Efficacy of two iodine teat dips based on reduction of naturally occurring new intramammary infections

The efficacy of 2 teat dips, product 1 (Della Care with 5 to 8 ppm of free iodine, used as a positive control) and product 2 (New Della Care with 12 to 16 ppm of free iodine), was compared using a natural exposure trial on dairy cattle. The trial was based on National Mastitis Council guidelines and performed over 9 mo. Both teat dips contained 0.25% iodine. Product 2 reduced the infection rate 57.6% for major pathogens and 53.7% for minor pathogens, compared with the positive control. Product 2 gave highly significant reductions for Staphylococcus aureus, coagulase-negative staphylococci, and Corynebacterium bovis. Teat skin, teat ends, and teat hyperkeratosis were evaluated during trial. No significant difference in teat condition was observed between these 2 products.     

Noninferiority trial on the efficacy of premilking teat disinfectant against naturally occurring new intramammary infections using a novel 2-step diagnostic process

The objective of the study was to evaluate premilking teat disinfectant efficacy with the use of a novel diagnostic protocol against a positive control. The evaluation of efficacy was based on establishing noninferiority of a new premilking teat disinfectant compared with an existing premilking teat disinfectant. Approximately 200 cows were randomly allocated to 1 of 2 groups. Study personnel were blinded as to cow allocation and identification of the premilking disinfectants. Quarters were disinfected using a dip cup before milking with either the control or experimental product. The disinfectant was left on the teat for approximately 30 s before being wiped off in preparation for milking. Quarter-level bacteriological infection status was established at the beginning of the study and quarter milk samples were collected biweekly thereafter. Bacteriological analyses were performed only when somatic cell counts in milk samples crossed a parity-specific threshold. Poisson regression models were used to analyze data. The difference in the rate of new intramammary infections was small and the upper bound of the 95% confidence interval of the rate difference was smaller than a predefined noninferiority limit. Based on the observed difference in new intramammary infections rate between the experimental and control product, it was concluded that the experimental disinfectant was not inferior compared with the positive control. The protocol used in this study proposes a valid and economically attractive methodology to evaluate the efficacy of teat disinfectants relative to a positive control.     

Effectiveness of an internal teat seal in the prevention of new intramammary infections during the dry and early-lactation periods in dairy cows when used with a dry cow intramammary antibiotic

The objectives of this study were to determine the effect of infusion with an internal teat seal at dry off, when used as an adjunct to long-acting antibiotic infusion at dry off, on the risk for acquiring a new intramammary infection (IMI) during the dry period, prevalence of IMI and linear score (LS) after calving, and risk for experiencing a clinical mastitis event between dry off and 60 DIM. A total of 437 cows from 2 dairy herds, with no clinical mastitis and 4 functional quarters, were enrolled at dry off. Prior to the final milking, all quarters were sampled for bacteriological culture and SCC analysis. After milking, all 4 quarters were infused with a commercially available long-acting dry cow antibiotic. Two contralateral quarters were then infused with an internal teat seal (Orbeseal, Pfizer Animal Health, New York). Following calving the teat seal was stripped out at first milking. Duplicate milk samples were collected between 1 to 3 DIM and again between 6 to 8 DIM for culture and SCC analysis. Quarters treated with Orbeseal had significantly lower prevalence of IMI at 1 to 3 DIM (tx = 22.8%, control = 29.1%), had significantly fewer quarters that acquired a new IMI between dry off and 1 to 3 DIM (tx = 20.2%, control = 25.4%), and had significantly fewer quarters affected by a clinical mastitis event between dry off and 60 DIM (tx = 5.9%, control = 8.0%). Multivariable analysis showed a significant effect of treatment, with treated quarters being 30% less likely to develop a new IMI between dry off and 1 to 3 DIM, 31% less likely to have an IMI present at 1 to 3 DIM, 33% less likely to experience a clinical mastitis event between dry off and 60 DIM, and having significantly lower linear score measures at 1 to 3 DIM and 6 to 8 DIM, compared with control quarters.     

