M-score and wound healing assessment of 2 nonantibiotic topical gel treatments of active digital dermatitis lesions in dairy cattle.

This open-label, randomized clinical trial with positive control compared the treatment of active digital dermatitis (DD) lesions (stages M1, M2, and M4.1) on dairy cattle hind feet with an enzyme alginogel or a copper and zinc chelate gel (coppergel). Upon recruitment (d 0), active DD lesions were cleaned, photographed, treated, and bandaged. This procedure was repeated on d 3 and d 7, with treatment and bandaging discontinued for those lesions that had transitioned to the M0, M3, or M4 stage on d 7. Day 10 was considered the end of the treatment trial, and all recruited feet were cleaned and photographed. Treatment effect of the 2 products was assessed not only using the M-score but also using general wound healing progress criteria. Improvement of M-score was defined as transition to M0, M3, or M4 stages, or to lesions with a smaller ulcerative area (e.g., M2 stage to M1 stage). Lesions with improved wound healing had at least one of the following criteria when compared with the previous observation: decreased defect size, healthier granulation tissue color (pink-red instead of purple-grayish), more regular aspect of granulation tissue surface, wound contraction, or epithelization starting from the surrounding skin. Both primary outcomes were assessed using a multivariable logistic regression analysis. Lesions treated with the enzyme alginogel had a decreased adjusted odds ratio for M-score improvement (aOR: 0.04; 95% confidence interval: 0.01-0.11). Lesions treated with the coppergel mostly transitioned to chronic lesions, whereas lesions treated with the enzyme alginogel mostly remained active lesions. The wound healing progress of almost 70% of the lesions treated with coppergel could not be scored, for the greater part due to the presence of crust materials. With these unscorable lesions classified as "improved," there was no treatment effect on wound healing progress (aOR: 0.99; 95% confidence interval: 0.34-3.05), whereas with unscorable lesions classified as "not improved," the enzyme alginogel outperformed the coppergel with regard to wound healing progress (aOR: 2.48; 95% confidence interval: 1.07-5.79). None of the products used in our study achieved high cure rates (transition to the M0 stage) for active DD lesions. Low cure rates of topical treatment of DD, together with the important role of chronic lesions in the epidemiology of DD, indicate that future research should investigate how to achieve successful wound management of DD lesions, thereby mitigating pain associated with the lesions and reducing both transmission and prevalence of DD within herds.

Reproductive hormone use and its association with herd-level factors on Dutch dairy farms.

We studied the use of the 3 commonly used reproductive hormones, namely prostaglandins, GnRH, and progesterone, and associated herd-level factors on 760 Dutch dairy farms from 5 veterinary clinics. From 2017 to 2019 we collected data on the sales of reproductive hormones, converted this data into the number of reproductive hormone doses conducted, and expressed this as the annual number of reproductive hormone doses per 100 adult dairy cows. Additional herd-level information was available for 2019. Due to the excess of zeros in the data set (i.e., a substantial number of farms did not use any hormones), we used a zero-inflated negative binomial model to identify related herd-level factors for the use of reproductive hormones. In the entire study period of 2017 to 2019, 5.8% of the dairy farms did not use any reproductive hormones, with the proportion of nonusers varying between 0.0 and 10.3% per veterinary clinic. This proportion was around 13.5% on an annual basis. Prostaglandins were the most frequently used reproductive hormone in Dutch dairy cows (62.9%), followed by GnRH (33.1%) and progesterone (4.0%). Furthermore, participating in a veterinary herd health management program had a significant effect on reproductive hormone use. These farms used more reproductive hormones than farms that did not participate in a herd health management program and were less represented in the group of nonuser farms. Technologies, such as pedometers and automatic milking systems, also had an effect on reproductive hormone use. The presence of pedometers or activity monitors did not reduce the use of the reproductive hormones but was associated with a greater frequency of users. Farms with an automatic milking system used more reproductive hormones than farms with a conventional milking system. With this study, we have made a first step in achieving transparency in the Dutch dairy industry by providing an objective overview of reproductive hormone use on Dutch dairy farms and identifying associations with some herd-level factors.

Dry period management and new high somatic cell count during the dry period in Dutch dairy herds under selective dry cow therapy.

