Effect of 2% meloxicam injection in Holstein dairy cows on acute clinical mastitis without systemic symptoms.

This study aimed the efficacy of meloxicam (MX) in treating acute clinical mastitis (ACM) without systemic symptoms in Holstein cows by studying improvement in udder pain, changes in prostaglandin E2(PGE2) and bradykinin (BK) levels in the milk, and milk yield (MY) after healing. Forty-two cows with ACM were randomly assigned to the MX treatment group (T group; n=21) and the control group (C group; n=21). At onset of illness (day 0), the T group received a 0.5 mg/kg subcutaneous (SC) injection of MX whereas the C group received 15 mL SC of saline solution as a placebo. Udder tenderness (UT) was measured, and milk samples were collected on days 0-3. There was little change in the MY of the T group before and after healing, whereas MY in the C group was significantly lower than after healing. UT on day 3 in the T group was significantly lower than that in the C group. PGE2 levels significantly decreased from day 0 to day 3 in both groups. A significant negative correlation between PGE2 and linear score was observed on day 1 in the T group, but not in the C group. In ACM without systemic symptoms, the administration MX may be useful for restoring MY and reducing udder pain after healing.

Association between somatic cell count or morbidity of chronic subclinical mastitis and longevity in dairy herds in Eastern Hokkaido, Japan: a cross-sectional study.

An epidemiological analysis was conducted on production records in Hokkaido, Japan, to investigate the potential association between improved milk quality and longevity outcomes. The study found significant variations in herd somatic cell count levels and chronic subclinical mastitis morbidity based on geographical area and herd size. The analysis also revealed a positive correlation between herd somatic cell count and chronic subclinical mastitis morbidity. Although the hypothesis of a causal link between milk quality and longevity was examined, no such association was found. However, intensive assistance for identified high-risk areas and farms is expected to enhance overall milk quality.

Predicting an increased risk of severe clinical mastitis and economic loss using a threshold value of bovine leukemia virus proviral load.

OBJECTIVE: To establish a threshold value of bovine leukemia virus (BLV) proviral load (PVL) to identify increased risk of severe clinical mastitis, and to examine the prognosis and economic loss of clinical mastitis based on the newly established PVL cut-off value. ANIMALS: 97 lactating Holstein cows with clinical mastitis. METHODS: Blood and milk samples were collected aseptically from each cow. Youden index was used for receiver-operating characteristic curve analysis with the severity rate of clinical mastitis as the dependent variable and PVL as an independent variable. PVL cut-off value was used as a criterion to compare the severity rate of clinical mastitis, percentage of cows with and without systemic treatments, number of treatments, cost of treatment, and prognosis. RESULTS: PVL cut-off value was 17.8 copies/10 ng DNA for the dependent variable MILD vs SEVERE. The severity rate of clinical mastitis, percentage of cows given systemic treatments, and technical fees for medical treatment were significantly higher in the group above the PVL cut-off value than in the group below the PVL cut-off value and the negative group. Number of treatments was significantly higher in the group above the cut-off value than in the group below the cut-off value. There was no significant difference in prognosis after mastitis among the 3 groups. CLINICAL RELEVANCE: These results suggested that PVL cut-off value of 17.8 copies/10 ng DNA was a useful threshold for increased economic losses in BLV-infected cows; it may also serve as a new standard value for the detection and culling of BLV-infected cows in Japan.

Effects of Intramammary Antimicrobial Treatment on the Milk Microbiota Composition in Mild Clinical Bovine Mastitis Caused by Gram-Positive Bacteria.

