Diagnosis of clinical or subclinical mastitis in ewes

Coagulase-Negative Staphylococci as an Etiologic Agent of Ovine Mastitis, with a Focus on Subclinical Forms

The objective of this review is to investigate the distribution and the characteristics of coagulase-negative Staphylococci (CoNS) implicated in ovine mastitis, and especially in subclinical cases, in order to provide a global perspective of the current research data and analyze specific critical aspects of the issue. PRISMA guidelines were implemented in the search of the last 20 years of the related literature in two databases. In total, 139 studies were included in this review. Relevant data were tracked down, assembled, and compared. Regarding the geographical distribution, most studies originated from Europe (68), followed by South America (33). Lacaune was the most examined breed, while S. epidermidis was the predominantly identified species, representing approximately 39% of the obtained isolates. Antibiotic resistance in the relevant bacteria was documented mostly for Penicillin (32.8%) and Amoxicillin (32.1%), while biofilm- and toxin-associated genes were encountered in variable rates because significant inequalities were observed between different articles. Significantly higher rates of antimicrobial resistance were detected in Asia and South America compared to Europe. Finally, the diagnostic procedures carried out in the respective studies were evaluated. Conventional culture and biochemical tests were mostly performed for simple strain identification; therefore, further molecular investigation of isolates should be pursued in future studies, as this will provide important data regarding specific aspects of the implication of CoNS in ovine mastitis.

Animal board invited review: Practical applications of genomic information in livestock

Access to high-dimensional genomic information in many livestock species is accelerating. This has been greatly aided not only by continual reductions in genotyping costs but also an expansion in the services available that leverage genomic information to create a greater return-on-investment. Genomic information on individual animals has many uses including (1) parentage verification and discovery, (2) traceability, (3) karyotyping, (4) sex determination, (5) reporting and monitoring of mutations conferring major effects or congenital defects, (6) better estimating inbreeding of individuals and coancestry among individuals, (7) mating advice, (8) determining breed composition, (9) enabling precision management, and (10) genomic evaluations; genomic evaluations exploit genome-wide genotype information to improve the accuracy of predicting an animal's (and by extension its progeny's) genetic merit. Genomic data also provide a huge resource for research, albeit the outcome from this research, if successful, should eventually be realised through one of the ten applications already mentioned. The process for generating a genotype all the way from sample procurement to identifying erroneous genotypes is described, as are the steps that should be considered when developing a bespoke genotyping panel for practical application.

Bovine Milk Proteome: Milk Fat Globule Membrane Protein Is the Most Sensitive Fraction in Response to High Somatic Cell Count

The impacts of high milk somatic cell count (SCC) on different milk fractions are not well understood. In this study, proteins in milk exosomes, milk fat globule membrane (MFGM), and whey from cows with low (<105 cells/mL, CG) and high SCC (>5 × 105 cells/mL, HSG) were identified using a tandem mass tag proteomic approach. In total, 1568, 2160, and 1002 proteins were identified, with 65, 552, and 98 proteins being altered by high SCC in exosomes, MFGM, and whey, respectively. With high SCC, the exosome marker (ACTB) was increased in the exosomes of HSG. The main MFGM proteins (BTN1A1, PLIN3, FABP3, and MFGE8) and functional proteins (MUC1, IGSF5, TLR5, and CD36/14) were decreased, while the lipid/energy metabolism-related proteins were increased in the MFGM of HSG. The glycolysis-related proteins were increased in the whey of HSG. Also, the host defense/inflammation-related proteins were changed in three fractions under high SCCs. MFGM was the most sensitive fraction to a high SCC, followed by whey. These findings provide guidance for the early detection of unhealthy mammary glands.

Unique Peptides of Cathelicidin-1 in the Early Detection of Mastitis-In Silico Analysis

Based on the results of previously performed clinical studies, cathelicidin-1 has been proposed as a potential biomarker for the early diagnosis of mastitis in ewes. It has been hypothesized that the detection of unique peptides (defined as a peptide, irrespective of its length, that exists in only one protein of a proteome of interest) and core unique peptides (CUPs) (representing the shortest peptide that is unique) of cathelicidin-1 may potentially improve its identification and consequently the diagnosis of sheep mastitis. Peptides of sizes larger than those of the size of CUPs, which include consecutive or over-lapping CUPs, have been defined as 'composite core unique peptides' (CCUPs). The primary objective of the present study was the investigation of the sequence of cathelicidin-1 detected in ewes' milk in order to identify its unique peptides and core unique peptides, which would reveal potential targets for accurate detection of the protein. An additional objective was the detection of unique sequences among the tryptic digest peptides of cathelicidin-1, which would improve accuracy of identification of the protein when performing targeted MS-based proteomics. The potential uniqueness of each peptide of cathelicidin-1 was investigated using a bioinformatics tool built on a big data algorithm. A set of CUPs was created and CCUPs were also searched. Further, the unique sequences in the tryptic digest peptides of cathelicidin-1 were also detected. Finally, the 3D structure of the protein was analyzed from predicted models of proteins. In total, 59 CUPs and four CCUPs were detected in cathelicidin-1 of sheep origin. Among tryptic digest peptides, there were six peptides that were unique in that protein. After 3D structure analysis of the protein, 35 CUPs were found on the core of cathelicidin-1 of sheep origin and among them, 29 were located on amino acids in regions of the protein with 'very high' or 'confident' estimates of confidence of the structure. Ultimately, the following six CUPs: QLNEQ, NEQS, EQSSE, QSSEP, EDPD, DPDS, are proposed as potential antigenic targets for cathelicidin-1 of sheep. Moreover, another six unique peptides were detected in tryptic digests and offer novel mass tags to facilitate the detection of cathelicidin-1 during MS-based diagnostics.

Physiological Aspects of Milk Somatic Cell Count in Small Ruminants—A Review

The aim of this review was to focus on the physiological aspects of milk somatic cell count (SCC) in small ruminants (SM). The SCC is an important component naturally present in milk and is generally used as an indicator of milk quality and udder health in milk producing ruminants. SCC contains the following cells: polymorphonuclear neutrophils (PMN), macrophages, lymphocytes, and many milk epithelial (MEC) cells, cell fragments, and cytoplasmic particles/vesicles. PMN (40–80%) represent the major cell type in milk in healthy uninfected goats, whereas the macrophages (45–88%) are the major cell type in sheep’s milk. However, dairy goats and sheep have an apocrine secretory system that produces cytoplasmic cellular particles/vesicles and large numbers of cell fragments, resulting in the physiological SCC limit being exceeded. It is obvious that the SCC level in milk of SM can be affected by various influencing factors, such as milk fraction, breed, stage of lactation, parity, type of birth, milking system, and others. An increase in the SCC above the physiological level not only indicates an udder or general health problem but reduces milk production, changes the milk composition, and hence affects milk processing. Moreover, the milking machine plays an important role in maintaining udder health in SM and stable SCC at physiological levels in the milk obtained. So far, there are no healthy or pathological physiological SCC levels defined in SM milk. Furthermore, a differential cell count (DCC) or even a high resolution DCC (HRDCC), which were recently developed for cattle milk, could also help in SM to gain deeper insight into the immunology of the mammary gland and find biomarkers to assess udder health. In conclusion, SCC is an indication of udder health or exposure of the udder to infectious agents or mechanical stress and should therefore always be considered a warning sign.