The aim of this study was to describe the current management practices that could influence udder health during the dry period and to investigate the associations between management and new high SCC during the dry period. In 2008 the Netherlands started to improve transparency and decrease the use of antimicrobials in animal husbandry. Prevention of new high SCC during the dry period via antimicrobial dry cow treatment (DCT) was no longer allowed in animals with a low SCC before the dry period. An increase of new high SCC during the dry period was expected in dairy cows without antimicrobial protection, but was not observed. In 2018 an online questionnaire was conducted among 1,942 Dutch dairy farms using 12 different veterinary clinics. The questionnaire asked about the management of dry cows at the start of and during the dry period, and around calving, considerations in the use of DCT, and knowledge of the 2012 guidelines for selective DCT. A total of 690 farmers (36%) responded to the questionnaire. Data on new high SCC during the dry period, use of antimicrobials for intramammary DCT and mastitis treatment, herd size, and milking system were available from other sources. Descriptive statistics were used to evaluate the associations between the different variables. For analysis of new high SCC on herd level, explanatory variables were analyzed using a generalized linear mixed model. Respondents indicated that the most important management factor to reduce the risk of new high SCC was reduction of milk yield before dry-off. The variables associated with a lower proportion of new high SCC on herd level during the dry period were the use of dip or spray after drying off, a higher animal-defined daily dose of intramammary antimicrobials for DCT, the use of DCT in low-SCC cows based on SCC or mastitis history, correct knowledge of the guideline, and awareness of importance of low infection rate and good hygiene during dry-off. The variables associated with a higher proportion of new high SCC on herd level were dry cow housing other than cubicles and a higher animal-defined daily dose for intramammary antimicrobials for mastitis. This research clearly indicates that farmers can balance limited use of antimicrobials at dry-off with management measures to maintain good udder health during the dry period.

An observational study on the management of digital dermatitis through a repeated risk assessment on 19 Dutch dairy herds.

The etiopathogenesis of bovine digital dermatitis (DD) is not well understood, but its risk factors on dairy farms have been studied extensively. The objective of this study was to identify associations between a DD risk score [determined by a DD risk assessment questionnaire (RAQ)] and DD prevalence (determined by an in-parlor M-score). We also investigated whether feedback for farmers on their DD management using the DD RAQ resulted in changes that decreased DD prevalence in their herds. The DD RAQ consisted of multiple-choice questions related to foot health, housing, and general management that were used to create a total risk score (TRS). In 2016 and 2018, the DD RAQ-together with a DD prevalence determination in the lactating herd-was used on 19 Dutch dairy farms from 1 veterinary practice. After each visit, farmers and their consulting veterinarians received a 1-page summary that identified herd-specific strengths and weaknesses in DD management. In 2018, the summary included suggestions for improvement. In 2019, farmers and veterinarians were contacted to ask whether the use of the DD RAQ and the 1-page summary had led them to implement changes in their DD management in 2016 and 2018. We tested the association between TRS and DD prevalence using linear mixed model analysis. The TRS ranged from 13 to 65% and 20 to 68% in 2016 and 2018, respectively. Herd DD prevalence ranged from 15 to 59% and 27 to 69% in 2016 and 2018, respectively. For both years, the DD RAQ identified that DIM, herd size, and breed were often present in a manner associated with increased risk for DD. The linear mixed model analysis identified that each 10-point increase in TRS was associated with an increase in herd DD prevalence of less than 1%. The association between TRS and herd DD prevalence was caused mainly by risk factors related to housing. We found no important relationship between change in TRS and change in DD prevalence between the 2 visits. Only a few farmers indicated some form of change in their DD management following a visit. Veterinarians in general said that they discussed the 1-page summaries and DD control with farmers during a routine visit, but the majority admitted a lack of follow-up. We propose that the DD RAQ could be used as a tool to start a discussion on DD control on farm, but simply undertaking a DD RAQ and providing a 1-page summary of the results was insufficient to initiate behavioral change that led to a decrease in DD prevalence.

Bacterial flora associated with udder cleft dermatitis in Dutch dairy cows.

Udder cleft dermatitis (UCD) or udder sores is a skin lesion, characteristically located around the anterior junction between the udder and abdomen of dairy cows. It is a worldwide problem in dairy herds with a large effect on animal welfare. The etiology and possible infectious origins of UCD are largely unknown; however, specific bacterial or parasitic causes are suggested in the literature. Therefore the aim of this study was to investigate the possible bacteriological, mycological, or parasitic involvement in clinically scored UCD lesions. Bacteriological culture was performed on subcutaneous tissue samples taken postmortem at a depth of 5 to 10 mm of 87 mild or severe UCD lesions or from the same place in healthy cows. Fungal culture was performed on a subset of 22 subcutaneous tissue samples of severe UCD postmortem. To investigate the superficial flora, swabs were taken from normal skin or skin lesions of 15 live animals equally divided over 3 groups: healthy skin or mild and severe UCD lesions. Histopathology, to describe and classify the lesions and to assess the presence of mites, fungi, or bacteria, was performed on 128 tissue samples, taken separately. In severe UCD lesions, Trueperella pyogenes and Bacteroides pyogenes were more frequently present in deep tissue layers and in superficial layers, compared with the same layers in mild UCD lesions or healthy skin. Culturing and histopathology indicated no sign of involvement of treponemes, Staphylococcus aureus, Escherichia coli, fungi, or mites in the UCD lesions. Histopathological examination showed that the majority of the lesions were characterized by chronic aspecific inflammation. Severe UCD lesions more frequently showed chronic active inflammation on histopathology, compared with mild UCD lesions. Due to the cross-sectional character of this study, it is difficult to differentiate cause and effect; however, future preventive and curative measures against UCD should take into account the chronic and anaerobic nature of this illness.