Efficacy of two barrier iodine teat dips under natural exposure conditions

The efficacy of 2 iodine barrier teat dips was compared with a conventional iodine postmilking teat dip. The products were evaluated using a natural exposure trial on a 250-cow dairy based on the National Mastitis Council guidelines. Bacteriological samples were taken every 2 wk over 6 mo. All dips contained 1.0% available iodine and high levels of free iodine for germicidal efficacy. Barrier 1 was an experimental dip containing 14 to 20 ppm of free iodine, barrier 2 contained 8 to 14 ppm of free iodine, and the nonbarrier control contained 12 to 16 ppm of free iodine. The average free iodine for barrier 1 and barrier 2 combined was 14 ppm, which was equal to the average free iodine for the positive control. A 21% reduction of new intramammary infections (IMI) was observed for the 2 barrier dips combined when compared with the nonbarrier control. A significant reduction of 38% was observed for the clinical infection rate for barrier 1 when compared with barrier 2; however, barrier 1 did not significantly reduce the subclinical IMI when compared with barrier 2. Barrier 1 significantly reduced the combined clinical and subclinical IMI by 24% when compared with the positive control. The skin condition showed slight variation among the dips over the course of the trial, but no difference was observed at the end of the trial. Barrier 1, with the highest concentration of free iodine, gave the best efficacy results of all 3 dips.     

Associations of soft flooring materials in free stalls with milk yield, clinical mastitis, teat lesions, and removal of dairy cows

The objective was to test if there was an association between free-stall base softness and milk yield, incidence of clinical mastitis (CM), teat lesions, and removal of cows. In a questionnaire sent to 1,923 dairy farms presumed to be using free-stall housing, farmers were asked for information regarding housing and stall base; for example, the year of installation and the product name or brand of their mats or mattresses. This information was merged with data for milk yield, CM, teat lesions, and removal of cows extracted from the Norwegian Dairy Herd Recording System for the years after installation of mats or mattresses. After exclusion of invalid contributions, the data set consisted of 29,326 lactations for milk yield distributed over 363 free-stalled herds in Norway. The farms were stratified into 5 categories according to the softness of the stall surface measured as millimeter impact of a sphere with a diameter of 120 mm at 2-kN load: 1 = concrete, softness of 0 mm; 2 = rubber, softness of 1 to 8 mm; 3 = soft mats, softness of 9 to 16 mm; 4 = multilayer mats, softness of 17 to 24 mm; and 5 = mattresses, softness over 24 mm. Lactation curves were estimated as modified Wood's lactation curves using test-day data and mixed models with repeated measurements, adjusting for days in milk, parity, and softness of free-stall flooring. Herds on concrete free-stall bases yielded 6,727 ± 146 kg of milk from 5 to 305 days in milk. In comparison, herds showed a decrease of 0.3% on rubber, an increase of 2.4% on soft mats, an increase of 4.5% on multilayer mats, and an increase of 3.9% on mattresses. Compared with concrete, the hazard ratio (HR) of CM was less on rubber, multilayer mats, and mattresses [HR = 0.89 (0.79-0.99), 0.85 (0.73-0.996), and 0.80 (0.73-0.88), respectively]. Compared with concrete, the HR of teat lesions was less on rubber, soft mats, multilayer mats, and mattresses [HR = 0.41 (0.26-0.65), 0.33 (0.24-0.44), 0.12 (0.04-0.38), and 0.47 (0.33-0.67), respectively]. The HR of removal of cows was less on mattresses compared with concrete, rubber, soft mats, and multilayer mats, with HR = 0.90 (0.84-0.97), 0.88 (0.80-0.97), 0.86 (0.80-0.93), and 0.85 (0.76-0.95), respectively. A soft free-stall base contributed significantly to increased milk yield and fewer incidences of CM, teat lesions, and removal of cows.     

Effects of an automatic postmilking teat dipping system on new intramammary infections and iodine in milk

A technology of automatically applying a postmilking teat dip via the milking machine prior to machine detachment was compared to manual postmilking teat dipping with a teat dip cup for effects on new IMI and iodine content in milk. One hundred twenty Holstein cows were experimentally challenged in a 22-wk trial with Streptococcus agalactiae and Staphylococcus aureus and 148 Holstein cows were experimentally challenged with Streptococcus uberis in another 22-wk trial. The bacterial suspensions were applied to teats of all of the cows after premilking udder preparation and immediately prior to milking machine attachment. In both trials, cows were divided among four treatments: no postmilking teat dipping; manual postmilking teat dipping with a proven efficacious iodophor teat dip; manual postmilking teat dipping with an iodophor teat dip formulated for an automatic postmilking teat dipping system; and automatically postmilking teat dipping via milking machines with an iodophor teat dip formulated for the automatic postmilking teat dipping system. The postmilking teat dipping treatments reduced new Staph. aureus IMI by 64.5, 76.5, and 88.2%; new Strep. agalactiae IMI by 61.5, 77.8, and 94.4%; and new Strep. uberis IMI by 63.5, 82.5, and 93.8%, respectively, against the treatment of no postmilking teat dipping. The treatment applying the postmilking teat dip automatically via milking machines had the lowest number of new IMI caused by the three pathogens. Teat end and teat skin condition were characterized as normal at the end of the study with no differences between treatments. There were no differences with regard to iodine content in milk between treatments.     

