Evaluation of selected risk factors for different stages of digital dermatitis in Dutch dairy cows.

Digital dermatitis (DD) is a painful infectious disease in dairy cattle that causes ulcerative lesions of the skin just above the coronary band, mainly of the hind legs. Estimates for DD prevalence at cow level in the Netherlands range from 20% to 25%. In this study, risk factors for the various stages of DD were identified and quantified. The hind legs of 6766 cows on 88 farms were scored by trained interns, using the M-scoring system (M0-M4.1). Farms in this study were a convenience sample, based on the prevalence of DD as recorded at the latest herd trim, geographical location and willingness of the farmers to participate. A survey with questions about cow environment and herd management was conducted by the intern at the day of scoring. The data were collected between August 2017 and January 2018. DD was found on 38.6% of the scored legs; 49.8% of the cows had DD on at least one leg and M4 was the most frequent stage (20.9%). Not removing manure on a regular basis resulted in lower odds for M2, M4 and M4.1 compared to cleaning by automatic scrapers ten times a day or more (odds ratio [OR]= 0.16, 0.49 and 0.18, respectively). The odds for M2 and M4 lesions were higher in cows aged 3-5 years than in first-calved cows (OR> 1.5 and > 1.7, respectively). Rubber flooring in the passageways resulted in lower odds for both M1 and M2 (OR, 0.06 and 0.32, respectively). Prophylactic use of footbaths treatment with an alternative active compound resulted in significant higher odds for M4 lesions than formalin and a combination of formalin and copper sulphate (OR= 1.69 and 2.04 respectively). The odds for an M4.1 lesion were lower in cows from smaller herds (n = 50-100) compared to large herds (n >100; OR= 0.67).

Dynamics of Mycoplasma bovis in Dutch dairy herds during acute clinical outbreaks.

Mycoplasma bovis (M. bovis) can cause serious illness in cattle, presenting as arthritis and mastitis in dairy cows and pneumonia, arthritis and otitis media in calves. This study aimed to provide insight into the dynamics of M. bovis within dairy herds, experiencing an acute outbreak in dairy cows. Twenty farms were followed with laboratory testing of suspected dairy cows. Each outbreak farm was sampled five times, at 2-3 week intervals, sampling blood and milk and conjunctival fluid from clinically suspected dairy cows and healthy animals from three different age groups: dairy cows, young stock (7-24 months) and calves (1-6 months). Additionally, bulk tank milk was sampled every visit and environmental samples were taken on the first and last visits. The presence of M. bovis was tested by evaluating antibody titres in blood, bacterial DNA in conjunctival fluid and environmental samples and viable bacteria in milk samples. All data were analysed using logistic regression models, corrected for repeated sampling and within-herd correlation. Sixty percent (12/20) of the herds showed a combination of arthritis and mastitis, while other herds experienced only clinically mastitis (3/20) or arthritis (5/20). From the time an outbreak was confirmed, M. bovis infection was not only present in dairy cows, but also in young stock and calves (80% of the farms). Laboratory tests also confirmed the presence of M. bovis in healthy animals. The M. bovis PCR levels of calves and young stock were highly correlated at all visits (rtotal = 0.81, P < 0.01). Furthermore, M. bovis was present in the environment of the animals. At the end of the 3-month study period, none of the 20 clinical outbreak farms were M. bovis-'negative', based on laboratory testing, although hardly any clinical cases were observed at that time.

Invited review: Genetics and claw health: Opportunities to enhance claw health by genetic selection.

