Dutch Cattle Research Articles

BREEDING HERITAGE OF DAIRY CATTLE OF UKRAINE – UKRAINIAN WHITE-HEADED BREED

BREEDING HERITAGE OF DAIRY CATTLE OF UKRAINE – UKRAINIAN WHITE-HEADED BREED

Presence of pesticides and biocides at Dutch cattle farms participating in bird protection programs and potential impacts on entomofauna

In spite of meadow bird protection programs, a severe decline of meadow birds is taking place in the Netherlands. It is hypothesized that pesticides and other agrochemicals may contribute to this decline through a negative impact on the entomofauna; a very important food source of meadow birds and especially of their chicks. The present study analysed the presence of 664 pesticides (including biocides and some metabolites) in soil, concentrated feed, manure and some fodder samples from 23 cattle farms in the province of Gelderland (the Netherlands). Furthermore, the presence of 21 anti-parasitic medicines in manure from storage facilities was analysed. For farms practicing field grazing, the number of dung beetles in field samples of fresh manure was determined and a potential relationship with the presence of pesticide residues was explored. Of the 23 farms included in present study, 22 participated in meadow bird protection schemes. A total of 129 different pesticides (including biocides and metabolites) was detected, of which 115 at the 15 conventional farms and 69 at the 8 certified organic farms. The average total amount of pesticide residues detected tended to be lower at organic cattle farms than at conventional farms; for organic concentrated feed this difference was significant at a factor of 3.7. A significant negative correlation was found between the estimated daily intake of insecticides by cattle through the consumption of concentrated feed and hay, and the numbers of dung beetles detected in fresh manure samples in the field. We discuss the most important insecticides detected in concentrated feed and hay, and conclude that their quantities in manure and feed, if compared with LR50 values, give a reason for concern. More research is needed to establish the role of agrochemicals in the decline of meadow birds.

Evaluation of the association between the introduction of data-driven tools to support calf rearing and reduced calf mortality in dairy herds in the Netherlands

Between 2009 and 2017, calf mortality in the Dutch dairy sector showed a slight but steady increase. The Dutch dairy industry decided to act and supported the development of several data-driven tools that were implemented from 2018 on. The tools informed farmers about their calf mortality rates and stimulated them to improve. The Trend Analysis Surveillance Component of the Dutch cattle Health Surveillance System provided the possibility to evaluate the calf mortality in Dutch dairy herds before and after implementation of these tools. The aim of this study was to evaluate the association between calf mortality and i) all actions that were taken by the Dutch dairy industry to improve the quality of calf rearing and ii) other potential management or environmental factors associated with calf mortality in Dutch dairy herds.Census data from approximately 98 % of all Dutch dairy herds were available from July 2014 until June 2019. Four different calf mortality indicators were defined: perinatal calf mortality risk (i.e., mortality before, during, or shortly after the moment of birth up to the moment of ear-tagging), postnatal calf mortality risk (ear-tagging till 14 d), preweaned calf mortality rate (15 d-55 d) and weaned calf mortality rate (56 d-1 yr.). All data were aggregated to herd and monthly level and were analysed using Population-Averaged Generalized Estimating Equations (PA GEE models) with a Poisson distribution and log link function.When the period before implementation of the tools (2016–2017) was compared to the period thereafter (2018–2019), all four calf mortality indicators decreased. The relative decrease varied from 3 % (postnatal calves) and 10 % (perinatal calves) up to 18 % and 30 % in preweaned and weaned calves, respectively. Registrations of veterinary treatments such as antimicrobial use, vaccinations (calf or cow) and antiparasitic treatments were associated with calf mortality. Additionally, herds with a higher level of metabolic problems in transition cows had a higher calf mortality and also extreme outside temperatures were associated with higher calf mortality.Given that the different tools were implemented nation-wide and a control group was lacking, we could not prove that implementing the different tools caused the reduction in calf mortality. We do however, believe that all the actions and communication towards improvement of calf rearing in dairy herds led to an increased awareness among farmers towards the importance of calf rearing management and therefore a reduction in calf mortality on national level.

