Messenger RNA expression and immunolocalization of psoriasin in the goat mammary gland and its milk concentration after an intramammary infusion of lipopolysaccharide

Effect of low milking frequency on the concentration of antimicrobial proteins in goat milk

This study examined the effects of low frequency milking on the concentrations of antimicrobial components in goat milk. Sixteen goats were divided into two groups of eight each: milking once every 2 d three times (for six days, three times group) or five times (for 10 days, five times group). On other days, milking was performed once daily. Milk was collected, and milk yield, somatic cell count (SCC), and the concentrations of some antimicrobial proteins such as lactoferrin (LF), S100A7, IgA, and sodium ions (Na+) in milk were measured. Milk yield significantly decreased in both the groups during the low-milking frequency period, followed by an increase above the low frequency milking period in both groups. In contrast, SCC and LF concentrations in milk increased in both groups during the low frequency milking period. The concentration of S100A7 in milk temporarily decreased after the low frequency milking period, followed by a significant increase. The S100A7 concentration during this period was higher in the five times group than in the three times group. These results indicated that low frequency milking induced a gradual decrease in milk yield and a concomitant increase in antimicrobial components, such as LF and S100A7, in milk. This increase in the antimicrobial components may be useful in preventing mastitis.

Concentrations of antimicrobial components in milk of Japanese Black cows and their differences from dairy cows

The components of milk from beef cows remain to be elucidated. This study examined the differences in the antimicrobial components of milk between dairy and beef cows. Quarter milk was collected from both Japanese Black (beef type) and Holstein (dairy type) cows to compare the concentrations of antimicrobial components. The concentration of lingual antimicrobial peptide (LAP) was higher, whereas that of the other antimicrobial components (lactoferrin, S100A7, and S100A8) was lower in beef cows than in dairy cows. Overall, these results indicate that the differences in antimicrobial components between beef and dairy cows may be associated with the difference in the prevalence of mastitis between them.

Effects of topical application of resveratrol on tight junction barrier and antimicrobial compound production in lactating goat mammary glands

In mammary glands, the formation of less-permeable tight junctions (TJs) and the production of antimicrobial compounds like lactoferrin and defensins are important for preventing mastitis. Resveratrol, a polyphenol contained in red grapes, is known to protect mammary epithelial cells (MECs) from oxidative stress; however, oral administration of resveratrol causes a decrease in certain biological processes through conjugation and metabolic conversion. In this study, we determined the beneficial effects of resveratrol on TJs and antimicrobial compounds in cultured goat MECs by adding it to the medium, and in lactating goat mammary glands by topical application for percutaneous absorption. TJ barrier function was evaluated by transepithelial resistance and expression or localization pattern of claudins for culture model in vitro and by somatic cell count, Na+, albumin, and IgG in milk for topical application in vivo. Concentrations of antimicrobial compounds and cytokines were measured using ELISA. Activation of STAT3 was evaluated by Western blotting. Resveratrol strengthened TJ barrier function by upregulating claudin-3 in cultured MECs and topical application to udders reduced somatic cell count, Na+, albumin, and IgG in milk. Resveratrol increased β-defensin and S100A7 levels in cultured MECs and milk. In addition, resveratrol down-regulated cytokine production and STAT3 pathway. These findings suggest that the topical application of resveratrol to udders may be effective in preventing mastitis.

Concentrations of antimicrobial components in milk at dry off and postpartum and their relationships to new high somatic cell counts at quarter level in dairy cows

We investigated the antimicrobial components in cow milk at dry off and postpartum and their contribution in preventing new high SCC at quarter level. Milk samples from 72 quarters of 19 lactating cows were collected at last milking before dry off and at 7 d after parturition. Milk yield of each cow was recorded and SCC, IgG, IgA, lactoferrin, lingual antimicrobial peptide (LAP), and S100A7 concentrations in each quarter milk sample were measured. The postpartum milk yield was significantly higher than that at dry off. The IgG, IgA and lactoferrin concentrations in milk at dry off were significantly higher than those at postpartum, whereas the LAP concentration was lower. Quarters with SCC < 300 000 cells/ml at both dry off and postpartum were classified as persistent low SCC (PL) whereas those that rose above that same threshold postpartum were classified as new high SCC (NH). At dry off, IgG and LAP concentrations in milk were significantly higher in PL than in NH. These results suggest that high LAP concentrations during the dry period may contribute toward the prevention of new high SCC.

