Antimicrobial use in organic and conventional dairy herds.

Use of antimicrobials for food-producing animals is a major public concern due to the risk of antimicrobial resistance. Although dairy production has a relatively low usage of antimicrobials, the potential for further reduction should be explored. The objective of the study was to estimate the current differences in antimicrobial use in Danish organic and conventional dairy herds and to describe the differences between them. Based on data from three different sources, 2604 herds (306 organic and 2298 conventional) were identified for the study. These herds had been either organic or conventional for the entire period from 2015 to 2018. Antimicrobial use was calculated as the treatment incidence in Animal Daily Doses (ADDs)/100 animals/day for three age groups: adult cattle, young stock and calves. For adult cattle, the ratio of median treatment incidence between conventional and organic production ranged from 2.8 : 1 to 3.4 : 1, depending on the specific year. For cows, 25% of the organic herds had a higher treatment incidence than the 25% of conventional herds with the lowest treatment incidence. Antimicrobial use for young stock was low and at a similar level in both the organic and conventional production systems. For calves, the median treatment incidence was 1.2 times higher in conventional herds and 1.6 times higher for the 75th percentile. Analyses of treatment incidence in adult cattle showed an overall decrease from 2015 to 2018 in both organic and conventional herds. The decrease was greater for the conventional herds (0.12 ADD/100 animals/day) compared to the organic herds (0.04 ADD/100 animals/day) over the 4-year period. In addition, herd size was an important risk factor for treatment incidence in conventional herds, increasing by 0.07 ADD/100 animals/day per 100 cows, whereas herd size had a minor influence on the treatment incidence in organic herds. The results of this study demonstrate the large variation in antimicrobial use within both organic and conventional herds, suggesting that further reduction is possible. Furthermore, herd size appears to be a risk factor in conventional herds but not in organic herds - an aspect that should be studied in more detail.

Evaluation of systematic California Mastitis Tests and vaginal examinations as measures of antimicrobial use in dairy herds.

Antimicrobial use is a commonly applied proxy for animal health and welfare impairment related to disease status in dairy herds. The objective of this study was to estimate the association between antimicrobial use and the results of systematic clinical examinations for metritis and mastitis. Data was collected from 109 Danish dairy herds over a 5-year period. Statistical analysis demonstrated that the results of vaginal examinations and California mastitis tests on fresh cows were poor predictors of antimicrobial use at the herd level and 52% of the variance in the clinical data could be explained by herd-level factors. The results could be explained by the concept of a treatment threshold within each herd. We suggest that antimicrobial use should be categorised as a decision made by the herd manager rather than an approximation of disease status in the herd.

The effect of individual quarter dry-off in management of subclinical mastitis on udder condition and milk production in organic dairy herds: A randomized field trial.

The objective of the study was to evaluate the effect of individual quarter dry-off in management of subclinical mastitis on clinical development, behavior during milking, and short-term production loss. The study was conducted as a controlled randomized trial in 5 commercial organic dairy herds. Seventy cows meeting the inclusion criteria were randomly allocated to 1 of 2 treatments: individual quarter dry-off (QDO) or continued milking. The inclusion criteria constituted an increase in somatic cell count from below to above 400,000 cells/mL at milk recording and identification of a quarter scoring of at least 3 and higher than the remaining quarters at California mastitis testing (scale 1-5). Quarters were evaluated clinically for atrophy, swelling, firmness, signs of pain, and milk leakage, and rectal temperature of the cows was measured. Behavior during milking was assessed as average frequency of hind limb tripping and kicking during milking obtained by registrations on video recordings. Milk production loss was estimated based on average daily milk yield for 19 d subsequent to treatment start, with reference to average daily milk yield in 19 d before treatment. The QDO treatment was associated with quarter swelling and increased quarter firmness around d 10 from treatment start and with quarter atrophy around d 40 from treatment start. However, around d 40 from treatment start 35% of the dried-off quarters remained nonatrophic and only 6% of the quarters were completely dry. The QDO was associated with signs of pain related to the dried-off quarter. No obvious effects on behavior during milking of QDO treatment was observed. On average the production loss associated with QDO was 4.1 kg/d (95% confidence interval: 3.1-5.0) greater than for continued milking. The production loss depended on parity, days in milk, and prior yield on the quarter subjected to dry-off (Q1). The production loss increased with increasing prior yield on Q1. For the majority of cows the increase in production loss was below 1 kg of milk/d when the prior yield on Q1 increased by 1 kg of milk/d, demonstrating a compensatory production potential of the nontreated quarters. Early lactation multiparous cows showed the greatest compensatory potential. Further studies into the effect on welfare, cure rates, and transmission are needed to determine the feasibility of individual quarter dry-off.