Comparison of the Efficacy of Intramammary or Injectable Antibiotic Administration against Staphylococcal Mastitis in Ewes

The objectives of the work were (a) to compare the efficacy of two routes for antibiotic administration in the treatment of mastitis in ewes and (b) to assess the potential importance of the timing of the initiation of the therapeutic regime on the outcome of the treatment. The ewes were allocated at random into three equal groups; intramammary inoculation with a Staphylococcus simulans isolate was performed, and clinical mastitis developed. The ewes in groups T1 (n = 6) and T2 (n = 6) were treated by the intramammary administration of ampicillin and dicloxacillin (two administrations with a 12-h interval). The ewes in group T3 (n = 6) were treated by the intramuscular injection of ampicillin and dicloxacillin (0.75 mL per 10 kg bodyweight, three injections with a 24-h interval). In the ewes in groups T1 and T3, treatment started immediately when the clinical signs of mastitis were first detected during the periodic examination of the ewes; in the ewes in group T2, treatment started 24 h after the clinical signs of mastitis were first detected. The animals were monitored clinically; mammary secretion samples were collected for bacteriological and cytological examinations. The median duration of the clinical signs was 4.75, 7.13, and 4.75 d for T1, T2, and T3; significant differences in clinical severity between the groups were seen until the 7th day post-treatment. The median duration of bacterial recovery was 3.25, 8.00, and 8.00 d for T1, T2, and T3; significant differences in the frequency of bacterial recovery between the groups were seen until (64.1%, 94.9%, and 96.2% of the samples) and after (2.9%, 16.7%, and 11.8%) the 7th day post-treatment. The median period required for the complete cure (clinical, bacteriological, and cytological) was shorter in the T1 than in the T2 and T3 ewe groups: 20.0, 32.0, and 24.5 d, respectively. The findings cover a gap in the available literature regarding the treatment of clinical mastitis in ewes. Early treatment resulted in the improved cure of the infection. The comparison of the intramammary and injectable routes for antibiotic administration indicated some benefit for the former, primarily in the post-treatment somatic cell counts.

Effects of management strategies during early lactation and weaning on etiological agents of ovine subclinical mastitis and antimicrobial susceptibility of milk-derived bacterial isolates

Subclinical mastitis is a common intramammary disease in sheep production systems. Expenses associated with compromised animal performance, therapeutic interventions, and decreased ewe longevity make efforts to minimize its prevalence worthwhile. The objectives of this study were to (i) quantify the prevalence of subclinical mastitis throughout lactation, (ii) evaluate the impact of bedding treatments on subclinical mastitis during early lactation, (iii) evaluate the efficacy of prophylaxis and feed restriction during weaning on subclinical mastitis cure rates, (iv) and identify levels and types of antimicrobial resistance in milk-derived bacteria. Ewe milk samples were collected at d 1, 2, and 28 post-partum, weaning, and 3-d post-weaning for bacterial identification via culture-based methods. Staphylococcus spp. and Streptococcus spp. isolates were subjected to in vitro antimicrobial susceptibility testing. The overall prevalence of subclinical mastitis defined by culture growth ranged between 22 and 66% and differences were observed between post-weaning and d 1 and 28 milk samples. Commonly isolated bacteria include coagulase-negative staphylococci (CoNS; 59%), Bacillus spp. (35%), Mannheimia haemolytica (10%), Staphylococcus aureus (8%), Streptococcus spp. (5%), and Corynebacterium spp. (5%). Early milk samples (d 1 and 2) were compared between jug bedding treatment: jugs were recently vacated, cleaned, and dusted with barn lime before adding fresh straw (CLEAN) or jugs were previously vacated and fresh straw was added atop soiled bedding (SOILED). Jug bedding treatment did not affect the prevalence of subclinical mastitis, though CoNS had greater sulfadimethoxine resistance in SOILED isolates than CLEAN isolates (P = 0.03). Three different weaning treatments were used: ewes were injected with penicillin at weaning (PENN), ewes had restricted feed access 48 h prior to and 72 h post-weaning (FAST), or a combination of these treatments (COMBO). Weaning treatment did not affect the prevalence of subclinical mastitis or cure rate from weaning to 3-d post-weaning, though all PENN and no FAST milk S. aureus isolates were resistant against tetracycline (P = 0.08). Subclinical mastitis prevalence tended to decrease from weaning to post-weaning (P = 0.08). These data show subclinical mastitis is common throughout lactation and the levels of antimicrobial resistance of bacteria isolated from ewe milk are generally low against commonly used antimicrobials.

Relationship Between Somatic Cell Counts and Mammary Gland Parenchyma Ultrasonography in Buffaloes

The aim of the present study was to determine whether the echotextural features of the mammary gland parenchyma in buffaloes during lactation at different somatic cell levels could be used to diagnose mastitis. This study was divided into two parts. In the first experiment, experimental buffaloes (n = 65) with somatic cell counts (SCC) tests (n = 94) in different seasons, including spring (n = 22), summer (n = 24), autumn (n = 37), and winter (n = 11), were used to obtain ultrasonic variables for each quarter of mammary gland that could best explain the corresponding somatic cell level. In the second part of the study, the first part's experimental results were verified by subjecting at least one-quarter udder of eight buffaloes to ultrasonography seven times during mid-July to mid-August for obtaining ultrasonic values at different somatic cell levels. The echo textural characteristics [mean numerical pixel values (NPVs) and pixel heterogeneity (pixel standard deviation, PSD)] were evaluated using 16 ultrasonographic images of each buffalo with Image ProPlus software. The effects of SCC, days in milk (DIM), scanning order (SO), season, as well as the scanning plane and udder quarter (SP + UQ) on both the PSD and NPVs of the mammary gland were significant (p < 0.05). The correlation coefficient between pre-milking sagittal PSD and somatic cell score (SCS) was the highest (r = 0.4224, p < 0.0001) with fitted linear model: y = 0.19445x (dependent variable: SCS, independent variables: pre-milking sagittal PSD; R² = 0.84, p < 0.0001). In addition, SCC and ultrasonic of udder quarter were followed for 1 month, confirming that pre-milking sagittal PSD of mammary gland value could explain the SCC variation in milk. The current study demonstrated that the ultrasonographic examination of the udder could be one of the complementary tools for diagnosing subclinical mastitis in buffaloes.

Effect of Palpable Udder Defects on Milk Yield, Somatic Cell Count, and Milk Composition in Non-Dairy Ewes

In non-dairy ewes, udder defects hinder the survival and weight gain of their pre-weaned lambs. The objectives of this study were to determine the effects of palpable udder defects on milk yield, somatic cell count (SCC), and milk composition in non-dairy Romney ewes. Ewes with a history of udder defects or normal udders were selected for the study. Of a total of 48 ewes that lambed, 30 ewes reared at least one lamb, and were milked six times, once weekly, for the first six weeks of lactation. Udder halves were palpated and scored at each milking event. Multivariate linear mixed models examined the impacts of udder defects on udder-half and whole-udder milk yield, SCC, and milk composition (fat, protein, lactose, total solids, and solids non-fat (SNF)). Across the six examinations, 24.7% of the total 352 udder-half examinations were observed to be defective. Udder halves that were defective at least once produced on average 57.9% less (p < 0.05) milk than normal udder halves, while normal udder halves with a contralateral defective half yielded 33.5% more (p < 0.05) milk than normal udder halves. Successive occurrence of both hard and lump udder defect categories in an udder-half, udder defect detection early in lactation, and a high frequency of udder defect detection were all associated with udder-half milk yield loss (p < 0.05). At the whole-udder level, no differences in milk yield (p > 0.05) were observed between those with one udder-half defective and both normal udder-halves. However, udders in which one udder half was categorised as hard but progressed to lump and remained as lump until 42 days of lactation produced less (p < 0.05) milk compared with normal udders. With the exception of SNF, there were no significant associations (p > 0.05) between milk composition parameters and udder defect. Overall, these findings emphasise the importance of udder health in non-dairy ewes and the potential effect of udder defects on their lambs.