Effect of milking time on yield, composition, and antimicrobial components of milk in lactating goats

Various studies have attempted to improve the milk yield and composition in dairy animals. However, no study has examined the effects of milking at different times on milk yield and composition. Therefore, this study aimed to compare the yield, composition, and antimicrobial components of milk obtained from milking at different times in lactating goats. Eight goats were milked once daily at different times for three consecutive weeks (first week: 06:00 h; second week: 09:00 h; and third week: 12:00 h). The light ranged from 06:30 to 19:00 h. Milk and blood samples were collected once a day during milking time. Milking at 09:00 h resulted in a significantly higher milk yield than that obtained after milking at 06:00 and 12:00 h. Prolactin levels in plasma and the fat, Na+, β-defensin, and S100A7 (antimicrobial component) levels in milk were the lowest in the 09:00 h milking. These results indicate that milk yield, composition, and antimicrobial components can be affected by milking time, which may be related to the altered concentration of prolactin in the blood. These findings provide a rational basis for achieving maximal milk production with strong immunity by changing to a more effective milking time.

Immunolocalization of antibacterial peptide S100A7 in mastitis goat mammary gland and lipopolysaccharide induces the expression and secretion of S100A7 in goat mammary gland epithelial cells via TLR4/NFκB signal pathway

The antimicrobial peptide S100A7, with antimicrobial activities for a broad spectrum of bacteria, has attracted more and more attention for the prevention and treatment of mastitis. However, there is little information about the expression and regulation mechanism of S100A7 in mastitis goats. This study revealed that S100A7 was mainly expressed in the stratified squamous epithelium of teat skin and streak canal, and S100A7 was present weakly in the healthy goat alveolus yet densely in the mastitis goat collapsed alveolus. Goat mammary epithelial cells (MECs) were isolated and treated with 2.5, 5, 10 and 20 µg/mL lipopolysaccharide (LPS) respectively for a different time, S100A7 mRNA expression and protein secretion were upregulated significantly with LPS treatment for 3 h, and the secretion level of S100A7 descended after 48 h treatment for all of these four groups. Moreover, after treatment with LPS, the mRNA levels of Toll-like receptor 4 (TLR4) and MyD88 were up-regulated, and the phosphorylation of p65 was up-regulated markedly. However, adding TLR4 inhibitor TAK-242 or/and NF-κB inhibitor QNZ significantly suppressed the phosphorylation of p65, and then inhibited the expression and secretion of S100A7 induced by LPS treatment. In conclusion, LPS induced the expression and secretion of S100A7 in goat MECs via TLR4/NF-κB signaling pathway.

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.

Effects of oral administration of lipopolysaccharide derived from Pantoea agglomerans on innate immunity of mammary glands in dairy goats

This study aimed to evaluate the effect of orally administered lipopolysaccharide (LPS) derived from Pantoea agglomerans (LPSpa) on innate immune functions, including the concentrations of antimicrobial components and interleukin (IL)-10 in goat milk, for the prevention of goat mastitis. Twelve Tokara goats were divided into two groups of six goats. Goats in the LPSpa and control groups were orally administrated with 0.4 g/kg dextrin with or without 0.02 mg/kg LPSpa for 7 days (day 0-6), respectively. After treatment (i.e., day 7), 1 μg LPS from Escherichia coli O111 (LPSec) was infused into one side of the udder in both groups to induce mastitis. Milk from all sides of the udder, saliva, and feces were collected on days 0 and 7. After LPSec infusion into the udders, milk was collected from the infused side of the udder on days 8, 10, and 12. Milk yields and somatic cell counts were recorded during the examination period. The concentrations of immunoglobulin (Ig) A in saliva, feces, and milk and the concentrations of lactoferrin, goat β defensin-1 (GBD1), S100A7, and IL-10 in milk were measured. After LPSpa oral administration, the concentrations of GBD-1 and IL-10 in the milk of the LPSpa group were significantly higher on day 7 than those in the control group, and the concentration of IgA in the feces tended to be higher than that in the control group. After LPSec intramammary infusion, S100A7 concentration on day 12 was significantly lower in the LPSpa group than in the control group. These findings suggest that the oral administration of LPSpa may prevent mastitis by increasing the concentration of GBD1 in milk.

