The Relationship between Mastitis and Antimicrobial Peptide S100A7 Expression in Dairy Goats

S100A7 is an inflammation-related protein and plays an essential role in host defenses, yet there is little research about the relationship between mastitis and S100A7 expression in dairy goats. Here, according to the clinical diagnosis of udders, SCC, and bacteriological culture (BC) of milk, 84 dairy goats were grouped into healthy goats (n = 25), subclinical mastitis goats (n = 36), and clinical mastitis goats (n = 23). The S100A7 concentration in subclinical mastitis goats was significantly upregulated than in healthy dairy goats (p = 0.0056) and had a limited change with clinical mastitis dairy goats (p = 0.8222). The relationship between log10 SCC and S100A7 concentration in milk was positive and R = 0.05249; the regression equation was Y = 0.1446 × X + 12.54. According to the three groups, the log10 SCC and S100A7 were analyzed using the receiver operating characteristics (ROC) curve; in subclinical mastitis goats, the area under the ROC curve (AUC) of log10 SCC was 0.9222 and p < 0.0001, and the AUC of S100A7 concentration was 0.7317 and p = 0.0022, respectively; in clinical mastitis goats, the AUC of log10 SCC was 0.9678 and p < 0.0001, and the AUC of S100A7 concentration was 0.5487 and p = 0.5634, respectively. In healthy goats, S100A7 was expressed weakly in the alveolus of the mammary gland of healthy goats while expressed densely in the collapsed alveolus of mastitis goats. Moreover, S100A7 expression increased significantly in mastitis goats than in healthy dairy goats. In this research, results showed the effects of mastitis on the S100A7 expression in the mammary gland and S100A7 concentration in milk and the limited relationship between SCC and mastitis, which provided a new insight into S100A7's role in the host defenses of dairy goats.

Licury Cake in Diets for Lactating Goats: Intake, Digestibility, Feeding Behavior, Milk Production and Composition, and Nitrogen Metabolism

The objective of this study was to determine the effects of licury cake (LC) inclusion in the diets of lactating goats on productive and metabolic performance. Twelve lactating goats, eight Saanen and four Anglo-Nubian, were distributed in a triplicate 4 × 4 Latin square design, with four treatments (0, 66.7, 133.3, and 200 g kg-1 of dry matter-DM). On the one hand, the LC inclusion increased neutral detergent fiber, indigestible neutral detergent fiber, and potentially digestible neutral detergent fiber (p < 0.001) intake. On the other hand, LC inclusion reduced ether extract and non-fibrous carbohydrate (p < 0.001) intake. There was a reduction in dry matter digestibility (p = 0.018) and an increase in neutral detergent fiber digestibility (p = 0.036). Feeding (p = 0.005) and rumination (p < 0.001) efficiencies increased with LC inclusion. The nitrogen balance was similar for all tested diets; however, we observed recycling metabolism. Based on the studied parameters, mainly milk production and composition, we recommend the LC inclusion of up to 200 g kg-1 DM in diets for lactating goats.

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.

Milk Pathogens in Correlation with Inflammatory, Oxidative and Nitrosative Stress Markers in Goat Subclinical Mastitis

Goat mastitis is still frequently diagnosed in dairy farms, with serious consequences on milk quality and composition. The aim of this study was to establish correlations between milk microorganisms and biochemical parameters in goats with no signs of clinical mastitis. Thus, 76 milk samples were collected from a dairy goat farm, Carpathian breed, followed by microbiological, molecular (16S rRNA sequencing) and somatic cells analysis, determination of lactate dehydrogenase (LDH), β-glucuronidase, catalase (CAT), glutathione peroxidase (GPx) activity, total antioxidant capacity (TAC), nitric oxide (NO) and lipid peroxides (LPO) using spectrophotometry and the ELISA method for 8-hydroxy-deoxyguanosine (8-OHdG) as the oxidative DNA damage indicator. Samples positive for bacterial growth showed a significant (p < 0.05) increase in the number of somatic cells, LDH and β-glucuronidase activity, as well as higher levels of CAT, GPx, NO, LPO and 8-OHdG compared with pathogen-free milk whereas TAC was lower in milk from an infected udder. These findings suggest that subclinical mastitis is associated with increased enzymatic activity and induction of oxidative stress. Nevertheless, changes in biochemical parameters tended to vary depending on the pathogen, the most notable mean values being observed overall in milk positive for Staphylococcus aureus.

