Status of claw recordings and claw health in Danish dairy cattle from 2013 to 2017.

Since 2009, Danish claw trimmers have been able to record claw health digitally during trimming. The records are owned by the farmer and can be used locally in the herd and on a large scale by breeding organisations to improve claw health. The objective of this study was to describe data on claw recording routines and describe the prevalence of digital dermatitis (DD), interdigital hyperplasia (IH), sole ulcer (SU) and white line abscess (WLA) recorded by claw trimmers (TrimmerID) at trimming. More than 5.18 million records of cows with claw recordings and 2.75 million records of claw trimming with 2.4 million concurrent claw diseases from 62 TrimmerIDs from 705,803 animals from 1635 herds over a 5-year period from 2013 to 2017 were included in the dataset. Data on cow level was used for the descriptive statistics. The data was restricted to, and grouped by, heifers from 12 months of age, first, second and third or older parity cows from the breeds Holstein, Danish Red Dairy, Jersey and crossbreds. The number of recorded trimmings per TrimmerID per year varied from 132 to 48,040 with a mean of 9556 and increased during the period studied. The overall prevalence across breed and parity groups of DD, IH, SU and WLA was 21%, 6%, 7% and 3%, respectively. The prevalence of the lesions remained quite constant during the 5-year period. DD was recorded in 95% of the herds in 2017. The prevalence of IH, SU and WLA increased with increasing parity. Digital recording of claw lesions may be a good indicator of claw health. However, the recording routines and quality of the recordings must be considered.

Mortality, diarrhea and respiratory disease in Danish dairy heifer calves: Effect of production system and season.

Diarrhea and respiratory disease are major health problems for dairy calves, often causing calf mortality. Previous studies have found calf mortality to be higher in organic dairy herds compared to conventional herds. The aim of this study was to investigate the association between production system (conventional/organic), season (summer/winter) and calf mortality risk, diarrhea, signs of respiratory disease and ocular discharge, respectively, for dairy heifer calves aged 0-180 days. Sixty Danish dairy herds, 30 conventional and 30 organic, were visited once during summer and once during winter. During the herd visits, calves were clinically examined for signs of diarrhea, hampered respiration, nasal discharge, coughing and ocular discharge. Data on mortality were obtained from the Danish Cattle Database. Data were analyzed using logistic regression models, with mortality risk and disease measures as outcome variables for each of three calf age groups: 0-28, 29-90 and 91-180 days. In organic herds, odds of mortality among calves aged 0-28 days were 2.09 (95% confidence interval (CI): 1.38-3.15) times higher during winter compared to summer. Odds of nasal discharge for calves 0-28 days in organic herds were 10.3 (95% CI: 2.27-46.6), 10.7 (95% CI: 2.40-40.0) and 5.97 (95% CI: 1.29-27.6) times higher for organic and conventional herds during winter (OW and CW) and conventional herds during summer (CS) respectively, compared to organic herds during summer (OS). For calves aged 29-90 days, odds of nasal discharge were 8.22 (95% CI: 3.88-17.4), 8.06 (95% CI: 3.18-20.4) and 2.86 (95% CI: 1.08-7.55) times higher for OW, CW and CS respectively, compared to OS. Odds of nasal discharge for calved aged 91-180 days were 7.03 (95% CI: 3.95-12.5) and 4.27 (95% CI: 1.81-10.1) times higher for OW and CW respectively compared to OS. For calves aged 29-90 days, odds of coughing were 2.23 (95% CI: 1.06-4.71) and 3.82 (95% CI: 1.76-8.21) times higher for OW and CW compared to OS, while odds of coughing for calves aged 91-180 days were 2.09 (95% CI: 1.19-3.67) and 2.55 (95% CI: 1.39.4.67) times higher for OW and CW compared to OS. Odds of ocular discharge for calves aged 29-90 days were 0.22 (95% CI: 0.10-0.52), 0.27 (95% CI: 0.11-0.66) and 0.42 (95% CI: 0.18-0.99) times higher for OW, CW and CS compared to OS. In conclusion, mortality and morbidity of Danish dairy heifer calves are, for some variables and in certain age groups, dependent on production system and season.