Herd-level associations between human-animal relationship, management, fecal cortisol metabolites, and udder health of organic dairy cows.

Impact patterns of human-animal relationship (HAR) and herd stress level on udder health were investigated in a cross-sectional study on 30 German and Danish organic dairy herds also taking into account influencing factors regarding housing and management. Cow behavior (avoidance distance, tolerance to tactile interaction, release behavior) was assessed in tests, milkers' behavior recorded during milking, and information about contacts with animals during routine work gathered by interview. Additionally, stockpersons' attitudes were recorded via questionnaires. Fecal cortisol metabolites were measured in approximately 30 focal cows on each farm and used as a proxy to determine the level of distress within the herd. Management and housing were assessed on-farm. The following herd udder health indicators were calculated: the prevalence of mastitis quarters (≥100,000 cells/mL), and, from milk recording data over 1 yr retrospectively, the average somatic cell score and the self-cure rates during lactation per herd. Multivariable regression models with stepwise selection were calculated at herd level. The following HAR-related factors were associated with better udder health (in at least 1 of the final models): stockpersons' higher agreement on patience being important when moving the cows and on necessary contact to cows being pleasant, higher amount of positive interactions with cows during milking, more docile cows in the release behavior test, no routine change of milkers, more contact time during routine work, no active heifer habituation to milking, and performance of barn controls beyond routine work. Lower fecal cortisol metabolite levels were related to higher self-cure rates during lactation. Concerning housing, management, and herd characteristics, the following known factors were related to impaired udder health for at least 1 of the indicators: straw yards, automatic milking system, higher average lactation number, and less antibiotic udder treatments. The results confirm earlier findings that HAR is associated with udder health and should therefore be considered in future research and mastitis control programs. First indications of negative associations between herd stress level and mastitis curing capacity should be followed up in future studies.

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.

Sow level risk factors for early piglet mortality and crushing in organic outdoor production.

Piglet mortality is a major problem in organic pig production affecting both farm economy and animal welfare. Knowledge is scarce on the risk factors of piglet mortality in Danish commercial organic pig production. The objectives of this study were to evaluate season, litter size, parity, sow body condition and stillborn littermates as risk factors for early piglet mortality and crushing of liveborn piglets from parturition until castration at day 3 to 5 postpartum (pp). The study was conducted over a 1-year period in nine commercial Danish organic pig herds practicing outdoor farrowing all year round. Data included recordings on 3393 farrowings with 50 284 liveborn piglets of which 14.8% died before castration. A subset of the dead piglets were collected and necropsied to identify crushed piglets. The average number of liveborn piglets per litter was 14.8 (SD=3.7) and the average time from parturition until castration was 4.1 (SD=1.7) days. A negative binomial regression analysis was used to model the effect of the predictive variables on the early piglet mortality accounting for different time periods from parturition to castration. An increase in maternal body condition score (BCS) and parity significantly increased the risk of dying between parturition and castration. Early mortality was found to be lowest during spring (March to May) and highest during summer (June to August). Being born into a litter with one or more stillborn littermates increased the risk of early mortality. The risk factors for crushing of piglets were evaluated using a logistic analysis. A significant effect of parity and litter size was found where the odds of at least one piglet in a litter with mortality was diagnosed as crushed increased with increasing parity and litter size. In conclusion, being born during summer (June to August), high parity and maternal BCS and stillborn littermates were found to be risk factors for piglet mortality between parturition and castration. In addition, parity and increasing litter size were found to be risk factors for crushing of piglets in litters with mortality.

Lesions found at routine meat inspection on finishing pigs are associated with production system.