Monitoring udder health on routinely collected census data: Evaluating the short- to mid-term consequences of implementing selective dry cow treatment

In 2013, the preventive use of antimicrobials in Dutch livestock was prohibited, including a ban on the blanket application of antimicrobial dry cow treatment (BDCT). Since then, selective dry cow treatment (SDCT) has become the standard approach. In this study, we aimed to determine the effect of the ban on BDCT and the extent of the subsequent adoption of SDCT on antimicrobial usage (AMU) and udder health on Dutch dairy farms. In the Dutch cattle health surveillance system, AMU for dry cow treatment (AMUDCT), AMU for intramammary treatment at any point in time (AMUIMM), and udder health indicators are routinely and continuously monitored. This provided the opportunity to study associations among SDCT, udder health, and AMU on census data of approximately 17,000 dairy herds, with about 1.67 million cows in total (>2 yr old) at one moment in time in the period from 2013 until 2017. Six udder health parameters were evaluated using multivariable population-averaged generalized estimating equation models. The year in which the ban on BDCT was introduced (2013) was compared with the period thereafter (2014-2017). Additionally, AMUIMM and AMUDCT were included as independent variables to evaluate whether the extent to which SDCT was implemented on the herd level was associated with udder health. Demographic parameters were included as potential confounders. Since the ban on BDCT, overall declines of 63% in AMUDCT and 15% in AMUIMM were observed. The raw data show an improvement in 5 out of 6 evaluated udder health parameters between 2013 and 2017. Nevertheless, the multivariable model results showed that the period since the ban on BDCT was associated with a small but significant increase in the percentage of cows with high somatic cell count (HSCC) and new HSCC (+0.41% and +0.06%, respectively). Additionally, the probability of belonging to the group of herds with more than 25% of primiparous cows having HSCC during the start of lactation increased slightly, associated with the period after which BDCT was banned (odds ratio = 1.08). The probability of belonging to the group of herds with more than 25% cows having a persistent HSCC during the dry period was not affected and bulk milk somatic cell count showed a slight but significant reduction. The only udder health parameter that notably worsened during the study period was the probability of belonging to the group of herds with more than 25% of multiparous cows with a new HSCC after the dry period, during the start of lactation (odds ratio = 1.23). In herds where the farmer decided not to apply any dry cow therapy (≈20% of all herds), all udder health parameters were poorer compared with herds in which dry cow therapy was applied to some extent. The ban on BDCT and implementation of SDCT in the Netherlands was associated with a considerable reduction in AMU without a major impairment in udder health at the national level. Although negative effects of changed dry cow management were observed in some herds, we conclude that SDCT can be introduced without substantial negative effects on udder health.

Characterization of Genetic Diversity Conserved in the Gene Bank for Dutch Cattle Breeds

In this study, we characterized genetic diversity in the gene bank for Dutch native cattle breeds. A total of 715 bulls from seven native breeds and a sample of 165 Holstein Friesian bulls were included. Genotype data were used to calculate genetic similarities. Based on these similarities, most breeds were clearly differentiated, except for two breeds (Deep Red and Improved Red and White) that have recently been derived from the MRY breed, and for the Dutch Friesian and Dutch Friesian Red, which have frequently exchanged bulls. Optimal contribution selection (OCS) was used to construct core sets of bulls with a minimized similarity. The composition of the gene bank appeared to be partly optimized in the semen collection process, i.e., the mean similarity within breeds based on the current number of straws per bull was 0.32% to 1.49% lower than when each bull would have contributed equally. Mean similarity could be further reduced within core sets by 0.34% to 2.79% using OCS. Material not needed for the core sets can be made available for supporting in situ populations and for research. Our findings provide insight in genetic diversity in Dutch cattle breeds and help to prioritize material in gene banking.

Farmers' relationship with different animals: the importance of getting close to the animals. Case studies of French, Swedish and Dutch cattle, pig and poultry farmers