Livestock drivers' knowledge about dairy cow fitness for transport - A Danish questionnaire survey.

Dairy cows are transported by road to slaughter after their productive life. Cull cows are vulnerable to transport stress, and can only be transported when fit for the intended journey. However, the decision, as to whether a cow is fit is rather subjective and relies on the farmer and the livestock driver. Using a questionnaire survey, we aimed to describe knowledge about, and experiences with, dairy cow fitness for transport among Danish livestock drivers. During nine days of data collection at the three largest Danish cattle slaughterhouses, 66 drivers (55% of the national population of cattle drivers) answered a questionnaire (response rate: 97%). They were Danish males (mean age: 49years), of which 94% stated that they knew the rules regarding fitness for transport. More than half of the respondents said that physical conditions (light, space) before loading animals allowed proper assessment of fitness for transport, and 85% answered that time constraints were not a challenge for this. Thirty-five percent reported to be in doubt regarding fitness for transport of specific cows at least frequently, and given two specific questions on legislation concerning fitness for transport, only 52% of the respondents answered both correctly. The results add new knowledge about livestock drivers' approach to animal welfare. As drivers are held partly responsible for fitness for transport of animals sent to slaughter, and descriptions of fit/unfit are rather vague, livestock drivers seem to need additional education, training, assessment tools or feedback in order to optimize the welfare of animals to be transported.

Invited review: A systematic literature review and meta-analysis of mortality and culling in dairy cattle.

Dairy industries and individual farmers are concerned about mortality and culling of dairy animals. This is because the timing and fates of animals that exit dairy farms have important animal welfare and economic consequences that reflect the conditions under which they are farmed and the efficiency of their production systems. Reports from a few countries have indicated increased incidence of mortality, and occasionally culling, of dairy animals in recent decades, and these changes have been associated with intensification of production systems. Dairy industries and farmers need benchmarks for culling and mortality against which they can compare themselves, as well as improved understanding of the extent of any change and of any associated factors. We reasoned that a systematic literature review and meta-analysis of scientific articles published between 1989 and 2014 would allow us to determine whether these reports were universal, to quantify any change over time, and to investigate whether production systems or study factors were associated with culling and mortality. From 3,275 articles retrieved from databases and manual searching of cited articles, 118 articles were appraised independently by 2 assessors, and 51 articles representing 54 studies were determined to be eligible for review and meta-analysis. We estimated that both the annual incidence risk (IR) and incidence density of mortality of cows had increased significantly from 0.02 per cow and 2.32 per 100 cow-years, to 0.04 per cow and 3.75 per 100 cow-years, an increase per decade of 0.02 per cow and 1.42 per 100 cow-years, respectively. We also estimated that the annual IR of culling attributed to low production had declined significantly from 0.07 to 0.05 and that the IR of perinatal, but not neonatal, mortality had increased significantly from 0.04 to 0.06 per decade. We found no evidence of change in overall annual IR of culling of cows over time or any association between study design factors and the IR or incidence density of culling or mortality. These findings provide benchmarks for describing culling and mortality, and should encourage farmers and researchers in countries with modern dairy industries to discover and implement management strategies to reduce the animal welfare and economic costs associated with these changes.

Lameness detection via leg-mounted accelerometers on dairy cows on four commercial farms.