Incidence of milk leakage after dry-off in European dairy herds, related risk factors, and its role in new intramammary infections.

The incidence of milk leakage (ML) after dry-off (DO) and related risk factors was studied in 1,175 dairy cows from 41 commercial herds in 8 European countries: Belgium, Czech Republic, Denmark, France, Germany, Italy, the Netherlands, and Spain. Milk leakage was assessed twice for 30 s each during 3 visits at 20 to 24 h, 30 to 34 h, and 48 to 52 h after DO. Information related to dry-cow management and udder health was collected at herd and cow level, including individual somatic cell count (ISCC) from test-day controls and occurrence of clinical mastitis cases from DO until 30 d in lactation. Mixed-effect logistic regression analyses were used to identify possible risk factors for ML and to study the association between ML and new intramammary infections. Intramammary infections were defined as clinical mastitis cases during the dry period and in the first 30 d in lactation or a rise in ISCC from before to after the dry period (threshold: 200,000 cells/mL) or both. Milk leakage was observed in 24.5% of the cows between 20 and 52 h after DO, where the herd incidence varied between 0.0 and 77.8%. The reduction in number of milkings in the weeks before DO had statistically significant effect on the ML incidence. When the milking frequency was reduced from 3 times/d to 2 or maintained at twice a day, cows had 11 (95% CI = 3.43-35.46) or 9 (95% CI = 1.85-48.22) times higher odds of leaking milk, respectively, compared with cows where the milking frequency was reduced from twice to once a day. Also, the milk production 24 h before DO was associated with ML incidence. Hence, cows with a milk production between 13 and 21 L or above 21 L had 2.3 (95% CI = 1.48-3.53) and 3.1 (95% CI = 1.79-5.3) times higher odds of leaking milk, respectively, compared with cows with a milk production below 13 L. A higher ML incidence was present in the group of cows with an average ISCC in the last 3 mo before DO ≥200,000 cells/mL (odds ratio = 1.7; 95% CI = 1.13-2.41) compared with cows with an average ISCC <100,000 cells/mL. Quarters with ML tended to have 2.0 times higher odds of developing clinical mastitis compared with quarters not leaking milk. Cows with ML tended to have 1.5 times higher odds of intramammary infections (i.e., an increase of ISCC or clinical mastitis) compared with cows without ML.

Antimicrobial use and farmers' attitude toward mastitis treatment on dairy farms with automatic or conventional milking systems.

Mastitis is one of the major causes for antimicrobial use on dairy cattle farms. On farms with an automatic milking system (AMS), diagnostics differ from those with a conventional milking system (CMS), with potentially a different attitude toward mastitis treatment. This may result in differences in antimicrobial usage (AMU) between these 2 types of farms. The aims of this study were (1) to compare AMU between AMS and CMS farms, (2) to identify variables associated with AMU in both types of herds, and (3) to describe the distribution of mastitis-causing pathogens and their antimicrobial resistance patterns. Data on AMU was collected for 42 AMS and 254 CMS farms in the Netherlands and was expressed as animal-defined daily dose (ADDD). The ADDD variables were total usage (ADDDTOTAL), intramammary usage during lactation (ADDDIMM), usage for dry cow therapy (ADDDDCT), and usage by injection (ADDDINJ). Eighteen AMS farms and 24 CMS farms participated in a survey on factors potentially related to AMU. These farmers collected 5 quarter milk samples from quarters with clinical mastitis or high somatic cell count, which were subjected to bacteriological culture and antimicrobial susceptibility testing. In addition, routinely collected udder health data of these farms were used in the analysis. Nonlinear principal component analysis (NLPCA) was used to explore associations between AMU, udder health, and questionnaire variables. The ADDDTOTAL and ADDDDCT were comparable between AMS and CMS farms, whereas ADDDIMM tended to be lower and ADDDINJ higher on AMS farms than on CMS farms. The NLPCA yielded 3 principal components (PC) that explained 48% of the variation in all these variables. The AMS farms were not distinguished from CMS farms in the principal component space. The 3 PC represented different aspects of udder health, ADDDTOTAL, and treatment strategy. Differences in treatment strategy were unrelated to total antimicrobial usage or overall udder health. The distribution of mastitis-causing pathogens and their antimicrobial resistance were comparable between AMS and CMS farms. In conclusion, our study shows that AMU on AMS farms was similar to that of CMS farms, but AMS farmers tend to apply more injectable and fewer intramammary treatments during lactation than CMS farmers. Across both farm types, farmers' attitudes toward udder health in general and toward mastitis treatment are associated with AMU.

Interobserver agreement of digital dermatitis M-scores for photographs of the hind feet of standing dairy cattle.