Routine recording of claw health status at claw trimming of dairy cattle has been established in several countries, providing valuable data for genetic evaluation. In this review, we examine issues related to genetic evaluation of claw health; discuss data sources, trait definitions, and data validation procedures; and present a review of genetic parameters, possible indicator traits, and status of genetic and genomic evaluations for claw disorders. Different sources of data and traits can be used to describe claw health. Severe cases of claw disorders can be identified by veterinary diagnoses. Data from lameness and locomotion scoring, activity information from sensors, and feet and leg conformation traits are used as auxiliary traits. The most reliable and comprehensive information is data from regular hoof trimming. In genetic evaluation, claw disorders are usually defined as binary traits, based on whether or not the claw disorder was present (recorded) at least once during a defined time period. The traits can be specific disorders, composite traits, or overall claw health. Data validation and editing criteria are needed to ensure reliable data at the trimmer, herd, animal, and record levels. Different strategies have been chosen, reflecting differences in herd sizes, data structures, management practices, and recording systems among countries. Heritabilities of the most commonly analyzed claw disorders based on data from routine claw trimming were generally low, with ranges of linear model estimates from 0.01 to 0.14, and threshold model estimates from 0.06 to 0.39. Estimated genetic correlations among claw disorders varied from -0.40 to 0.98. The strongest genetic correlations were found among sole hemorrhage (SH), sole ulcer (SU), and white line disease (WL), and between digital/interdigital dermatitis (DD/ID) and heel horn erosion (HHE). Genetic correlations between DD/ID and HHE on the one hand and SH, SU, or WL on the other hand were, in most cases, low. Although some of the studies were based on relatively few records and the estimated genetic parameters had large standard errors, there was, with some exceptions, consistency among studies. Various studies evaluate the potential of various data soureces for use in breeding. The use of hoof trimming data is recommended for maximization of genetic gain, although auxiliary traits, such as locomotion score and some conformation traits, may be valuable for increasing the reliability of genetic evaluations. Routine genetic evaluation of direct claw health has been implemented in the Netherlands (2010); Denmark, Finland, and Sweden (joint Nordic evaluation; 2011); and Norway (2014), and other countries plan to implement evaluations in the near future.

Presence and species identity of rumen flukes in cattle and sheep in the Netherlands.

The purpose of the study was to gain knowledge about the prevalence and identity of rumen flukes (RF) in cattle and sheep in the Netherlands. Routine faecal examinations of diagnostic submissions between May 2009 and September 2014 showed a mean annual herd or flock RF prevalence of 15.8% for cattle and 8.0% for sheep. Prevalence in cattle was higher after 2012 than before, which may reflect a change in detection method as well as an increase in true prevalence. During November and December 2014, an abattoir survey was conducted to allow for scoring of rumen fluke burden and to obtain specimens for molecular species characterization. Over 8 visits to 5 abattoirs in areas deemed to pose a high risk for trematode infection, 116 cows and 41 sheep from 27 herds and 10 flocks were examined. Prevalence of RF was higher in beef cattle than in dairy cattle and higher in cattle than in sheep. Median fluke burden was >100 specimens per animal for most positive animals. Using a semi-quantitative RF density score as a gold standard, sensitivity and specificity of a modified quantitative Dorsman egg counting method were estimated at 82.6% and 83.3%, respectively. Of 14 collected adult rumen flukes, twelve (8 bovine and 4 ovine specimens) were identified as Calicophoron daubneyi. The other two, of bovine origin, were identified as Paramphistomum leydeni, which was unexpected as in other European countries all recently collected rumen flukes in both cattle and sheep were identified as C. daubneyi. The findings implicate that multiple rumen fluke species, intermediate host species and transmission cycles may play a role in rumen fluke infections in the Netherlands.

Comparing the curative efficacy of topical treatment with thiamphenicol and oxytetracycline on digital dermatitis lesions in dairy cattle.