The purpose of this study was to clarify the effects of antimicrobial treatment for mild mastitis caused by Gram-positive bacteria on the milk microbiota in dairy cattle. Sixteen quarters of sixteen cows with mild clinical mastitis from the same herd were included in the study. On the day of onset (day 0), the cows were randomly allocated to a no-treatment (NT; n = 10) group or an intramammary antimicrobial treatment (AMT) group that received AMT starting on day 0 (AMT-AMT group; n = 6). The next day (day 1), the cows in the NT group were randomly allocated into an NT group (NT-NT group; n = 3) that received no treatment or an AMT group that received AMT starting on day 1 (NT-AMT group; n = 7). Milk samples were collected on days 0, 1, 3 and 7, and the milk microbiota of each sample was comprehensively analyzed via 16S rRNA gene amplicon sequencing of the milk DNA. During the treatment period, the milk microbiota of the NT-NT group did not change, but those of the NT-AMT and AMT-AMT groups changed significantly on days three and seven. Thus, the use of antimicrobials for mild mastitis caused by Gram-positive bacteria changes the milk microbiota composition.

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

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

Effects of ozonized glycerin on inflammation of mammary glands induced by intramammary lipopolysaccharide infusion in goats.

Although ozone shows antimicrobial activity against mastitis-causing pathogens in ruminants, its anti-inflammatory effect on mammary glands remains unclear. The aim of this study was to examine the anti-inflammatory effects of ozonized glycerin (OG) on experimentally induced inflammation in the mammary glands of six Shiba and two Tokara lactating goats. We infused 1 µg lipopolysaccharide (LPS) into all udders on day -1. On day 0, post LPS infusion, OG (ozone group), and glycerin (control group) were infused into the right and left sides of the udders, respectively. Milk samples were collected once daily from days -1 to 7. The somatic cell count and lactoperoxidase (LPO) activity, along with the interleukin-1ß (IL-1ß), tumor necrosis factor-α, IL-8, IL-10, lactoferrin, and sodium ion concentrations in milk were measured. IL-8, IL-10, and lactoferrin levels after LPS infusion in the ozone group were significantly lower than those in the control group, and the LPO activity tended to be lower than that observed in the control group. This study showed that OG has anti-inflammatory potential against LPS-induced inflammation in the mammary glands.

Effect of glycyrrhizin administration followed by symptom-based antimicrobial selection therapy on antimicrobial use in clinical mastitis without systemic symptoms.

In bovine mastitis, antimicrobial treatment is often initiated before the causative organism is identified a problem in the prudent use of antimicrobials. In this study, we aimed to reduce the total amount of antimicrobials used in mastitis treatment by administering glycyrrhizin, an anti-inflammatory drug, instead of antimicrobials at the onset of clinical mastitis without systemic symptoms, followed by symptom-based antimicrobial selection therapy (ST), to examine the effect of this treatment strategy on treatment outcomes and antimicrobial use. Comparisons between cases that received antimicrobial treatment starting from the day of diagnosis (blanket antibiotic therapy [BT] group: 33 cases) and cases that received ST starting from the day after the diagnosis (ST group: 57 cases) revealed no difference in the cure rate, milk withholding period, or recurrence rate. However, the ST group had a significantly lower amount of antimicrobials than the BT group. Additionally, a single administration of glycyrrhizin before ST significantly relieved the udder symptoms and reduced the antimicrobial amount when compared with cases without glycyrrhizin administration. Thus, a single administration of glycyrrhizin followed by ST can reduce the total antimicrobial use.

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.

Examination of the microbiota of normal cow milk using MinIONTM nanopore sequencing.

The aim of this study was to evaluate the microbiota of normal milk in dairy cows and their relationship with host factors, such as the age of the cow (Age), somatic cell counts in milk (SCCs), and days in milk (DIM). We investigated 48 milk samples from 22 cows with no systemic or local clinical signs using MinIONTM nanopore sequencing for a 16S rRNA gene amplicon. Bacterial richness was positively correlated with the DIM (P=0.043), and both the Shannon-Wiener Index and Simpson's Index, which are metrics of alpha-diversity, were also significantly positively correlated with the SCC (P<0.001). The composition ratios of both Actinobacteria at the phylum level and Kocuria spp. at the genus level in the milk microbiota were significantly correlated with the SCC (P<0.001 and P<0.001, respectively). In the beta-diversity test, the one-way analysis of similarities test showed a significant difference (P=0.0051) between the low- and high-SCC groups. This study clarified that the composition of the normal milk microbiota in this herd was related to the SCC. It also raised the possibility of variations in bacterial genera in the normal milk microbiota between the low- and high-SCC groups. However, to clarify the actual condition of the milk microbiota and to elucidate the relationship with the SCC, it is necessary to perform further analyses taking into account not only the relative abundance, but also the absolute abundance of microbes.