Digital dermatitis (DD) is the leading infectious cause of lameness in dairy cattle, and it affects their welfare and productivity worldwide. At the herd level, DD is often assessed while cows are standing in a milking parlor, and lesions are most commonly evaluated using the M-score. The objective of this study was to examine the interobserver agreement for M-scores of the feet of standing cattle, based on digital color photographs of dairy cattle hind feet. A total of 88 photographs and written descriptors of the M-score were sent to 11 scorers working at 10 different institutions in 5 countries. The scorers received no formal training immediately before scoring the photographs; however, all regularly used the M-score to score DD. The answers for 36 photographs were excluded from the analysis because the photograph either had more than 1 M-stage as mode or not all scorers assigned an M-score to it. The M-scores of the 11 scorers from 52 photographs were available for analysis. Interobserver agreement was tested using Gwet's agreement coefficient (AC1) and the mode was assumed correct. Overall, moderate agreement emerged for the M-score (AC1 = 0.48). For the individual M-stages, almost perfect agreement existed for M0 (AC1 = 0.99), M1 (AC1 = 0.92), and M3 (AC1 = 0.82), and substantial agreement for M2 (AC1 = 0.61), M4 (AC1 = 0.65), and M4.1 (AC1 = 0.71). This outcome indicates the degree of individual variation in M-scoring in this context by unstandardized, experienced European observers, particularly for the M2, M4, and M4.1 stages. Standardized training is likely to improve the consistency of M-scoring and thus the generalizability of future DD research results on this important endemic disease.

A randomized clinical trial of topical treatments for mild and severe udder cleft dermatitis in Dutch dairy cows.

Udder cleft dermatitis (UCD) is a skin lesion in dairy cows affecting the anterior parts of the udder, with the lesions often needing a long time to heal. The lesions can be characterized as mild or severe. The etiology of UCD is not fully understood and studies on the effectiveness of topical treatments have not been published. The objective of this study, therefore, was to conduct a randomized clinical trial to investigate the effectiveness of 2 different topical treatments, one for mild and one for severe UCD lesions, compared with untreated control groups. The treatment and control groups were randomized within herd for mild and severe UCD. The treatments were applied for a maximum period of 12 wk on 8 Dutch dairy farms. Mild UCD lesions were treated once a d 3 times a week on fixed days with a non-sting barrier film. Severe UCD lesions were first stratified into class A (lesion length <5 cm) or class B (lesion length ≥5 cm) and then randomly allocated to treatment or control groups within herd. Both severe lesion classes were treated once per day every day with an enzyme alginogel. Every week, the lesions of affected animals were inspected and photographed by the investigator. These photographs were reviewed weekly by an external wound expert who classified the lesions as mild, severe class A, severe class B, or healed. Based on this classification, the investigator judged weekly whether the lesions had improved compared with their classification of the previous week. For mild UCD lesions, improvement was defined as occurring when lesions were healed. For severe UCD lesions, improvement was defined as a transition from class B to class A, transition from any severe UCD lesion (class A or B) to a mild UCD lesion, or when the lesion was defined as healed. Data were analyzed using a discrete time survival analysis with time to first improvement as dependent variable. In total, data from 214 animals were analyzed to estimate the effectiveness of treatment. Results showed that treatment of mild UCD lesions had no influence on improvement compared with untreated lesions. Treated severe lesions, however, showed 3.4 times more improvement compared with the untreated controls. Improvement varied between herds, and cows with a parity of 5 or higher showed significantly less improvement than first parity animals. Early identification of severe UCD lesions followed by prompt treatment with an enzyme alginogel supports the healing process.

Effects of reduced intramammary antimicrobial use during the dry period on udder health in Dutch dairy herds.

Dry cow therapy (DCT) in the Netherlands changed from mainly blanket to selective antimicrobial DCT. This transition was supported by a national guideline, with the individual somatic cell count (SCC) at the last milk recording before dry-off as the main selection criterion for antimicrobial DCT. The aim of this retrospective observational study is to evaluate the SCC dynamics during the dry period at the herd and individual dry period level following the national transition from mainly blanket to selective antimicrobial DCT. At the herd level, we used 2 data sets to evaluate the SCC dynamics during the dry period: (1) a national data set containing 3,493 herds with data available from 2011 through 2015 and (2) a veterinary practice data set containing 280 herds with data available from 2013 through 2015. The herd level analysis was carried out using key performance indicators provided via milk recording (CRV, Arnhem, the Netherlands): the percentage of cows that developed a new intramammary infection (IMI) during the dry period and the percentage of cows cured of an IMI during the dry period. The effect of DCT at individual dry period level was analyzed with a mixed-effects logistic regression model based on 4,404 dry periods from 2,638 cows in 20 herds within the veterinary practice data set. For these 20 herds, individual SCC data from milk recordings and individual cow DCT were available from 2013 through 2015. No significant changes were observed to the SCC dynamics during the dry period at the herd level. The percentage of cows that developed a new IMI during the dry period ranged between 16 and 18%, and the percentage of cows cured from an IMI during the dry period ranged between 74 and 76%. At the individual dry period level, a low SCC at the first milk recording following a dry period was associated with the use of intramammary antimicrobial DCT with or without the concurrent use of an intramammary teat sealer [odds ratio (OR) = 2.16 and OR = 2.07, respectively], the use of DCT with an intramammary teat sealer only (OR = 1.35), and a low SCC at the last milk recording before dry-off (OR = 1.78). This study demonstrates that the selection of cows for DCT without antimicrobials based on SCC thresholds at the last milk recording is possible without significant changes to udder health and reduced the use of antimicrobials.