Randomized noninferiority field trial evaluating a postmilking teat dip for the prevention of naturally occurring intramammary infections

The aim of this study was to perform a positive-controlled field study under natural exposure conditions to test the efficacy of a newly developed chlorine dioxide-based postmilking teat disinfectant (experimental product, EX) for noninferiority compared with an already established chlorine dioxide-based teat disinfectant (positive control product, PC). After blocking by parity, approximately 200 Holstein cows in early to mid-lactation stages from a dairy farm near Padua, Italy, were randomly assigned to one of 2 groups. Over a 13-wk period between September and December 2021, the teats of cows were dipped with the EX or the PC after each milking. Milk samples were collected from individual quarters of enrolled cows for 13 wk to determine infection status. Teat condition was assessed at wk 1, 5, and 9. Mixed logistic regression was used to analyze the effect of treatment on the incidence of new intramammary infections. For the noninferiority analysis, the upper limit of the 95% confidence interval for the difference in new intramammary infection (NIMI) rate between the 2 treatments (EX − PC) had to be to the left of the critical value d (0.035) to conclude that EX was noninferior to PC in terms of the risk of NIMI. The results showed that the incidence of new infections in the quarters treated with EX (3.1%) was not different from that in the udder quarters treated with PC (2.6%). No overall difference was found between the treatments in terms of teat condition. As the upper limit of the 95% confidence interval of the NIMI rate difference was smaller than the predefined noninferiority limit, we concluded that the EX was noninferior compared with the PC.     

The use of an internal teat sealant in combination with cloxacillin dry cow therapy for the prevention of clinical and subclinical mastitis in seasonal calving dairy cows

Cows (n = 2,053) from 6 seasonally calving dairy herds were enrolled in a trial to compare the efficacy of 2 dry cow treatments. Cows received either a combination dry cow therapy of 600 mg of cloxacillin (CL) followed by an internal teat sealant (ITS) containing 2.6 g of bismuth subnitrate in all 4 quarters immediately following their final milking for the season, or only an intramammary infusion of 600 mg of CL. All cases of clinical mastitis were recorded and cultured during the first 150 d of lactation in each herd, and cow somatic cell count (SCC) was measured between 7 and 50 d postcalving. A large difference was found between treatment groups in the rate at which cows were diagnosed with clinical mastitis over the first 21 d of lactation, after which time the rate at which cows were diagnosed with clinical mastitis was similar between treatment groups. Analysis of the relative proportions of cows with clinical mastitis was performed at both the gland and cow levels. The relative risk (RR) of clinical mastitis diagnosed within 21, 30, and 100 d of calving in a gland treated with the ITS-CL combination was, respectively, 0.30 [95% confidence interval (CI) = 0.21-0.44], 0.39 (0.28-0.53), and 0.58 (0.46-0.75) that of the CL group. An interaction between treatment and previous SCC was found when clinical mastitis was analyzed at the cow level. In a subset of cows that had low SCC in their previous lactation, the RR of mastitis in cows with the ITS-CL combination within 21, 30, and 100 d of calving was, respectively, 0.54 (95% CI = 0.33-0.87), 0.57 (0.37-0.88), and 0.69 (0.50-0.99) that of cows that received only CL at drying off. In the subset of cows that had at least 1 high SCC in the previous lactation, the RR of mastitis in the ITS-CL combination group within 21, 30, and 100 d of calving was, respectively, 0.26 (95% CI = 0.16-0.44), 0.37 (0.24-0.57), and 0.72 (0.55-0.96) that of the CL-only group. The ITS-CL combination of dry cow treatments was associated with a reduction in subclinical mastitis [SCC ≥250,000 cells/mL; RR = 0.80 (95% CI = 0.65-0.98)] when compared with treatment with CL alone. The use of an ITS in combination with CL dry cow treatment was associated with significantly lower clinical and subclinical mastitis in the following lactation, with a greater difference found in cows that had a history of subclinical mastitis in the previous lactation.     