Estradiol Regulates the Expression and Secretion of Antimicrobial Peptide S100A7 via the ERK1/2-Signaling Pathway in Goat Mammary Epithelial Cells

S100A7 has received extensive attention in the prevention and treatment of mastitis across a broad spectrum, yet there is a little information about its mechanism, especially in the immunomodulatory effects of estrogen. In the present study, based on the milk bacteriological culture (BC) of 30 dairy goats, the concentration of both estrogen and S100A7 in the BC-positive samples was not significantly different than in the BC-negative samples; the estrogen abundance in subclinical and clinical mastitis samples also showed only a limited difference; compared with healthy samples, the S100A7 abundance in subclinical mastitis samples differed little, while it was significantly decreased in clinical mastitis samples. Moreover, the relationship between estrogen and S100A7 was positive, and the regression equation was y = 0.3206x + 23.459. The goat mammary epithelial cells (gMECs) were isolated and treated with 1, 10, 100 nM E2 and/or 5 μg/mL lipopolysaccharide (LPS), respectively, for 6 h. Compared with control samples, 5 μg/mL LPS, 10 nM E2 and 100 nM E2 markedly induced S100A7 expression and secretion. More than separated treatment, the cooperation of LPS and E2 also significantly increased S100A7 expression, rather than S100A7 secretion. The p-ERK was up-regulated markedly with 100 nM E2 treatment, while the expression of p-JNK, p-p38 and p-Akt had little effect. The G protein-coupled estrogen receptor 1(GPER1) agonist G1 markedly induced S100A7 expression and secretion in gMECs, and the estrogen nuclear receptor antagonist ICI and GPER1 antagonist G15 significantly repressed this process. In conclusion, E2 binds to nuclear and membrane receptors to regulate the expression and secretion of S100A7 via the ERK1/2-signaling pathway in gMECs.

Distribution of somatic cell count and udder pathogens in Norwegian dairy goats

Compared with dairy cows, goat somatic cell count (SCC) is higher and probably more affected by physiological factors such as parity, stage of lactation, and season. Thus, SCC is believed to be a less precise indicator of intramammary infections in dairy goats, and no consensus exists on SCC thresholds for considering goats as infected. The Norwegian Goat Recording System maintains individual goat production records and results from microbiological analyses of milk samples. In this retrospective observational study, we used recordings over a 10-yr period (2010 to 2020) to describe the association between individual goat SCC and noninfectious factors, as well as intramammary infections. The median SCC in the 1,000,802 milk recordings included in the study was 440,000 cells/mL, and the mode was 70,000 cells/mL. Somatic cell count increased with parity, days in milk, estrus, pasture season, and intramammary infections. The effect of parity and stage of lactation was significantly higher in infected compared with uninfected goats. Staphylococci dominated as causes of intramammary infections, with Staphylococcus aureus as the udder pathogen associated with highest SCC. The most prevalent non-aureus staphylococci were Staphylococcus warneri, Staphylococcus epidermidis, and Staphylococcus caprae. This study provides guidelines for interpretation of goat SCC at different parities and stages of lactations under Norwegian management conditions. We revealed a considerable variation in SCC associated with physiological factors, indicating that the cutoff for identifying infected goats should be a dynamic threshold adjusted for parity, stage of lactation, and season.

Incidence, Etiology, and Risk Factors of Clinical Mastitis in Dairy Cows under Semi-Tropical Circumstances in Chattogram, Bangladesh

Simple Summary

Bovine clinical mastitis is an inflammatory disease of the mammary gland associated with visual changes in the milk and/or the udder. We show that the incidence of clinical mastitis in commercial dairy farms in Bangladesh is high but with large variation between farms. Streptococci and non-aureus Staphylococci were the most frequently isolated bacteria from quarter milk samples. Staphylococcus aureus and non-aureus Staphylococci were often resistant against penicillin and oxacillin. This work suggests an urgent need for improved udder health management and specifically a more prudent use of antimicrobial agents following a treatment protocol.