Immune response during the onset of coliform mastitis in dairy cows vaccinated with STARTVAC®.

The immune response during the onset of coliform mastitis in vaccinated cows was investigated by measuring lactoferrin (LF), interleukin-8 (IL-8), and interleukin-1ß (IL-1ß) concentrations and somatic cell counts in 28 milk samples at the onset of acute coliform mastitis (ACM) and 73 milk samples at the onset of peracute coliform mastitis (PCM). Vaccinated ACM, unvaccinated ACM, and vaccinated PCM showed significantly higher values for LF and IL-1ß levels than unvaccinated PCM (p < .01). The IL-8 concentration was lower in vaccinated PCM than in unvaccinated PCM (p < .05). There was no significant difference in somatic cell counts for each parameter. There were no significant differences in the parameters between vaccinated and unvaccinated ACM cows, or vaccinated ACM and PCM cows. From the above results, it is suggested that mastitis vaccination improved the early immune response, particularly at the onset of PCM, and played a large role in host defense against the initial infection.

A case study of improving milking cow performance and milking system performance with using a flow simulator.

Efforts to improve dairy performance have been focused on increasing milk productivity of cows through improved feeding systems and genetic potential. However, methods for evaluating milking system performance based on milk productivity have not yet been established. Milking system performance was evaluated by measuring the claw vacuum at five flow rates (1.9-8.7 kg/min) produced using a flow simulator for a single eight-swing milking parlor with a high-line system. Based on these results, a double eight-parallel milking parlor with a low-line system was installed and tested. Farmers can take data obtained from evaluations of milking system performance into account for future management decisions, such as renewing the milking system. By renewing the milking system, average milking productivity, somatic cell linear score (LS) of bulk milk, and LS of each cow were significantly improved in the year after installing the new system (p < .01). In addition to checking conventional milking systems, this novel diagnostic method using a flow simulator can be used for checking new installations and also for proposing renovations.

Changes in ionized calcium concentration in the blood of dairy cows with peracute coliform mastitis.

We determined the clinical signs and blood ionized calcium (iCa) levels in dairy cows with peracute coliform mastitis (PCM). The clinical scores at the onset of the disease (day 0) and on day 2 and subsequent days were significantly (P<0.01) higher than those of healthy cows. We found a positive correlation (r=0.894, P<0.01) between iCa and total calcium (TCa) concentrations in the blood of healthy cows ; however there was no correlation from day 0 to day 3 in the blood of PCM cows. Multiple regression analysis revealed that the concentration of iCa was correlated with rectal temperature, hematocrit value, platelet count, and albumin level of PCM cows at the onset of disease (r= -0.804, r=0.6576, r=0.6182, r=0.284, P<0.01, respectively). There was no correlation between the TCa concentration and these parameters for PCM cows at day 0. Low blood iCa concentration at day 0 for PCM cows was related to symptoms of septic shock involving hypothermia, activation of the blood coagulation system, and dehydration.

Analysis of results from 21 years of milking system inspections in Japanese dairy farms.