Potential effects of gingerol topical application on components of the innate immunity in lactating goat mammary glands

In the mammary glands, production of antimicrobial components and formation of less-permeable tight junctions (TJs) are important for safe milk production. Previously, we reported that local heat treatment of udders using disposable heating pad enhances the components of innate immunity in lactating goat mammary glands. Gingerol is a polyphenol present in ginger that can induce heat-like effects. However, oral administration of polyphenols causes a decrease in biological activity through conjugation and metabolic conversion. Here, we investigated the effects of gingerol on antimicrobial components and TJs by topically applying it to lactating goat udders. Gingerol application increased the somatic cell count, cathelicidin-2 concentration, and proportion of polymorphonuclear cells in the milk and interleukin-8 production. Moreover, gingerol treatment enhanced β-defensin-1 production in milk, cultured mammary epithelial cells, and cultured somatic cells. Contrastingly, gingerol treatment did not affect the concentrations of blood-derived components (Na+, albumin, and IgG) in the milk or the TJ barrier function of cultured mammary epithelial cells. These findings suggest that the topical application of gingerol, similar to local heat treatment, to udders enhances the components of innate immunity in mammary glands. These findings may be useful for the prevention of mastitis in milk-producing animals and, hence, safe and stable dairy production.

Valine Treatment Enhances Antimicrobial Component Production in Mammary Epithelial Cells and the Milk of Lactating Goats Without Influencing the Tight Junction Barrier

The production of antimicrobial components and the formation of less-permeable tight junctions (TJs) are important in the defense system of lactating mammary glands and for safe dairy production. Valine is a branched-chain amino acid that is actively consumed in the mammary glands and promotes the production of major milk components like β-casein; additionally, branched-chain amino acids stimulate antimicrobial component production in the intestines. Therefore, we hypothesized that valine strengthens the mammary gland defense system without influencing milk production. We investigated the effects of valine in vitro using cultured mammary epithelial cells (MECs) and in vivo using the mammary glands of lactating Tokara goats. Valine treatment at 4 mM increased the secretion of S100A7 and lactoferrin as well as the intracellular concentration of β-defensin 1 and cathelicidin 7 in cultured MECs. In addition, an intravenous injection of valine increased S100A7 levels in the milk of Tokara goats without influencing milk yield and milk components (i.e., fat, protein, lactose, and solids). In contrast, valine treatment did not affect TJ barrier function either in vitro or in vivo. These findings indicate that valine enhances antimicrobial component production without influencing milk production and TJ barrier function in lactating mammary glands; thus, valine contributes to safe dairy production.

Menthol application on healthy and inflamed goat udders changes antimicrobial components in milk

Mammary glands with mastitis are usually treated with antibiotics in combination with anti-inflammatory drug application on the udder skin. Menthol is an anti-inflammatory drug. The aim of the present study was to investigate the effect of surface application of menthol on goat udders on the production of antimicrobial components in milk. Goats (5 Shiba and 11 Tokara goats) were subjected to menthol application to the udder under both healthy and inflammatory conditions. An intramammary infusion of lipopolysaccharides was carried out to induce inflammatory conditions in the udder. Milk samples were collected to determine somatic cell count (SCC) and sodium ion (Na⁺ ), antimicrobial component and cytokine concentrations. In healthy udders, menthol application increased the concentration of antimicrobial components (S100A7 and S100A8), but not in the control. In the inflamed udder, antimicrobial component (lactoferrin, S100A7, and S100A8) and inflammatory cytokine (IL-1β) concentrations were higher in the menthol group than in the control group. These results suggest that menthol application on udders augments the antimicrobial component concentration in the mammary gland under both healthy and inflammatory conditions.

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.

Immune defenses of the mammary gland epithelium of dairy ruminants

The epithelium of the mammary gland (MG) fulfills three major functions: nutrition of progeny, transfer of immunity from mother to newborn, and its own defense against infection. The defense function of the epithelium requires the cooperation of mammary epithelial cells (MECs) with intraepithelial leucocytes, macrophages, DCs, and resident lymphocytes. The MG is characterized by the secretion of a large amount of a nutrient liquid in which certain bacteria can proliferate and reach a considerable bacterial load, which has conditioned how the udder reacts against bacterial invasions. This review presents how the mammary epithelium perceives bacteria, and how it responds to the main bacterial genera associated with mastitis. MECs are able to detect the presence of actively multiplying bacteria in the lumen of the gland: they express pattern recognition receptors (PRRs) that recognize microbe-associated molecular patterns (MAMPs) released by the growing bacteria. Interactions with intraepithelial leucocytes fine-tune MECs responses. Following the onset of inflammation, new interactions are established with lymphocytes and neutrophils recruited from the blood. The mammary epithelium also identifies and responds to antigens, which supposes an antigen-presenting capacity. Its responses can be manipulated with drugs, plant extracts, probiotics, and immune modifiers, in order to increase its defense capacities or reduce the damage related to inflammation. Numerous studies have established that the mammary epithelium is a genuine effector of both innate and adaptive immunity. However, knowledge gaps remain and newly available tools offer the prospect of exciting research to unravel and exploit the multiple capacities of this particular epithelium.