The article analyses how cattle and poultry farmers in the Netherlands described their relationship with their farm animals and explores the factors that influence their level of attachment to them. The analysis draws upon Willkie’s (2005) framework of farmer-animal relationship, which distinguishes between different levels of attachment and detachment. This framework was useful for explaining why farmers developed different levels of attachment to animals, with the species, farm sector and housing system all playing roles in influencing this. Farmers tended to be more attached to cows than to chickens and felt more attachment towards breeding, as opposed to fattening, animals. Breeding, especially of cows, linked the animal to the personal histories of farmers, since their ancestors had often established the bloodlines of dairy cows. Farmers’ relationships with their animals were also influenced by the organization of production at the farm: the number of animals, their length of stay on the farm and the housing system. These factors all influenced the visibility of the animal as an individual and as a ‘real’ animal and not a living tool of production. The species and function of an animal and the organization of production largely defined the frequency, intensity and intimacy of farmers’ contact with individual animals. Practically all farmers (across sectors) perceived taking good care of animals and avoidance of suffering as a core element of their job and caring about animals as central to their definition of a ‘good farmer’. Beyond this, different groups of farmers showed clear differences in their level of attachment to their animals. In general dairy farmers felt more strongly attached to their dairy cows than farmers to their beef cattle or veal, whereas most poultry farmers felt rather detached from their chicken, and tended to perceive them as part of a flock and ‘living production tools’. These animals were not only de-individualized; at times and when seen solely as part of a meat and egg production system they were almost de-animalized.

Development of a genetic tool for determining breed purity of cattle

Breed registries have been established for livestock species to maintain the purity of breeds and to document the ancestry of animals. However, a significant number of animals are unregistered with no or incomplete pedigree data and uncertain ancestral breed origin. Although many local livestock breeds are “at risk” on the basis of the number of purebred breeding females in a breed registry, there is often also a reservoir of unregistered animals that may belong to the same breed. However, due to the missing pedigree it is not possible for breed societies or herd books to include those animals in their breeding program for purebred animals. A genetic test was developed to unequivocally determine the breed origin of cattle without pedigree data. Such a test will open up the possibility to incorporate animals without pedigree data in the breed registry that turn out to be purebred based on the test results. In this study we developed and validated such a test. Genotype data (50k SNP array) were used to compose reference populations for six local Dutch cattle breeds. The combination Principal Component Analysis and Random Forest was used to perform SNP selection. A total of 133 informative SNPs were selected to determine breed composition of individual animals. Overall, 82.0% of the animals in the test population are correctly assigned to the breed in question. For Dutch Red and White Friesian and Deep Red Cattle we suggest that if an animal has a percentage for its own breed <0.775 to use the combined percentage of two breeds (Deep Red Cattle with Meuse‐Rhine‐Yssel and Dutch Red and White Friesian with Dutch Friesian). Using this criteria 88.9% (104 out of 117) of the animals in the test population is correctly assigned.The developed test was successful and will be implemented in practice to identify (partly) unregistered individuals as being purebred (or not) for one of the Dutch local cattle breeds.

The impact of using old germplasm on genetic merit and diversity-A cattle breed case study.

Artificial selection and high genetic gains in livestock breeds led to a loss of genetic diversity. Current genetic diversity conservation actions focus on long-term maintenance of breeds under selection. Gene banks play a role in such actions by storing genetic materials for future use and the recent development of genomic information is facilitating characterization of gene bank material for better use. Using the Meuse-Rhine-Issel Dutch cattle breed as a case study, we inferred the potential role of germplasm of old individuals for genetic diversity conservation of the current population. First, we described the evolution of genetic merit and diversity over time and then we applied the optimal contribution (OC) strategy to select individuals for maximizing genetic diversity, or maximizing genetic merit while constraining loss of genetic diversity. In the past decades, genetic merit increased while genetic diversity decreased. Genetic merit and diversity were both higher in an OC scenario restricting the rate of inbreeding when old individuals were considered for selection, compared to considering only animals from the current population. Thus, our study shows that gene bank material, in the form of old individuals, has the potential to support long-term maintenance and selection of breeds.

A quantitative risk-analysis for introduction of Bovine Viral Diarrhoea Virus in the Netherlands through cattle imports