Longitudinal study of udder cleft dermatitis in 5 Dutch dairy cattle herds.

Udder cleft dermatitis (UCD) is a skin lesion in dairy cows, most often located between anterior parts of the udder and abdomen, but also found between the front quarters. A few recent studies have investigated the prevalence of UCD, but relatively little is known about its pathogenesis, clinical course, and duration. Therefore, the aim of this study was to investigate the incidence and recovery of UCD on high-prevalence herds. Five Dutch dairy herds with a UCD prevalence of at least 6% were visited weekly for 19 wk, followed by visits every other week for 26 wk. During each visit, all dry and lactating cows were inspected for the presence of UCD signs. If a UCD case was detected, the affected skin was photographed and the photo was subsequently examined by a research assistant. Cows were then classified according to the appearance of the skin into 3 categories: healthy (no photo: no signs), mild (photo: affected skin but no wound), or severe (photo: open wound). The overall mean within-herd prevalence of UCD was 38% and the overall mean incidence was 1.94 UCD episodes per 100 cow-weeks at risk. Incidence of UCD was significantly higher in cows in third or higher parity and significantly increased with DIM. Median observed duration of UCD was 16 wk. The UCD recovery was 3 times more likely for mild than for severe lesions. The probability of moving from one category to another between 2 consecutive visits was very low, indicating that rapid changes in appearance did not occur. The observed incidence of UCD was rather low, and the relatively high prevalence in the selected herds was most likely due to the long duration of lesions rather than a high incidence of new UCD cases.

Addition of meloxicam to the treatment of clinical mastitis improves subsequent reproductive performance.

A blinded, negative controlled, randomized intervention study was undertaken to test the hypothesis that addition of meloxicam, a nonsteroidal anti-inflammatory drug, to antimicrobial treatment of mild to moderate clinical mastitis would improve fertility and reduce the risk of removal from the herd. Cows (n=509) from 61 herds in 8 regions (sites) in 6 European countries were enrolled. Following herd-owner diagnosis of mild to moderate clinical mastitis within the first 120 d of lactation in a single gland, the rectal temperature, milk appearance, and California Mastitis Test score were assessed. Cows were randomly assigned within each site to be treated either with meloxicam or a placebo (control). All cows were additionally treated with 1 to 4 intramammary infusions of cephalexin and kanamycin at 24-h intervals. Prior to treatment and at 14 and 21 d posttreatment, milk samples were collected for bacteriology and somatic cell count. Cows were bred by artificial insemination and pregnancy status was subsequently defined. General estimating equations were used to determine the effect of treatment (meloxicam versus control) on bacteriological cure, somatic cell count, the probability of being inseminated by 21 d after the voluntary waiting period, the probability of conception to first artificial insemination, the number of artificial insemination/conception, the probability of pregnancy by 120 or 200 d postcalving, and the risk of removal by 300 d after treatment. Cox's proportional hazards models were used to test the effect of treatment on the calving to first insemination and calving to conception intervals. Groups did not differ in terms of age, clot score, California Mastitis Test score, rectal temperature, number of antimicrobial treatments given or bacteria present at the time of enrollment, but cows treated with meloxicam had greater days in milk at enrollment. Cows treated with meloxicam had a higher bacteriological cure proportion than those treated with the placebo [0.66 (standard error=0.04) versus 0.50 (standard error=0.06), respectively], although the proportion of glands from which no bacteria were isolated posttreatment did not differ between groups. No difference was observed in the somatic cell count between groups pre- or posttreatment. The proportion of cows that underwent artificial insemination by 21 d after the voluntary waiting period was unaffected by treatment. Treatment with meloxicam was associated with a higher proportion of cows conceiving to their first artificial insemination (0.31 versus 0.21), and a higher proportion of meloxicam-treated cows were pregnant by 120 d after calving (0.40 versus 0.31). The number of artificial inseminations required to achieve conception was lower in the meloxicam compared with control cows (2.43 versus 2.92). No difference was observed between groups in the proportion of cows pregnant by 200 d after calving or in the proportion of cows that were culled, died, or sold by 300 d after calving (17% versus 21% for meloxicam versus control, respectively). It was concluded that use of meloxicam, in conjunction with antimicrobial therapy, for mild to moderate cases of clinical mastitis, resulted in a higher probability of bacteriological cure, an increased probability of conception to first artificial insemination, fewer artificial inseminations, and a greater proportion of cows pregnant by 120 d in milk.