Genome Wide Prediction, Mapping and Development of Genomic Resources of Mastitis Associated Genes in Water Buffalo

Water buffalo (Bubalus bubalis) are an important animal resource that contributes milk, meat, leather, dairy products, and power for plowing and transport. However, mastitis, a bacterial disease affecting milk production and reproduction efficiency, is most prevalent in populations having intensive selection for higher milk yield, especially where the inbreeding level is also high. Climate change and poor hygiene management practices further complicate the issue. The management of this disease faces major challenges, like antibiotic resistance, maximum residue level, horizontal gene transfer, and limited success in resistance breeding. Bovine mastitis genome wide association studies have had limited success due to breed differences, sample sizes, and minor allele frequency, lowering the power to detect the diseases associated with SNPs. In this work, we focused on the application of targeted gene panels (TGPs) in screening for candidate gene association analysis, and how this approach overcomes the limitation of genome wide association studies. This work will facilitate the targeted sequencing of buffalo genomic regions with high depth coverage required to mine the extremely rare variants potentially associated with buffalo mastitis. Although the whole genome assembly of water buffalo is available, neither mastitis genes are predicted nor TGP in the form of web-genomic resources are available for future variant mining and association studies. Out of the 129 mastitis associated genes of cattle, 101 were completely mapped on the buffalo genome to make TGP. This further helped in identifying rare variants in water buffalo. Eighty-five genes were validated in the buffalo gene expression atlas, with the RNA-Seq data of 50 tissues. The functions of 97 genes were predicted, revealing 225 pathways. The mastitis proteins were used for protein-protein interaction network analysis to obtain additional cross-talking proteins. A total of 1,306 SNPs and 152 indels were identified from 101 genes. Water Buffalo-MSTdb was developed with 3-tier architecture to retrieve mastitis associated genes having genomic coordinates with chromosomal details for TGP sequencing for mining of minor alleles for further association studies. Lastly, a web-genomic resource was made available to mine variants of targeted gene panels in buffalo for mastitis resistance breeding in an endeavor to ensure improved productivity and the reproductive efficiency of water buffalo.

Do we automatically detect health- or general welfare-related issues? A framework

The early detection of health disorders is a central goal in livestock production. Thus, a great demand for technologies enabling the automated detection of such issues exists. However, despite decades of research, precision livestock farming (PLF) technologies with sufficient accuracy and ready for implementation on commercial farms are rare. A central factor impeding technological development is likely the use of non-specific indicators for various issues. On commercial farms, where animals are exposed to changing environmental conditions, where they undergo different internal states and, most importantly, where they can be challenged by more than one issue at a time, such an approach leads inevitably to errors. To improve the accuracy of PLF technologies, the presented framework proposes a categorization of the aim of detection of issues related to general welfare, disease and distress and defined disease. Each decision level provides a different degree of information and therefore requires indicators varying in specificity. Based on these considerations, it becomes apparent that while most technologies aim to detect a defined health issue, they facilitate only the identification of issues related to general welfare. To achieve detection of specific issues, new indicators such as rhythmicity patterns of behaviour or physiological processes should be examined.

Growth of Staphylococcus epidermidis on the Surface of Teatcups from Milking Parlours

The growth of two Staphylococcus epidermidis isolates (one biofilm-forming and one not) on teatcups for cattle (made of rubber) or sheep (made of silicone) were assessed in nine multiplicates for 24 h post-smearing on the teatcup surface. Staphylococci were smeared on an area of 0.0003142 m² on the material and their growth and expansion further on were monitored for 24 h. There were no differences in the frequency of recoveries between the two isolates (p > 0.82 for all comparisons). There were more recoveries from sheep teatcups than from cattle teatcups: 1280/1728 (74.1%) versus 942/1728 (54.5%), for both isolates (p < 0.0001). Significance was observed only 6 h to 15 h after smearing (p < 0.0001 for all comparisons). The median speed of linear dissemination of the isolates was 0.00000021 m s⁻¹ on cattle teatcups and 0.00000033 m s⁻¹ on sheep teatcups (p < 0.0001). The increased growth and faster expansion of staphylococci on silicone teatcups raise important points from a clinical viewpoint. The model could be used in the testing of staphylococcal growth in the material of milking parlours in various conditions.

Staphylococcus aureus Isolated from Ruminants with Mastitis in Northern Greece Dairy Herds: Genetic Relatedness and Phenotypic and Genotypic Characterization

Staphylococcus aureus is the most common mastitis-related pathogen in dairy cattle, goats, and sheep worldwide. However, the population structure and genomic characteristics of mastitis-associated S. aureus in small ruminants are limited. Furthermore, the genotypic and phenotypic characteristics involved in the pathogenicity of S. aureus have been thoroughly defined, yet their association with the severity of mastitis is not fully established. Here, we performed genotyping by pulsed-field gel electrophoresis (PFGE) and spa analyses to assess the genetic diversity and relatedness of 162 S. aureus strains recovered from clinical mastitis (CM) and subclinical mastitis (SCM) cases from goats, sheep, and bovines. PFGE analysis revealed 108 distinguishable pulsotypes and 3 main clusters that comprised isolates from the three host species, while according to spa typing, 32 different spa types were identified. Genotypic analysis revealed a spreading of genetically related or indistinguishable S. aureus strains among ovine, caprine, and bovine farms of distant geographical regions. In total, 28 different staphylococcal enterotoxin (SE) gene profiles were observed, revealing a diverse range of SE genes among isolates. By evaluating the antimicrobial resistance, we found low phenotypic antimicrobial resistance among all ruminant isolates. We also performed multiple correspondence analysis, which indicated that the presence of the sec gene, biofilm production, and high autoaggregation ability are associated with CM cases.

MLST-Based Analysis and Antimicrobial Resistance of Staphylococcus epidermidis from Cases of Sheep Mastitis in Greece

Staphylococcus epidermidis is an important causal agent of ovine mastitis. A literature search indicated a lack of systematic studies of causal agents of the infection by using multi-locus sequence typing (MLST). The objectives were to analyse MLST-based data and evaluate the antimicrobial resistance of S. epidermidis isolates from ovine mastitis in Greece. The database included 1593 isolates from 46 countries: 1215 of human, 195 of environmental and 134 of animal origin, distributed into 949 sequence types (STs) and cumulatively with 450 alleles therein. Among mastitis isolates, bovine isolates were distributed into 36 different STs and ovine ones into 15 STs. The 33 isolates from ovine mastitis in Greece were in 15 different STs, 6 of these (ST677, ST678, ST700, ST 709, ST710, ST711) assigned for the first time; in addition, 5 alleles (65 for arcC, 59 for aroE, 56 and 57 for gtr and 48 for tpiA) were identified for the first time. The spanning tree of these isolates included 15 nodes and 14 edges (i.e., branches). Among these isolates, 19 showed resistance to antimicrobial agents (tetracycline, penicillin, fucidic adic, erythromycin, clindamycin, cefoxitin). Resistance-related genes (tetK, tetT, msrA, tetM, tetS, ermC, mecA) were detected. There was no association between STs and resistance to antimicrobial agents. Isolates with antimicrobial resistance were recovered more often from flocks where hand-milking was practised.