Composition of the teat canal and intramammary microbiota of dairy cows subjected to antimicrobial dry cow therapy and internal teat sealant

Antimicrobial dry cow therapy (DCT) is an important component of mastitis control programs aimed to eliminate existing intramammary infections and prevent the development of new ones during the dry period. However, to what extent the microbiota profiles of different niches of the udder change during the dry period and following administration of DCT remains poorly understood. Therefore, the main objective of the present study was to qualitatively evaluate dynamics of the microbiota of teat canal (TC) and mammary secretions (i.e., milk and colostrum) of healthy udder quarters subjected to DCT using a long-acting antimicrobial product, containing penicillin G and novobiocin, in combination with internal teat sealant. To this end, TC swabs (n = 58) and their corresponding milk (n = 29) and colostrum samples (n = 29) were collected at the time of drying off and immediately after calving from clinically healthy udder quarters of Holstein dairy cows from a commercial dairy farm. All samples were subjected to DNA extraction and high-throughput sequencing of the V1–V2 hypervariable regions of bacterial 16S rRNA genes. Overall, shifts were more pronounced within the microbiota of mammary secretions than the TC. In particular, microbiota of colostrum samples collected immediately after calving were less species-rich compared with the pre-DCT milk samples. Proportions of several bacterial genera belonging to the phylum Proteobacteria, including Pseudomonas, Stenotrophomonas, and unclassified Alcaligenaceae, were enriched within the microbiota of colostrum samples, whereas Firmicutes genera, including Butyrivibrio, unclassified Clostridiaceae, and unclassified Bacillales, were overrepresented in pre-DCT milk microbiota. Apart from shifts in the proportion of main bacterial genera and phyla, qualitative analysis revealed a high degree of commonality between pre-DCT and postpartum microbiota of both niches of the udder. Most importantly, a considerable number of bacterial genera and species commonly regarded as mastitis pathogens or opportunists (or both), including Staphylococcus spp., unclassified Enterobacteriaceae, and Corynebacterium spp., were shared between pre-DCT and postpartum microbiota of mammary secretions. Percentage of shared bacterial genera and species was even higher between pre-DCT and postpartum microbiota of TC samples, suggesting that the DCT approach of the present study had limited success in eliminating a considerable proportion of bacteria during the dry period.     

Efficacy of nisin in treatment of clinical mastitis in lactating dairy cows

Nisin is an antimicrobial polypeptide produced by Lactococcus lactis and is believed nontoxic to humans. The objective of this study was to evaluate a nisin-based formulation for the treatment of bovine clinical mastitis in lactating dairy cattle. A total of 92 cows with 107 clinically mastitic quarters were randomly assigned to nisin- (48 cows with 51 quarters) and gentamicin (GM)-treated (44 cows with 56 quarters) groups. In the nisin-treated group, cows received an intramammary infusion of nisin at a dose of 2,500,000 IU; in the GM-treated group, intramammary infusion of GM was administered at a dose of 0.8 g. Results indicated that nisin offered a clinical cure rate similar to GM (90.2 vs. 91.1%) and no difference in bacteriological cure rate than GM-treated group (60.8 vs. 44.6%, respectively). Proportion of the quarters with milk somatic cell counts <500,000 cells/mL was not different in the nisin-treated group (50.0 and 47.8%) compared with the GM-treated group (33.3 and 37.3%) 1 and 2 wk after treatment. Of 17 Staphylococcus aureus isolates, 82.5% were resistant to penicillin, and 35.3% to GM, but none of them to nisin. Nisin therapy eliminated 54.5% (6 of 11) of S. aureus IMI, whereas GM eliminated 33.3% (2 of 6). Nisin in milk (4.5 ± 0.8 IU/mL) was detected only at 12 h following intramammary infusion, which was much lower than the upper limit (500 mg/mL) allowed as preservative in milk by the China authority. Because of its efficacy in the treatment of bovine clinical mastitis, especially resistant Staph. aureus-caused IMI, as well as its safety in humans, nisin deserves further study to clarify its effects on mastitis caused by different mastitis pathogens on a larger scale.     

Factors associated with concentrations of select cytokine and acute phase proteins in dairy cows with naturally occurring clinical mastitis