The efficacy of two topically applied antibiotics for the treatment of painful ulcerative stage of bovine digital dermatitis (BDD) lesions was compared in a clinical trial conducted on five dairy farms in the Netherlands during the autumn of 2015. A total of 109 cows with an ulcerative (M2) stage of BDD were randomly appointed a treatment with an antibiotic-based spray. One treatment contained thiamphenicol as active ingredient (TAF). The other treatment had oxytetracycline as active ingredient (ENG). The experimental unit for this study was the hind claw with the presence of an ulcerative BDD lesion. On day 0, claws with ulcerative BDD lesions were trimmed, cleaned, photographed and thereafter treated randomly either with TAF or ENG. Cure was defined as the transition of an ulcerative lesion into a non-painful chronic (M4) or into a healed (M0) stage of BDD at day 28 post-treatment. The cure rate at day 28 of M2 BDD lesions treated with TAF was 89 per cent (95 per cent CI 0.78 to 0.94), and for ENG 75 per cent (95 per cent CI 0.67 to 0.86). So the difference in cure rate was 14 per cent (95 per cent CI 0.00 to 0.27), which was statistically significant. The P value in this experiment is very close to 0.05 indicating that the effect is quite small. If a two-sided test would be used, the small significant effect, in this experiment, will disappear. Overall, the significant better curative effect of TAF on BDD M2 lesions was small, compared with ENG.

Cross-sectional study of the prevalence of and risk factors for hoof disorders in horses in The Netherlands.

Information is scarce on the prevalence of hoof disorders in horses. In this study, we examined the prevalence of and risk factors for hoof disorders in a population of horses in The Netherlands. In a group of 942 randomly selected horses, hoof health was scored during regular foot trimming (one horse/farm). Hooves were assessed for the occurrence of one of 12 hoof disorders by a group of 21 certified farriers in two periods i.e. winter and summer of 2015. The mean age of the group of horses was 11.2±5.6years. They were mainly used for recreation (28.2%), dressage (26.8%), other disciplines (such as carriage driving and breeding) (18.7%), showjumping (17.6%) or combinations of these activities (8.6%). The horse farms studied were evenly distributed throughout the country. The horses were housed on different types of bedding, including straw (51.0%), shavings (17.5%), flax (16.1%) or other materials (11.0%), or were kept at pasture (4.4%). In 85% of the horses, at least one hoof disorder was observed during regular foot trimming. Most of the lesions were mild. The most frequently diagnosed hoof disorders were: thrush (T; 45.0%); superficial hoof wall cracks (SHWC; 30.4%); growth rings (GR; 26.3%); and sole bruises (SB; 24.7%). Less frequently observed hoof disorders included: perforating hoof wall cracks (PHWC; 16.4%); white line disease (WLD; 17.8%); and white line widening (WLW; 11.8%). Horizontal hoof cracks (5.2%), chronic laminitis (3.9%), quarter cracks (2.7%), keratoma (1.8%) and frog cancer (1.0%) were less frequently observed. Factors significantly associated with the occurrence of thrush comprised a wet stable floor (OR 1.6 and 2.9, for somewhat wet to wet respectively, compared to dry), the use of straw as bedding (OR=1.5, compared to flax), the housing strategy (e.g. permanent housing in contrast to permanent pasturing) (OR=1.7) and poor horn quality (OR=3.4). A higher prevalence of WLD was associated with less frequent hoof picking (OR=2.1 if performed weekly instead of daily), the use of flax bedding (OR=2.1, compared to straw) and poor horn quality (OR=8.1). A higher prevalence of SB was observed in horses used for multiple disciplines (OR=3.5, compared to dressage), with white-coloured hooves (OR=5.0, compared to black hooves), with longer intervals between trimming sessions (OR=4.8 in case of 8-10 weeks compared to weekly) and with poor horn quality (OR=5.4). A higher prevalence of WLW was observed in older horses (OR=15.5 for horses >19years, compared to <5years), in those with longer intervals between trimming sessions (OR=1.8 in case of 8-10 weeks compared to weekly), and in certain breeds (OR=3.2 for Friesian horses, 2.9 for Welsh ponies and 13.1 for Shetland ponies, all compared to Dutch Warmblood). In conclusion, although most of the hoof disorders identified were only in a mild stage, still an unexpectedly high prevalence of hoof disorders was observed during regular hoof trimming. Analysis of the data showed that some parameters, such as the use of flax bedding, may be protective for certain hoof disorders but a risk factor for others. This study provides useful guidelines for monitoring hoof health, reducing lameness and optimizing equine welfare.