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.

Extensive Countrywide Field Investigation of Somatic Cell Counts and Total Bacterial Counts in Bulk-Tank Raw Milk in Sheep Flocks in Greece

Objectives were to investigate somatic cell counts (SCC) and total bacterial counts (TBC) in the raw bulk-tank milk of sheep flocks in Greece, to study factors potentially influencing increased SCC and TBC in the bulk-tank milk of sheep and to evaluate possible associations of SCC and TBC with milk content. Throughout Greece, 325 dairy sheep flocks were visited for collection of milk sampling for somatic cell counting, microbiological examination and composition measurement. Geometric mean SCC were 0.488 × 10⁶ cells mL^-1; geometric mean TBC were 398 × 10³ cfu mL^-1; 228 staphylococcal isolates were recovered form 206 flocks (63.4%). Multivariable analyses revealed annual incidence risk of clinical mastitis, age of the farmer and month into lactation period (among 53 variables) to be significant for SCC > 1.0 × 10⁶ cells mL^-1 and month into lactation period at sampling and availability of mechanical ventilators (among 58 variables) to be significant for TBC > 1500 × 10³ cfu mL^-1. Negative correlation of SCC with fat, total protein and lactose and positive correlation of SCC with added water were found. With SCC > 1.0 × 10⁶ cells mL^-1, significant reduction of protein content (2%) was observed, whilst in flocks with SCC > 1.5 × 10⁶ cells mL^-1, significantly lower annual milk production per ewe (42.9%) was recorded.

The Differential Composition of Whey Proteomes in Hu Sheep Colostrum and Milk during Different Lactation Periods

Colostrum and milk proteins are essential resources for the growth and development of the newborns, while their kinds and amounts vary greatly during the lactation period. This study was conducted to better understand whey proteome and its changes at six lactation time points (0 d, 3 d, 7 d, 14 d, 28 d, and 56 d after lambing) in Hu sheep. Using two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF/TOF MS) technologies, a total of 52 differentially expressed protein spots (DEPS), corresponding to 25 differentially expressed proteins (DEPs), were obtained. The protein spots abundance analysis revealed that the proteins are the most abundant at 0 d after lambing. Gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were used to explore the biological functions of the DEPs. The biological process was mainly involved in localization, the single-organism process, the cellular process, and a series of immune processes. The cellular components engaged in the extracellular region were the cell, organelle, and membrane. The most prevalent molecular function was binding activity. In addition, the DEPs were involved in nine significant pathways, including the Hippo signaling pathway and Complement and coagulation cascades. These results intuitively presented the changes in Hu sheep whey proteins during a 56-d lactation period, and revealed potential biological functions of the DEPs, providing a scientific basis for early weaning.

Novel Biomarkers of Mastitis in Goat Milk Revealed by MALDI-TOF-MS-Based Peptide Profiling

Mastitis is the most common infection of dairy goats impairing milk production and quality, which is usually recognized by mammary gland visual inspection and palpation. Subclinical forms of the disease are also widely represented, which lack the typical signs of the clinical ones but are still associated with reduced production and safety for human consumption of milk, generally presenting a high bacterial count. In order to obtain novel analytical tools for rapid and non-invasive diagnosis of mastitis in goats, we analyzed milk samples from healthy, subclinical and clinical mastitic animals with a MALDI-TOF-MS-based peptidomic platform, generating disease group-specific spectral profiles whose signal intensity and mass values were analyzed by statistics. Peculiar spectral signatures of mastitis with respect to the control were identified, while no significant spectral differences were observed between clinical and subclinical milk samples. Discriminant signals were assigned to specific peptides through nanoLC-ESI-Q-Orbitrap-MS/MS experiments. Some of these molecules were predicted to have an antimicrobial activity based on their strong similarity with homolog bioactive compounds from other mammals. Through the definition of a panel of peptide biomarkers, this study provides a very rapid and low-cost method to routinely detect mastitic milk samples even though no evident clinical signs in the mammary gland are observed.

Scientometrics Approach to Research in Ovine Mastitis from 1970 to 2019 (with a Complete List of Relevant Literature References)

The present study is a scientometrics evaluation of refereed publications on bacterial mastitis in sheep; the objectives were the evaluation of the relevant papers and the presentation of quantitative characteristics regarding their scientific content and bibliometric details. The Web of Science platform was used with search terms: [mastitis OR *mammary infection*] AND [sheep OR ewe* OR ovine] for papers from 1970 tο 2019; only ‘articles’, ‘reviews’, ‘proceedings papers’, or ‘data papers’ were evaluated, whilst documents related solely to contagious agalactia, mammary aspects of lentiviral infections, or infections of the teats and the udder skin were excluded. Finally, 580 papers were considered in detail. The number of published papers increased from 8 during the 1970s to 273 during the 2010s. These papers originated from 43 countries (most from Greece or Spain, n = 87 from each) and 240 institutions (145 universities and 95 other establishments), of which 35 produced ≥ 5 papers each. Most papers present original studies (n = 539) with a few reviews (n = 41). The original papers refer to dairy (n = 428), meat (n = 113), or wool (n = 1) production systems and present field (n = 329), laboratory (n = 163), or experimental (n = 67) work; the papers report aetiology (n = 146), risk factors (n = 100), pathogenesis (n = 92), diagnosis (n = 88), effects (n = 66), treatment (n = 50), control (n = 36), or descriptive epidemiology (n = 32) of the disease. Papers related to dairy production present more field and fewer experimental work than papers related to meat production; also, in papers describing work performed in dairy sheep, studies about aetiology, risk factors, and diagnosis of the disease predominate, whilst in papers performed in meat sheep, studies about aetiology, pathogenesis, and effects/diagnosis are reported more often. The papers were published in 175 scientific journals (most in Small Ruminant Research, n = 90, or Journal of Dairy Science, n = 54). On average, the papers received 16.8 total citations and 1.6 yearly citations (h-index = 47). Most papers were published in Scimago classification Q1 (n = 240) or Q2 (n = 230) journals and received 23.4 or 15.4 total citations, respectively. Reviews received more citations than original papers; among the latter, papers with work referring to dairy production received more yearly citations than papers referring to meat production; no differences in citations were seen according to type of work or mastitis aspect covered. Most citations were received by papers from France. Papers published in Journal of Dairy Science or Small Ruminant Research received the most citations. In total, there were 1558 individual authors of the papers, with 24 authors having co-authored > 10 papers each (max: 73 papers); on average, there were 5.2 co-authors per paper (min–max: 1–25). Average number of co-authors progressively increased from 2.1 in the 1970s to 6.3 in the 2010s, with original papers having a higher number of co-authors than reviews: 5.3 and 3.7, respectively. Papers from France had highers number of co-authors (7.9). The findings of this first ever scientometrics study into ovine mastitis indicate that the disease has not been studied as other sheep diseases and that future studies in it should be directed to its control.

Coagulase-positive methicillin-resistant Staphylococcus aureus circulating in clinical mastitic goats in Bangladesh

BACKGROUND AND AIM

Staphylococcus aureus is argued as one of the principal organisms responsible for mammary gland infection in lactating goats, causing both clinical and subclinical mastitis. Being highly zoonotic potential, pathogen emergence of methicillin-resistant S. aureus (MRSA) has a significant clinical impact on treatment and management of clinical mastitis. We conducted a cross-sectional study to investigate the prevalence of coagulase-positive S. aureus (CoPS), antimicrobial resistance profile of Staphylococcus spp., prevalence of MRSA, and association between different clinical parameters with CoPS.