The objective of the current observational study was to determine the potential associations between cow factors, clinical mastitis (CM) etiology, and concentrations of select acute phase proteins and cytokines in milk from affected quarters of cows with CM. Cows with CM (n = 197) were grouped based on systemic disease severity, milk culture result, parity, days in milk (DIM), previous CM occurrence, and season of the year when CM occurred. Concentrations of lipopolysaccharide-binding protein (LBP), haptoglobin (Hp), BSA, IFN-γ, tumor necrosis factor-α (TNF-α), IL-1β, IL-8, IL-10, IL-12, transforming growth factor (TGF)-α, and TGF-β and activity of lactate dehydrogenase (LDH) were evaluated. Differences in the least squares means log₁₀ transformed concentrations of these proteins were compared using multiple linear regression mixed models. The milk concentrations of LBP, Hp, IL-1β, IL-10, and IL-12, and activity of LDH in milk were higher in cows with moderate to severe versus mild systemic disease. The concentrations of Hp, BSA, IL-1β, and IL-10 in milk were higher in cows with a gram-negative versus gram-positive milk culture result. Season of the year when CM occurred was associated with the concentration of all proteins evaluated except for IL-1β and IL-12. Concentrations were higher in the winter versus summer except for Hp and TGF-β, for which the opposite was true. Concentrations of LBP, IL-10, and IL-12, and LDH activity in milk were associated with DIM group. Except for LBP, these proteins were lower in cows with CM during the first 60 DIM versus those in mid or later lactation. Interferon-γ, TNF-α, and IL-8 were undetectable in 67, 31, and 20% of samples, respectively. Detection of IFN-γ and IL-8 was associated with season, and detection of TNF-α and IL-8 was associated with systemic disease severity. The current study provides the most comprehensive report of milk concentrations of innate immune response proteins in cows with naturally occurring CM and identifies factors that potentially influence those concentrations. Further investigation into the seasonal variation of cytokine production and its potential effect on the outcome of CM is warranted. Furthermore, the results of this study provide useful data for planning future studies examining the role of the innate immune response in CM.     

Efficacy and clinical safety of pegbovigrastim for preventing naturally occurring clinical mastitis in periparturient primiparous and multiparous cows on US commercial dairies

Periparturient dairy cows experience impaired immune function, exhibited as a transient decrease in neutrophil function. This decrease in immune competence is associated with an increase in susceptibility to bacterial infections, including mastitis and metritis. Bovine granulocyte colony stimulating factor (bG-CSF) is an endogenous protein that enhances neutrophil bactericidal functions and increases the production of neutrophils from bone marrow precursors. Administration of pegbovigrastim (recombinant bG-CSF covalently bound to polyethylene glycol) around the time of calving has been shown to reduce the incidence of new clinical mastitis cases in a natural disease model system. To further explore the application of pegbovigrastim under herd management systems typical of those found in the US dairy industry, we conducted a multicenter field study to evaluate the efficacy and clinical safety of pegbovigrastim administered to multiparous cows and heifers approximately 7 d before calving and within 24 h of calving. Responses of treated cows were compared with those of animals treated with sterile saline. Animals treated with pegbovigrastim exhibited 4- to 5-fold increases in circulating neutrophil numbers within 24 h of treatment initiation, and this increase persisted at least a week beyond the second dose. Pegbovigrastim-treated animals exhibited a 35% decrease in the incidence of clinical mastitis relative to the controls during the first 30 d of lactation. Animals treated with pegbovigrastim also exhibited a 52% reduction in failure to return to visual estrus within 80 d of calving. We observed no differences in somatic cell count or milk composition between treated and control animals. We also found no differences in the duration of pregnancy or proportion of viable calves in treated cows relative to control animals. These results indicate that administration of pegbovigrastim provides a well-tolerated, novel approach to overcoming periparturient immune suppression, resulting in reduced susceptibility to clinical mastitis during early lactation.     

Characterization of clinical mastitis occurring in cows on 50 large dairy herds in Wisconsin

In recent years, the US dairy industry has experienced significant demographic changes, with an increase in the number of large herds. The objectives of the present study were to characterize clinical mastitis occurring in cows on large dairy herds in Wisconsin. Participating herds (n = 50) were required to have a minimum of 200 lactating animals, participate in monthly DHI testing (including monthly individual cow somatic cell count), use computerized herd records, use a milking routine that included fore-stripping quarters for detection of mastitis, and use antimicrobials to treat affected cows. After study personnel visited the farm, each herd was instructed to enroll the next 17 cows that experienced clinical mastitis, regardless of severity. At detection of clinical mastitis and 14 to 21 d after treatment ended, duplicate quarter milk samples were collected from all affected quarters and used for microbiological analysis. Treatments of affected cows were performed according to existing individual farm protocols. Cow level follow-up data was collected for 90 d after enrollment. Microbiological diagnoses at enrollment included gram-negative (35.6%), no growth (27.3%), gram-positive (27.5%), and other (9.6%). Of the 741 cases, the most prevalent pathogens were Escherichia coli (22.5%), followed by environmental streptococci (12.8%), Klebsiella spp. (6.9%), and coagulase-negative staphylococci (6.1%). Bacteriological cure was 75.0% for cases caused by gram-negative pathogens (n = 136), 50.8% for cases caused by gram-positive pathogens (n = 128), 47.5% for cases caused by other pathogens (n = 40), and 73.2% for cases which did not result in microbial growth (n = 123). Of the 583 cases with severity recorded, the distribution of mild, moderate, and severe symptoms was 47.8, 36.9, and 15.3%, respectively. The majority of cases presenting with severe symptoms were caused by gram-negative pathogens. Treatment cure was greater for gram-negative pathogens and cases for which no pathogens were recovered as compared with cases caused by other etiologies. Cows experiencing severe cases were more likely to receive multiple antimicrobial treatments.     