Association between Dictyocaulus viviparus status and milk production parameters in Dutch dairy herds.

The objective of this study was to estimate the association between Dictyocaulus viviparus bulk tank milk (BTM) test results and milk production and milk composition parameters in adult Dutch dairy cattle herds. Bulk tank milk samples were collected in August and November 2013, and ELISA tests were performed. Two hundred BTM positive (BTM+) and 200 BTM negative (BTM-) herds were selected based on their BTM test result of November 2013, obtained from a list of farms that participated in the Dutch GD Animal Health voluntary monitoring program for controlling nematode infections. The relationship between D. viviparus BTM status and 3 production parameters (milk production, milk fat %, and milk protein %) in summer (June to August 2013) and autumn (September and October 2013) was investigated using generalized linear mixed models. Production data were available for 126 BTM- herds and 109 BTM+ herds. Results showed that a positive D. viviparus status was associated with decreased milk production (June: -1.01, July: -1.19, August: -1.68, September and October: -1.33kg/cow per d). Milk fat percentage was 0.14% and 0.08% lower during summer and autumn, respectively, in BTM+ herds. No significant association was demonstrated between a positive BTM test result and milk protein percentage. Because a strong correlation was present between the BTM status for D. viviparus and that for Ostertagia ostertagi, these losses cannot be attributed to one of the two parasites. However, it is clear that these parasite infections have a considerable effect on production.

A descriptive review of the prevalence and risk factors of hock lesions in dairy cows.

This article reviews the literature on hock lesions in dairy cattle, focusing in particular on their prevalence and associated clinical signs, as well as the scoring systems used to assess them and the data on risk factors. This analysis was limited to hock lesions where there was inflammation and damage of the skin and the subcutaneous tissue only without involvement of the joint. The presence of hock lesions, or tarsal peri-arthritis, is strongly related to time spent lying on abrasive surfaces, prolonged high local pressure or friction of the hock on hard surfaces, and collisions of the hock with cubicle fittings. Since hocks have almost no fatty tissue or muscles between the bones and skin, there is no protection against these types of trauma and skin damage occurs (resulting in hock lesions). The risk of these lesions becoming infected is strongly dependent on the hygiene of the lying area. The prevalence of hock lesions in dairy cows is generally reported as high (>50%). As hock lesions are often correlated with lameness, they are associated with economic losses and impaired welfare, as well as negative societal perception of the dairy sector. Alterations in cubicle characteristics, bedding material, pasture access and lameness prevention may all lower the prevalence of hock lesions; nevertheless, the actual relationship between housing design and other cow- and management-related risk factors on the occurrence of hock lesions appears to be complex and interrelated.

Comparison of two serum and bulk-tank milk ELISAs for diagnosing natural (sub)clinical Dictyocaulus viviparus infection in dairy cows.

Lungworm antibody ELISAs developed in Germany (DE) and The Netherlands (NL) were compared using four sets of serum (S) and bulk-tank milk (BTM) samples from adult dairy cows. The samples originated from 37 farms with or without a suspected clinical lungworm infection during August-October 2010 (Dataset 1), from cows excreting lungworm larvae or not during August-October 2010 (n=59) or May-June 2011 (n=164) (Dataset 2), from 305 farms in a national survey during October 2010 (Dataset 3), and 14 zero-grazing farms during February-April 2011 (Dataset 4). During August-October 2010, covering the second half of the grazing season, the NL-S and NL-BTM ELISA outperformed the DE-S and DE-BTM ELISAs in terms of sensitivity. For at least the NL-S and DE-S ELISA the opposite was found during May-June 2011, covering the end of the winter housing period and the early grazing season. Of the 305 farms in the survey 62.6% were found positive with the NL-BTM ELISA, whereas 2.6% was found positive with the DE-BTM ELISA. ODR values for the zero-grazing farms indicated that a cut-off value of 30% for the DE-BTM ELISA might be more appropriate than the currently used 41%. Results suggest that the NL ELISAs also respond to lungworm antigens other than Major Sperm Protein as used in the DE ELISAs. It is concluded that the generally higher sensitivity of the NL-BTM ELISA makes it better suited for large-scale prevalence studies and herd health monitoring programmes than the DE-BTM ELISA, positivity of which is more associated with the presence of clinical lungworm infection. Reducing the cut-off value of the DE-BTM ELISA from the original 49.3% to the current 41% or the possibly more appropriate 30% increased its sensitivity for detecting lungworm infections, but did not lead to similar sensitivity estimates as found for the NL-BTM ELISA.