Many countries have implemented control programmes aiming to eradicate Bovine Viral Diarrhoea Virus (BVDV). After obtaining the free status, a risk of re-introduction of the virus through import may remain. Therefore the risk of introduction of BVDV through cattle imports in the Netherlands was quantified and the effectiveness of subsequent intervention measures was assessed.Data, literature and expert opinion were used to estimate values for input parameters to feed a stochastic simulation model. The probability that BVDV was imported was differentiated into persistently infected (PI) cattle, trojan cows that transmitted the virus vertically resulting in a PI foetus (TR) and transient infected cattle (TI). The import risk was stratified to beef, dairy, small scale, suckler, trade, veal and young stock herds. The intervention scenarios that were evaluated consisted of virus testing, a combination of virus testing and antibody testing in pregnant cows, abolishment of imports from high risk countries (i.e. countries with a BVDV prevalence >15%) and a combination of import restrictions and testing prior to import.Each year, 334 (5th and 95th percentile: 65–902) Dutch cattle herds were estimated to be infected with BVDV through import. Veal herds account for most infections associated with import (87%), whereas in the other herd types, only 9 beef, 6 dairy, 2 small scale, 16 suckler, 10 trade and 2 young stock herds are infected through imports per year. Import of PI cattle is the most important risk for introduction in veal herds, while import of TR cows is the main source of BVDV introduction in dairy, small scale and suckler herds. With the intervention scenarios, the number of BVDV infected herds in the Netherlands could be reduced to 81 and 58 herds per year when respectively virus testing or a combination of virus and antibody testing was applied or to 108 herds when import from high risk countries was abolished. With the scenario in which both import from high risk countries was abolished combined with virus and antibody testing, the number of BVDV infected herds could be reduced to 17 herds per year. The risk assessment showed that BVDV is regularly imported in the Netherlands. The import risk can effectively be reduced by implementing diagnostic testing prior to import and only import cattle with a favourable result, eventually combined with certain trade restrictions.

Conservation priorities for the different lines of Dutch Red and White Friesian cattle change when relationships with other breeds are taken into account

From a genetic point of view, the selection of breeds and animals within breeds for conservation in a national gene pool can be based on a maximum diversity strategy. This implies that priority is given to conservation of breeds and animals that diverge most and overlap of conserved diversity is minimized. This study investigated the genetic diversity in the Dutch Red and White Friesian (DFR) cattle breed and its contribution to the total genetic diversity in the pool of the Dutch dairy breeds. All Dutch cattle breeds are clearly distinct, except for Dutch Friesian breed (DF) and DFR and have their own specific genetic identity. DFR has a small but unique contribution to the total genetic diversity of Dutch cattle breeds and is closely related to the Dutch Friesian breed. Seven different lines are distinguished within the DFR breed and all contribute to the diversity of the DFR breed. Two lines show the largest contributions to the genetic diversity in DFR. One of these lines comprises unique diversity both within the breed and across all cattle breeds. The other line comprises unique diversity for the DFR but overlaps with the Holstein Friesian breed. There seems to be no necessity to conserve the other five lines separately, because their level of differentiation is very low. This study illustrates that, when taking conservation decisions for a breed, it is worthwhile to take into account the population structure of the breed itself and the relationships with other breeds.

Selection of SNP from 50K and 777K arrays to predict breed of origin in cattle1

Reliable breed assignment can be performed with SNP. Currently, high density SNP chips are available with large numbers of SNP from which the most informative SNP can be selected for breed assignment. Several methods have been published to select the most informative SNP to distinguish among breeds. In this study, we evaluated Delta, Wright's FST, and Weir and Cockerham's FST, and extended these methods by adding a rule to avoid selection of sets of SNP in high linkage disequilibrium (LD) providing the same information. The SNP that had a r2 value>0.3 with any of the SNP already selected were discarded. The different selection methods were evaluated for both the 50K SNP and 777K Bovine BeadChip. Animals from 4 cattle breeds (989 Holstein Friesian, 97 Groningen White headed, 137 Meuse-Rhine-Yssel, and 64 Dutch Friesian) were genotyped. After editing 30,447 and 452,525 SNP were available for the 50K and 777K SNP chip, respectively. All selection methods showed that only a small set of SNP is needed to differentiate among the 4 Dutch cattle breeds, whereas comparison of the selection methods showed only small differences. In general, the 777K performed marginally better than the 50K BeadChip, especially at higher confidence thresholds. The rule to avoid selection of SNP in high LD reduced the required number of SNP to achieve correct breed assignment. The Global Weir and Cockerham's FST performed marginally better than other selection methods. There was little overlap in the SNP selected from the 2 BeadChips, whereas the number of SNP selected was about the same.