Influence of dry period bacterial intramammary infection on clinical mastitis in dairy cows

Milk samples were taken from 1920 quarters (480 cows, six herds) on four occasions to examine the relationship between quarter level intramammary infection (IMI) during the dry period and clinical mastitis in the next lactation. All quarters were sampled at drying off and within 1 wk of calving, and two quarters from each cow were sampled both 0 to 7 and 8 to 14 d before calving. Milk samples were collected from all cases of clinical mastitis during the following lactation. Logistic regression models were developed to investigate the associations between IMI present during the sampling period and clinical mastitis. The probability of a quarter succumbing to clinical mastitis increased when Streptococcus dysgalactiae, Streptococcus faecalis, Escherichia coli, or Enterobacter spp. were cultured at drying off and when Escherichia coli, coagulase-positive staphylococcus, Serratia spp., or Streptococcus faecalis were cultured in two out of three late dry and post-calving samples. Quarters from which Corynebacterium spp. were isolated at drying off were at an increased risk of clinical mastitis, whereas the presence of Corynebacterium spp. in the late dry and post-calving samples was associated with a reduction in the risk of clinical mastitis. The risk of mastitis for specific pathogens increased if the same species of bacteria that had caused mastitis was isolated at least twice in the late dry and post-calving samples. Kaplan-Meier survival plots indicated that clinical mastitis associated with dry period infections was more likely to occur earlier in lactation than clinical mastitis not associated with dry period infections. There was evidence of quarter susceptibility to IMI or the possibility that infection with one organism led to clinical mastitis with another.     

Typeability of MALDI-TOF assay for identification of non-aureus staphylococci associated with bovine intramammary infections and teat apex colonization

Matrix-assisted laser desorption/ionization time of flight (MALDI-TOF), a culture-dependent assay, has recently been implemented for routine identification of non-aureus staphylococci (NAS) species from milk, but the assay has never been investigated for NAS from nonmilk or environmental samples. The objective of this study was to evaluate the typeability of the MALDI-TOF assay for the identification and differentiation of bovine-associated NAS species on aseptically collected quarter milk and teat skin samples in dairy herds. In 8 herds, 14 to 20 cows with elevated somatic cell count were randomly selected for teat skin swabs and foremilk samples from right hind and left front quarters. Teat skin swabs and milk samples were collected aseptically for preliminary identification using bacterial culture on chromogenic and calf blood agars. Colonies from milk and teat skin samples with suspicion of having NAS were identified to species-level by MALDI-TOF assay. Out of 511 isolates from 284 quarters (142 cows), 78% (n = 399) were identified by MALDI-TOF. The percentage of correctly identified NAS from milk (91%, 105/115) using MALDI-TOF was higher than the percentage from teat skin (68%, 268/396). Out of the identified isolates, 93% (n = 373) were successfully identified as NAS, whereas the remaining 26 (7%) were shown to be other bacterial species. Out of 26 NAS isolates, 1 originated from milk (Corynebacterium stationis), whereas 25 originated from teat skin representing Aerococcus viridans (n = 7), Bacillus pumilus (n = 13), Enterococcus saccharolyticus (n = 1), Clostridium septicum (n = 1), Corynebacterium stationis (n = 2), and Corynebacterium casei (n = 1). The MALDI-TOF identified 85 (98/115) and 62% (245/396) of the isolates in the first test. Isolates that were not identified to species-level at first test were subjected to a second test, and 47 (8/17) and 32% (48/151) from milk and teat skin, respectively, were identified. After 2 rounds of MALDI-TOF, 22% (n = 112) of the isolates were not identified, representing 103 from teat skin and 9 from milk. Eighteen isolates without identification by MALDI-TOF were successfully identified to species-level using sequencing, where 16 were correctly identified as NAS, whereas the other 2 were Corynebacterium stationis. In conclusion, MALDI-TOF is a reliable assay for identification and typeability of NAS species from aseptically collected quarter milk samples. The assay may be used for identification of NAS species from teat skin swabs. However, confirmation using nucleic acid-based tools is vital for accurate species identification of some species and strains.     