Abstract

Clinical mastitis (CM) is an important production disease in dairy cows, but much of the knowledge required to effectively control CM is lacking, specifically in low-income countries where most farms are small and have specific dairy management, such as regular udder cleaning and practicing hand milking. Therefore, we conducted a 6-month-long cohort study to (a) estimate the incidence rate of clinical mastitis (IRCM) at the cow and quarter level, (b) identify risk factors for the occurrence of CM, (c) describe the etiology of CM, and (d) quantify antimicrobial susceptibility (AMS) against commonly used antimicrobial agents in S. aureus and non-aureus Staphylococcus spp. (NAS) in dairy farms in the Chattogram region of Bangladesh. On 24 farms, all cows were monitored for CM during a 6-month period. Cases of CM were identified by trained farmers and milk samples were collected aseptically before administering any antimicrobial therapy. In total, 1383 lactating cows were enrolled, which totaled 446 cow-years at risk. During the study period, 196 new cases of CM occurred, resulting in an estimated crude IRCM of 43.9 cases per 100 cow-years, though this varied substantially between farms. Among the tested CM quarter samples, Streptococci (22.9%) followed by non-aureus staphylococci (20.3%) were the most frequently isolated pathogens and resistance of S. aureus and NAS against penicillin (2 out of 3 and 27 out of 39 isolates, respectively) and oxacillin (2 out of 3 and 38 out of 39 isolates, respectively) was common. The IRCM was associated with a high milk yield, 28 to 90 days in milk, and a higher body condition score. Our results show that there is substantial room for udder health improvement on most farms.

Bayesian latent class evaluation of three tests for the screening of subclinical caprine mastitis in Bangladesh

Routine monitoring for subclinical infection is one of the key mastitis control approaches. However, the accuracy of the most commonly used screening tests has not yet been established. The aim of the present study was therefore to evaluate the accuracy of three screening tests, namely California mastitis test (CMT), white side test (WST), and surf field mastitis test (SFMT) for the screening of subclinical caprine mastitis. A cross-sectional study based on 484 randomly collected milk (242 goats) samples from three districts of Bangladesh was conducted for the screening of subclinical mastitis by the aforementioned tests. The Bayesian latent class model was implemented in WinBUGS to estimate the tests' characteristics and true prevalence of subclinical mastitis. The Bayesian posterior estimates of sensitivities with a 95% credible intervals (CrIs) were 98.60% (95.18-99.95%), 98.28% (94.56-99.92%), and 89.98% (83.39-95.03%), and specificities with 95% CrIs were 99.19% (98.11-99.96%), 99.27% (97.34-99.98%), and 99.28% (97.35-99.98%), respectively for CMT, WST, and SFMT. The true prevalence of subclinical caprine mastitis was estimated to be 43.49% (95% CrI 37.46-48.98%). The positive predictive values (PPV) of the three tests were similar. The serial and parallel interpretation of any test pairs increased the PPV and negative predictive value respectively close to 100%. Based on the simplicity, cost and performance as well WST and SFMT simultaneously could be recommended for the screening of caprine subclinical mastitis in Bangladesh.

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.

