Biomedical subjects

Jan Tind Sørensen

Publications and source records attributed to Jan Tind Sørensen.

6 recordsLinked to original sources

PubMed2007

Loser cows in Danish dairy herds: risk factors.

The objective of our study was to evaluate risk factors for the loser cow state in Danish dairy herds. A loser cow was defined on the basis of a clinical examination of the individual cow. Recordings of clinical signs were converted into a loser cow score and all cows with a loser cow score of 8 or more were defined as loser cows. We used correspondence analysis to give a first indication of the associations between the proportion of loser cows in the herd and potential risk factors. Risk factors were evaluated both at the herd level (39 herds) and at the cow level (6451 cows) using logistic regression. Conventional herds with a high average somatic cell count, hard cubicles and no grazing seem to be associated with a high proportion of loser cows. Odds ratio for the loser cow state was 4.18 in conventional herds compared to organic herds. Odds ratio for the loser cow state was 1.87 for an increase in average weighted mean bulk tank somatic cell count of 100,000 cells per ml. We found a statistically significant interaction between stall surface and the use of grazing. Odds ratio for the loser cow state in herds with soft cubicles and the use of grazing was 0.09 compared to herds with hard cubicles and no grazing. At the cow level, odds ratio for the loser cow state increases significantly with increasing parity. Odds ratios for the loser cow state were 1, 2.59 and 6.74 for parity 1, 2, and 3 or older, respectively. Odds ratio for the loser cow state was significantly higher (3.38) for cows giving birth to twins at the last calving before the scoring. Additionally, cows scored on pasture had a significantly lower odds ratio (0.26) for the loser cow state compared to cows scored in the barn.

Animals↗

PubMed2007

Loser cows in Danish dairy herds: definition, prevalence and consequences.

During the last few years, many Danish dairy farmers have expressed increasing concerns regarding a group of cows, which we have chosen to term 'loser cows'. Until now, a loser cow has not been described scientifically. We defined a loser cow on the basis of a clinical examination of the cow. A total of 15,151 clinical examinations were made on 6,451 individual cows from 39 randomly selected, large Danish dairy herds with loose-housing systems using a clinical protocol. Scores for the clinical signs lameness, body condition, hock lesions, other cutaneous lesions, vaginal discharge, condition of hair coat and general condition were converted into a loser cow score. Cows with a loser cow score of 8 or more were classified as loser cows. The overall prevalence of loser cows was 2.15%, 4.50% and 2.98% during the first, second and third round of herd visits, respectively. The associations between the loser cow state and milk production, mortality, morbidity, culling and workload for the farmer were evaluated using data from herd visits and from the Danish Cattle Database and a number of different statistical techniques. It was concluded that the loser cow state has significant negative consequences for both the farmer and the cow. On average, loser cows yielded 0.61 to 2.24 kg energy corrected milk less per day than non-loser cows depending on parity. Hazard ratio for death or euthanasia was 5.69 for loser cows compared to non-loser cows. Incidence rate ratio for disease treatments was 0.69 for non-loser cows compared to loser cows. Loser cows were often culled in an 'unfavourable' way and generally caused extra workload for the farmer. A simplified version of the loser cow score was evaluated and is recommended for future research and use in practice.

Animals↗

PubMed2006

A stochastic model simulating paratuberculosis in a dairy herd.

Paratuberculosis (PTB) causes severe economic losses to farmers and the infection has very complex effects (many indirect) on the production of a dairy herd. These indirect effects have not or only briefly been described by earlier PTB-simulation models, and therefore they were included in a new model called PTB-Simherd. Our aim was to develop the basis for a decision-support tool which can predict herd-specific production-related effects from introduction of different control strategies against PTB. The PTB-Simherd is a dynamic, stochastic, and mechanistic Monte-Carlo model simulating a dairy herd including young stock. Paratuberculosis and relevant control strategies against this infection were built into an existing herd simulation model. The model simulates epidemiological and production related consequences of PTB and control strategies against it in the herd. It also reflects indirect effects of PTB and control strategies through effects on replacements and herd demographics. Every animal in the herd is specified with biological parameters (including PTB state and test results) and it is updated in weekly time-steps. Management is specified at herd level with 353 parameters of which 78 are related to PTB. To demonstrate the basic characteristics of the model, scenarios with varying infection risks (sensitivity analyses) plus scenarios with seven different control strategies in two herds with good and poor reproduction were simulated for 10 years. Breaking of infection routes turned out to be the only strategy predicted to reduce the true prevalence of PTB in a herd. Supplementing this strategy with test-&-cull strategies had limited effect on prevalence and using test-&-cull alone just delayed the increase in prevalence. The effects of different PTB-control strategies on the production (especially sale/purchase of heifers, feed consumption and prevalences of other diseases) were predicted to be affected by other conditions like heat-detection success, replacement% and herd demographics--which were again affected by PTB infection of the herd. These links and indirect effects of control strategies thus seem important to include when modeling and predicting effects of PTB control in dairy herds.