Lameness in dairy herds is traditionally detected by visual inspection, which is time-consuming and subjective. Compared with healthy cows, lame cows often spend longer time lying down, walk less and change behaviour around feeding time. Accelerometers measuring cow leg activity may assist farmers in detecting lame cows. On four commercial farms, accelerometer data were derived from hind leg-mounted accelerometers on 348 Holstein cows, 53 of them during two lactations. The cows were milked twice daily and had no access to pasture. During a lactation, locomotion score (LS) was assessed on average 2.4 times (s.d. 1.3). Based on daily lying duration, standing duration, walking duration, total number of steps, step frequency, motion index (MI, i.e. total acceleration) for lying, standing and walking, eight accelerometer means and their corresponding coefficient of variation (CV) were calculated for each week immediately before an LS. A principal component analysis was performed to evaluate the relationship between the variables. The effects of LS and farm on the principal components (PC) and on the variables were analysed in a mixed model. The first four PC accounted for 27%, 18%, 12% and 10% of the total variation, respectively. PC1 corresponded to Activity variability due to heavy loading by five CV variables related to standing and walking. PC2 corresponded to Activity level due to heavy loading by MI walking, MI standing and walking duration. PC3 corresponded to Recumbency due to heavy loading by four variables related to lying. PC4 corresponded mainly to Stepping due to heavy loading by step frequency. Activity variability at LS4 was significantly higher than at the lower LS levels. Activity level was significantly higher at LS1 than at LS2, which was significantly higher than at LS4. Recumbency was unaffected by LS. Stepping at LS1 and LS2 was significantly higher than at LS3 and LS4. Activity level was significantly lower on farm 3 compared with farms 1 and 2. Stepping was significantly lower on farms 1 and 3 compared with farms 2 and 4. MI standing indicated increased restlessness while standing when cows increased from LS3 to LS4. Lying duration was only increased in lame cows. In conclusion, Activity level differed already between LS1 and LS2, thus detecting early signs of lameness, particularly through contributions from walking duration and MI walking. Lameness detection models including walking duration, MI walking and MI standing seem worthy of further investigation.

Preferences of lame cows for type of surface and level of social contact in hospital pens.

To investigate preferences of lame cows for flooring and level of social contact, 37 lame, lactating dairy cows (diagnosed with sole ulcer or white line disease) were housed individually for 6 d in experimental hospital pens, where they could choose between 2 equally sized areas (6m × 4.5m) with either deep-bedded sand or a rubber surface. On both surfaces, cows could choose between 2 equally sized areas either near or away from heifers in a neighboring group pen. Cows spent more time lying on the deep-bedded sand than on the rubber surface (870 vs. 71min/d), whereas they spent less time upright (standing or walking) on the sand than on the rubber surface (180 vs. 319min/d). In addition, cows spent less time self-grooming on the sand than on the rubber surface (2.2 vs. 4.7% of time spent upright). With regard to level of social contact, cows spent more time near the neighboring heifers than away from them; this was true both while lying (565 vs. 374min/d) and upright (276 vs. 223min/d). Self-grooming was seen significantly more near neighboring heifers than away from them (4.8 vs. 3.3% of time spent upright). When lying, cows more often positioned themselves in areas of the pen where they could maintain visual contact with neighboring heifers. Lame cows with sole ulcers or white line disease preferred deep-bedded sand for lying, and preferred to perform self-grooming while on the rubber surface. Similarly, they preferred to lie and to perform self-grooming while positioned near animals in a neighboring pen. These results suggest that provision of a deep-bedded lying area in hospital pens is important to the welfare of lame cows. We found no evidence of isolation-seeking behavior in animals with these diagnoses (and no systemic symptoms) while they were kept in individual hospital pens.

Risk factors associated with on-farm mortality in Swedish dairy cows.