To prevent mastitis caused by inappropriate milking systems, inspection of the system, and maintenance of optimal function are crucial. This study aimed to clarify the problems with milking systems in Japan by analyzing the results of milking system inspections over the past 21 years. A total of 190 dairy farms (358 systems; 153 high-line systems, 205 low-line systems) were inspected for the checkpoints of problems originating from installation (PI) or problems originating from insufficient maintenance (PIM). Results were divided into initial and periodic inspections, then analyzed by year of inspection or years elapsed since equipment installation. With increasing years, inadequacy of milk piping and regulator maintenance tended to increase for high-line systems. On the other hand, defects in milking units tended to increase for low-line systems. This difference was attributed to the structures of these milking systems. The present study revealed potential problem areas in high- and low-line milking systems from recent years. To maintain normal functioning in milking systems, the frequency and content of inspections as currently being conducted need to be reviewed.

Association between bovine leukemia virus proviral load and severity of clinical mastitis.

The purpose of this study was to clarify the effect of Bovine leukemia virus (BLV) infection on natural immunity in the bovine mammary gland and on the severity of clinical mastitis. We classified milk samples from clinical mastitic cows into BLV-positive (n=76) and BLV-negative (n=12). BLV-positive cows were further divided into cows with High BLV proviral load (H-PVL) (n=23) and Low BLV proviral load (L-PVL) (n=53). Severity of clinical mastitis was classified as MILD, MODERATE, or SEVERE. Multiple logistic regression analysis was performed on the host factors and environmental factors with severity of clinical mastitis as the objective variable. BLV proviral load (PVL) and season at onset of mastitis showed significant correlation with the severity of clinical mastitis. Binary logistic regression analysis was performed on natural immunity factors lactoferrin and lingual antimicrobial peptide (LAP) concentration in milk, with PVL as the objective variable. Of these natural immunity factors, LAP concentration in milk showed significant correlation with PVL. The results of the present study suggested that PVL and season are associated with severity of clinical mastitis, and that the immune function in the mammary gland is decreased in cows with H-PVL compared to that in cows with L-PVL.

Influence of oxytetracycline susceptibility as a first-line antibiotic on the clinical outcome in dairy cattle with acute Escherichia coli mastitis.

The purpose of this study was to clarify the therapeutic effects of oxytetracycline (OTC) as a first-line antibiotic in cattle with acute Escherichia coli mastitis and systemic signs. Drug susceptibility was determined by the minimum inhibitory concentration (MIC) of E. coli isolated from cows with acute E. coli mastitis (n=38). Cattle were divided into OTC-susceptible (S, n=30) and OTC-resistant (R, n=8) groups. They were further subdivided according to susceptibility to the antibiotic used as a second treatment, into susceptible-susceptible (SS, n=30), resistant-susceptible (RS, n=5), and resistant-resistant (RR, n=3) groups. Clinical signs on the day after initial treatment were compared between S and R groups as short-term indicators of treatment effects. The 28-day survival rate of cattle was then compared among SS, RS, and RR groups as a long-term indicator of treatment effects. There were no differences in clinical signs between S and R groups on the day after the first dose, but the 28-day survival rate was significantly greater in the SS group than in the RR group (P=0.04). The results demonstrated that an effective drug is essential for first-line treatment of acute coliform mastitis. However, anticipating the effectiveness of a first-line antibiotic based on clinical symptoms at the second day of treatment is impossible. It is important to build a picture of drug resistance trends in cattle herds for empirical selection of antibiotics to be administered.

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.

Randomized clinical trial to evaluate the effectiveness of enrofloxacin as a second-line antibiotic for treatment of acute Escherichia coli mastitis.

