtrials, examining clinical mastitis were included in the analysis. Internal teat sealants alone and in the presence of ADCT reduced the risk of clinical mastitis after calving in lactating cows by 29% (RR=0.71; 95% CI: 0.62 to 0.82), and 48% (RR=0.52; 95% CI: 0.37 to 0.75), respectively. The results of the meta-analysis on clinical mastitis with positive controls were homogeneous (I(2)=33.6%), whereas the results of studies with negative controls were heterogeneous (I(2)=60.4%). No farm or cow factors studied that had sufficient data to evaluate significantly contributed to the heterogeneity of the results. The estimated linear score (LS) of milk SCC after calving in published studies (n=3) and for studies that provided raw data (n=2), was significantly lower for cattle treated with internal teat sealants and ADCT in 3 studies than for cattle treated with internal teat sealants only. The estimated LS of pooled raw data of 3 studies from 32 herds showed that the LS of cows treated with internal teat sealant and ADCT was not significantly different than those treated with ADCT only. This study found that the application of internal teat sealants in the presence of ADCT or the use of internal teat sealants alone at dry off significantly reduced the incidence of IMI and clinical mastitis in lactating dairy cows compared with respective control groups. Further studies are needed to investigate the effect of internal teat sealants on postpartum milk SCC in lactating dairy cows.

Risks factors associated with subclinical mastitis in water buffaloes in Pakistan

The present study was carried to ascertain the association of various risk factors of mastitis in water buffaloes. The milk samples from buffaloes were collected and screened through California Mastitis Test for the presence of mastitis. In the present study, 15.2 % prevalence of subclinical mastitis was recorded both at the government (13.4 %) and private farms (15.5 %). The chi-square analysis showed significantly higher involvement of the right rear and front quarters. The analysis of variance technique showed significant difference in live body weight, milk yield, teat end to floor distance (P < 0.001), udder depth, teat length, and teat diameter in mastitic and healthy buffaloes. The frequency analysis also revealed significant difference between various groups including lactation stage, teat and/or udder pathology, teat shape, and udder shape (P < 0.001). The logistic regression analysis revealed significant positive association of mastitis with milk leakage, live body weight, milk yield, parity, calf suckling, pendulous udder, number of attendants at the farm, dirty hind legs, and udder depth.

Evaluation of clustering of new intramammary infections in the bovine udder, including the impact of previous infections, herd prevalence, and somatic cell count on their development

Evidence in the literature exists to support the theory that mastitis and intramammary infection (IMI) tend to cluster within herds, within cows, and within quarters, facts which may have overarching ramifications on mastitis management in modern dairy herds. Most previous studies, however, have been carried out on prevalent IMI instead of new IMI (NIMI), although reducing incidence of NIMI is a major step toward controlling mastitis. The Canadian Bovine Mastitis Research Network (Saint-Hyacinthe, QC, Canada) has a large mastitis database derived from a 2-yr data collection on a national cohort of dairy farms, and data from this initiative were used to investigate the effect of clustering on the acquisition of NIMI. Longitudinal milk samplings of clinically normal udders taken over several 6-wk periods as well as samples from cows pre-dry-off and postcalving were used (n=73,772 quarter milk samples). Multilevel logistic models were used to evaluate the effect of location of IMI in quarters of the bovine udder previous to occurrence of an NIMI with Staphylococcus aureus, coagulase-negative staphylococci, and Corynebacterium spp. Several factors were investigated, including the number and location of quarters infected with the pathogen of interest before occurrence of an NIMI, the number of quarters infected with any other pathogen before occurrence of an NIMI (a measure of susceptibility), somatic cell count of the quarter before occurrence of an NIMI, somatic cell count of the other 3 quarters before occurrence of an NIMI, prevalence of the specific pathogen in the herd, and the average somatic cell count of the herd. The amount of variation occurring at different levels (herd, cow, and quarter) for the various pathogens was also calculated. The presence of an IMI in the ipsilateral quarter was associated with an elevated risk of an NIMI occurring for all pathogens investigated. Risk of an NIMI increased considerably as herd prevalence of the pathogen rose. Substantial clustering was found at all levels, with roughly equal amounts of variation found in all 3 levels for coagulase-negative staphylococci, most variation at the cow-level for Corynebacterium spp., and most variation found at the quarter-level for Staph. aureus. Simulation was used to calculate exact values of intraclass correlation coefficients to estimate clustering within cows and within quarters--these exact values were, for the most part, lower than estimates calculated using the latent variable approach, but also increased as pathogen prevalence and number of infections in a cow at the previous sampling increased. These results of these analyses can be used to inform approaches to preventing NIMI in modern dairy operations.