MATERIALS AND METHODS

A total of 67 clinical mastitic goats were sampled based on clinical examination and California mastitis test. Standard bacteriological methods were performed to isolate and identify Staphylococcus spp. CoPS were confirmed by nuc gene using polymerase chain reaction (PCR). All staphylococcal isolates were further examined for antimicrobial susceptibility testing by disk diffusion method. MRSA was confirmed based on mecA gene-based PCR.

RESULTS

Here, 49 (73.13%; 95% confidence interval [CI], 61.41-82.35) samples were positive for Staphylococcus spp., of which 17 (34.69%; 95% CI, 22.88-48.73) isolates were CoPS and rest of the isolates (32; 65.30%; 95% CI, 51.27-77.12) were identified as coagulase-negative Staphylococcus spp. (coagulase-negative staphylococci [CNS]). Both, CoPS and CNS isolates displayed the highest resistance against tetracycline (76.47% and 75%, respectively) and oxacillin (70.58% and 68.75%, respectively). Notably, all staphylococcal isolates were multidrug-resistant (showed resistance to ≥3 classes of antimicrobials). mecA gene was found in 6 (8.96%; 95% CI, 3.84-18.52) CoPS isolates indicating MRSA strains. Among different clinical parameters, presence of high body temperature (p<0.05), firm udder consistency (p<0.01), bloodstained milk (p<0.00), and pus in milk (p<0.00) were significantly associated with the presence of CoPS in mastitic caprine milk.

CONCLUSION

To the best of our knowledge, this is the first report of MRSA isolated from clinical caprine mastitis cases in Bangladesh. The findings of this study would help in cautious selection as well as administration of antimicrobials for therapeutic management of mastitic goats.

Assessment of the Welfare of Extensively Managed Autochtonous Sheep Breed Vlasicka Zackel using Animal-Based Measurements

In the Balkan region, the state of sheep welfare is little known. In this context, the assessment of sheep welfare is important for the identification of health and behavioral problems that affect these animals, along with the deficiencies present in the environment. The study was conducted during the winter season on a farm of 220 autochthonous breed Vlašićka Zackel sheep reared in extensive systems on the mountain regions of Bosnia and Herzegovina. A total of 65 ewes, aged 2–4 years, were observed. The welfare assessment was performed according to the AWIN protocol for sheep. The authors found the following issues: dry ewes were significantly fat (p<0.001) in regard to pregnant and lactation ewes; 42.11% of pregnant ewes were thin while 31.25% of dry ewes were fat; most of the assessed animals (78.46%) had dry or damp, slightly soiled fleece; 32.31% of animals had lesions on face/muzzle while ocular discharge, respiratory problems, mild mastitis and minor lameness were present in 16.92%, 4.62%, 15.38% and 7.69% sheep, respectively. All animals showed a negative relationship with humans. Using this methodology, the welfare problems in animals may be detected, and thus certain segments in the production cycle may be improved. The on-farm welfare assessment is highly recommended for emphasizing the key points in improving sheep welfare in Balkan countries.

Cells and Cytokines in Milk of Subclinically Infected Bovine Mammary Glands after the Use of Immunomodulatory Composition GLP 810

The aim of this study was to investigate the effect of intramammary infusions of natural composition GLP 810 with immunomodulating properties on the local nonspecific cellular and humoral immune response in cows with subclinical mastitis. The composition GLP 810 consists of lactic acid, lysozyme, glycopeptides, and 0.9% solution of NaCl. The following parameters were studied: (1) leukocyte differential distribution in milk, (2) expression of cytokines in milk leukocytes, (3) antibacterial activity, and (4) milk quality. Nineteen mammary glands in five lactating cows were infused with 10 mL of GLP 810, and nineteen other glands from five control cows were treated with 10 mL 0.9% NaCl. The results showed that after intramammary administration of the composition GLP 810 three times with 48 h intervals, the following effects on leukocyte populations in milk were observed: (1) an increase in the number of polymorphonuclear leukocytes and lymphocytes and (2) a decrease in the number of macrophages. A reduction in the number of pathogenic bacteria was also detected. The analyses of tumour necrosis factor-alpha, interleukin-10, and beta-defensin-2 revealed that the production of the aforementioned cytokines significantly increased, whereas no significant effects on interleukin-1 and caspase-6 expression in milk leukocytes were recorded. However, there were significant differences between mammary glands with high and low milk somatic cell count. The results suggest that the composition GLP 810 has an immunomodulatory effect on mammary glands and it could be used for improving the immune response in cows with subclinical mastitis during lactation.

Relationship of Late Lactation Milk Somatic Cell Count and Cathelicidin with Intramammary Infection in Small Ruminants

Late lactation is a critical moment for making mastitis management decisions, but in small ruminants the reliability of diagnostic tests is typically lower at this stage. We evaluated somatic cell counts (SCC) and cathelicidins (CATH) in late lactation sheep and goat milk for their relationship with intramammary infections (IMI), as diagnosed by bacteriological culture (BC). A total of 315 sheep and 223 goat half-udder milk samples collected in the last month of lactation were included in the study. IMI prevalence was 10.79% and 15.25%, respectively, and non-aureus staphylococci were the most common finding. Taking BC as a reference, the diagnostic performance of SCC and CATH was quite different in the two species. In sheep, receiver operating characteristic (ROC) analysis produced a higher area under the curve (AUC) value for CATH than SCC (0.9041 versus 0.8829, respectively). Accordingly, CATH demonstrated a higher specificity than SCC (82.92% versus 73.67%, respectively) at comparable sensitivity (91.18%). Therefore, CATH showed a markedly superior diagnostic performance than SCC in late lactation sheep milk. In goats, AUC was <0.67 for both parameters, and CATH was less specific than SCC (61.90% versus 65.08%) at comparable sensitivity (64.71%). Therefore, both CATH and SCC performed poorly in late lactation goats. In conclusion, sheep can be screened for mastitis at the end of lactation, while goats should preferably be tested at peak lactation. In late lactation sheep, CATH should be preferred over SCC for its higher specificity, but careful cost/benefit evaluations will have to be made.

Detection of Cathelicidin-1 in the Milk as an Early Indicator of Mastitis in Ewes

The objective of the study was the investigation of the behaviour of cathelicidin-1 in the milk after experimental infection with two prominent bacterial pathogens (experiment 1: Mannheimia haemolytica, experiment 2: M. haemolytica and Staphylococcus chromogenes) as a potential early indicator for diagnosis of mastitis in sheep. In two experiments, after bacterial inoculation into the udder of ewes, bacteriological and cytological examinations of milk samples as well as proteomics examinations [two-dimensional gel electrophoresis analysis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF MS) analysis] were performed sequentially. Cathelicidin-1 was detected and spot densities obtained from PDQuest v.8.0 were recorded. Associations were calculated between cell content and spot densities as well as between presence of mastitis in a mammary gland at a given time-point and detection of cathelicidin-1 in the respective milk sample. All inoculated mammary glands developed mastitis, confirmed by the consistent bacterial isolation from mammary secretion and increased leucocyte content therein. Spot density of cathelicidin-1 in samples from inoculated glands increased 3 h post-inoculation; spot density of cathelicidin-1 in samples from inoculated glands was higher than in samples from uninoculated controls. There was clear evidence of correlation between cell content and cathelicidin-1 spot densities in milk samples. There was significant association between presence of mastitis in the mammary gland and detection of cathelicidin-1 in the respective milk sample; overall accuracy was 0.818-this was significantly greater during the first 24 h post-challenge (0.903) than after the first day (0.704). In conclusion, detection of cathelicidin-1 in milk was significantly associated with presence of mastitis in ewes. The associations were stronger during the first 24 h post-infection than after the first day. Cathelicidin-1 has the advantage that it can be a non-specific biomarker, as simply a "positive" / "negative" assessment would be sufficient.