Pigs raised under free-range conditions are expected to experience a higher level of animal welfare than conventionally raised pigs. However, free-range conditions may challenge prevention and treatment of diseases. In order to identify disease problems associated with raising conditions, this study compared slaughter lesions in pigs from conventional indoor, conventional free-range and organic free-range production systems. The study used data from 1,096,756 pigs slaughtered at one Danish abattoir from 1 January 2013 to 31 December 2015. Associations between production system and lesions at slaughter were tested in statistical models taking year, season and herd of origin into account. Both conventional free-range and organic free-range production systems were associated with increased population averaged odd ratios (ORPA) for several lesions compared with conventional indoor systems. Pigs raised in conventional free-range and organic free-range production systems had higher odds for white liver-spots (ORPA, 5-7), tail lesions (ORPA, 3-4), arthritis (ORPA, 3), skin lesions (ORPA, 3), bone fractures (ORPA, 2), septicaemia (ORPA, 1.1-1.5) and abscesses (ORPA, 1.1-1.3) at slaughter. Pairwise comparisons of the two free-range production systems did not reveal statistically significant differences (P>0.05). In all three production systems, airway infection was the most prevalent disease complex. In contrast to previous studies, this study did not find any association between airway infection and type of production (P>0.05). Three lesions (leg swellings (ORPA, 0.4-0.5), hernia (ORPA, 0.7-0.8) and hoof abscess (ORPA, 0.7-0.9)) had lower ORs in conventional free-range and organic free-range production compared with conventional indoor production. There was a marked herd effect (intraclass correlation coefficients 21-35%) on the occurrence of white liver-spots, tail lesions, skin lesions and airway infections. These results suggest possibilities for herd-level management interventions of the problems studied.

Sow-level risk factors for stillbirth of piglets in organic sow herds.

In Danish organic pig production, one-third of total born piglets die before weaning, and stillbirth has previously crudely been estimated to account for 27% of the total preweaning mortality. The objective of this study was to evaluate season, litter size, parity and body condition of the sow as risk factors for stillbirth in nine commercial Danish organic pig herds. The study was conducted over a 1-year period, and the data included registrations on 5170 farrowings with 82 906 total born piglets. The average number of total born piglets per litter was 16.0, and the number of stillborn piglets per litter was 1.1. A significant effect of season was seen with an odds ratio for stillbirth of 1.15 during summer (May to August) compared with the remaining part of the year. A non-linear effect of litter size was seen where an increase in litter size from 11 to 16 resulted in an odds ratio of stillbirth of 1.11. An increase in litter size from 16 to 21 resulted in an odds ratio of stillbirth of 1.45. A significant interaction between body condition and parity was present. In first parity sows, an increase in body condition score from 2 (thin) to 3 (moderate) and from 3 to 4 (fat) increased the probability of stillbirth with an odds ratio of 1.23 and 1.36, respectively. In sows with parity above 4, an increase in body condition score from 2 to 3 and from 3 to 4 decreases the probability of stillbirth with an odds ratio of 0.68 and 0.79, respectively. In conclusion, increasing litter size and being born during the summer months of May to August were found to be risk factors for stillbirth. Furthermore, an interaction between body condition and parity showed that thin sows with parity above 4 had a substantially increased risk of stillbirth compared with normal and fat sows with parity above 4. In contrast, for parity 1 sows risk of stillbirth was increased in fat sows.

Helminth infection is associated with hen mortality in Danish organic egg production.

The aim of this study was to investigate whether two highly prevalent helminth infections (Ascaridia galli and Heterakis species) are associated with an increased mortality rate for hens at the peak of lay. An observational event study with 11 farms was conducted between 2012 and 2013, with weekly mortality recordings and grouping of the farms into low-infected with A galli and Heterakis species (0-200 epg of faeces) or high-infected (over 200 epg of faeces). Survival analysis was performed using a discrete time proportional hazards model. The difference between the hazard functions for low-infected farms and high-infected farms in either summer (August to September) or winter (January to March) were analysed. No statistically significant associations were found between the mortality rate in winter and summer in low-infected farms. However, the mortality rate was doubled for hens from high-infected farms observed in the summer season compared with hens from low-infected farms (winter and summer), whereas high-infected farms observed in the winter did not have a significant association between mortality rate and season compared with low-infected farms (summer and winter). The results suggest that the mortality in organic egg production may be reduced by measures to control A galli and Heterakis species infections.

Influence of social mixing and group size on skin lesions and mounting in organic entire male pigs.

Alternatives to surgical castration are needed, due to stress and pain caused by castration of male pigs. One alternative is production of entire male pigs. However, changed behaviour of entire males compared with castrated males might adversely affect the welfare of entire males and changes in management procedures and production system might be needed. Elements from the organic pig production system might be beneficial in this aspect. The aim of this article is to investigate the effect of grouping strategy including social mixing and group size on levels of mounting behaviour and skin lesions, hypothesising that procedures that disrupt the social stability (e.g. regrouping) will have a larger negative effect in small groups compared with large groups. Approximately 1600 organic entire male pigs of the breed (Landrace×Yorkshire)×Duroc were reared in parallel in five organic herds, distributed across four batches in a 2×2 factorial design in order to test the influence of social mixing (presence or absence of social mixing at relocation) and group size (15 and 30 animals). Animals were able to socialise with piglets from other litters during the lactation period, and were all mixed across litters at weaning. A second mixing occurred at insertion to fattening pens for pigs being regrouped. Counting of skin lesions (1348 or 1124 pigs) and registration of mounting behaviour (1434 or 1258 pigs) were done on two occasions during the experimental period. No interactive effects were found between social mixing and group size on either skin lesions or mounting frequency. Herd differences were found for both mounting frequency and number of skin lesions. No association between skin lesions and mounting were revealed. Social mixing and group size were shown as interacting effects with herds on mounting frequency (P<0.0001), but with no consistent pattern across all herds. In addition, no effect of social mixing was found on mean number of skin lesions, but more lesions were observed in large groups (P<0.036). This could indicate that keeping entire male pigs in groups of 30 animals as compared with smaller groups of 15 may marginally decrease the welfare of these animals.