No long-term influence of movement restriction regulations on the contact-structure between and within cattle holding types in the Netherlands

BackgroundMore and more countries hold databases on cattle movements. The primary purpose of the registration of cattle movements is to provide data for quick tracing of contagious animals in case of disease outbreaks and food safety scares. Nevertheless, these data can also be used for analytical studies to get insight into the nature of the contact structure between and within cattle holding types. This paper focuses on the effect post-2001 FMD movement regulations have had on the number of cattle movements between different and within the same cattle holding types. Important characteristics and dynamics of cattle movement patterns of Dutch cattle holding types were identified using data on cattle movements after the 2001 FMD outbreak.ResultsThe results showed that in 2001, just after the FMD outbreak when strict movement restriction regulations were in force, a reduced number of cattle movements was seen compared to before the FMD outbreak. However, the number of cattle movements off-farm for live trade and the number of imported cattle increased in the period 2002–2004 to higher levels than expected, i.e. to levels almost as high as before the FMD outbreak, despite operative movement restriction regulations. As the number of cattle movements to and from traders strongly decreased just after the FMD outbreak in 2001, traders regained their central role again in the network in the years 2002–2004.ConclusionsQuantifying the Dutch cattle contact structure between and within holding types up to 3.5 years after the FMD outbreak gave evidence that the post-FMD movement restriction regulations were not able to reduce the number of cattle movements in the longer term. With that the risk of a large epidemic increased. Quantifying contact structures based on animal movement data between different and within the same cattle holding types is important for targeting disease control and for assessing compliance with legislation.

Low predictive value of seroprevalence of Toxoplasma gondii in cattle for detection of parasite DNA

The role of beef in human infections with Toxoplasma gondii is not clear. To get a better understanding of the value of seroprevalence as an indication of the role of beef in human infections with T. gondii we studied the seroprevalence of T. gondii in Dutch cattle and analysed the correlation between detection of antibodies and parasitic DNA. An indirect ELISA was developed and used to test a sample of the Dutch cattle population. Since validation of the ELISA was hampered by a lack of sufficient bovine reference sera, the results were analysed in two different ways: using a cut-off value that was based on the course of the OD in 27 calves followed from birth until 16months of age, and by fitting a mixture of two normal distributions (binormal mixture model) to the log-transformed ODs observed for the different groups of cattle in the study population. Using the cut-off value, the seroprevalence was estimated at 0.5% for white veal, 6.4% for rosé veal and 25.0% for cattle. However, using the frequency distributions the prevalences were higher: 1.9% for white veal, 15.6% for rosé veal and 54.5% for cattle. Next, for 100 cattle the results with two different serological assays (ELISA and Toxo-Screen DA) were compared with detection of parasites by our recently developed sensitive magnetic capture PCR. Toxoplasma gondii DNA was detected in only two seronegative cattle. This discordance demonstrates that seroprevalence cannot be used as an indicator of the number of cattle carrying infectious parasites. Demonstrating parasitic DNA in seronegative cattle and not in seropositive cattle suggests that only recent infections are detectable. Whether beef from these PCR-positive cattle is infectious to humans remains to be studied.

Bluetongue virus serotype 8 (BTV-8) infection reduces fertility of Dutch dairy cattle and is vertically transmitted to offspring

In 2007, BTV-8 re-emerged for the second year in the Netherlands and caused morbidity and increased mortality in cattle herds. In addition, cattle farmers reported reduced fertility in their cows. For this study, fifteen herds that were not vaccinated were selected. These were matched to 10 vaccinated herds by geographic region. At the start of the study, in July 2008, all cattle in the non-vaccinated herds >1 year old were sampled. All seronegative cows entered the study program and blood samples from these cows were tested for antibodies against BTV-8 in an ELISA. Cows were sampled at intervals of three weeks and sampling was stopped once a cow tested seropositive. Sampling ceased in all remaining cows in December 2008. Newborn calves originating from infected dams or from vaccinated dams were tested by PCR for BTV-8. Fertility data were obtained from the Royal Dutch Cattle Syndicate (CRV). Multi-level generalized latent and linear models were used for analyses. In 2008, 185 (17.2%) out of 1,074 initially seronegative non-vaccinated cattle seroconverted and were assumed to be infected with BTV-8. Infected cows were 5 (95% CI: 1.9–14.3) times more likely to return for insemination within 56 days after first insemination. In addition, these cows needed 1.7 (95% CI: 1.4–2.0) times more inseminations for an assumed pregnancy, and needed 2.5 (95% CI: 2.4–2.6) times more days between first and last insemination compared to the period prior to seroconversion and compared to cows not infected by BTV-8 in 2008. No association between BTV-8 infection and the chance to abort between 100 and 260 days after last insemination was found. In total, 48 calves originating from infected cows were tested by PCR for the presence of BTV-8. Ten (20.8%) out of these 48 calves were born PCR-positive. None of 256 calves from vaccinated dams tested PCR-positive. Further, cows infected during the second half of gestation had a 15.5 times (95% CI: 1.3–190.4) higher chance of a PCR-positive newborn calf compared to cows infected in the first half of gestation. This study showed that BTV-8 has a negative effect on fertility of dairy cattle.