Evaluation of minor pathogen intramammary infection, susceptibility parameters, and somatic cell counts on the development of new intramammary infections with major mastitis pathogens

Major mastitis pathogens such as Staphylococcus aureus, Streptococcus uberis, Streptococcus dysgalactiae, and coliforms are usually considered more virulent and damaging to the udder than minor mastitis pathogens such as Corynebacterium spp. and coagulase-negative staphylococci (CNS). The current literature comprises several studies (n=38) detailing analyses with conflicting results as to whether intramammary infections (IMI) with the minor pathogens decrease, increase, or have no effect on the risk of a quarter acquiring a new IMI (NIMI) with a major pathogen. The Canadian Bovine Mastitis Research Network has a large mastitis database derived from a 2-yr data collection on a national cohort of dairy farms, and data from this initiative were used to further investigate the effect of IMI with minor pathogens on the acquisition of new major pathogen infections (defined as a culture-positive quarter sample in a quarter that had been free of that major pathogen in previous samples in the sampling period). Longitudinal milk samplings of clinically normal udders taken over several 6-wk periods as well as samples from cows pre-dry-off and postcalving were used to this end (n=80,397 quarter milk samples). The effects of CNS and Corynebacterium spp. on the major mastitis pathogens Staph. aureus, Strep. uberis, Strep. dysgalactiae, and coliform bacteria (Escherichia coli and Klebsiella spp.) were investigated using risk ratio analyses and multilevel logistic regression models. Quarter-, cow- and herd-level susceptibility parameters were also evaluated and were able to account for the increased susceptibility that exists within herds, cows and quarters, removing it from estimates for the effects of the minor pathogens. Increased quarter-level susceptibility was associated with increased risk of major pathogen NIMI for all pathogens except the coliforms. Increased somatic cell count was consistently associated with elevated risk of new major pathogen infections, but this was assumed to be a result of low sensitivity of bacteriology to diagnose major pathogen NIMI expediently and accurately. The presence of CNS in the sample 2 samplings before the occurrence of a NIMI increased the odds of experiencing a Staph. aureus NIMI 2.0 times, making the presence of CNS a risk factor for acquiring a Staph. aureus NIMI. Even with this extensive data set, power was insufficient to make a definitive statement about the effect of minor pathogen IMI on the acquisition of major pathogen NIMI. Definitively answering questions of this nature are likely to require an extremely large data set dedicated particularly to minor pathogen presence and NIMI with major pathogens.

Invited review: Mastitis in dairy heifers: nature of the disease, potential impact, prevention, and control

Heifer mastitis is a disease that potentially threatens production and udder health in the first and subsequent lactations. In general, coagulase-negative staphylococci (CNS) are the predominant cause of intramammary infection and subclinical mastitis in heifers around parturition, whereas Staphylococcus aureus and environmental pathogens cause a minority of the cases. Clinical heifer mastitis is typically caused by the major pathogens. The variation in proportions of causative pathogens between studies, herds, and countries is considerable. The magnitude of the effect of heifer mastitis on an individual animal is influenced by the form of mastitis (clinical versus subclinical), the virulence of the causative pathogen(s) (major versus minor pathogens), the time of onset of infection relative to calving, cure or persistence of the infection when milk production has started, and the host's immunity. Intramammary infection in early lactation caused by CNS does not generally have a negative effect on subsequent productivity. At the herd level, the impact will depend on the prevalence and incidence of the disease, the nature of the problem (clinical, subclinical, nonfunctional quarters), the causative pathogens involved (major versus minor pathogens), the ability of the animals to cope with the disease, and the response of the dairy manager to control the disease through management changes. Specific recommendations to prevent and control mastitis in late gestation in periparturient heifers are not part of the current National Mastitis Council mastitis and prevention program. Control and prevention is currently based on avoidance of inter-sucking among young stock, fly control, optimal nutrition, and implementation of hygiene control and comfort measures, especially around calving. More risk factors for subclinical and clinical heifer mastitis have been identified (e.g., season, location of herd, stage of pregnancy) although they do not lend themselves to the development of specific intervention strategies designed to prevent the disease. Pathogen-specific risk factors and associated control measures need to be identified due to the pathogen-related variation in epidemiology and effect on future performance. Prepartum intramammary treatment with antibiotics has been proposed as a simple and effective way of controlling heifer mastitis but positive long-lasting effects on somatic cell count and milk yield do not always occur, ruling out universal recommendation of this practice. Moreover, use of antibiotics in this manner is off-label and results in an increased risk of antibiotic residues in milk. Prepartum treatment can be implemented only as a short-term measure to assist in the control of a significant heifer mastitis problem under supervision of the herd veterinarian. When CNS are the major cause of intramammary infection in heifers, productivity is not affected, making prepartum treatment redundant and even unwanted. In conclusion, heifer mastitis can affect the profitability of dairy farming because of a potential long-term negative effect on udder health and milk production and an associated culling risk, specifically when major pathogens are involved. Prevention and control is not easy but is possible through changes in young stock and heifer management. However, the pathogenesis and epidemiology of the disease remain largely unknown and more pathogen-specific risk factors should be identified to optimize current prevention programs.