Do nurse sows and foster litters have impaired animal welfare? Results from a cross-sectional study in sow herds.

Increasing litter size has led to introduction of so-called nurse sows in several EU countries. A nurse sow is a sow receiving piglets after having weaned her own piglets and thereby experiencing an extended lactation. In order to analyse whether nurse sows have more welfare problems than non-nurse sows a cross-sectional study was conducted in 57 sow herds in Denmark. Clinical observations were made on nurse and non-nurse sows and their litters. The clinical observations were dichotomized and the effect of being a nurse sow was analysed based on eight parameters: thin (body condition score<2.5), swollen bursae on legs, dew claw wounds, vulva lesions, poor hygiene, poor skin condition, shoulder lesions and cuts and wounds on the udder. Explanatory variables included in the eight models were: nurse sow (yes=1/no=0), age of piglets (weeks old, 1 to 7), parity (1 to 8+) and all first order interactions between these three variables. The effect of using nurse sows on piglet welfare was analysed with five models. The outcomes were: huddling, poor hygiene, lameness, snout cuts and carpal abrasions. The explanatory variables included in the five models were: nurse sow (yes=1/no=0), age of piglets (weeks old, 1 to 7), parity (1 to 8+) and all first order interactions between these three variables. Herd identity was included as a random factor in all models. The nurse sows had a significantly higher risk of swollen bursae on legs (P=0.038) and udder wounds (P=0.001). No differences in risk of being thin or having shoulder lesions were found. Foster litters had significantly higher risk of being dirty (P=0.026) and getting carpal abrasions (P=0.024) than non-foster litters. There was a tendency for higher lameness in foster litters than in non-foster litters (P=0.052). The results show that nurse sows and their piglets to some extent experience more welfare problems than non-nurse sows with piglets at a similar age.

Weight and season affects androstenone and skatole occurrence in entire male pigs in organic pig production.

To investigate the extent to which the level of androstenone and skatole decreases with a decrease in live weight and/or age at slaughter of entire male pigs produced under organic standards, 1174 entire male pigs were raised in parallel in five organic herds, distributed across four batches in summer and winter. The median androstenone level was high for organic entire male pigs (1.9 µg/g), but varied greatly both within and between herds. Median skatole level was 0.05 µg/g, also with a wide range both within and between herds. Decreasing live weight over the range of 110 ± 15.6 kg s.d. was found to decrease androstenone as well as skatole concentration, however, with different patterns of association. Age did not have significant direct effect on either androstenone or skatole levels. Androstenone levels were higher during winter than summer (P<0.0001), but no difference in skatole was found between seasons. The study concludes that decreasing live weight at slaughter could be an applicable management tool to reduce risk of boar taint and the level of tainted carcasses for a future production of entire male pigs within the organic pig production system, although further studies are needed as great variation in boar taint was found also for low weight animals.

Effect of faecal soiling on skatole and androstenone occurrence in organic entire male pigs.

