W.D.J. Kremer

Classification of newly calved cows into moderate and severe responders to experimentally induced Escherichia coli mastitis.

In the present study newly calved cows were tentatively classified as moderate and severe responders to experimentally induced Escherichia coli mastitis based upon the reactive oxygen species (ROS)-generating capacity of their blood neutrophils before infection. The groups differed in blood and milk composition prior to infection. This initial classification was supported by the corresponding variation in clinical symptoms and in the changes in milk production and composition measured during mastitis. Responses of newly calved cows to Esch. coli challenge varied from mild to severe symptoms of inflammation in infected glands and differed in the intensity of systemic disturbances and general illness. Losses in milk yield and compositional changes were most pronounced in inflamed glands and in severe responders. In inflamed glands milk yield and composition did not return to preinfection level in either moderate or severe responders. The yields of lactose, alpha-lactalbumin, casein and fat followed the same pattern as milk yield. It is concluded that the severe and long lasting systemic disturbances observed in severe responders can be ascribed to absorption of endotoxin from infected glands into circulation, indicating the important role of endotoxin in the pathology of coliform mastitis in periparturient cows. Evaluation of the ROS-generating capacity of blood neutrophils and blood and milk composition before infection might help to predict the cows sensitivity to Esch. coli mastitis.

The perception of veterinary herd health management by Dutch dairy farmers and its current status in the Netherlands: a survey.

The importance of veterinary herd health management (VHHM) is increasing in both dairy farming and veterinary practice. Little is known, however, about how VHHM is perceived by farmers in terms of structure, content and satisfaction. In 2007 a questionnaire, containing questions about these three items was therefore sent to 800 Dutch dairy farmers. Farmers received two questionnaires, one for participants in VHHM and one for non-participants, allowing them to choose the appropriate one. Results were summarized and statistically analyzed. Farmers who were participating in VHHM had better farm performance. They were satisfied with the way VHHM was executed on their farm. However, there were some pressure points. Goal setting and evaluation was still not a regular part of VHHM, even though it is said to be effective in literature. Time spent on VHHM not visible to the farmer was often not charged or not clearly specified on the bill. The differences in opinions between participants and non-participants of VHHM indicated a lack of communication and/or product differentiation. Satisfaction with the way VHHM was executed on the farm had no significant influence on 305-day production. There was, however, some influence on calving interval and bulk milk somatic cell count (BMSCC).

Effect of penethamate hydriodide treatment on bacteriological cure, somatic cell count and milk production of cows and quarters with chronic subclinical Streptococcus uberis or Streptococcus dysgalactiae infection.

A randomized, controlled field trial was performed in The Netherlands to determine the therapeutic efficacy of parenteral penethamate hydriodide (Leocillin) against naturally occurring, chronic, streptococcal mastitis during lactation. Quarter milk samples were collected from subclinical cases of Streptococcus uberis or Streptococcus dysgalactiae mastitis to determine the effect of treatment on bacteriological cure and somatic cell count (SCC) at quarter level. A quarter was considered to be cured when the bacterial species, isolated prior to treatment, was not isolated from the quarter milk samples taken on days 10 and 20 post-treatment (bacteriological cure), or when a quarter milk SCC (QMSCC) was <250000 cells/ml on days 10 and 20 post-treatment (SCC cure). Longitudinal data analysis was performed to determine the effect of antibiotic therapy on SCC and milk yield at cow level. Bacteriological cure occurred in 59% of 29 treated quarters, while no cure was observed in any of the 21 untreated control quarters. Treatment resulted in a significant decrease in SCC at cow and quarter level in comparison with untreated controls. There was no significant effect of treatment on milk production. Antibacterial treatment of subclinical streptococcal infections during lactation also prevented clinical mastitis. Furthermore, the treatment may contribute to reduction of bulk milk SCC and to prevention of pathogen spread in dairy herds.

Reliability of the bulk milk somatic cell count as an indication of average herd somatic cell count.