Experimental study for evaluation of the efficacy of a biofilm-embedded bacteria-based vaccine against Staphylococcus chromogenes-associated mastitis in sheep

Although coagulase-negative staphylococci are the primary aetiological agents of subclinical mastitis in ewes, there is little information regarding vaccination against that infection. The objective of this study was to evaluate the efficacy of a vaccine against staphylococcal mastitis in ewes under experimental conditions. The antigen in the vaccine is based on a bacterin of Staphylococcus aureus strain, expressing the exopolysaccharide poly-N-acetylglucosamine (PNAG), which is involved in biofilm formation by these bacteria. Ewes in groups A (n = 17) or B (n = 6) were given an initial vaccination 5 weeks before expected lambing, followed by a repeat administration 21 days later. Ewes in groups C (n = 8) or D (n = 6) were unvaccinated controls. Ewes in group A (n = 17) or C (n = 8) were challenged with a biofilm-forming S. chromogenes; animals in subgroups A1 or C1 were challenged on the 10th and those in A2 or C2 on the 50th day after lambing. Ewes in groups B or D were uninoculated controls. Clinical examinations of ewes, ultrasonographic examinations of udder, milk yield measurements, blood sampling for detection of anti-PNAG specific antibodies and milk sample collection for bacteriological and cytological examinations were performed up to 52nd day post-challenge. Finally, biopsies were performed for mammary tissue collection for histopathological examination. Among group A ewes, 29% developed systemic signs and 59% signs in the inoculated gland; the respective figures for group C were 50% and 100% (P =  0.040 for mammary signs). The median total clinical score was 2.0 for A and 5.5 for C ewes (P =  0.025). For A, but not for C, clinical scores decreased progressively during the study (P =  0.018 and P =  0.47, respectively). The duration of mastitis was shorter in A (4 days) than in C (17.5 days) ewes (P =  0.022). Bacterial counts were lower in milk samples from A than from C ewes, for samples collected from the inoculated and the uninoculated (P <  0.01) mammary glands of these ewes. Somatic cell counts in samples from inoculated and uninoculated mammary glands of A ewes were higher than in samples of C ewes (P <  0.02). There were differences for gray-scale evaluations during ultrasonographic examination and for milk yield measurements between groups (P <  0.01). Median bacterial counts in tissue samples from A ewes (0 cfu g^-1) were lower than in ones from C (6.5 cfu g^-1) ewes (P =  0.041). The median score for histopathological findings in tissue samples from inoculated glands of A was lower than that for C ewes: 1 versus 2 (P =  0.014). It is concluded that mastitis was less severe in vaccinated animals, as indicated by a wide array of measures.

Mammary Defences and Immunity against Mastitis in Sheep

The objectives of this review paper are to present udder defences, including teat of the udder, mammary epithelial cells, leucocytes, immunoglobulins, complement system and chemical antibacterial agents, to describe cooperation and interactions between them and to elaborate on potentials regarding their significance in mammary immunisation strategies. The teat of the udder provides initial protection to the mammary gland. The mammary epithelial cells synthesise antibacterial proteins and the leucocytes produce various inflammation mediators (cytokines or chemokines), phagocytose bacteria and recognise antigenic structures. In the mammary gland, four immunoglobulins (IgG1, IgG2, IgM and IgA) have important roles against bacterial pathogens. The complement system is a collection of proteins, participating in the inflammatory process through various pathways. Other components contributing to humoral mammary defence include lactoferrin, lysozyme and the lactoperoxidase/myeloperoxidase systems, as well as oligosaccharides, gangliosides, reactive oxygen species, acute phase proteins (e.g., haptoglobin and serum amyloid A), ribonucleases and a wide range of antimicrobial peptides. Management practices, genetic variations and nutrition can influence mammary defences and should be taken into account in the formulation of prevention strategies against ovine mastitis.

Role of staphylococci in mastitis in sheep

Staphylococci have been isolated from various sites of the body of healthy sheep, as well as from many infections of those animals, the main one being mastitis. The objective of this review is to appraise the importance and significance of staphylococci in causing mastitis in ewes. The review includes a brief classification and taxonomy of staphylococci and describes the procedures for their isolation and identification, as well as their virulence determinants and the mechanisms of resistance to antibacterial agents. Various staphylococcal species have been implicated in staphylococcal mastitis and the characteristics of isolates are discussed with regards to potential virulence factors. Staphylococcal mastitis is explicitly described, with reference to sources of infection, the course of the disease and the relevant control measures. Finally, the potential significance of staphylococci present in ewes' milk for public health is discussed briefly.

Evaluation of efficacy of a biofilm-embedded bacteria-based vaccine against staphylococcal mastitis in sheep-A randomized, placebo-controlled field study

Our objective was to evaluate the efficacy of a vaccine against staphylococcal mastitis in 5 dairy sheep farms, with 316 ewes in the vaccinated (V) group and 307 in the control (C) group studied throughout a lactation period. Two administrations of the vaccine were performed during the last stage of gestation of ewes. Starting 15 d after lambing and at monthly intervals thereafter, up to 9 milk samplings were performed for bacteriological and cytological examinations. Staphylococcal isolates recovered were examined for biofilm formation. Blood samples were collected for measurement of IgG poly-N-acetylglucosamine-specific antibodies. The most frequently isolated bacteria were staphylococci: 56.4 and 76.1%, respectively, of total isolates recovered from ewes of group V and C, respectively; staphylococci as causal agents of mastitis were isolated less frequently from V (5.3%) than in ewes in C (10.3%). Among mastitis-associated staphylococcal isolates recovered from V ewes, a smaller proportion was biofilm-forming than among ones from C: 53.2% versus 74.9% of isolates; biofilm-forming staphylococci as causal agents of mastitis were isolated less frequently from ewes in group V (2.3%) than in ewes in group C (6.0%). Anti-poly-N-acetylglucosamine-specific antibody values increased in V ewes and were higher than in C; a greater proportion of ewes with low antibody titers developed staphylococcal mastitis (41.4%) than of V ewes with high antibody titers (17.0%). Incidence risk of mastitis, staphylococcal mastitis, and biofilm-associated staphylococcal mastitis was smaller in V than in C: 36.7, 17.1, and 8.0% versus 44.3, 30.9, and 18.9%, respectively. The first case of staphylococcal mastitis occurred later in V than in C: third versus second sampling point. Overall, efficacy of the vaccine was 44.6% for staphylococcal mastitis, 57.7% for biofilm-associated staphylococcal mastitis, 33.1% for staphylococcal intramammary infection, and 51.5% for biofilm-associated staphylococcal intramammary infection. Nevertheless, vaccination should not be the only means for controlling mastitis; other udder health management measures should be included therein to improve control of the infection.