Production of entire male pigs could be a future strategy for organic pig production. However, production of entire males leads to increased risk of carcasses with elevated boar taint levels. It is hypothesized that skatole levels in pig meat are affected by faecal soiling and that organic housing facilities can increase the risk of pigs being heavily soiled. Therefore, the overall aim of this study was to investigate if increased pig and pen soiling increases skatole concentration in entire male pigs. In five herds, 1174 organic entire male pigs were reared in four batches across two seasons, summer and winter. Measurements of pig and pen soiling, as well as fat skatole and androstenone concentration and human nose sensory tests of fat odour, were performed. Skatole and androstenone concentrations varied greatly within and between herds with a 10% and 90% percentile for the overall population of 0.02 and 2.25 µg/g for skatole and 0.53 and 4.84 µg/g for androstenone. Human nose positive tests averaged 18.3% with great variation between herds and seasons. Pen soiling had significant effects on pig soiling. Moreover, outdoor pen soiling significantly affected skatole concentration in interactions with herd and season (P<0.001 and P=0.003) and affected human nose positive risk in interaction with herd (P=0.005). Soiling on indoor pen areas did not affect skatole levels and no effect on androstenone was found for any pen area. Soiling of pigs affected both skatole and androstenone levels, with the size of the head and abdomen body areas covered in manure showing significant positive effects on skatole concentration. No effect of density of the manure layer was found on either boar taint measure. Herd significantly affected both skatole and androstenone in fat as well as the human nose positive risk. The human nose test revealed no effect from pig soiling. A large variation in the different boar taint measures was found for both high and low scores of pen and pig soiling, and only a small difference in skatole and androstenone concentrations between the high and low soiling categories was found. Therefore, while increasing the hygiene management could be a strategy for reducing boar taint in production of organic entire male pigs, it should be emphasized that other factors would also need to be considered.

Assessing animal welfare in sow herds using data on meat inspection, medication and mortality.

This paper aims to contribute to the development of a cost-effective alternative to expensive on-farm animal-based welfare assessment systems. The objective of the study was to design an animal welfare index based on central database information (DBWI), and to validate it against an animal welfare index based on-farm animal-based measurements (AWI). Data on 63 Danish sow herds with herd-sizes of 80 to 2500 sows and an average herd size of 501 were collected from three central databases containing: Meat inspection data collected at animal level in the abattoir, mortality data at herd level from the rendering plants of DAKA, and medicine records at both herd and animal group level (sow with piglets, weaners or finishers) from the central database Vetstat. Selected measurements taken from these central databases were used to construct the DBWI. The relative welfare impacts of both individual database measurements and the databases overall were assigned in consultation with a panel consisting of 12 experts. The experts were drawn from production advisory activities, animal science and in one case an animal welfare organization. The expert panel weighted each measurement on a scale from 1 (not-important) to 5 (very important). The experts also gave opinions on the relative weightings of measurements for each of the three databases by stating a relative weight of each database in the DBWI. On the basis of this, the aggregated DBWI was normalized. The aggregation of AWI was based on weighted summary of herd prevalence's of 20 clinical and behavioural measurements originating from a 1 day data collection. AWI did not show linear dependency of DBWI. This suggests that DBWI is not suited to replace an animal welfare index using on-farm animal-based measurements.

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.

Herd- and sow-related risk factors for lameness in organic and conventional sow herds.

Lameness in sows is an animal welfare problem which also presents an economic challenge to pig producers. Information about the prevalence of herd lameness in organic sows is relatively scarce. The first objective of this study was to establish the prevalence of lameness and to identify risk factors associated with sow lameness in Danish outdoor organic sow herds by analysing the association between risk factors at both sow and herd level using clinical records of lameness. A total of 1850 sows from nine organic herds were included in the study. Second, the study examined differences in the prevalence of sow lameness between outdoor organic and indoor conventional herds. An additional aim here was to identify risk factors associated with clinical records of sow lameness in Danish sow herds by analysing the association between risk factors with lameness at sow and herd level. One thousand and fifty four gestation sows from 44 indoor conventional and nine organic sow herds were included in this study. The nine organic herds were visited twice: once in summer/autumn 2011, and once in winter/spring 2012. In winter/spring 2011, a total of 44 indoor conventional herds were visited. Risk factors included in the study were clinical parameters and factors related to the production system. Sows were examined visually by one of four trained observers. The organic sows were assigned scores for lameness, body condition, hoof length, bursitis, abscesses and leg wounds, while the conventional sows were assigned scores for lameness, body condition and bursitis. A multivariable analysis was carried out by logistic regression with the herd and observer as random effects. The average herd lameness prevalence in gestation and lactation sows in organic herds was 11% in summer/autumn and 4.6% in winter/spring. 'Wounds, bursitis and abscess' on legs (OR=4.7, P<0.001) and body condition score >3 (OR=1.79, P=0.008) were associated with increased risk of lameness in Danish organic sow herds. Season (winter/spring v. summer/autumn) lowered the risk of lameness (OR=0.37, P<0.001). Average prevalence of lameness in gestation sow herds in winter/spring in conventional herds was 24.4%, and in organic herds it was 5.4%. An organic sow had a decreased risk of lameness (OR=0.28, P<0.001) as compared with a conventional sow. Bursitis was associated with increased risk of lameness (OR=2.08, P=0.002) regardless of the production system (i.e. whether the herd was organic or conventional).

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.

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.