Dairy cow mortality (unassisted death and euthanasia) has increased, worldwide and in Sweden. On-farm mortality indicates suboptimal herd health or welfare and causes financial loss for the dairy producer. The objective of this study was to identify cow-level risk factors associated with on-farm cow mortality. Cows with at least one calving between 1 July 2008 and 30 June 2009 from herds enrolled in the Swedish official milk recording scheme with >40 cow-years were included. Each cow was followed from the day of calving until she calved again or left the herd (died, slaughtered or sold). The effects of potential risk factors on on-farm cow mortality were analysed using a Weibull proportional hazard model with a gamma distributed frailty effect common to cows within herd. The event of interest (failure) was euthanasia or unassisted death. An observation was right censored if the cow was slaughtered, sold, calved again or had an on-going lactation at 500 days after calving. The lactations were split into seasons (January to April, May to August and September to December) and at 30 and 100 days in milk in order to evaluate seasonal effects and the effect of disease in different lactation stages. Primiparous and multiparous cows were analysed separately. The highest hazards for both primiparous and multiparous cows were found for traumatic events and diseases, both in the lactation stage in which the cow died and in the preceding stage. The hazard was higher in early lactation and lower in 2nd parity compared to higher parities. Increased age at first calving (for primiparous cows), calving between January and April, dystocia and stillbirth also increased the mortality hazard. Differences were also found between breeds, between milk production parameters at first test milking and between management types. The results from this study show the importance of good management and preventive health actions, especially around calving, to avoid mortality in dairy cows.

Register-based predictors of violations of animal welfare legislation in dairy herds.

The assessment of animal welfare can include resource-based or animal-based measures. Official animal welfare inspections in Denmark primarily control compliance with animal welfare legislation based on resource measures (e.g. housing system) and usually do not regard animal response parameters (e.g. clinical and behavioural observations). Herds selected for welfare inspections are sampled by a risk-based strategy based on existing register data. The aim of the present study was to evaluate register data variables as predictors of dairy herds with violations of the animal welfare legislation (VoAWL) defined as occurrence of at least one of the two most frequently violated measures found at recent inspections in Denmark, namely (a) presence of injured animals not separated from the rest of the group and/or (b) animals in a condition warranting euthanasia still being present in the herd. A total of 25 variables were extracted from the Danish Cattle Database and assessed as predictors using a multivariable logistic analysis of a data set including 73 Danish dairy herds, which all had more than 100 cows and cubicle loose-housing systems. Univariable screening was used to identify variables associated with VoAWL at a P-value<0.2 for the inclusion in a multivariable logistic regression analysis. Backward selection procedures identified the following variables for the final model predictive of VoAWL: increasing standard deviation of milk yield for first lactation cows, high bulk tank somatic cell count (⩾250 000 cells/ml) and suspiciously low number of recorded veterinary treatments (⩽25 treatments/100 cow years). The identified predictors may be explained by underlying management factors leading to impaired animal welfare in the herd, such as poor hygiene, feeding and management of dry or calving cows and sick animals. However, further investigations are required for causal inferences to be established.

Farm characteristics related to on-farm cow mortality in dairy herds: a questionnaire study.

Dairy cow mortality is an important animal welfare issue that also causes financial losses. The objective of this study was to identify farm characteristics and herd management practices associated with high on-farm cow mortality in Swedish dairy herds. A postal questionnaire was sent to farmers that had either high or low mortality rates for 3 consecutive years. The questionnaire consisted of five sections: 'About the farm', 'Milking and housing', 'Feeding', 'Routines' and 'Lame and sick cows'. A total of 145 questionnaires were returned (response rate=33%). Ten of the 77 characteristics investigated met the inclusion criteria for multivariable analysis. The final logistic regression model included: herd size, breed, use of natural service bull, bedding improvement frequency and pasture system. Herds with Swedish Holstein as the predominant breed (odds ratio (OR) 22.9, 95% confidence interval (CI) 5.2 to 101.8) or with mixed breeds (OR 5.5, 95% CI 1.7 to 17.5) had a greater risk of being high mortality herds than herds that were predominantly Swedish Red (OR 1). Herds larger than 100 cows (OR 19.6, 95% CI 3.5 to 110.4) and herds with 50 to 99 cows (OR 13.8, 95% CI 3.2 to 60.6) had greater risk of mortality than herds numbering 35 to 50 cows (OR 1). Being a high mortality herd was also associated with having cows on exercise lots during the summer season (OR 3.6, 95% CI 1.3 to 9.9) compared with on pasture. A missing answer on the question of bedding improvement frequency was associated with high mortality herds. Overall, this study suggests that characteristics that are related to intensification of the dairy industry are also associated with high on-farm mortality of dairy cows.