An investigation of the dynamics of intramammary infections acquired during the dry period on European dairy farms.

The dry period is acknowledged as playing a key role in mastitis epidemiology and yet surprisingly few studies have explored dry period infection dynamics in detail. The aim of this study was to investigate the dynamics of intramammary infection across a cohort of dairy herds in Europe. Five hundred and twenty-two cows were recruited from 12 farms in 6 European countries. All cows received antibiotic dry cow therapy but teat sealants were not used. All quarters of all cows were sampled for bacteriology at drying off and in the week immediately postcalving. Two ipsilateral quarters were also sampled for bacteriology in each cow 2 and 6wk after drying off. Cows were body condition scored and teats assessed for cleanliness at all sampling time points and for the presence of a keratin plug during the dry period. Other cow-level parameters such as historic somatic cell counts and milk yields before drying off were collated from farm records. Univariable and multivariable analyses were undertaken to investigate the etiology, prevalence, and dynamics of infection during the dry period and associated influential factors. In summary, environmental mastitis pathogens predominated. Although gram-positive major pathogens were typically well controlled and did not increase in prevalence across the dry period, gram-negative pathogens generally increased in prevalence. There was an increase in the number of quarters that yielded no growth across the dry period, although this was driven by minor rather than major mastitis pathogen control. Other than the presence of a gram-positive or gram-negative pathogen 6wk after drying off, the measured parameters were not influential when considering their effect on the presence of pathogens postcalving. Analysis also suggested that the early and mid dry period may be more important with respect to the timing of acquisition of infection than previously thought. We observed substantial variation in the etiology and prevalence of different pathogens on different farms with, in all cases, at least one of the 12 herds experiencing the opposite of the others with respect to increases and decreases in pathogen prevalence. Overall, this study confirms the importance of the dry period in mastitis epidemiology but highlights the importance of assessing and understanding infection dynamics on individual units. The lack of influence of the cow and quarter factors measured in this study suggests that herd and management factors may be more influential.

Short communication: Protease activity measurement in milk as a diagnostic test for clinical mastitis in dairy cows.

Due to the increasing use of automated milking systems, automated detection of clinical mastitis is becoming more important. Various in- or on-line diagnostic tests are in use, but generally suffer from false mastitis alerts. In this study, we explored a new diagnostic approach based on measurement of protease activity using fluorogenic protease substrates, which can be performed on site, at high speed, and at low costs. Samples from cows with clinical mastitis submitted for bacteriological culture at the University Farm Animal Practice were collected during several months and kept at -20°C until protease activity measurement. A reference set of milk samples from clinically healthy cows were collected on 9 different farms and were tested for protease activity directly and after freezing at -20°C to allow for comparison with the samples from clinical cases. The protease activity in mastitic milk samples was significantly higher than in samples from healthy animals. Based on 71 clinical mastitis samples and 180 milk samples from clinically healthy quarters, the area under the receiver-operating characteristic curve was estimated to be between 0.88 and 0.90, and at a threshold of 38 fluorescence per minute the test had a specificity of 0.99 at a sensitivity of 0.58. Protease activity measured in fresh milk from clinically healthy cows was significantly associated with somatic cell count and parity, but not with electrical conductivity, whereas protease activity in milk that had been frozen was statistically significantly associated with all 3 parameters. This study indicates that protease activity measurement as a stand-alone test can be used for detecting mastitis samples, using milk samples that have been frozen. Because protease activity acts in part on a different biological mechanism than somatic cell count or electrical conductivity, this test may increase the accuracy of mastitis diagnosis in combination with currently available in- or on-line tests in automated milking systems.

Associations between farmer participation in veterinary herd health management programs and farm performance.