The objective of the present study was to evaluate the effectiveness of enrofloxacin (ERFX) as a second-line antibiotic for treatment of acute Escherichia coli (E. coli) mastitis. Forty-two cows with naturally occurring acute E. coli mastitis were enrolled. On the first day of treatment (day 0), empirically selected antibiotics (oxytetracycline: n = 32, kanamycin: n = 10) were administered. Although systemic signs improved in 10 cows (first-line group), the signs remained unchanged or worsened in 32 cows on day 1, including two cows that were found dead. The 30 surviving cows were randomly assigned to second-line groups constituting an ERFX group (n = 19) or a control group (n = 11) that was treated with other antibiotics. Response to each treatment was evaluated by measuring clinical signs from day 0 to day 3, subsequent quarter milk recovery, and the 60-day survival rate. Appetite on day 3 was significantly better in the ERFX group compared to the control group. No significant differences were observed in the 60-day survival rate or the subsequent milk recovery between the ERFX group and the control group. Thus, the use of ERFX as a second-line antibiotic for the treatment of acute E. coli mastitis could induce a rapid appetite recovery.

Blood ionized calcium levels and acute-phase blood glucose kinetics in goats after intramammary infusion of lipopolysaccharide.

The aim of this study was to determine the blood ionized calcium (Ca) levels and acute-phase blood glucose kinetics in goats with mastitis induced by an intramammary challenge of lipopolysaccharide (LPS). Five goats were subjected to intramammary challenge of either LPS (10 µg) or saline (control). Some clinical manifestations (rectal temperature, pulse rate, respiration rate, ruminal motility, physical activity, and dehydration) were observed, and blood was collected for the measurement of several parameters [ionized and total Ca levels, blood glucose level, pH, and white blood count (WBC)] at 0 (just before challenge), 1-4, 6, 8, 12 and 24 hr post-challenge in both the LPS and control phases. Milk was collected at 0 (just before challenge), 4, 8, 12 and 24 hr post-challenge to measure the somatic cell count (SCC) and N-acetyl-beta-D-glucosaminidase (NAGase) activity. In the LPS phase, increased rectal temperature, significantly decreased ionized Ca and total Ca levels and WBCs were observed compared with those at 0 hr, although there were no differences in all parameters between phases. LPS infusion significantly increased SCCs in milk and NAGase activity. The present results demonstrated that, during the acute phase of mastitis induced by intramammary challenge by LPS at a concentration sufficient to cause general symptoms in goats, a decreased blood ionized Ca level occurs, but not hypoglycemia.

Transrectal guidance of the ovaries reduces operative time during bovine laparoscopic ovariectomy.

The main objective of this study was to evaluate the effects of transrectal guidance of the ovaries by an assistant on operative time during bovine laparoscopic ovariectomy. Twenty four clinically healthy Holstein dairy cows were divided randomly into two groups. In the transrectal guidance group, an assistant grasped the ovaries via the transrectal route and pulled them to a position where they could be visualized with a camera. On the other hand, the control group was operated without guidance. The time required to remove both ovaries in the guidance group was shorter than that in the control group (P<0.01). We concluded that laparoscopic ovariectomy with transrectal guidance of the ovaries can substantially shorten operative time, thereby greatly contributing to animal welfare and to reducing the burden on the operator.

Control of Pseudomonas mastitis on a large dairy farm by using slightly acidic electrolyzed water.

The disinfection effect of slightly acidic electrolyzed water (SAEW) use in a farm where Pseudomonas mastitis has spread was evaluated. Despite the application of antibiotic therapy and complete cessation of milking infected quarters, numerous new and recurrent Pseudomonas aeruginosa clinical mastitis infections (5.8-7.1% of clinical mastitis cases) occurred on the farm from 2003 to 2005. Procedural changes and equipment modifications did not improve environmental contamination or the incidence of Pseudomonas mastitis. To more thoroughly decontaminate the milking parlor, an SAEW system was installed in 2006. All milking equipment and the parlor environment were sterilized with SAEW (pH 5-6.5, available chlorine 12 parts per million) before and during milking time. After adopting the SAEW system, the incidence of clinical and subclinical Pseudomonas mastitis cases decreased significantly (P < 0.0001) and disappeared. These findings suggest that SAEW effectively reduced the incidence of mastitis in a herd contaminated by Pseudomonas species. This is the first report to demonstrate the effectiveness of disinfection by SAEW against mastitis pathogens in the environment.