Track way distance and cover as risk factors for lameness in Danish dairy cows.

This study investigates the effect of length and cover of track ways between barn and pasture on lameness in Danish dairy cows. We hypothesised that short track distances would be associated with a lower lameness probability of dairy cows compared to longer distances and that track ways with prepared cover (asphalt, gravel, slag, concrete, rubber) compared to no prepared cover (sand, soil and/or grass) would be associated with a lower lameness probability of dairy cows in grazing herds. In total, 2084 dairy cows from 36 herds, grazing their dairy cows during summer, were individually assessed for their lameness status. The cows were further clinically examined for claw conformation and hock integument. Information on breed and parity per cow and size per herd was extracted from a national data base. Track way distance ranged from 0 to 700 m and was categorised as (1) <165 m or (2) ≥165 m. Cover of track way was categorised as (1) prepared (asphalt, gravel, slag, concrete, and/or rubber), (2) partly prepared or (3) not prepared (soil, sand, grass) for the surface of the majority of tracks used. The effect of track way distance and cover was evaluated for their impact on lameness using logistic analysis with a multi-level model structure. The probability for lameness did not change with track distance but increased with no (odds 4.0 times higher) or only partly prepared (odds 3.8 times higher) cover compared to prepared cover. In conclusion, we found that having a cover on the track way was associated with decreased severe lameness in Danish dairy cows.

Adjusting for multiple clinical observers in an unbalanced study design using latent class models of true within-herd lameness prevalence in Danish dairy herds.

The elimination of misclassification bias introduced by multiple observers was evaluated and discussed based on an illustrative example using lameness prevalence in 80 Danish dairy herds. Data from 5073 cows from loose-housed cubicle herds larger than 100 cows were included in the analysis. Four trained observers performed clinical scoring on cow level and undertook a calibration test with 39 video sequences. The calibration test served both the purpose of estimating inter-observer agreement (PABAK=0.69) in accordance with previous results and to estimate the sensitivity (Se) and specificity (Sp) for each observer. In the absence of a gold standard for the clinical observations, a latent class analysis (LCA) evaluating the true within-herd lameness prevalence was used. Sensitivity amongst observers was fairly low (0.24-0.81) inducing a general underestimation of the true prevalence. Comparative analyses were made to assess the effect of grazing on the lameness prevalence in order to demonstrate the consequences of using unadjusted apparent prevalences (AP) compared to the true prevalences (TP). Lameness prevalence was higher in grazing herds using AP estimates (19.0% zero-grazing, 20.2% grazing); while the TP estimates showed the expected higher lameness prevalence in zero-grazing herds (42.3% vs. 35.9%). Hence, this study emphasizes the importance of adjusting for observer Se and Sp to obtain true prevalence and avoid false interpretation.

Effect of grazing on the cow welfare of dairy herds evaluated by a multidimensional welfare index.

Structural development in the prime sector has led to increasing herd sizes and new barn systems, followed by less summer grazing for dairy cows in Denmark. Effects of grazing on single welfare measures in dairy cows - for example, the presence of integument alterations or mortality - have been studied under different conditions. However, the effect of grazing on welfare, conceptualised as the multidimensional physical and mental state of the animal, has not yet been studied in contemporary cubicle loose-housing systems. The aim of our study was to investigate, based on a Welfare Quality® inspired multidimensional dairy cow welfare assessment protocol, the within-herd effect of summer grazing compared with winter barn housing in Danish dairy herds with cubicle free-stall systems for the lactating cows. Our hypothesis was that cow welfare in dairy herds was better during summer grazing than during full-time winter housing. Furthermore, we expected improved welfare with an increase in daily summer grazing hours. In total, 41 herds have been visited once in the winter and once in the summer of 2010 to assess their welfare status with 17 different animal- and resource-based welfare measures. A panel of 20 experts on cattle welfare and husbandry evaluated the relative weight of the 17 welfare measures in a multidimensional assessment scheme. They estimated exact weights for a priori constituted severe compared with moderate scores of welfare impairment concerning each measure, as well as relevance of the measures in relation to each other. A welfare index (WI; possible range 0 to 5400) was calculated for each herd and season with a higher index indicating poorer welfare. The within-herd comparison of summer grazing v. winter housing considered all the 17 measures. The mean WI in summer was significantly lower (better) than in winter (mean 2926 v. 3330; paired t-test P = 0.0001) based on a better state of the integument, claw conformation and better access to water and food. Body condition and faeces consistence were worse in summer. Many daily grazing hours (range average above 3 to 9 h) turned out to be more beneficial than few daily grazing hours (range average above 9 to 21 h) for the welfare of the dairy herds. In conclusion, this study reports a positive within-herd effect of summer grazing on dairy cow welfare, where many daily grazing hours were more beneficial than few daily grazing hours.