Sodium Acetate and Sodium Butyrate Differentially Upregulate Antimicrobial Component Production in Mammary Glands of Lactating Goats

Short-chain fatty acids activate antimicrobial component production in the intestine. However, their effects on mammary glands remain unclear. We investigated the effects of acetate and butyrate on antimicrobial component production in mammary epithelial cells (MECs) or leukocytes cultured in vitro and in mammary glands of lactating Tokara goats in vivo. Our results showed that butyrate enhanced the production of β-defensin-1 and S100A7 in MECs. Additionally, the infusion of butyrate into mammary glands through the teats enhanced β-defensin-1 and S100A7 concentrations in milk. The infusion of acetate also increased β-defensin-1 and S100A7 concentrations along with those of cathelicidin-2 and interleukin-8, which are produced by leukocytes. Furthermore, acetate promoted cathelicidin-2 and interleukin-8 secretion in leukocytes in vitro. These findings suggest that acetate and butyrate differentially upregulate antimicrobial component production in mammary glands, which could help to develop appropriate treatment for mastitis, thereby reducing economic losses and improving animal welfare in farming environments.

C-Type Natriuretic Peptide Regulates the Expression and Secretion of Antibacterial Peptide S100A7 in Goat Mammary Gland Through PKG/JNK/c-Jun Signaling Pathway

During infection, the infected tissue secretes a variety of endogenous peptides to resist further invasion of pathogens. Among these endogenous peptides, the natriuretic peptides and the antimicrobial peptides attracted the most attention. C-type natriuretic peptide (CNP) and its receptor natriuretic peptide receptor B (NPR-B) were members of the natriuretic peptide system. The antimicrobial peptide S100A7 plays an important role to resist infection of bacteria in mastitis. It is reported that the expression of S100A7 is regulated by an activator protein-1 (AP-1)-responsive promoter. As a subunit of AP-1, c-Jun is a downstream target of CNP/NPR-B signaling pathway. Therefore, it is a hypothesis that the CNP/NPR-B signaling pathway induces the expression and secretion of S100A7 in mammary glands to take part in local mammary gland innate immunity. To verify this hypothesis, goat mammary gland and isolated mammary epithelial cells (MECs) were used to explore the expression of CNP/NPR-B and their physiological roles in goat mammary gland. The results showed that goat mammary gland expressed NPR-B, but not CNP. The expression and secretion of S100A7 in goat MECs were obviously induced by CNP/NPR-B signaling pathway. After treatment with CNP, the cyclic guanosine monophosphate (cGMP) level in goat MECs was significantly upregulated. Along with the upregulation of cGMP level, the phosphorylation levels of c-Jun N-terminal kinase (JNK) and its target c-Jun were also increased gradually. KT5823 is a specific inhibitor for protein kinase G (PKG). KT5823 remarkably inhibited the phosphorylation of JNK and c-Jun induced by CNP. Correspondingly, KT5823 evidently inhibited the expression and secretion of S100A7 induced by CNP. On the other hand, the expression of NPR-B and S100A7 was upregulated in the mastitis goat mammary gland. But, there was no significant difference in expression of CNP between healthy and mastitis goat mammary gland tissues. The goat mastitis model was established in vitro using goat MECs treated by lipopolysaccharide (LPS). LPS treatment also could increase the expression of NPR-B and S100A7. In conclusion, goat mammary gland expressed NPR-B, indicating mammary gland was the target organ for natriuretic peptide system. Moreover, CNP, through NPR-B/JNK/c-Jun signaling pathway to regulate the expression and secretion of S100A7 in MECs, played an important role in mammary gland innate immunity.

Regression tree analysis of the relationship between the concentrations of antimicrobial components and the microbiota of normal milk from dairy cows

The purpose of this study was to determine the concentrations of antimicrobial components (immunoglobulin A (IgA), lactoferrin (LF), lingual antimicrobial peptide (LAP), and S100A7) in normal milk and their relation to host factors (Age, somatic cell count (SCC), days in milk, richness, and alpha diversity of the milk microbiota) in dairy cows using multivariate regression tree analyses, and to clarify how the milk microbiota is related to the obtained results. Thirty normal milk samples were collected from a commercial dairy farm in June 2020. The thresholds that predicted the concentration of each antimicrobial component in milk were obtained by regression tree analysis, and the beta-diversity of the milk microbiota composition between groups divided according to each threshold was compared by an analysis of similarities test. The IgA and LF concentrations were mainly predicted by the SCC (177,500 and 70,000 cells/ml, respectively), and the LAP and S100A7 concentrations were predicted by Age (29.667 and 40.3 months, respectively). No relationship was observed between the concentration of IgA, LAP, or S100A7 and the milk microbiota composition between the groups divided by the threshold for prediction, but the milk microbiota composition was significantly different between the groups divided by the threshold for predicting the LF concentration. Our results indicated that the LF concentration in normal milk may be associated with the milk microbiota composition.