The BSE Risk of Processing Meat and Bone Meal in Nonruminant Feed: A Quantitative Assessment for the Netherlands

The total ban on use of meat and bone meal (MBM) in livestock feed has been very successful in reducing bovine spongiform encephalopathy (BSE) spread, but also implies a waste of high-quality proteins resulting in economic and ecological loss. Now that the BSE epidemic is fading out, a partial lifting of the MBM ban might be considered. The objective of this study was to assess the BSE risk for the Netherlands if MBM derived from animals fit for human consumption, i.e., category 3 MBM, would be used in nonruminant feed. A stochastic simulation model was constructed that calculates (1) the probability that infectivity of undetected BSE-infected cows ends up with calves and (2) the quantity of infectivity (Q(inf)) consumed by calves in case of such an incident. Three pathways were considered via which infectivity can reach cattle: (1) cross-contamination in the feed mill, (2) cross-contamination on the primary farm, and (3) pasture contamination. Model calculations indicate that the overall probability that infectivity ends up with calves is 3.2%. In most such incidents the Q(inf) is extremely small (median = 6.5 x 10(-12) ID(50); mean = 1.8 x 10(-4) ID(50)), corresponding to an average probability of 1.3 x 10(-4) that an incident results in >or=1 new BSE infections. Cross-contamination in the feed mill is the most risky pathway. Combining model results with Dutch BSE prevalence estimates for the coming years, it can be concluded that the BSE risk of using category 3 MBM derived from Dutch cattle in nonruminant feed is very low.

The Use of Data from Sampling for Bacteriology for Genetic Selection Against Clinical Mastitis

One breeding objective of Dutch cattle breeders is to improve genetic resistance against clinical and subclinical mastitis. Because of a lack of direct mastitis information, udder health breeding values are based on indirect traits. Inclusion of direct information on clinical mastitis could improve reliability of breeding values. The aim of this study was to investigate whether data from milk samples sent in for bacteriology are potential sources of information for the occurrence of mastitis, which may be used in animal breeding, and if so how this data can be used. Although there are 2 separate flows of milk samples for bacteriology in the Netherlands, it was not considered necessary to account for the origin of the samples. In both flows, the majority of the samples are visually normal and flow-specific traits are highly correlated. Therefore, information from these flows is combined for genetic analysis. Nearly two-thirds of the bacteriology data could be linked to milk recording and pedigree records. Relatively few farmers (<3%) took 5 or more samples for bacteriology between January 1, 2003, and March 31, 2006. Their herds had, on average, greater milk production and lower cell counts than herds for which no samples were taken. However, the range and variation within both groups of herds for these variables was similar and there was a large overlap in sires used within both groups. Whether or not samples were taken for bacteriology turned out to be a potentially useful indicator for clinical mastitis at the cow level, because this trait had a strong positive genetic correlation with clinical mastitis registered by farmers (0.84 or 0.89, depending on the data set) and similar heritability (2%) and genetic variation. Also, genetic correlations of bacteriology with SCC traits were similar to those for farmer-registered clinical mastitis. An important advantage of these bacteriology data is that they are already collected routinely and stored in a central database in the Netherlands; this is not the case for registration of clinical cases. Thus, data from bacteriological culturing can be used for genetic improvement of udder health.

Cattle transfers between herds under paratuberculosis surveillance in The Netherlands are not random

The rate and structure of cattle transfers between 206 Dutch cattle herds with a ‘ Mycobacterium avium subsp. paratuberculosis (Map)-free’ status by November 2002, were analyzed over a 3-year period (November 1999–November 2002). Of the 206 ‘Map-free’ herds, 184 were closed herds during the period studied. In total, 280 cattle had been introduced into 22 herds at an average rate of 0.33 animals per year per 100 cattle present in the 206 herds. Assuming a random herd-contact structure, the observed rate of cattle transfers between certified ‘Map-free’ herds was sufficiently low to relax the surveillance scheme to biennial herd examinations by pooled fecal culture of all cattle ≥2 years of age. The cattle transfers were not randomly distributed over the herds. Forty-four of the 280 cattle originated from 12 other ‘Map-free’ herds. The other 236 cattle did not originate from a ‘Map-free’ herd and were introduced into a herd before it obtained the ‘Map-free’ status. No cattle were introduced into any of the ‘Map-free’ herds from which cattle were transferred to other ‘Map-free’ herds. Thus, continued propagation of the infection by cattle transfers was impossible in the group of herds studied during the study period. Therefore the surveillance scheme may be further relaxed, and may be differentiated regarding the risk herds pose to other herds.