Daily grazing time as a risk factor for alterations at the hock joint integument in dairy cows.

Structural changes lead to increasing sizes of dairy herds and a reduction in grazing use. Thus, cows spend more time in the barn and become more exposed to the barn environment. The cubicle surface can result in damages of the cows' hock joint integument. Pasture is generally seen as a beneficial environment for cows. We hypothesized that a higher number of daily grazing hours reduce the probability of hock joint alterations in dairy cows from large herds. In total, 3148 lactating cows from 36 grazing and 20 zero-grazing dairy herds, with an average herd size of 173 cows, were assessed individually on one randomly selected body side for alterations in hock integument (score 0 for no alterations or hairless areas <2 cm, 1 for at least one hairless area of ≥2 cm, 2 for lesion or swelling). The cows were further assessed for lameness and cleanliness. Information on breed, parity and days in milk per cow was extracted from a national database. Cubicle surface was evaluated for each herd. Daily grazing hours 30 days before herd visits were recorded by the stockmen and later categorized as follows: zero hours (zero-grazing), few hours (3 to 9) and many hours (>9 to 21). The effects of daily grazing hours and other potential cow and herd-level risk factors were evaluated for their impact on hock integument alterations using a logistic analysis with a multi-level model structure. The probability for hock integument alterations such as hair loss, lesions or swellings decreased with increasing amount of grazing hours (odds of 3 to 9 h 2.2 times and odds of >9 to 21 h 4.8 times lower than of zero-grazing). The probability for only lesions or swellings decreased with >9 to 21 grazing hours (odds 2.1 times) but not with 3 to 9 h (odds 1.0 times) compared with zero-grazing. Lameness, hard cubicle surface and Danish Holstein v. other breeds showed an increasing effect on the probability for integument alterations. Increase in days in milk only showed an increasing effect on the probability for lesions and swellings. We concluded that a long daily stay on pasture is most beneficial for the hock joint integument of a dairy cow.

Necropsy as a means to gain additional information about causes of dairy cow deaths.

High mortality among dairy cows constitutes a problem both financially and in relation to animal welfare. Knowledge about causes of death is a fundamental step toward reducing cow mortality. Several studies have evaluated causes of dairy cow deaths. However, the vast majority of studies describing causes of death are based on questionnaires with farmers or veterinarians. It is uncertain to what degree such information is sufficient and reflects the true cause of death or euthanasia. In this study, proximate causes of death were evaluated based on a thorough necropsy of a random sample of 79 Danish dairy cows at an incineration plant. The necropsy was combined with information about the farmer's perception regarding the cause of death and information about disease treatments from the Danish Cattle Database. Pneumonia and locomotor disorders were found to be the most predominant proximate causes of death. Often the death occurred after a prolonged period during which the cow suffered several different disorders, even though this was often not noticed by the farmer. Causes of death stated by the farmers agreed with the necropsy results in 50 to 64% of cases. Information about disease treatments from the Danish Cattle Database agreed with the necropsy results in 34 to 39% of cases. All 3 sources of information about cause of death agreed in only 1 out of 4 cases, and even when the farmer and the disease recordings did agree with the necropsy results, the latter often gave additional information about the cause of death. In many situations, therefore, a necropsy may be a valuable tool when trying to control excessive cow mortality in a herd.

