A cross-sectional study was conducted to evaluate the prevalence of extended-spectrum β-lactamase (ESBL)- and plasmid-mediated AmpC-producing Escherichia coli and associated risk factors in dairy herds. One hundred dairy herds were randomly selected and sampled to study the presence of ESBL- and AmpC-producing E. coli in slurry samples. The sensitivity of testing slurry samples for ESBL/AmpC herd status is less than 100%, especially for detecting herds with a low ESBL/AmpC prevalence. Therefore, whereas herds that tested positive for ESBL/AmpC-producing E. coli in slurry were defined as positive herds, herds with negative slurry samples were defined as unsuspected. Isolates of ESBL- and AmpC-producing E. coli were further characterized by detection and typing of their ESBL/AmpC gene. At the initial sampling, a comprehensive questionnaire was conducted at the participating farms. The farmers were asked questions about management practices potentially associated with the ESBL/AMPC herd status. Also, data on antimicrobial purchases during 2011 were acquired to evaluate whether the animal-defined daily dose of antimicrobials per year at farm level was associated with the ESBL/AmpC herd status. Multivariable logistic regression models were used to determine the association between management practices and the ESBL/AmpC herd status. Six months after the initial slurry sampling, 10 positive herds and 10 herds that had an unsuspected ESBL/AmpC herd status during the first visit were resampled. At each farm, slurry samples and feces from 24 individual cows were collected to evaluate within herd dynamics. During the first sampling, ESBL/AmpC-producing E. coli were isolated from the slurry samples collected at 41% of the herds. In total, 37 isolates were further characterized, revealing 7 different ESBL genes (blaCTX-M-1, -2, -14, -15, -32, -55 and blaTEM-52), 1 plasmid-encoded AmpC gene (blaCMY-2), and 1 chromosomally encoded ampC gene (ampC type 3). The total animal-defined daily dose of antimicrobials per year at farm level was not significantly different between ESBL/AmpC-positive and unsuspected dairy herds. The use of third- and fourth-generation cephalosporins, however, was found to be associated with ESBL/AmpC status, with higher use of these antimicrobials resulting in a significant higher odds to be ESBL/AmpC-positive. Management factors that were associated with a higher odds of being ESBL/AmpC-positive were treatment of all cases of clinical mastitis with antimicrobials, a higher proportion of calves treated with antimicrobials, not applying teat sealants in all cows at dry off, and the use of a floor scraper. This last association, however, was considered a methodological effect rather than a true risk factor. On 5 of the 10 initially positive farms, no ESBL/AmpC-producing E. coli were cultured from the slurry or any of the individual cow samples collected during the second sampling. In 4 of the initially unsuspected farms, slurry or individual cow samples tested positive during the second sampling. In conclusion, ESBL/AmpC could frequently be cultured from slurry samples collected from Dutch dairy farms and the ESBL/AmpC genes carried by the isolates were consistent with those reported earlier. The use of third- and fourth-generation cephalosporins appeared to be associated the ESBL/AmpC herd status.

Infections with Schmallenberg virus (SBV) are associated with congenital malformations in ruminants. Because reporting of suspected cases only could underestimate the true rate of infection, we conducted a seroprevalence study in the Netherlands to detect past exposure to SBV among dairy cattle. A total of 1,123 serum samples collected from cattle during November 2011–January 2012 were tested for antibodies against SBV by using a virus neutralization test; seroprevalence was 72.5%. Seroprevalence was significantly higher in the central-eastern part of the Netherlands than in the northern and southern regions (p<0.001). In addition, high (70%–100%) within-herd seroprevalence was observed in 2 SBV-infected dairy herds and 2 SBV-infected sheep herds. No significant differences were found in age-specific prevalence of antibodies against SBV, which is an indication that SBV is newly arrived in the country.

The Welfare Quality multi-criteria evaluation (WQ-ME) model aggregates scores of single welfare measures into an overall assessment for the level of animal welfare in dairy herds. It assigns herds to 4 welfare classes: unacceptable, acceptable, enhanced, or excellent. The aim of this study was to demonstrate the relative importance of single welfare measures for WQ-ME classification of a selected sample of Dutch dairy herds. Seven trained observers quantified 63 welfare measures of the Welfare Quality protocol in 183 loose housed- and 13 tethered Dutch dairy herds (herd size: 10 to 211 cows). First, values of welfare measures were compared among the 4 welfare classes, using Kruskal-Wallis and Chi-squared tests. Second, observed values of single welfare measures were replaced with a fictitious value, which was the median value of herds classified in the next highest class, to see if improvement of a single measure would enable a herd to reach a higher class. Sixteen herds were classified as unacceptable, 85 as acceptable, 78 as enhanced, and none as excellent. Classification could not be calculated for 17 herds because data were missing (15 herds) or data were deemed invalid because the stockperson disturbed behavioral observations (2 herds). Herds classified as unacceptable showed significantly more very lean cows, more severely lame cows, and more often an insufficient number of drinkers than herds classified as acceptable. Herds classified as acceptable showed significantly more cows with high somatic cell count, with lesions, that could not be approached closer than 1m, colliding with components of the stall while lying down, and lying outside the lying area, and showed fewer cows with diarrhea, more often had an insufficient number of drinkers, and scored lower for the descriptors "relaxed" and "happy" than herds classified as enhanced. Increasing the number of drinkers and reducing the percentage of cows colliding with components of the stall while lying down were the changes most effective in allowing herds classified as unacceptable and acceptable, respectively, to reach a higher class. The WQ-ME model was not very sensitive to improving single measures of good health. We concluded that a limited number of welfare measures had a strong influence on classification of dairy herds. Classification of herds based on the WQ-ME model in its current form might lead to a focus on improving these specific measures and divert attention from improving other welfare measures. The role of expert opinion and the type of algorithmic operator used in this model should be reconsidered.