Evaluation of milk cathelicidin for detection of bovine mastitis

Mastitis due to intramammary infection is one of the most economically relevant diseases in dairy cows, causing reductions in milk quality and quantity. Currently, mastitis monitoring is based on somatic cell count (SCC) and bacteriologic culture (BC) of milk. Nevertheless, inflammation-specific protein markers might provide more sensitive and reliable assays, enabling immunoassay-based screening strategies. Cathelicidin is an inflammatory protein released in milk that has recently demonstrated fair reliability and diagnostic potential for ewe mastitis. To assess its performance in cows, 531 quarter milk samples from 2 herds were tested using cathelicidin ELISA, SCC, and BC. We found that 29.0% of samples were positive for cathelicidin, 18.8% had SCC >200,000 cells/mL, and 13.7% were BC-positive. Cathelicidin showed a strong positive correlation with SCC as demonstrated by receiver operating characteristics curve analysis and by the clustering of cathelicidin-negative and cathelicidin-positive samples in association with low and high SCC values, respectively. For evaluating the diagnostic performance of a novel test, BC cannot be considered a reliable gold standard for true disease status because of its known limitations. Therefore, we assessed the sensitivity (Se) and specificity (Sp) of the milk cathelicidin ELISA using a latent class analysis approach together with BC and SCC by considering different diagnostic thresholds to identify the preferred Se/Sp combination. We modeled conditional dependence of cathelicidin and SCC to account for their close association. The cathelicidin ELISA showed higher Se than SCC and BC for almost all threshold combinations. In fact, at the best-performing threshold combination, the Se of cathelicidin was 80.6%, 6.2 percentage points higher than that of SCC >200,000 cells/mL (74.4%) and similar to that of SCC >100,000 cells/mL (80.2%). Most importantly, this Se was obtained with a loss in Sp of only 1.4 percentage points compared with SCC >200,000 cells/mL (94.9% Sp for cathelicidin vs. 96.3% for SCC >200,000). The limited Se of BC (38.8%) was also confirmed in this study, and BC showed a slightly lower Sp than both cathelicidin and SCC for most of threshold combinations. This study confirmed that cathelicidin is released in the milk of cows with mastitis and that its presence is highly correlated with SCC. The measurement of cathelicidin by ELISA may hold significant potential for improving the sensitivity of mastitis detection in dairy cows while maintaining high specificity.

Bacterial subclinical mastitis and its effect on milk yield in low-input dairy goat herds

The objectives of this study were (1) to record the major pathogens associated with subclinical mastitis (SCM), (2) to calculate their incidence during the milking period, and (3) to estimate the effect of SCM on daily milk yield (DMY) for goats reared under low-input management schemes. Dairy goats (n=590) of Skopelos and indigenous Greek breeds from 4 herds were randomly selected for the study. The study included monthly monitoring, milk yield recording, and bacteriological analyses of milk of individual goats during the course of 2 successive milking periods. Incidence and cumulative incidence were calculated for SCM cases. Moreover, 2 mixed linear regression models were built to assess the effects of (1) SCM and (2) different pathogens isolated from SCM cases, on DMY. The estimated incidence and cumulative incidence of SCM for the first and the second year of the study were 69.5 and 96.4 new cases of SCM/1,000 goat-months, and 24.1 and 31.7%, respectively. A total of 755 milk samples were subjected to microbiological examination, resulting in 661 positive cultures. Coagulase-negative and coagulase-positive staphylococci were isolated from 50.2 and 34.5% of the positive cultures, respectively. The incidence of infections (new infections per 1,000 goat-months) for the first and the second year of the study were 34 and 53 for coagulase-negative staphylococci, 23 and 28 for coagulase-positive staphylococci, 3 and 5 for Streptococcus/Enterococcus spp., and 5.5 and 9.1 for gram-negative bacteria. Goats with SCM had lower DMY when compared with goats without SCM (ca. 47g/d, corresponding to a 5.7% decrease in DMY). In particular, goats with SCM due to coagulase-positive staphylococci infection produced approximately 80g/d less milk (a reduction of ca. 9.7%) compared with uninfected ones, whereas SCM due to gram-negative bacteria resulted in approximately 15% reduction in DMY. Investigating the epidemiology of SCM and its effects on production traits is critical for the establishment of effective preventive measures against SCM and for the assessment of the sustainability of production in low-input dairy goat herds.

Prevalence and pathogens of subclinical mastitis in dairy goats in China

Subclinical mastitis, a costly disease for the dairy industry, is usually caused by intramammary bacterial infection. The aim of this study was to investigate the prevalence of and pathogens involved in subclinical mastitis in dairy goats in China. A total of 683 dairy goats in the main breeding areas of China were selected, and milk samples were collected. Out of these, 313 (45.82 %) goats were detected distinct or strong positive for subclinical mastitis by using California mastitis test. Among these positive goats, 209 milk samples were used to identify the causing agents by a multiplex PCR assay, and results were listed as follows: coagulase-negative staphylococci (59.52 %), Staphylococcus aureus (15.24 %), Escherichia coli (11.43 %), and Streptococcus spp. (10.95 %). In conclusion, subclinical mastitis is a highly prevalent disease in dairy goats in China, and coagulase-negative staphylococci are the predominant pathogens.