Efficacy of systemic ceftiofur as a therapy for severe clinical mastitis in dairy cattle

The objectives of this study were to determine the efficacy of intramuscular administration of ceftiofur to reduce the incidence of case-related death and culling following severe clinical mastitis in lactating dairy cattle. A total of 104 cows with severe clinical mastitis (systemic signs) were enrolled in the study and randomly assigned to one of two treatment groups. Immediately after detection of the case, one group was administered 2.2 mg/kg of ceftiofur intramuscularly, and the dose repeated at 24-h intervals for a total of five doses. The second group of cows did not receive systemic antibacterial therapy. Additionally, all cows in both treatment groups received intramammary pirlimycin (Pirsue) in the affected quarter every 24 h for a total of up to three doses. Also at the onset of the case, all cows on the trial were administered a supportive therapeutic regimen of fluids and anti-inflammatory agents that varied from farm to farm, but was standard within each herd at the discretion of the herd manager and veterinarian. Of all cases 14/104 (13.5%) resulted in a lost cow (died or culled). The proportion of cases that resulted in a lost cow and were treated with ceftiofur (4/51; 7.8%) did not statistically differ from cows that were not treated with ceftiofur (10/53; 18.9%). However, the proportion of cases that resulted in lost cows was higher for those cases that yielded a coliform organism on culture (14/56; 25.0%) than cases that did not yield coliforms (0/48; 0.0%; P < 0.001). Thus, among coliform cases, cows that were not treated with ceftiofur were more likely to be culled or die (10/27, 37.0%; P < 0.05) than cows treated with ceftiofur (4/29, 13.8%). We conclude that intramuscular administration of ceftiofur did not affect the outcome of severe clinical mastitis when all etiologic agents are included in the analysis. However, for severe clinical mastitis cases caused by coliform organisms, ceftiofur therapy reduced the proportion of cases that resulted in cow death or culling. This benefit may be realized because of the amelioration of bacteremic-related pathogenesis.     

Evaluation of a postmilking teat disinfectant containing a phenolic combination for the prevention of mastitis in lactating dairy cows

A trial was conducted for 12 months in a herd of 120 Holstein cows in order to determine the efficacy of a teat disinfectant, which contained a phenolic combination, for the prevention of bovine intramammary infections during lactation. Postmilking teat disinfection was compared to a negative control using a split-udder experimental design. The percentage of quarters newly infected by mastitis pathogens was 45% lower in mammary glands with teats that had been dipped in the experimental teat disinfectant after milking than it was in undipped controls. New infections caused by Streptococcus uberis, Staphylococcus aureus, coagulase-negative Staphylococcus species, and Corynebacterium bovis were significantly lower in mammary glands with teats that had been dipped in the experimental teat disinfectant than in undipped controls. No statistical differences in the incidence of clinical mastitis between treatment groups were observed. No irritation or chapping of teats dipped in the experimental teat disinfectant were observed. The results of this study suggest that the experimental teat disinfectant containing a phenolic combination is an effective postmilking teat disinfectant for use in the prevention of new intramammary infections by both contagious and environmental mastitis pathogens.     

Efficacy of extended ceftiofur intramammary therapy for treatment of subclinical mastitis in lactating dairy cows

Little research has focused on treatment of cows with subclinical mastitis during lactation. Ceftiofur is a new broad-spectrum, third-generation cephalosporin antibiotic for veterinary use that inhibits bacterial cell wall synthesis by interfering with enzymes essential for peptidoglycan synthesis. Ceftiofur should be effective against a wide range of contagious and environmental mastitis pathogens. Objectives of the present study were to evaluate the efficacy of ceftiofur for treatment of subclinical mastitis in lactating dairy cows, and to determine if extended therapy regimens enhanced efficacy of ceftiofur. Holstein and Jersey dairy cows (n = 88) from 3 dairy research herds were used. Cows were enrolled in the study based on milk somatic cell counts >400,000/mL and isolation of the same mastitis pathogen in 2 samples obtained 1 wk apart. Cows with one or more intramammary infections (IMI) were blocked by parity and DIM and allocated randomly to 1 of 3 different ceftiofur treatment regimens: 2-d (n = 49 IMI), 5-d (n = 41 IMI), and 8-d (n = 38 IMI) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. Eighteen cows with 38 IMI were included as an untreated negative control group. A bacteriological cure was defined as a treated infected mammary quarter that was bacteriologically negative for the presence of previously identified bacteria at 14 and 28 d after the last treatment. Efficacy of ceftiofur therapy against all subclinical IMI was 38.8, 53.7, and 65.8% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Four of 38 (10.5%) IMI in control cows were cured spontaneously without treatment. All 3 ceftiofur treatment regimens were significantly better than the negative control, and the 8-d extended ceftiofur treatment regimen treatment group was significantly better than the standard 2-d treatment group. Pathogen groups had significantly different cure rates from one another. The cure rate for the 8-d extended ceftiofur treatment regimen was 70% for Corynebacterium bovis, 86% for coagulase-negative Staphylococcus species, 36% for Staph. aureus, 80% for Streptococcus dysgalactiae ssp. dysgalactiae, and 67% for Strep. uberis.     