Bulk milk somatic cell count (BMSCC) is a frequently used parameter to estimate the subclinical mastitis prevalence in a dairy herd, but it often differs considerably from the average SCC of all individual cows in milk. In this study, first the sampling variation was determined on 53 dairy farms with a BMSCC ranging from 56 000 to 441 000 cells/ml by collecting five samples on each farm of the same bulk tank. The average absolute sampling variation ranged from 1800 to 19 800 cells/ml. To what extent BMSCC represents all lactating cows was evaluated in another 246 farms by comparing BMSCC to the average herd SCC corrected for milk yield (CHSCC), after the difference was corrected for the sampling variation of BMSCC. On average BMSCC was 49 000 cells/ml lower than CHSCC, ranging from -10 000 cells/ml to 182 000 cells/ml, while the difference increased with an increasing BMSCC. Subsequently, management practices associated with existing differences were identified. Farms with a small (<20%) difference between BMSCC and CHSCC administered intramuscular antibiotics for the treatment of clinical mastitis more often, used the high SCC history when cows were dried off more frequently and had a higher number of treatments per clinical mastitis case compared with farms with a large (20%) difference. Farms feeding high-SCC milk or milk with antibiotic residues to calves were 2.4-times more likely to have a large difference. Although sampling variation influences the differences between BMSCC and CHSCC, the remaining difference is still important and should be considered when BMSCC is used to review the average herd SCC and the subclinical mastitis prevalence.

Assessment of competence in clinical reasoning and decision‐making under uncertainty: the script concordance test method

Real‐life, complex problems often require that decisions are made despite limited information or insufficient time to explore all relevant aspects. Incorporating authentic uncertainties into an assessment, however, poses problems in establishing results and analysing their methodological qualities. This study aims at developing a test on clinical decision‐making in veterinary medicine and establishing its reliability and validity. The test is based on the script concordance test method and covers a large sample of authentic cases and uncertainties. The answer key was compiled with reference to the professional judgements and decisions of a panel of experienced practitioners. From a substantive appraisal of the cases and items, the analysis of the test results and the responses from the experienced practitioners, it is concluded that this test validly represents the problems, decisions and uncertainties of clinical practice. In spite of the hindrances caused by the uncertainties included in the test, the reliability and validity of the test and its results could be evaluated and proved to meet measurement criteria.

Associations between farmer participation in veterinary herd health management programs and farm performance

In the past few decades, farms have increased in size and the focus of management has changed from curative to preventive. To help farmers cope with these changes, veterinarians offer veterinary herd health management (VHHM) programs, whose major objective is to support the farmer in reaching his farm performance goals. The association between farm performance and participation in VHHM, however, remains unknown. The aim of this paper was to compare farm performance parameters between participants and nonparticipants in VHHM and to differentiate within participation to evaluate the possible added value of VHHM on the farm. Five thousand farmers received a questionnaire about the level of VHHM on their farm. Farm performance parameters of these 5,000 farms were provided. For all respondents (n=1,013), farm performance was compared between participants and nonparticipants and within level of participation, using linear mixed and linear regression models. Farmers who participated in VHHM produced 336 kg of milk/cow per year more and their average milk somatic cell count (SCC) was 8,340 cells/mL lower than farmers who did not participate in VHHM. Participating herds, however, had an older age at first calving (+12d), a lower 56-d nonreturn rate percentage (-3.34%), and a higher number of inseminations per cow (+0.09 inseminations). They also had more cows culled per year (+1.05%), and a lower age at culling (-70 d). Participants in the most-extended form of VHHM (level 3) had a lower SCC (-19,800 cells/mL), fewer cows with high SCC (-1.70%), fewer cows with new high SCC (-0.47%), a shorter calving interval (-6.01 d), and fewer inseminations per heifer (-0.07 inseminations) than participants in the least-extended form of VHHM (level 1). Level 3 participants, however, also had more cows culled per year (+1.74%) and a lower age at culling (-103 d). Discussing specific topics with the veterinarian (milk production, fertility, and udder health) had only marginal effects on improving the farm performance parameters related to those topics. Given the relevance of fertility on the farm and the focus on longevity by society, it is important to determine underlying reasons for the negative associations of these topics with participation in VHHM. A longitudinal study could provide answers to this. For now, veterinarians should be aware of the associations. The increased milk production and milk quality could help the marketing of VHHM to farmers.