In the past few decades, farms have increased in size and the focus of management has changed from curative to preventive. To help farmers cope with these changes, veterinarians offer veterinary herd health management (VHHM) programs, whose major objective is to support the farmer in reaching his farm performance goals. The association between farm performance and participation in VHHM, however, remains unknown. The aim of this paper was to compare farm performance parameters between participants and nonparticipants in VHHM and to differentiate within participation to evaluate the possible added value of VHHM on the farm. Five thousand farmers received a questionnaire about the level of VHHM on their farm. Farm performance parameters of these 5,000 farms were provided. For all respondents (n=1,013), farm performance was compared between participants and nonparticipants and within level of participation, using linear mixed and linear regression models. Farmers who participated in VHHM produced 336 kg of milk/cow per year more and their average milk somatic cell count (SCC) was 8,340 cells/mL lower than farmers who did not participate in VHHM. Participating herds, however, had an older age at first calving (+12d), a lower 56-d nonreturn rate percentage (-3.34%), and a higher number of inseminations per cow (+0.09 inseminations). They also had more cows culled per year (+1.05%), and a lower age at culling (-70 d). Participants in the most-extended form of VHHM (level 3) had a lower SCC (-19,800 cells/mL), fewer cows with high SCC (-1.70%), fewer cows with new high SCC (-0.47%), a shorter calving interval (-6.01 d), and fewer inseminations per heifer (-0.07 inseminations) than participants in the least-extended form of VHHM (level 1). Level 3 participants, however, also had more cows culled per year (+1.74%) and a lower age at culling (-103 d). Discussing specific topics with the veterinarian (milk production, fertility, and udder health) had only marginal effects on improving the farm performance parameters related to those topics. Given the relevance of fertility on the farm and the focus on longevity by society, it is important to determine underlying reasons for the negative associations of these topics with participation in VHHM. A longitudinal study could provide answers to this. For now, veterinarians should be aware of the associations. The increased milk production and milk quality could help the marketing of VHHM to farmers.

Comparison of two intravaginal progesterone releasing devices (PRID-Delta vs CIDR) in dairy cows: blood progesterone profile and field fertility.

Objectives were to compare circulating progesterone (P4) profile and pregnancies per AI (P/AI) of two commercial intravaginal P4 devices (PRID-Delta(®) vs CIDR(®)). In Experiment 1, ovariectomized dairy cows (PRID-Delta, n=6 vs CIDR, n=6) were sampled throughout 7 days to measure circulating P4. In Experiment 2 (PRID-Delta, n=399 vs CIDR, n=375), cows were assigned to treatments, as follows: D0, an intravaginal P4 device containing 1.38g of P4 (CIDR) or 1.55g of P4 (PRID-Delta); D6: 25mg PGF2α (Dinoprost) and P4 devices were removed 24h later. Insemination was performed at 56h after P4 removal. Cows visually detected in estrus between days 18 and 24 after 1st synchronized AI were re-inseminated. PRID-Delta produced greater circulating P4 compared to CIDR, particularly within 4 days after insertion (P<0.01). The logistic regression analysis indicated a tendency for improved P/AI at 1st AI in PRID-Delta cows compared to CIDR (36% vs 31%, P=0.10). More cows were detected in estrus in the following cycle nearly 21d after 1st AI when treated with PRID-Delta (28% vs 16%), but P/AI in the returning-natural estrus breedings did not differ (PRID-Delta=56% vs CIDR=55%; P=0.91). As a result, final cumulative P/AI was greater in cows receiving PRID-Delta (46% vs 37%, P=0.02). These results indicate that PRID-Delta seem to maintain greater circulating P4 levels as compared to CIDR in non-lactating dairy cows. This might explain potential benefits in fertility of dairy cows found in Experiment 2. Underlying physiological consequence of greater circulating P4 during synchronization programs in lactating cows in terms of oocyte quality and other reproductive structures warrants further investigation.

Veterinary herd health management programs on dairy farms in the Netherlands: use, execution, and relations to farmer characteristics.

Veterinary herd health management (VHHM) programs are of growing importance to the dairy industry; they support farmers in the shift from curative to preventive health management, caused by increased herd sizes and quality standards in dairy farming. Farmers participating in VHHM are visited every 4 to 6 wk by their veterinarian, who checks the animals and herd management to intervene in a proactive way with problems regarding animal health and animal welfare. At present, no good overview exists of how VHHM is executed on Dutch dairy farms, and whether different farmers require different types of VHHM. Aims of this study were to (1) map out how many farmers participate in VHHM, (2) describe how VHHM is executed on the farms, and (3) see whether certain farmer characteristics are related to farmers' participation in VHHM. In 2011, a questionnaire was sent to 5,000 Dutch dairy farmers per e-mail. Part 1 of the questionnaire focused on participation in and execution of VHHM and part 2 focused on farmer characteristics regarding external information. Returned questionnaires (n=1,013) were summarized and statistically analyzed. In this study 68.6% of the responding farmers participated in any form of VHHM. The most important activities were fertility checks and advice about fertility; the least important were housing and claw health. Relationships between farmer characteristics (use of and trust in information) and participation in VHHM were found.

First-calving age and first-lactation milk production on Dutch dairy farms.