Animals↗

PubMed2006

Simulated economic effects of improving the sensitivity of a diagnostic test in paratuberculosis control.

Low sensitivity (Se) of diagnostic tools is often mentioned as a major problem in the control of paratuberculosis (PTB) and much effort is put into the improvement of these tests. The hypothetical perspectives of improving the Se of a milk-antibody ELISA (hereafter: milk-ELISA) used in test-&-cull strategies against PTB in dairy cattle were investigated by simulations. The current Se varies between 10 and 80%, increasing with increasing lactation stage, parity and infection stage. We simulated the effects on a dairy herd's production of improving this Se to 80% (independent of these factors) and assumed no concomitant decrease in specificity. By using a PTB model called PTB-Simherd, 12 scenarios were simulated to study three test-&-cull strategies in each of four herds with 200 dairy cows. To show the maximal effect of using test-&-cull with such an improved test we simulated three strategies: (1) no testing, (2) testing with milk-ELISA test with the current Se and culling of positive cows immediately and (3) testing with milk-ELISA test with a Se improved to 80% and culling positive cows immediately. The four herds were defined by a moderate (25%) or high (80%) initial true within-herd prevalence (including young stock), and a poor or good heat-detection success of 40 or 60%. We assumed that these factors influenced the effects of improving the Se of the milk-ELISA. Management both concerning calf management and in general was specified to represent a typical Danish herd. Using an improved milk-ELISA was predicted to reduce the prevalence of PTB more effectively than the current ELISA, and over 10 years bring the production of a herd with moderate initial prevalence up to a production level comparable to a non-infected herd (unlike if the current ELISA had been used). In a herd with high initial prevalence (80%) milk production was increased more by using the improved milk-ELISA, but after 10 years the replacement rate was still very high causing problems with having enough recruitment animals-especially in high-prevalence herds with poor reproductive performance. Economically important measurements in all four herds benefited from the improvement of the test over a 10-year period. However, in the first 3-5 years the improved test would be more expensive to use than the current test, due to increased replacement (reduced net annual revenue per cow euro15 on average) but after that, net annual revenue increased continuously; after 10 years it was euro70-90 higher, than if the current milk-ELISA was used. Also, the milk-ELISA test with its current Se seemed to be profitable already after 2 years in high-prevalence herds using a test-&-cull strategy based on the milk-ELISA alone.

Animals↗

PubMed2004

Mortality (including euthanasia) among Danish dairy cows (1990-2001).

Mortality among Danish dairy cows was examined using data from the Danish Cattle Database (DCD) and a questionnaire survey. Mortality risk has increased from approximately 2% in 1990 to approximately 3.5% in 1999. The increased mortality was seen for all dairy breeds and all age groups. Mortality among older dairy cows (parity 3 and older) was approximately twice the mortality among younger cows. 30-40% of deaths were during the first 30 days of the lactation. Approximately, 58% of dead dairy cows had been euthanised. Replies from the questionnaire indicate that the proportion of euthanised cows has increased in the past 5 years. In 86% of all deaths (questionnaire survey) a primary reason could be identified; 25% were for locomotor disorders.

Aging↗

PubMed2002

Expert opinions of strategies for milk fever control.

Dairy cows have several risk factors for milk fever. The most-suitable strategy to control milk fever in a specific herd will depend on herd-specific circumstances such as the attitude and skills of the farmer, the opportunities available in the production system and the economic consequences of a certain strategy. To develop feasible strategies in a modern loose-housing dairy herd, we carried out an expert opinion study. Animal husbandry advisors and veterinary practitioners were used as experts. The experts quantified the effect on milk fever and time needed by the farmer for two preselected options: Ca-gel fed orally peripartum and a low dietary cation-anion-difference in the dry-cow ration. The estimated mean relative risk (compared to no strategy) was 0.45 and 0.42, respectively, and the median time needed by the farmer was 7 and 33 min, respectively, per cow year. The experts also suggested 12 control strategies. The two control strategies, which were predicted to be the most, relevant were Ca-gel fed orally peripartum used alone and used in combination with a low Ca dry-cow diet.

Animal Feed↗