Effect of 6‐n‐propyl‐2‐thiouracil or dexamethasone administration on the responses of antimicrobial components in goat milk to intramammary lipopolysaccharide infusion

Heat stress impacts the immune system of dairy animals by altering the hypothalamic-pituitary-adrenal axis and thyroid function, leading to conditions such as hypothyroidism and hypercortisolism. This study aimed to elucidate the effect of hypothyroidism and hypercortisolism on the response of mammary innate immune function to inflammation caused by Escherichia coli in dairy goats. To induce hypothyroidism and hypercortisolism, we administered 6-n-propyl-2-thiouracil (PTU; for 21 days) and dexamethasone (DEX; for 5 days), respectively, to six goats each; six goats without treatment were used as the control group. After treatment, lipopolysaccharide (LPS) from E. coli O111 was infused into the mammary gland. Somatic cell counts (SCC) and levels of lactoferrin (LF), S100A7, immunoglobulin A (IgA), and interleukin-8 (IL-8) in milk until 7 days after LPS infusion were measured. An increase in SCC after LPS infusion was inhibited in both PTU and DEX groups, and an increase in LF after LPS infusion was inhibited in PTU group, compared with that in the control group. The results of the present study suggest that the recruitment of neutrophils and LF production decreased under hypothyroidism or hypercortisolism, which may be one of the causes underlying increased incidence of mastitis in dairy animals under heat stress conditions.

Local Heat Treatment of Goat Udders Influences Innate Immune Functions in Mammary Glands

Heat stress and mastitis adversely affect milk production in dairy ruminants. Although the udder temperature is elevated in both conditions, the influence of this local temperature rise on milk production and immune function of ruminant mammary glands remains unclear. To address this question, we heated the mammary glands of goats by covering one half of the udder with a disposable heating pad for 24 h, the other uncovered half served as a control. Sixteen Tokara goats (1-5 parity) and three Shiba goats (1-2 parity) at the mid-lactation stage were individually housed, fed 0.6 kg of hay cubes and 0.2 kg of barley per day, and had free access to water and trace-mineralized salt blocks. Milk samples were collected every 6 h for 24 h after covering (n = 16), and deep mammary gland tissue areas were collected after 24 h (n = 5). The concentrations of antimicrobial components [lactoferrin, β-defensin-1, cathelicidin-2, cathelicidin-7, and immunoglobulin A (IgA)] in milk were measured by the enzyme-linked immunosorbent assay (ELISA). The localization of IgA was examined by immunohistochemistry. The mRNA expression and protein concentrations of C-C motif chemokine ligand-28 (CCL-28) and interleukin (IL)-8 in the mammary gland tissue were measured using quantitative polymerase chain reaction and ELISA, respectively. The somatic cell count in milk was significantly higher in the local heat-treatment group than in the control group after 12 h of treatment. The treatment group had significantly higher concentrations of cathelicidin-2 and IgA than the control group after 24 h of treatment. In addition, the number of IgA-positive cells in the mammary stromal region and the concentration of CCL-28 in the mammary glands were increased by local heat treatment. In conclusion, a local rise in udder temperature enhanced the innate immune function in mammary glands by increasing antimicrobial components.

Effect of oral administration of colostrum on inflammation in the udders of dairy cows suffering from mastitis

The present study was undertaken to examine whether oral administration of colostrum to mastitic cows reduced inflammation in the udder. Fifty milliliters of a colostrum whey product was administered orally daily for 3 days to cows suffering from mastitis. Milk was collected on day 0 and 7 of colostrum administration. For Experiment 1, milk from 11 udder quarters with high somatic cell counts (SCC) in four cows was used. SCC in milk decreased significantly after colostrum administration, whereas colostrum administration increased sodium and IgA concentrations significantly compared with those before administration. In Experiment 2, cows with clinical mastitis were divided into two groups, with and without colostrum administration, whereas all cows with subclinical mastitis were administered colostrum. Antibiotics were infused into the mammary gland from the first day of colostrum administration for 2–4 days. There was no significant decrease in SCC after colostrum administration in any group. However, udder firmness in both clinical mastitis groups was reduced after administration regardless of colostrum administration. IgA concentration in both clinical mastitis groups was significantly increased after colostrum administration compared to that before administration, although there was no significant difference between them. These results suggest the possibility that oral administration of colostrum attenuates inflammation of the mammary gland. Further studies are required to examine the effect of colostrum more precisely using cows with subclinical and chronic mastitis and longer duration of colostrum administration.