A longitudinal study into the effect of grazing on claw disorders in female calves and young dairy cows.

To estimate the prevalence of claw disorders in youngstock and first parity heifers and to evaluate the effect of grazing on claw disorders, 10 Dutch dairy herds participated in a 2-year longitudinal study. Five herds were zero-grazed, while in the other five herds cows and youngstock had access to pasture during the summer. Twenty female calves <1 year of age and 20 females between 1 and 2 years of age were randomly selected on each farm, and were individually monitored at 3 monthly intervals for 2 years. Data from 366 animals with at least five observations were analysed using linear mixed models with a binomial error distribution. Independent variables were grazing, age, month of observation and previous occurrence of the disorder, while herd and animal were included as random effects. Of these 366 animals, 287 had calved once and 76 twice at the end of the study. Analytic results were obtained for digital dermatitis (DD), interdigital dermatitis/heel horn erosion (IDHE) and sole haemorrhages (SH), all of which had a prevalence of >15%. The prevalence of DD increased considerably around first calving on both the grazing and the zero-grazing farms. The prevalence of IDHE increased with age while SH prevalence showed a more fluctuating pattern. Digital dermatitis was less frequently observed in pastured animals than in permanently housed animals (OR=0.12-0.64 depending on month of observation; P<0.05), with the strongest effect being seen during the period when the herds which grazed cattle actually had animals at pasture (May to August). Grazing was also associated with lower levels of IDHE and SH, again particularly during the grazing season.

[Diarrhea and loss of production on Dutch dairy farms caused by the Schmallenberg virus]. / Diarree en productiedaling op Nederlandse melkveebedrijven door het Schmallenbergvirus.

At the end of August and the first two weeks of September 2011 dozens of veterinary practitioners reported to GD Veekijker (Animal Health Service) several dairy herds with cows with sudden decreased milk production, watery diarrhea and sometimes fever. In the beginning these reports came from the Eastern region of the Netherlands, after that also from the other three regions. The percentages of diseased herds per veterinary practice varied from a few till dozens per cent. Extensive bacteriological, virological and parasitological testing of the feces of sick cows did not reveal an infectious cause of the clinical problems. Recently, 50 stored blood samples of clinically diseased cattle were tested for the Schmallenbergvirus using a PCR, and 36% (18/50) tested positive. A large group of control cows (n=115) was also tested with the PCR and all cattle tested negative. Likely the Schmallenbergvirus was the primary cause of the clinical symptoms in the Dutch dairy herds. Further research will be done to confirm this.

The value of a bulk-tank milk ELISA and individual serological and faecal examination for diagnosing (sub)clinical Dictyocaulus viviparus infection in dairy cows.