Validation of Nordic dairy cattle disease recording databases--completeness for locomotor disorders.

The Nordic countries Denmark (DK), Finland (FIN), Norway (NO) and Sweden (SE) all have unique national databases holding the disease records of dairy cows. The objective of this study was to estimate and compare completeness for locomotor disorders in the four Nordic national databases. Completeness figures for farmer-recorded disease events were calculated on two different levels: the first refers to disease events that were observed on the farm regardless of whether a veterinarian had been involved (FARMER); the second refers to farmer records of cases attended by a veterinarian, i.e. to veterinarian-treated disease events (VET). A sample of herds with 15 or more cows was obtained from a simple random sample of dairy farms in FIN, NO and SE, and from a systematic random sample in DK. There were 105, 167, 179 and 129 participating farmers in DK, FIN, NO and SE, respectively, and during two 2-month periods in 2008 these farmers recorded the disease events they observed on the farm. Data from the four national databases were extracted in May 2009. The two data sources, farmer recordings and national databases, were managed in a comparable way in all four countries, and common diagnostic codes were created and added to match recordings appearing in both datasets. In all 555 farmers completed data records in the first data-recording period, and 515 farmers did so in the second period. In DK, FIN, NO and SE, 55%, 77%, 82% and 75%, participating farmers completed the recordings during the first recording period, respectively; the corresponding figures for the second recording period were 71%, 82%, 83% and 91%. To calculate completeness, disease cases recorded in the national databases were compared with the farmer recordings using an exact match for the locomotor complex defined as same country, herd identification number (id), cow id, and event date at the levels of FARMER and VET. Completeness at FARMER level were 0.22, 0.21, 0.23 and 0.12 in DK, FIN, NO and SE, respectively. At VET level they were 0.37, 0.27, 0.34 and 0.17. To compare differences in completeness between countries exact 95% confidence intervals were calculated. There were significant differences in completeness between DK and SE at both FARMER and VET level. The completeness indicate that the ability to estimate true disease occurrences in the four national databases varies and is in general poor. Completeness should be taken into account when disease occurrences in different countries are compared.

Herd-level risk factors associated with cow mortality in Swedish dairy herds.

An increase in on-farm mortality (euthanasia and death) in dairy herds has been reported in several countries in the last decade. This does not only imply possible problems with animal welfare, but it also causes economic losses to the farmer. The objective of this study was to evaluate time trends in on-farm dairy cow mortality in Sweden and identify potential herd-level risk factors. Data were retrieved on all Swedish dairy herds enrolled in the milk recording scheme between 2002 and 2010. Herds with a herd size of <20 cows or a mortality rate (MR) of >40 dead or euthanized cows per 100 cow-years were excluded. Two different models were used: 1 multiple-year analysis, which included 6,898 herds during the period 2002 to 2010 and 1 single-year analysis including 4,252 herds for the year 2010, where other variables that were not present during the entire multiple year study were analyzed. The outcome variable was the number of euthanized and dead cows per year and season. A negative binomial regression model, adjusted for clustering within herd, was applied to both models. Fixed effects in the multiple-year analysis were breed, calving interval, herd size, milk yield, region, season, pasture period, and year. The fixed effects in the single-year analysis were breed, calving interval, conventional versus organic farming, herd size, housing system, milk yield, region, and season. The results demonstrated that MR gradually increased from 5.1 to 6.6 events per 100 cow-years during the study period. Swedish MR are consequently on par with, or even greater than, MR among dairy herds in other comparable countries. Higher mortality was associated with larger herd size, longer calving intervals, and herds that had Swedish Holstein as the predominant breed. Lower mortality was observed in herds with a higher herd average milk yield, during the fall and winter, and in organically managed herds. There were regional differences in mortality. An interaction between herd size and season was found in both models. Also, an interaction between housing system and milk yield was found in the single-year analysis. This first assessment of on-farm mortality in Swedish dairy herds confirmed that the MR has increased over the last few years. The study also identified some herd-level risk factors.