Bile salts regulate zinc uptake and capsule synthesis in a mastitis-associated extraintestinal pathogenic Escherichia coli strain

Extraintestinal pathogenic Escherichia coli (ExPEC) are major causes of urinary and bloodstream infections. ExPEC reservoirs are not completely understood. Some mastitis-associated E. coli (MAEC) strains carry genes associated with ExPEC virulence, including metal scavenging, immune avoidance, and host attachment functions. In this study, we investigated the role of the high-affinity zinc uptake (znuABC) system in the MAEC strain M12. Elimination of znuABC moderately decreased fitness during mouse mammary gland infections. The ΔznuABC mutant strain exhibited an unexpected growth delay in the presence of bile salts, which was alleviated by the addition of excess zinc. We isolated ΔznuABC mutant suppressor mutants with improved growth of in bile salts, several of which no longer produced the K96 capsule made by strain M12. Addition of bile salts also reduced capsule production by strain M12 and ExPEC strain CP9, suggesting that capsule synthesis may be detrimental when bile salts are present. To better understand the role of the capsule, we compared the virulence of mastitis strain M12 with its unencapsulated ΔkpsCS mutant in two models of ExPEC disease. The wild type strain successfully colonized mouse bladders and kidneys and was highly virulent in intraperitoneal infections. Conversely, the ΔkpsCS mutant was unable to colonize kidneys and was unable to cause sepsis. These results demonstrate that some MAEC may be capable of causing human ExPEC illness. Virulence of strain M12 in these infections is dependent on its capsule. However, capsule may interfere with zinc homeostasis in the presence of bile salts while in the digestive tract.

Effect of temporary cessation of milking on the innate immune components in goat milk

Temporary cessation of milking is widely used during the dry period of dairy cows. Temporary cessation of milking induces an increase in the somatic cell count (SCC) and level of several inflammatory components of milk, which is believed to be a local adaptation and defense mechanism of the mammary gland. In Japan, temporary cessation of milking combined with antibiotic administration is widely used to treat mastitis. The present study aimed to elucidate the role of the innate immune system during temporary cessation of milking in a goat model by investigating the concentration of several innate immune components in milk during and around the temporary cessation. In experiment 1, 6 goats were subjected to cessation of milking for 3 d in both udder halves, whereas in experiment 2, 6 other goats were subjected to cessation of milking for 3 d only in 1 udder half. In experiment 1, the milk yield was lower on d 5 and 6, whereas the mean SCC was higher on d 5 compared with d 0 before temporary milking cessation. The concentrations of goat DEFB1, S100A7, cathelicidin-2 and 7 (CATHL-2 and 7), IgA, and lactoferrin were increased after temporary cessation of milking. In experiment 2, the milk yield was lower between d 5 and 7, whereas the mean SCC was higher between d 4 and 7 compared with d 0. The concentrations of CATHL-2, IgA, and lactoferrin were increased after temporary cessation of milking only in the udder half subjected to milking cessation. These results suggest that temporary cessation of milking increase the SCC and concentration of several innate immune components in milk without infection, which may contribute to mastitis treatment.

Concentration patterns of antibacterial factors and immunoglobulin A antibody in foremilk fractions of healthy cows

Antibacterial factors act as innate immune components, which respond as soon as bacteria enter a living organism. To prevent and treat mastitis in cattle, understanding the concentrations of these substances inside the udder is important; however, they remain to be studied. In this investigation, the concentration of lingual antimicrobial peptide (LAP), S100 protein (S100A7), lactoferrin (LF), and immunoglobulin antibody were measured in the different fractions of foremilk. Lactating Holstein cows were examined, and 10 foremilk fractions were obtained from sequential samples up to 150 ml. The LAP concentrations in milk samples increased until 25 ml. The LF concentrations increased up to the 10 ml fraction, then stabilized at low level after the 50 ml fraction. For S100A7, some fractions had significantly higher (p < .05) concentrations than the 5 or 10 ml fractions. The IgA antibody concentration increased up to the 5 ml fraction, then after 50 ml fraction showed relatively low concentrations. This investigation determined the concentration patterns of LAP, LF, S100A7, and IgA antibody secreted in milk inside the udders of healthy lactating cows as baseline data. These distinct concentration patterns might indicate various protective responses.