Genetic Parameters for Claw Disorders in Dutch Dairy Cattle and Correlations with Conformation Traits

Impaired claw health is one of the major problems causing production loss and reduced animal welfare in dairy cattle. In response, the Dutch Animal Health Service (GD) Ltd. initiated this study, in which claws of lactating and near-term cows and heifers in 430 herds were trimmed by hoof trimmers and the health status of the rear claws recorded. Only herds with >75% of the animals having feet trimmed were considered, resulting in records on 21,611 animals. Eight claw disorders were scored: digital dermatitis (DD), interdigital dermatitis/heel horn erosions (IDHE), sole hemorrhage (SH), chronic laminitis (CL), sole ulcer (SU), white line disease (WLD), interdigital hyperplasia (HYP), and interdigital phlegmona (IP). The prevalence varied from 0.6% (IP) to 39.9% (SH). More than 70% of the animals had at least one claw disorder. Conformation traits and locomotion were recorded once during the animal's first lactation by trained classifiers of the Royal Dutch Cattle Syndicate and completely independent of the moment of claw trimming. Heritabilities were estimated using a sire model, and ranged from <0.01 (IP) to 0.10 (DD and HYP). Genetic correlations of incidences of claw disorders with locomotion were variable, ranging from 0.13 (SH) to −0.91 (CL). Genetic correlations with the rear leg conformation traits were lower, ranging from 0.04 (ID with rear leg side view) to −0.69 (IP with rear leg rear view).

Zero-tolerance for faecal contamination of carcasses as a tool in the control of O157 VTEC infections

The Dutch government, the meat producers organisation and the meat industry have recognised O157 VTEC as an important public health hazard, and agreed on the necessity to improve the hygiene in Dutch cattle- and calf-slaughtering establishments. This paper reports activities within a national action programme to achieve this objective, “Zero-tolerance for faecal contamination during slaughter of cattle and calves”. The study included inspection of hygienic performances in slaughterhouses, and visual and microbiological (aerobic plate counts, Enterobacteriaceae counts and O157 VTEC presence/absence on visually clean cattle and calf carcasses) assessment of carcass cleanliness. Initial studies concluded that the hygienic performances in the Dutch cattle and calf slaughterhouses should be immediately improved. In 52% of the slaughterhouses inspected, carcasses were observed to be contaminated with hide, hair or faeces. Around 45% of the slaughterhouses had constructural deficiencies likely to lead to structural cross-contamination of carcasses, by direct carcass–carcass contact, or by indirect contacts with floors, walls or steps. In 39% of the slaughterhouses, cleaning and disinfection procedures were inadequate. Visual inspection of chilled carcasses found that in 11 of the 27 slaughterhouses visited, more than 10% of the carcasses were visibly contaminated. In 6 of the 27 slaughterhouses visited, more than 50% of the carcasses inspected were visibly contaminated. Microbiological analysis of visually clean carcasses noted contamination levels similar to those reported from other countries. O157 VTEC were not isolated during this study. Circulation of these findings lead to increased efforts by all parties to fulfil the requirements of the statutory “Zero-tolerance” programme. A follow-up study noted a significant decrease in the proportions of faecally contaminated carcasses, i.e., 7% of chilled carcasses were visibly contaminated with faeces, as opposed to 22% contamination during the initial study. The follow-up study also noted a greater awareness of the importance of good hygienic practices among slaughterhouse personnel and government meat inspectors.

Presence of bovine herpesvirus 1 gB-seropositive but gE-seronegative Dutch cattle with no apparent virus exposure

Two hundred and thirty-seven of 2052 cattle which had not been vaccinated against bovine herpesvirus 1 (BHV-1) were seropositive in a glycoprotein B (gB)-blocking ELISA, but seronegative in a glycoprotein...