Farmers attempting to reduce first-calving age (FCA) need to understand which rearing management factors influence FCA and first-lactation milk production (FLP). Reduced FCA might be associated with lower FLP. This study describes the association between herd FCA, FLP, and several herd-level health and rearing management variables and describes the association between FCA and FLP at the cow level. It uses data from a 2010 survey of 100 Dutch dairy farms about general management, colostrum and milk feeding, housing, cleanliness, healthcare, disease, and breeding. It also used available data on FCA and 305-d FLP at both cow and herd level. The associations between median FCA and median FLP of the herd and herd-level health and rearing management variables were determined using multivariate regression analysis. The median FCA was associated with minimum age of first insemination, feeding of waste milk, and the amount of milk given preweaning. The median FLP was associated with median FCA and vaccination status for bovine respiratory syncytial virus. The association between FCA and FLP (based on 8,454 heifers) was analyzed with a single-effect linear mixed model, where the dependent variable was either FCA or relative FCA (defined as the difference between FCA of the heifer and median FCA of the herd to which they belonged). Heifers having an FCA of 24 mo produced, on average, 7,164 kg of milk per 305 d, and calving 1 mo earlier gave 143 kg less milk per 305 d. When FCA did not deviate from the median herd FCA, heifers produced, on average, 7,272 kg of milk per 305 d. From the median FCA of the herd, heifers calving 1 mo earlier produced 90 kg of milk per 305 d less, and heifers calving 1 mo later produced 86 kg per 305 d more. This is the first study that explained FLP using relative FCA. It assumes that heifers raised within the same farm have similar development because they are similarly managed. Similar management is reflected by the median FCA of the herd, with a deviation of the heifer's FCA from median FCA reflecting the heifer's development relative to the herd's average. The advantage of using relative FCA was that it accounts for between-farm differences in rearing management. It showed that earlier insemination without adjusting management to ensure sufficient development lowers FLP. An economic optimum exists between rearing costs, FCA, and FLP and, as a consequence, decisions with regard to young stock management should be made with care.

Short communication: Identification of coagulase-negative staphylococcus species from goat milk with the API Staph identification test and with transfer RNA-intergenic spacer PCR combined with capillary electrophoresis.

Coagulase-negative staphylococci (CNS) are the most commonly isolated bacteria from goat milk, but they have often been identified with phenotypic methods, which may have resulted in misclassification. The aims of this paper were to assess the amount of misclassification of a phenotypic test for identifying CNS species from goat milk compared with transfer RNA intergenic spacer PCR (tDNA-PCR) followed by capillary electrophoresis, and to apply the tDNA-PCR technique on different capillary electrophoresis equipment. Milk samples were collected from 416 does in 5 Californian dairy goat herds on 3 occasions during lactation. In total, 219 CNS isolates were identified at the species level with tDNA-PCR and subjected to the API 20 Staph identification test kit (API Staph; bioMérieux, Durham, NC). If the same species was isolated multiple times from the same udder gland, only the first isolate was used for further analyses, resulting in 115 unique CNS isolates. According to the tDNA-PCR test, the most prevalent CNS species were Staphylococcus epidermidis, Staphylococcus caprae, and Staphylococcus simulans. Typeability with API staph was low (72%). Although the API Staph test was capable of identifying the majority of Staph. epidermidis and Staph. caprae isolates, sensitivity for identification of Staph. simulans was low. The true positive fraction was high for the 3 most prevalent species. It was concluded that the overall performance of API Staph in differentiating CNS species from goat milk was moderate to low, mainly because of the low typeability, and that genotypic methods such as tDNA-PCR are preferred.

Differences between coagulase-negative Staphylococcus species in persistence and in effect on somatic cell count and milk yield in dairy goats.

Coagulase-negative staphylococci (CNS) are the most commonly isolated bacteria from goat milk. The goal of this study was to explore and describe differences between CNS species in persistence of intramammary infection (IMI) and in effect on somatic cell count (SCC) and milk yield (MY). Milk samples were collected from 530 does from 5 Dutch dairy goat herds on 3 occasions during 1 lactation. Coagulase-negative staphylococci species were identified at the species level by transfer RNA-intergenic spacer PCR (tDNA-PCR) followed by capillary electrophoresis. The most prevalent CNS species were Staphylococcus caprae, Staphylococcus epidermidis, Staphylococcus simulans, and Staphylococcus xylosus, but large differences were seen in species distribution between herds. Staphylococcus caprae and Staph. xylosus appeared to be more persistent than other species, but confidence intervals were overlapping. The effect of IMI caused by the 4 most prevalent CNS species on SCC and on MY was determined with linear regression models, and Staph. aureus and Corynebacterium bovis were included in the analyses as reference organisms. Most species were associated with a significantly higher SCC than noninfected udder halves, but the effect of CNS species on SCC was much smaller than the effect of Staph. aureus on SCC. We found a significant positive association between infection with Staph. caprae and MY. Intramammary infection caused by Staph. xylosus, on the other hand, had a negative association with milk yield, comparable to the effect of Staph. aureus, but these effects were not significantly different from zero. Intramammary infections with CNS species have a high prevalence in goats and are persistent, but have a limited effect on SCC compared with IMI with Staph. aureus. The effect of CNS species on MY differed between species, but differences were nonsignificant because limited numbers per species were available for analysis. Therefore, CNS species appear to behave as minor pathogens in goats, but larger studies are needed to give better estimates for the effect on MY.