Effect of use of teat sealants at drying off on the uptake of colostral antibodies by calves, as estimated by measuring gamma-glutamyl transferase activity

AIM

To determine the effect of using internal teat sealants in cows at drying off on the immune status of their calves, as indicated by activity of gamma glutamyl transferase (GGT) in serum, within 24 h of birth.

METHODS

Cows in one herd were treated at drying off with intramammary 600-mg cloxacillin and either no additional treatment or treatment with internal teat sealant containing bismuth subnitrate. Subsequently after calving, blood samples were collected from 35 calves after separation from their dams and prior to being fed pooled colostrum. Calves were collected once daily. Activity of GGT in serum was measured. The influence of treatment of the dam with teat sealant on activity of GGT in serum of the calf, and thus the transfer of colostral antibodies directly from the dam to the calf, was assessed.

RESULTS

Activity of GGT in serum ranged from 8 to 8,560 IU/L. Of the 35 calves sampled only three (two from dams that were not treated with internal teat sealant) had GGT activity < 200 IU/L, indicative of the failure of passive transfer of antibodies. Median activity of GGT in calves from dams treated with teat sealant was 2,643 IU/L while that in calves from dams which were not treated with teat sealant was 2,286 IU/L. There was no effect of treatment with teat sealant or date of sampling on activity of GGT in serum (p > 0.1).

CONCLUSIONS

Treatment of cows with internal teat sealant at drying off had no effect on transfer of colostral antibodies following calving.

CLINICAL SIGNIFICANCE

The use of teat sealants is not likely to impact on colostrum uptake on farms where direct transfer of colostral antibodies between dam and calf is good. On farms where such direct transfer is poor, early supplementation of all calves with colostrum is likely to be required to prevent the failure of passive transfer, so any impact of teat sealants on uptake of colostrum is likely to be of little consequence.

Functional adaptations of the transcriptome to mastitis-causing pathogens: the mammary gland and beyond

Application of microarrays to the study of intramammary infections in recent years has provided a wealth of fundamental information on the transcriptomics adaptation of tissue/cells to the disease. Due to its heavy toll on productivity and health of the animal, in vivo and in vitro transcriptomics works involving different mastitis-causing pathogens have been conducted on the mammary gland, primarily on livestock species such as cow and sheep, with few studies in non-ruminants. However, the response to an infectious challenge originating in the mammary gland elicits systemic responses in the animal and encompasses tissues such as liver and immune cells in the circulation, with also potential effects on other tissues such as adipose. The susceptibility of the animal to develop mastitis likely is affected by factors beyond the mammary gland, e.g. negative energy balance as it occurs around parturition. Objectives of this review are to discuss the use of systems biology concepts for the holistic study of animal responses to intramammary infection; providing an update of recent work using transcriptomics to study mammary and peripheral tissue (i.e. liver) as well as neutrophils and macrophage responses to mastitis-causing pathogens; discuss the effect of negative energy balance on mastitis predisposition; and analyze the bovine and murine mammary innate-immune responses during lactation and involution using a novel functional analysis approach to uncover potential predisposing factors to mastitis throughout an animal's productive life.

Pathogen group specific risk factors at herd, heifer and quarter levels for intramammary infections in early lactating dairy heifers

Risk factors for intramammary infections caused by coagulase-negative staphylococci, contagious major pathogens and environmental major pathogens in early lactating heifers were evaluated at the herd, heifer and quarter levels. In total, 764 quarters of 191 dairy heifers in 20 randomly selected farms in Flanders (Belgium) were sampled. Quarter milk samples were collected between 1 and 4 days in milk and between 5 and 8 days in milk for bacteriological culture. Data were analyzed using multivariable, multilevel logistic regression analysis. Higher average herd milk somatic cell count (>200,000 cells/mL), not having an effective fly control strategy, contact with lactating cows prior to calving and moderate to severe udder edema prior to calving increased the odds of intramammary infections caused by contagious major pathogens. Poor heifer hygiene and lack of mineral/vitamin supplementation prior to calving were risk factors for intramammary infection caused by environmental major pathogens. Teat apex colonization with coagulase-negative staphylococci prior to calving seemed to protect quarters against intramammary infections caused by major pathogens. Poor heifer hygiene before calving, a non-clipped udder and not practicing of teat dipping prior to calving increased the odds of intramammary infection with coagulase-negative staphylococci. Although management is important in the prevention and control of intramammary infections in early lactating heifers, most variation in the prevalence of intramammary infections resided at the heifer and quarter levels, indicating that the susceptibility for intramammary infections around calving is mainly determined by heifer and quarter characteristics.