Veterinary on-farm counselling on dairy farms: the veterinarians’ vision

At present most Dutch veterinary practices offer on-farm counseling to dairy farmers. Goal of this study was to determine how Dutch veterinary practices defined on-farm counseling and what problems they experienced interacting with dairy farmers. In January 2011 ten randomly selected Dutch veterinary practices involved in on-farm counseling within the scope of herd health programs on dairy farms were asked to participate in this study. Upon agreement an appointment was made at the veterinary practice where one veterinarian, providing on-farm counseling in practice, was interviewed. During the interview a list of questions were asked in a semi-structured fashion. The interviews were recorded with a voice recorder and later transcribed in full. The definition of on-farm counseling differed between practices. Some practices defined it as fertility checks, while others included structural advice on aspects of dairy farming such as animal health, housing and prevention. According to the veterinarians, the way on-farm counseling was executed was fully dependent on the farmers’ wishes. However, farmers were not actively asked for their wishes. During on-farm counseling goal setting and evaluation were used only by two veterinarians. Three veterinarians provided a written advice afterwards. Most veterinarians experienced difficulties communicating advices to dairy farmers; they indicated they found it difficult to change farmers’ behavior and experienced difficulties explaining the value of the advice. Most advices were followed only partially. An important observation in this study was that veterinarians who were enthusiastic about the concept of on-farm counseling saw possibilities to expand it in their practice and experienced less communication problems. Problems with udder health and production level were detected earlier and dealt with in a more preventive and structural way. Veterinarians also had fewer difficulties selling their advice to farmers, and perceived their farmers as motivated more often.

Effectiveness of a programme design for the development of competence in solving clinical problems

Background: To apply what has been learned theoretically in a clinical context is for many students a major challenge. In order to ease their transition into practice, a training programme was developed, focusing on learning to solve clinical problems. Aims: The programme is designed for veterinary medicine students in the preclinical phase with already a sound theoretical base in biomedical and clinical sciences. The design is based on the engagement in learning and work processes derived from clinical practice and exposure to a large variety of real and paper-based cases. This article addresses the effectiveness of this programme design. Method: Programme effectiveness was defined in terms of the progress made by the students. This progress was established using methodological triangulation of the results from student questionnaires, performance observations and (pre and post) assessment. Results: On all dimensions of effectiveness, the results consistently showed that the programme was perceived as effective and led to improved performances in solving clinical problems and better solutions in the assessment. The students’ progress was substantial. Conclusions: At preclinical level, a course design based on the work processes in clinical practice and a mixture of real and paper-based patients is effective in enhancing problem-solving competence.

An attempt to control lungworm disease and parasitic gastroenteritis on commercial dairy farms by the use of an adaptation of Michel's dose‐and‐move system

On seven dairy farms an attempt was made to control lungworm disease in calves by turnout on a pasture grazed earlier by cows, followed by a move to aftermath and ivermectin treatment 2 months later. Transmission of lungworm was observed on all farms. Lungworm disease occurred on four farms at treatment. Coughing re-occurred on three of these farms in some animals 2 months later. Owing to poor performance between turnout and treatment, weight gain was below the norm on the farm with the highest infections and most severe respiratory signs. On the other farms respiratory signs did not result in poor weight gain. Gastrointestinal nematode infections remained low on all farms. The conclusion is that this dose and move scheme cannot be recommended for the control of lungworm.

Prediction of the herd somatic cell count of the following month using a linear mixed effect model

An accurate prediction of the average somatic cell count (SCC) for the next month would be a valuable tool to support udder health management decisions. A linear mixed effect (LME) model was used to predict the average herd SCC (HSCC) for the following month. The LME model included data on SCC, herd characteristics, season, and management practices determined in a previous study that quantified the contribution of each factor for the HSCC. The LME model was tested on a new data set of 101 farms and included data from 3 consecutive years. The farms were split randomly in 2 groups of 50 and 51 farms. The first group of 50 farms was used to check for systematic errors in predicting monthly HSCC. An initial model was based on older data from a different part of the Netherlands and systematically overestimated HSCC in most months. Therefore, the model was adjusted for the difference in average HSCC between the 2 sets of farms (from the previous and current study) using the data from the first group of 50 farms. Subsequently, the data from the second group of 51 farms were used to independently assess this final model. A null model (no explanatory variables included) predicted 48 and 59% of the HSCC within the predetermined range of 20,000 and 30,000 cells/mL, respectively. The final LME model predicted 72 and 81% of the HSCC of the next month correctly within these 2 ranges. These outcomes indicate that the final LME model was a valid additional tool for farmers that could be useful in their short-term decisions regarding udder health management and could be included in dairy herd health programs.