Effects of oral administration of colostrum whey in peripartum goat on antimicrobial peptides in postpartum milk

The present study was conducted to examine whether colostrum supplementation in peripartum goats increases the antimicrobial peptides in their milk. Goats were orally administered 2 ml of colostrum whey products (colostrum group) or water (control group) daily, from 2 weeks before until 2 weeks after kidding. Body weights of mothers and kids were measured. Blood, milk, and fecal samples were collected from the mothers, and blood samples were collected from the kids. Concentrations of milk antimicrobial peptides (beta-defensin, cathelicidin, lactoferrin, S100A7, lactoperoxidase, and immunoglobulin A [IgA]) were determined. IgA and nutritional parameters (glucose, total cholesterol, triglyceride, ketone bodies, and non-esterified fatty acids) were also determined in the blood of mothers and kids. Milk IgA and lactoferrin concentrations were higher in the colostrum group than in the control group. Conversely, lower milk concentrations of S100A7 were observed in the colostrum group than that in the control group. Plasma IgA concentrations were higher for kids from the colostrum group than for those from the control group. These results suggest that oral administration of colostrum in pregnant goats increases IgA concentration in postpartum milk, which can subsequently improve the health of their kids.

Seasonal variations in the concentration of antimicrobial components in milk of dairy cows

The incidence of bovine mastitis and the bulk milk somatic cell count (BMSCC) are influenced by season, which may be associated with innate immune functions, including antimicrobial components in mammary glands. Therefore, the present study was conducted to examine the effect of season on antimicrobial components in milk. Rectal temperature and plasma cortisol, thyroxine, and derivatives of reactive oxygen metabolites (d-ROMs) were measured as stress parameters. Concentrations of lactoferrin (LF), lingual antimicrobial peptide (LAP), psoriasin (S100A7), and Immunoglobulin A (IgA) in milk were measured as indicators of innate immune function. LF and LAP concentrations were significantly lower in summer than in winter and spring, respectively, whereas the concentration of S100A7 was significantly lower in winter than in spring and autumn. The rectal temperature was significantly higher in summer than in other seasons, whereas plasma cortisol, thyroxine, and d-ROMs did not exhibit any seasonal variation. In conclusion, even though stress parameters were not changed, the concentration of antimicrobial components, such as LF and LAP, decreased in summer, which may explain the frequent occurrence of mastitis during this season.

Short communication: Production of antimicrobial peptide S100A8 in the goat mammary gland and effect of intramammary infusion of lipopolysaccharide on S100A8 concentration in milk

This study aimed to determine the production site of antimicrobial peptide S100A8 in the goat mammary gland and changes in its concentration in milk after lipopolysaccharide (LPS) challenge. Sixteen Tokara goats were used in this study for mammary gland tissue, blood leukocyte, and milk somatic cell collection and LPS challenge. The mRNA expression and protein localization of S100A8 in the mammary gland parenchyma and teat, blood leukocytes, and milk somatic cells were examined by reverse-transcription PCR and immunohistochemistry. The S100A8 concentration in milk was measured at 0 to 144 h after intramammary challenge of LPS by enzyme immunoassay. The mRNA of S100A8 was expressed in the parenchyma and teat, leukocytes isolated from blood, and milk somatic cells. Antimicrobial peptide S100A8 was immunolocalized in the outermost layer of the teat skin of udders with and without LPS infusion, whereas in the mammary gland it was immunolocalized only in the leukocytes infiltrated in the alveoli after LPS infusion. Antimicrobial peptide S100A8 was also immunolocalized in the blood and milk leukocytes. The number of S100A8-positive cells in milk was higher than that in blood. The concentration of S100A8 in milk increased significantly at 72 h after intramammary infusion of LPS. These results suggest that S100A8 is produced in the leukocytes and that its secretion into milk is affected by LPS stimulation.

Effect of intramammary lipopolysaccharide infusion on milk pH of uninfused udder in goat

The change in milk composition in response to intramammary infusion of Escherichia coli lipopolysaccharide (LPS) was investigated. Four clinically healthy goats were infused with LPS (100 µg) by intramammary administration to the left udder. Clinical manifestations (rectal temperature and physical activity), selected blood parameters (pH and white blood cell count) and milk compositions (somatic cell count and pH) were evaluated at 0 hr (just before challenge) and at multiple time points over the first 24 hr post-challenge. After intramammary LPS challenge, the pH of milk from both udders increased. Thus, this study revealed that LPS-induced mastitis in goat can result in increased pH in milk from the unchallenged (contralateral) udder.