Subclinical and clinical mastitis in heifers following the use of a teat sealant precalving

This study investigated the effect in heifers of infusion of a bismuth subnitrate teat-canal sealant and bacterial intramammary infection (IMI) precalving on prevalence of postcalving IMI and incidence of clinical mastitis in the first 2 wk postcalving. Glands (n = 1,020) from heifers (n = 255) in 5 seasonally calving, pasture-fed dairy herds were randomly assigned within heifer to 1 of 4 treatment groups (no treatment; mammary gland secretion collection; infusion of a teat sealant; or sample collection with infusion of teat sealant). Heifers within a herd were enrolled on one calendar day, 31 d on average before the planned start of the seasonal calving period. Duplicate milk samples were collected from each gland within 4 d after calving for bacterial culture. Herd owners collected duplicate milk samples, before treatment, for bacterial culture from glands they defined as having clinical mastitis. The gland prevalence of IMI precalving was 15.5% and did not differ between herds. Bacteria isolated precalving included coagulase-negative staphylococci (76.9% of all bacteriologically positive samples), Streptococcus uberis (14.1%), Staphylococcus aureus (5.1%), Corynebacterium spp. (3.8%), and others (0.1%). The presence of an IMI precalving increased the risk of an IMI postcalving 3.6-fold and the risk of clinical mastitis 4-fold, relative to no IMI precalving. Infusion of the teat sealant reduced the risk of postcalving IMI due to Strep. uberis by 84%, and of clinical mastitis by 68%. Sampling the glands precalving had no effect on postcalving IMI or on clinical mastitis incidence. Use of an internal teat canal sealant in heifers precalving may be a useful tool for reducing the risk of subclinical and clinical mastitis in heifers.     

Treatments of clinical mastitis occurring in cows on 51 large dairy herds in Wisconsin

Antimicrobials are frequently used for treatment of bovine mastitis and few studies have examined modern treatment strategies on large US dairy farms. The objective of this study was to describe treatment practices for clinical mastitis occurring in cows on large dairy herds in Wisconsin. Treatments performed on 747 cows experiencing cases of mild, moderate, or severe symptoms of clinical mastitis were recorded on 51 Wisconsin dairy farms. Duplicate milk samples were collected from the affected quarter for microbiological analysis at the onset of clinical mastitis and 14 to 21 d after treatment ended. Cows were treated according to individual farm protocol. Drugs and doses used for treatments were recorded for each case. Among all herds, 5 intramammary (IMM) antimicrobials (amoxicillin, hetacillin, pirlimycin, ceftiofur, and cephapirin) were used to treat cows for clinical mastitis. Of 712 cows with complete treatment data, 71.6% were treated with IMM ceftiofur either solely or combined with other antimicrobials (administered either IMM or systemically). Of cows experiencing severe symptoms of clinical mastitis, 43.8% received IMM treatment concurrent with systemic antimicrobials. Of all cows treated, 23.1% received an additional secondary treatment (either IMM, systemic, or both) because of perceived lack of response to the initial treatment. The majority of IMM treatments were administered to cows with a microbiological diagnosis of no growth (34.9%) or Escherichia coli (27.2%). Half of the cows experiencing cases caused by E. coli were treated using systemic antimicrobials in contrast to only 6.8% of cows experiencing cases caused by coagulase-negative staphylococci. In conflict with FDA regulations, which do not allow extra-label treatments using sulfonamides, a total of 22 cows from 8 farms were treated with systemic sulfadimethoxine either solely or in combination with oxytetracycline. Antimicrobial drugs were used on all herds and many cows received extra-label treatments. Great opportunity exists to improve mastitis therapy on large dairy herds, but use of more diagnostic methodologies is necessary to guide treatments. Farmers and veterinarians should work together to create protocols based on the herd needs considering reduced inappropriate and excessive use of antimicrobials.