A study of the dynamics of digital dermatitis in 742 lactating dairy cows.

Digital dermatitis (DD) is a contagious disease of cattle affecting the skin of the claw. The disease presents with a range of severities and can be associated with lameness. Information about the disease dynamics of DD is scarce. Parity and lactation stage have been identified as risk factors for DD and studies have also indicated that not all cows are equal regarding their risk of recurrent disease and prospects for cure from DD. The aim of this study was to investigate host heterogeneity to DD and to identify disease patterns of DD and factors associated with the development and resolution of lesions. In three commercial dairy herds, 742 lactating cows were observed for DD lesions weekly for 11 or 12 weeks. The effects of parity, lactation stage and duration of preceding episode on the hazard of transitions between healthy and lesion states were analysed using a multilevel multistate discrete-time model. One or more DD lesions were observed in 460 cows and lesions were observed in 2426 out of 10,585 observations. In total, 1755 uncensored episodes with DD lesions were observed. Early lactation was associated with a reduced risk of developing lesions compared with mid and late lactation. Lesions that developed in late lactation had a greater likelihood of resolution compared with lesions that developed during early lactation. There was a reduced risk of lesions developing in parity 3 compared with parity 1 cows, but an increased risk of lesions developing in parity 2 compared with parity 1 cows. In the present study, the mean duration of uncensored DD episodes was 1.7 weeks indicating that the duration of the majority of DD lesions might be shorter than the 42 days reported previously. The transitions between disease states suggest that DD is a dynamic disease, and that the early stage lesions are more transient than expected from previous studies. We conclude that studies with shorter observation intervals than one week are needed to fully understand and describe the individual and group dynamics of DD.

The effect of grazing on cow mortality in Danish dairy herds.

The effect of summer grazing in large Danish dairy herds and certain management characteristics of grazing were studied for their impact on dairy cow mortality. Mortality data (from the Danish Cattle Database) from 391 Danish dairy herds (>100 cows) were combined with information from a questionnaire survey of grazing procedures on these herds in 2008. In all, 131 of the herds were identified as summer grazing and 260 as zero-grazing herds. The mortality was affected by an interaction of summer grazing and milking system. The risk of a cow dying was reduced to 46% in a grazing compared to a zero-grazing herd having automatic milking system. In traditional milking system, mortality was reduced to 75% in grazing compared to zero-grazing herds. Within the grazing herds, the risk of mortality decreased with increasing number of hours on pasture during the season. Free access between barn and pasture was associated with increased cow mortality.

Identifying risk factors for poor hind limb cleanliness in Danish loose-housed dairy cows.

The objective of this study was to identify possible risk factors for poor cow hind limb cleanliness in Danish loose-housed, lactating dairy cows. The study was conducted as a cross-sectional study of 1315 cows in 42 commercial Danish dairy herds with primarily Danish Holstein cows. The effect of four cow-level factors (parity, days in milk, daily lying time and lameness) and eight herd-level factors (herd size, milk production, milking system, floor type, access to pasture grazing, floor scraping frequency, hoof bathing frequency and hoof washing frequency) on the risk of having dirtier hind limbs were analysed using ordinal logistic regression fitting a proportional odds model. Cow hind limb cleanliness was scored using an ordinal score from 1 to 4: 1 being clean and 4 being covered in dirt. The odds ratios (ORs) estimated from the proportional odds model depict the effect of a risk factor on the odds of having a higher rather than a lower cleanliness score. First parity cows had an increased risk of being dirtier compared with third parity or older cows (OR=1.70). Compared with late lactation, early and mid lactation were associated with an increased risk of being dirtier (OR=2.07 and 1.33, respectively). Decreasing the daily time lying by 30 min was associated with an increased risk of being dirtier (OR=1.05). Furthermore, an increased risk of being dirtier was found in herds with no pasture access (OR=3.75).