Cellular and soluble components decrease the viable pathogen counts in milk from dairy cows with subclinical mastitis

The present study was undertaken to clarify the factors that reduce the viable pathogen count in milk collected from the udders of subclinical mastitic cows during preservation. Milk was centrifuged to divide somatic cells (cellular components, precipitates) and antimicrobial peptides (soluble components, supernatants without fat layer); each fraction was cultured with bacteria, and the number of viable bacteria was assessed prior to and after culture. In 28.8% of milk samples, we noted no viable bacteria immediately after collection; this value increased significantly after a 5-hr incubation of milk with cellular components but not with soluble components (48.1 and 28.8%, respectively). After culture with cellular components, the numbers of bacteria (excluding Staphylococcus aureus and Streptococcus uberis) and yeast decreased dramatically, although the differences were not statistically significant. After cultivation with soluble components, only yeasts showed a tendency toward decreased mean viability, whereas the mean bacterial counts of S. uberis and T. pyogenes tended to increase after 5-hr preservation with soluble components. These results suggest that most pathogens in high somatic cell count (SCC) milk decreased during preservation at 15 to 25°C, due to both the cellular components and antimicrobial components in the milk. Particularly, the cellular components more potently reduced bacterial counts during preservation.

Effect of steroid hormones on the innate immune response induced by Staphylococcus aureus in the goat mammary gland

The objective of this study was to compare the dynamics of innate immune components after intramammary infusion of Staphylococcus aureus (SA) under conditions of high oestrogen and high progesterone in goats. In one group ("E-group"), controlled internal drug release (CIDR) devices were inserted intravaginally from days -11 to -4. Prostaglandin F2α was administered immediately after removal of the CIDR device at day -3, and then oestradiol benzoate (E) was injected intramuscularly once a day from days -2 to 3. Heat-inactivated SA was then administered via intramammary infusion to the left udder at day 0, whilst only saline was infused to the right udder as a control. In a second group ("P-group"), CIDR devices were inserted intravaginally from days -3 to 7 and SA was infused at day 0 in the same way as in the E-group. The milk yield and the concentration of innate immune components (somatic cell count (SCC), lactoferrin (LF), S100A7 and goat ß-defensin 1 (GBD-1)) in the milk were measured. Milk yield decreased drastically in both SA and control udders in the E-group, whereas the P-group exhibited increased milk yield in both SA and control udders. SCC increased after SA infusion in both E- and P-groups, although it was higher in the E-group than in the P-group. There was no significant change in LF concentration in the E-group, but a decrease was observed in the P-group. Concentrations of S100A and GBD-1 were significantly increased after SA infusion in the E-group but not in the P-group. These results suggest that E enhances the innate immune response induced by SA in the goat mammary gland. This effect may be due to the reduction in milk yield and upregulation of innate immune components.

Change in viable bacterial count during preservation of milk derived from dairy cows with subclinical mastitis and its relationship with antimicrobial components in milk

The objectives of the present study were to investigate the change in the number of viable pathogens during preservation of milk obtained from cows with subclinical mastitis and the association between the decreasing ratio of viable bacteria during preservation and the somatic cell count (SCC) and the values of lingual antimicrobial peptide (LAP), lactoferrin (LF) and lactoperoxidase (LPO). After preservation of milk at room temperature for 0, 0.5, 1, 2, 3, 4 and 5 hr, the bacterial colonies in the milk were counted to determine the number of colony forming units (CFUs). Fresh skim milk was used to determine the values of LAP, LPO and LF. Bacteria were not detected in 19.4% of milk samples, and this percentage increased up to 30% after 5 hr of preservation. The number of Staphylococcus aureus and Streptococcus uberis in milk did not change significantly during the 5-hr incubation, whereas significant decreases were observed in the number of coliforms, coagulase-negative staphylococci, yeasts and Corynebacterium bovis. High SCC significantly decreased CFUs of S. aureus and yeast after preservation of milk for 4 to 5 hr. High LF concentration in milk was associated with decrease in CFU of S. aureus during 4-hr preservation. These results suggest that the viable counts of some pathogens in milk decreased during preservation at room temperature after collection, which may be attributed to the leukocytes and antimicrobial components present in milk.