Concentration of penicillin G in mammary tissue and secretion of end-term dairy heifers following systemic prepartum administration of penethamate hydriodide

The aim of this study was to assess the concentration of penicillin G in mammary tissue and secretion of dry heifers following systemic administration of penethamate hydriodide. Six dairy heifers in late gestation received a single intramuscular injection of 10 g penethamate hydriodide and were sacrificed 24, 48 or 144 h after treatment. Penicillin G concentrations were measured in mammary tissue and secretion samples using HPLC. Penicillin G was detected in the udder of two animals euthanized at 24 h (mammary tissue and secretion) and at 48 h post treatment (mammary secretion only) after administration at concentrations still close to or above MIC90 values reported for the pathogens associated with heifer mastitis. Antibiotic concentration shortly after administration will have been substantially higher indicating a potential for systemic treatment with penethamate hydriodide to control prepartum intramammary infections in heifers without the disadvantages of local therapy such as teat contamination or risk of trauma for the administrator.

Response to somatic cell count-based selection for mastitis resistance in a divergent selection experiment in sheep

A divergent selection experiment in sheep was implemented to study the consequences of log-transformed somatic cell score (SCS)-based selection on resistance to natural intramammary infections. Using dams and progeny-tested rams selected for extreme breeding values for SCS, we created 2 groups of ewes with a strong divergence in SCS of approximately 3 genetic standard deviations. A survey of 84 first-lactation ewes of both the High and Low SCS lines indicated favorable responses to SCS-based selection on resistance to both clinical and subclinical mastitis. All clinical cases (n = 5) occurred in the High SCS line. Additionally, the frequency of chronic clinical mastitis, as detected by the presence of parenchymal abscesses, was much greater in the High SCS line (n = 21) than in the Low SCS line (n = 1). According to monthly milk bacteriological examinations of udder halves, the prevalence of infection was significantly greater (odds ratio = 3.1) in the High SCS line than in the Low SCS line, with predicted probabilities of 37 and 16%, respectively. The most frequently isolated bacteria responsible for mastitis were staphylococci: Staphylococcus auricularis (42.6% of positive samples), Staphylococcus simulans, Staphylococcus haemoliticus, Staphylococcus xylosus, Staphylococcus chromogenes, Staphylococcus lentus, Staphylococcus warneri, and Staphylococcus aureus. The incidence of positive bacteriology was greater in the High SCS line (39%) than in the Low SCS line (12%) at lambing, indicating that High SCS line ewes were especially susceptible to postpartum subclinical mastitis. Negativation of bacteriological results from one sampling time point to the next was markedly different between lines after weaning (e.g., 41 and 84% in the High and Low SCS lines, respectively). This result was consistent with differences in the duration of infection, which was much greater in the High SCS line compared with the Low SCS line. Finally, ewes from the High SCS line consistently had greater SCS in positive milk samples than did ewes from the Low SCS line (+2.04 SCS, on average), with an especially large difference between lines during the suckling period (+3.42 SCS). Altogether, the preliminary results suggest that the better resistance of Low SCS line ewes, compared with High SCS line ewes, was principally characterized by a better ability to limit infections during the peripartum period, to eliminate infections during lactation, and quantitatively to limit the inflammation process and its clinical consequences.

Prevalence of pathogens in milk samples of dairy cows with clinical mastitis and in heifers at first parturition

Prevalence of mastitis pathogens in milk samples from dairy cows and heifers was studied over a period of 1 year (Aug 2005-Aug 2006) in ten dairy herds in Germany. Milk samples (n=8240) were collected from heifers without clinical mastitis at parturition (n=6915), from primiparous cows with clinical mastitis (n=751) and from older cows with clinical mastitis (n=574). Coagulase negative staphylococci (CNS) were the predominant group of bacteria isolated (46.8% of samples) from clinically healthy quarters of primiparous cows around parturition, followed by streptococci (12.6%), coliforms (4.7%) and Staphylococcus aureus (4.0%). Thirty-three percent of samples were negative on culture (range on farm level, 12.0-46.4%). In cases of clinical mastitis in primiparous and older cows, streptococci were the predominant finding (32.1 and 39.2%) followed by CNS (27.4 and 16.4%), coliforms (10.3 and 13.1%) and Staph. aureus (10.0 and 11.7%). Negative results were obtained from 21.3% (range, 0.0-30.6%) and 19.5% (range, 0.0-32.6%) of these samples. Results indicated substantial differences in the prevalence of pathogens among herds. There was a positive within-herd correlation between the monthly prevalences for Streptococcus dysgalactiae between the three groups of samples. This correlation was also found between clinical samples of primiparous and older cows for Staph. aureus. These correlations were not found for the other pathogens. Besides herd, prevalence of pathogens was influenced by parity, type of sample and season.