The relationship between mastitis and the B-mode, colour Doppler ultrasonography measurements of supramammary lymph nodes in cows

This research communication aims to test the hypothesis that B-Mode, colour Doppler ultrasonographic measurements and characteristics can identify mastitis in dairy cows. A total of 102 lactating cows were divided into 3 groups: cows in which all mammary quarters were CMT-negative, cows with CMT-positive mammary quarters and cows with clinical mastitis in at least one quarter. Colour Doppler ultrasonography measurements of the supramammary lymph nodes revealed that distortion-type vascular morphology, the rate of type 4 vascular densities and the incidence of mixed-type vascular distributions were highest in the clinical mastitis group, whereas the frequency of avascularity in supramammary lymph nodes was highest in the CMT-negative group. All differences were significant. In conclusion, the use of B-mode and colour Doppler ultrasonographic measurements of the supramammary lymph nodes can provide useful information about the current condition of mastitis in cows, although its diagnostic potential remains to be determined.

Differential quantitative proteomics study of experimental Mannheimia haemolytica mastitis in sheep

Objective was the differential quantitative proteomics study of ovine mastitis induced by Mannheimia haemolytica; clinical, microbiological, cytological and histopathological methods were employed for confirmation and monitoring. Proteins were separated by two-dimensional gel electrophoresis (2-DE) for all samples and differentially abundant proteins were identified by mass spectrometry; comparisons were performed with pre- (blood, milk) and post- (milk of contralateral gland) inoculation findings. Animals developed mastitis, confirmed by isolation of challenge strain and increase of neutrophils in milk and by histopathological evidence. In blood plasma, 33 differentially abundant proteins (compared to findings before challenge) were identified: 6 with decrease, 13 with new appearance and 14 with varying abundance. In a post-challenge milk whey protein reference map, 65 proteins were identified; actin cytoplasmic-1, beta-lactoglobulin-1/B, cathelicidin-1 predominated. Further, 89 differentially abundant proteins (compared to findings before challenge) were identified: 18 with decrease, 53 with new appearance, 3 with increase and 15 with varying abundance; 15 proteins showed status changes in blood plasma and milk whey. Differential abundance from inoculated and contralateral glands revealed 74 proteins only from the inoculated gland. Most differentially abundant proteins in milk whey were involved in cell organisation and biogenesis (n = 17) or in inflammatory and defence response (n = 13). SIGNIFICANCE: The proteomes of blood and milk from ewes with experimental mastitis caused by Mannheimia haemolytica and the differential proteomics in sequential samples after challenge are presented for the first time. This is the first detailed proteomics study in M. haemolytica-associated mastitis in ewes. An experimental model fully simulating natural mastitis has been used. Use of experimentally induced mastitis minimised potential variations and allowed consistency of results. The study included evaluation of changes in blood plasma and milk whey. Protein patterns have been studied, indicating with great accuracy changes that had occurred as part of the disease process and development, during the acute phase of infection. Relevant protein-protein interactions were studied. The entirety of proteomics findings has suggested that affected ewes had mounted a defence response that had been regulated by many proteins (e.g., cathelicidins, haptoglobin, serum amyloid A) and through various pathways (e.g., acute phase response, binding and transporting significant ions and molecules); these were interdependent at various points. Potential biomarkers have been indicated for use in diagnostic assays of mastitis.

Antimicrobial Agent Susceptibility and Typing of Staphylococcal Isolates from Subclinical Mastitis in Ewes

Objective was to study susceptibility to antimicrobial agents of 142 staphylococcal isolates from subclinical mastitis in ewes. In total, 41.5% of these were resistant and 5.6% multidrug resistant. More coagulase-negative staphylococci (47.0%) were resistant than Staphylococcus aureus (18.5%) isolates. Resistance was greater to penicillin (22.5%), tetracycline, or ampicillin (18.3%). More biofilm-forming (20.6%) isolates were resistant to tetracycline than nonbiofilm-forming (0.0%) ones. Presence of tetK was associated with presence of icaA in the same strains. Further, 76.6% of resistant isolates versus 57.7% of susceptible ones were recovered immediately postpartum and 23.4% of resistant isolates versus 9.9% of susceptible ones were recovered in farms that practiced routine administration of antimicrobial agents at the end of a lactation period. Most S. aureus (59.3%) were classified in ST133 and most Staphylococcus epidermidis were classified in ST100, ST142, or ST152 (19.0% each). There was no association of sequence types with resistance. Whole genome sequencing showed that, in a Staphylococcus lentus strain, the ermB gene was part of transposon Tn917 integrated into the chromosome; also, a small plasmid was observed in an ermC-carrying Staphylococcus hominis strain and, finally, in an S. aureus and an S. epidermidis strains, small tetK-carrying plasmids (pSau-2716Lar, pSau-3893Lar) of 4.439 kb were found.

Use of contrast-enhanced ultrasonographic examination to evaluate health status of mammary glands of ewes at the end of a lactation period

This research communication describes the use of contrast-enhanced ultrasonographic examination (CEUS) in mammary glands of ewes for diagnosis of chronic mastitis; this is the first report of the use of this modality in diagnostic imaging of mammary glands of ruminants. For this purpose, a convex transducer was used, with the following settings: frequency: 2·0/4·0 MHz, mechanical index: 0·09, power: 22 dB, scanning depth: 70 mm, and sulphur hexafluoride in microbubbles at a dose of 20 µl as the contrast agent. In four healthy mammary glands (2 ewes), CEUS examination revealed a steady biphasic pattern of contrast agent kinetics characterised by initial uptake within 15–40 s post-injection, at which time intensity peaked with strong enhancement (130–200 AEU) followed by a gradual wash-out phase. In three mammary glands with history of clinical mastitis (2 ewes), the pattern was particularly inconsistent and unclear, with weak enhancement (<100 AEU) (P < 0·01) lasting for a short period. Notwithstanding issues regarding cost and withdrawal period of contrast-agent, this imaging modality may contribute to improved diagnosis of mastitis cases, especially on occasions when abnormalities cannot be easily confirmed by more conventional methods.

Extensive countrywide field investigation of subclinical mastitis in sheep in Greece

The objectives of this work were (1) to investigate prevalence of subclinical mastitis, (2) to identify etiological agents involved, and (3) to study factors potentially predisposing ewes to subclinical mastitis. Milk samples were collected from 2,198 ewes in 111 farms with a total population of 35,925 ewes, in all 13 administrative regions of Greece, for bacteriological and cytological examination. Prevalence of subclinical mastitis was 0.260. Main etiological agents were staphylococci (Staphylococcus aureus and coagulase-negative species), which accounted for 0.699 of all isolates recovered; prevalence of staphylococcal mastitis was 0.191. In a multivariable mixed-effects analysis, the primary factor found to be associated with increased prevalence of subclinical mastitis was the management system practiced in flocks (flocks under a semi-intensive system had the highest prevalence). Other factors that were included in the multivariable model were the stage of lactation period (ewes in the 2nd month postpartum showed the highest prevalence) and application of postmilking teat dipping. In contrast, measures taken at the end of a lactation period (e.g., intramammary administration of antimicrobial agents) were not found to have an effect on prevalence of subclinical mastitis. The results confirmed the significance of subclinical mastitis as a frequent problem of ewes, with staphylococci as the primary etiological agent. The findings confirm the multifactorial nature of subclinical mastitis and indicate that its control should rely on many approaches.