To test the value of a recently developed bulk-tank milk (BTM) ELISA for diagnosing (sub)clinical Dictyocaulus viviparus infection in lactating dairy herds under field conditions, bulk milk samples were collected from farms with or without clinical symptoms suspected to be caused by lungworm infection. Results of the BTM ELISA were compared against individual examinations for lungworm larvae in faeces and lungworm antibodies in serum from up to 20 heifers (parity 1) and up to 20 cows (parity ≥ 2) on the same farms. This also allowed, for the first time, to examine the value of individual faecal and serological examinations in the diagnosis of (sub)clinical lungworm infections. In total, 33 farms participated. Of these, 16 reported clinical symptoms possibly related to lungworm infection (defined as a suspected positive clinical status or CS(+)) and 17 reported having no such symptoms (CS(-)). In total, 503 heifers and 649 cows were sampled. Of all faeces samples positive for lungworm larvae, 94 were from heifers (18.9% of all heifers) and 75 from cows (11.7% of all cows) (P<0.001). Of all sera positive for lungworm antibodies, 130 were from heifers (26.1% of all heifers) and 113 from cows (17.5% of all cows) (P<0.001). Of the CS(-) farms 41% had at least one heifer or cow shedding larvae and 71% had at least one seropositive heifer or cow. Of the CS(+) farms this was 81% and 94%, respectively. There were only 4 farms, all CS(-), where none of the animals were found shedding larvae and all animals tested seronegative. This implies that on 76% of the CS(-) farms lungworm infection circulated unnoticed. On all CS(+) farms the suspicion that lungworm caused the respiratory symptoms was confirmed by the individual faecal and serological examinations, whereas the BTM ELISA confirmed presence of lungworm on half of the CS(+) farms. The latter in particular occurred on farms with the more severe outbreaks. Overall, of 32 available BTM samples 10 tested positive (8 of 15 CS(+) and 2 of 17 CS(-) farms). For diagnosing suspected lungworm disease it was concluded that testing a BTM sample might suffice in case of moderate to severe outbreaks. However, in case of a mild outbreak with just a few animals coughing, examining individual animals has to be preferred over testing a BTM sample. The likelihood to detect lungworm infection is higher if heifers are sampled compared to cows. Sensitivity of the BTM ELISA was 35.7% if the presence of at least one seropositive and/or one larvae shedding animal in the herd was used to define lungworm positive farms. On average, at least 30% of the herd had to be seropositive before the BTM ELISA was found positive for lungworm antibodies. Results indicate that the BTM ELISA in its current form does not appear to be suitable for surveys on the prevalence of lungworm presence on farms. However, this BTM ELISA might be used in large-scale surveys to detect, for instance, annual changes in percentage positive farms, as long as it is recognized that positivity is more closely related to incidence of lungworm disease than to prevalence of lungworm infection.

Toxocara vitulorum in suckling calves in The Netherlands.

A Dutch farmer with beef cattle and suckling calves noticed one of the calves suffering from diarrhoea and observed large white worms near the perineum. In the faeces of this calf, eggs of Toxocara vitulorum were found. The majority of the cows in the herd were of the Piemontese breed previously imported from southern France. Treatment with albendazole was successful. Two other calves had positive faecal egg counts. One month after treatment of these calves with doramectin, no eggs were found. To prevent further infections on the farm and dissemination of this uncommon infection to other farms, the farmer decided to have all his cattle slaughtered.

Failure to eradicate the lungworm Dictyocaulus viviparus on dairy farms by a single mass-treatment before turnout.

On two dairy farms it was attempted to eradicate lungworm, Dictyocaulus viviparus, by means of a single mass-treatment of all cattle that had been grazed the previous year(s), before turnout in the spring. Both farms experienced two years of lungworm outbreaks in the adult dairy herd prior to this study. Following confirmation that both herds contained lungworm carriers, all animals older than approximately 6 months were treated with eprinomectin in March 2007. One week after treatment none of the animals were shedding lungworm larvae. Subsequently, animals were pastured according to normal farm routine. From August to November all first-calving heifers were coprologically and serologically monitored for lungworm infection. During 2007 both farms remained lungworm-negative and did not report any clinical sign indicative for a lungworm infection. The following year, on one of the farms replacements grazing on cow pastures, started showing signs of parasitic bronchitis which was serologically confirmed. The other herd remained free of parasitic bronchitis until at least the fourth year after the mass treatment, although some coughing was noticed in 2008 among first-lactation heifers. It was concluded that a single mass-treatment before the grazing season may be useful to break a series of annual lungworm outbreaks. However, it is not a secure method to prevent parasitic bronchitis for more than one year.