New mastitis phenotypes suitable for genomic selection in meat sheep and their genetic relationships with udder conformation and lamb live weights

Mastitis can prove expensive in sheep reared for meat production due to costs associated with treatment methods, poor lamb growth and premature culling of ewes. The most commonly used method to detect mastitis, in dairy systems, is somatic cell counts. However, in many meat-producing sheep flocks ewes are not routinely handled, thus regular milk sampling is not always possible. It is, therefore, worthwhile to investigate alternative phenotypes, such as those associated with udder conformation and methods of evaluating somatic cell counts in the milk, such as the California Mastitis Test. The main objectives of this study were therefore: (a) to estimate genetic parameters of traits relating to mastitis and udder conformation in a meat sheep breed; (b) estimate the level of association between somatic cell counts and the California Mastitis Test and (c) assess the relationships between mastitis and both udder conformation and lamb live weights. Data were collected from Texel ewes based on 29 flocks, throughout the UK, during 2015 and 2016. The ewes were scored twice each year, at mid- and late-lactation. Eight different conformation traits, relating to udder and teat characteristics, and milk samples were recorded. The data set comprised of data available for 2957 ewes. The pedigree file used contained sire and dam information for 31 775 individuals. The animal models used fitted relevant fixed and random effects. Heritability estimates for traits relating to mastitis (somatic cell score and the California Mastitis Test), ranged from 0.08 to 0.11 and 0.07 to 0.11, respectively. High genetic correlations were observed between somatic cell score and the California Mastitis Test (0.76 to 0.98), indicating the California Mastitis Test to be worthwhile for assessing infection levels, particularly at mid-lactation. The strongest correlations observed between the mastitis traits and the udder conformation traits were associated with udder depth (0.61 to 0.75) also at mid-lactation. Negative phenotypic correlations were estimated between mastitis and the weight of lamb reared by the ewe (-0.15 to -0.23), suggesting that lamb weights fell as infection levels rose. Genetic correlations were not significantly different from zero. Reducing mastitis will lead to improvements in flock productivity and the health and welfare of the animals. It will also improve the efficiency of production and the resilience to disease challenge. The economic benefits, therefore, of these results combined could be substantial not only in this breed but also in the overall meat sheep industry.

First Description in Greece of mphC-Positive Staphylococci Causing Subclinical Mastitis in Ewes

The aim of the present study was to describe the first mphC-positive staphylococci, including two Staphylococcus lentus (Sle-087lar and Sle-091lar) and one Staphylococcus xylosus (Sxy-228lar), isolated from samples of animal origin, in Greece. Isolates Sle-087lar and Sxy-228lar were resistant to erythromycin, whereas Sle-091lar was resistant to erythromycin and lincomycin. All three isolates were susceptible to the remaining antibiotics. PCR screening showed that isolate Sle-091lar carried also ermB. For Sxy-228lar, whole-genome sequencing (WGS) and de novo assembly obtained an mphC-positive contig of 57.3-kb exhibiting high similarity with the genome of mphC-negative S. xylosus S170. However, mphC of Sxy-228lar was 91% similar to that found in plasmid pJW2311 from S. xylosus JW2311. Additionally, WGS data showed that Sle-087lar and Sle-091lar harbored mphC-carrying sequences being highly similar to the recently announced genome of the mphC-carrying S. lentus isolate 050AP from Tanzania. However, differences were observed in the mphC environment, suggesting the independent acquisition of the gene by each isolate. Sle-091lar also harbored transposon Tn917, which carries ermB resistance gene, integrated into S. lentus chromosome. These findings indicated that acquisition of resistance genes can lead to the emergence of multiresistant staphylococci, causing animal infections with economic burden.

Evaluation of Animal-Based Indicators to Be Used in a Welfare Assessment Protocol for Sheep

Sheep are managed under a variety of different environments (continually outdoors, partially outdoors with seasonal or diurnal variation, continuously indoors) and for different purposes, which makes assessing welfare challenging. This diversity means that resource-based indicators are not particularly useful and, thus, a welfare assessment scheme for sheep, focusing on animal-based indicators, was developed. We focus specifically on ewes, as the most numerous group of sheep present on farm, although many of the indicators may also have relevance to adult male sheep. Using the Welfare Quality^® framework of four Principles and 12 Criteria, we considered the validity, reliability, and feasibility of 46 putative animal-based indicators derived from the literature for these criteria. Where animal-based indicators were potentially unreliably or were not considered feasible, we also considered the resource-based indicators of access to water, stocking density, and floor slipperiness. With the exception of the criteria “Absence of prolonged thirst,” we suggest at least one animal-based indicator for each welfare criterion. As a minimum, face validity was available for all indicators; however, for many, we found evidence of convergent validity and discriminant validity (e.g., lameness as measured by gait score, body condition score). The reliability of most of the physical and health measures has been tested in the field and found to be appropriate for use in welfare assessment. However, for the majority of the proposed behavioral indicators (lying synchrony, social withdrawal, postures associated with pain, vocalizations, stereotypy, vigilance, response to surprise, and human approach test), this still needs to be tested. In conclusion, the comprehensive assessment of sheep welfare through largely animal-based measures is supported by the literature through the use of indicators focusing on specific aspects of sheep biology. Further work is required for some indicators to ensure that measures are reliable when used in commercial settings.

Intramammary infusion of a live culture of Lactococcus lactis in ewes to treat staphylococcal mastitis

PURPOSE

Alternatives to antibiotic therapy for mastitis in ruminants are needed. We present an evaluation, in two trials, of the efficacy of an intramammary infusion of a live culture of Lactococcus lactis for the treatment of subclinical and clinical mastitis in ewes.

METHODOLOGY

In total, 67 animals were enrolled: 19 lactating ewes (study 1), including healthy (N=6) and coagulase-negative staphylococci (CNS)-infected ewes (N=13); and 48 lactating ewes (study 2) with either CNS mastitis (N=32), or Staphylococcus aureus mastitis (N=16), for a total of 123 mammary glands. Intramammary infusions were performed with either L. lactis or PBS for 3 (study 1) or 7 (study 2) consecutive days. Antibiotic-treated and untreated control glands were included. Milk samples for microbiology, somatic cell analysis and milk production were collected before and after treatment.Results/Key findings.L. lactis rapidly activated the mammary glands' innate immune response and initiated an inflammatory response as evidenced by the recruitment of polymorphonuclear neutrophils and increased somatic cell counts. But while leading to a transient clearance of CNS in the gland, this response caused mild to moderate clinical cases of mastitis characterized by abnormal milk secretions and udder inflammation. Moreover, S. aureus infections did not improve, and CNS infections tended to relapse.

CONCLUSION

Under our experimental conditions, the L. lactis treatment led to a transient clearance of the pathogen in the gland, but also caused mild to moderate clinical cases of mastitis. We believe it is still early to implement bacterial formulations as alternatives in treating mastitis in ruminants and further experimentation is needed.

Diagnosis of subclinical mastitis in Santa Inês and Morada Nova sheep in southeastern Brazil

The objective of this study was to evaluate different screening limits for the California mastitis test (CMT) and the somatic cell count (SCC) in previous diagnoses of subclinical mastitis in Santa Inês and Morada Nova ewes, which were reared under the same management conditions. Additionally, cutoff points were defined for SCC in accordance with the sensitivity and specificity of the test. A total of 907 mammary halves were subjected to CMT and SCC. The disease was confirmed by means of microbiological identification. Coagulase-negative staphylococci (CNS) were the microorganisms with highest occurrence. The CMT score of 1+ provided adequate sensitivity and specificity at all periods of lactation investigated. This score showed good agreement with SCC, >400,000 cells mL(-1). Higher cell counts favored higher diagnostic specificity. They can be used when producers have financial difficulties relating to treatment or culling of sheep with subclinical mastitis. However, producers should be warned about the risk of false-negative results in the flock.