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Biomedical subjects

A A Dijkhuizen

Publications and source records attributed to A A Dijkhuizen.

At least 19 recordsLinked to original sources
PubMed1996

[I&R (identification and registration) system cattle: an analysis of its use during a foot-and-mouth-disease outbreak in The Netherlands].

The performance of the Dutch cattle I&R system was analysed, with emphasis on the potential use of the system for the control of an outbreak of foot and mouth disease (FMD). The analysis showed that not all mutations were centrally registered within the three working days that are allowed to pass between the actual change and the obligatory report. In particular, young calves and cattle heading for slaughter were reported too late. During an outbreak of FMD, the best strategy to trace animals off a farm seems to be first to identify all animals on the farm, using a preprocessed list of the animals that should be present on the farm according to the I&R system. Then all the animals that have left the farm during the last month can be traced in the central I&R computer or by asking the person to whom the farmer sold the cattle (the next owner). In the present study, 54% of the animals were localized within one day, and 94% within one week. Finally, some suggestions for improvement for the system are given.

Animal Husbandry↗
PubMed1996

Basic framework for the economic evaluation of animal health control programmes.

The further integration of international markets means that co-ordinated policies against contagious animal infections have become increasingly important, and stricter demands for control and eradication should be expected in the future. To meet these demands, it would be desirable to create a computer simulation environment in which 'what if?' scenarios could be performed, in order to explore the epidemiological and economic effects of various infections and control strategies. The authors propose a flexible economic framework and illustrate this framework with an example. The framework has four elements: changes in the percentage of infectious herds, changes in product quantities, changes in product prices and economic integration. Each element is specifically defined and has its own input and output data, depending on the control strategy under consideration. In an illustration of the framework, probability distributions of the different control strategies are compared and the optimal strategy is chosen, according to the attitude of the decision-maker towards risk. Such a framework can be considered as a new standardised approach for comparing and selecting animal health control strategies, by integrating technical and economic data and principles.

Animal Diseases↗
PubMed1994

Optimizing the herd calving pattern with linear programming and dynamic probabilistic simulation.

Until recently, little attention has been paid to the influence of seasonal variation in performance and prices on the optimal calving pattern of a herd. A method was developed to determine the herd calving pattern that is farm-specific and optimal with use of linear programming. The required technical and economic parameters are calculated with a dynamic probabilistic simulation model of the dairy herd. The approach was illustrated with a situation in which the objective was to maximize the gross margin of the herd and the annual milk production of the herd was restricted, resulting in an optimal calving pattern: all heifers calved during August. When, in addition, only home-reared replacement heifers were allowed to enter the herd, heifer calvings took place from July to October. The gross margin was reduced by only Dfl. .13/100 kg of milk ($1 US = 1.80 Dfl.) as a result of the additional constraint. The sensitivity of the optimal calving pattern of herd was determined for lower reproductive performance and when seasonal price variation was ignored. The method described herein is a flexible tool for determining the optimal calving pattern of herd, taking into account farm-specific inputs and constraints.

Animal Feed↗
PubMed1994

Optimal replacement of mastitic cows determined by a hierarchic Markov process.

Farmers frequently have to decide whether to keep or to replace cows that suffer from clinical mastitis. A dynamic programming model was developed to optimize these decisions for individual cows within the herd, using the hierarchic Markov process technique. This technique provides a method to model a wide variety of cows, differing in age, productive performance, reproductive status, and clinical mastitis occurrence. The model presented was able to support decisions related to 63% of all replacements. Results--for Dutch conditions--showed the considerable impact of mastitis on expected income of affected cows. Nevertheless, in most cases, the optimal decision was to keep and to treat rather than to replace the cow. Clinical mastitis occurring in the previous lactation negligibly influence expected income. Clinical mastitis in current lactation, especially in the current month, however, had a significant effect on expected income. Total losses caused by clinical mastitis were US$83/yr per cow. Farm level treatment, which reduced incidence by 25%, on a farm with 10 clinical quarter cases per 10,000 cow days, may cost at maximum US$27/yr per cow.

Animals↗
PubMed1993

Short- and long-term production losses and repeatability of clinical mastitis in dairy cattle.

Between 1985 and 1990, a study of 5313 lactations of 2477 Black and White cows was carried out. A stepwise least squares method was used to obtain unbiased estimates of milk, fat, and protein losses that were due to clinical mastitis and the carry-over effect from the previous lactation. Logistic regression was used to estimate the probability that a cow would have clinical mastitis in the next month. The effect of clinical mastitis on production within one lactation was estimated at 527 kg of milk (8.1%), 22.7 kg of fat (8.0%), and 13.7 kg of protein (6.2%) for > or = 3 cases of clinical quarters in the second lactation. One or 2 cases of clinical quarters in a lactation did not significantly affect the production in the next lactation. The negative carry-over effect of > or = 3 cases of clinical quarters was estimated at 381 kg of milk (5.9%), 23.7 kg of fat (8.4%), and 10.1 kg of protein (4.6%) up to and including mo 8 of the second lactation. The fat content in milk produced after the onset of mastitis decreased, and the protein content increased. The risk of clinical mastitis infection in the following month was influenced by month of lactation (a higher risk early in lactation), lactation number (risk increased with lactation number), production level (higher risk for high producing cows), number of clinical quarters in the previous lactation, number of clinical quarters in the previous months of the current lactation, and occurrence of clinical mastitis in the current month.

Animals↗
PubMed1992

[Porcine Epidemic Abortion and Respiratory Syndrome (PEARS)-positive and PEARS-negative diagnoses in pig breeding and reproduction farms in The Netherlands using statistical methods].

The diagnoses Porcine Epidemic Abortion and Respiratory Syndrome (PEARS)-positive and PEARS-negative can be made using the following data on herd performance: the average number of stillborn piglets per litter, the average number of live piglets per litter and the average piglet mortality before weaning. Depending on the number of litters used in calculating the averages, the extent to which two out of the three performance data should deviate to arrive at the diagnosis PEARS-positive is given in tables and figures. The same farm will only be diagnosed PEARS-negative if after some time at least two out of the three performance data deviate less than other criteria also provided in tables and figures.

Abortion, Veterinary↗
PubMed1990

[Economic consequences of an infection with the bovine diarrhea virus (BVD virus) in 15 dairy farms].

In outbreaks of disease with the bovine virus diarrhoea virus (BVD virus), the economic loss to fourteen dairy farms was determined on the basis of the amount of loss per dairy cow. The patients included cases of abortion, stillbirths, delivery of calves showing lesions, lesions of the feet, mucosal disease and animals persistently infected with BVD virus. BVD virus was isolated from several cases of disease on all farms. It was not possible, however, directly to examine all individuals for the presence of the virus. The amount of loss caused by BVD virus was Dfl. 136,- per average dairy cow. The amount varied between individual farms from Dfl. 42,- to Dfl. 285,- per dairy cow.

Animals↗
PubMed1989

[An economic comparison of replacement decisions for sows in the field and in model conditions].

On twelve farms in the Netherlands, using the VAMPP herd health and management information system, were collected and analysed detailed sow culling data over the period from 1985 to 1986. A total number of 1617 sows were culled, resulting in an annual culling rate of 50 percent, more than half of which was due to reproductive problems (34 percent) and low productivity (17 per cent). When the calculated model recommendations and the actual decisions were compared, there was a striking resemblance for sows culled because of low productivity. With regard to reproductive problems, however, sows not showing any heat were culled too early after weaning and sows which failed to conceive too late. The total calculated losses due to premature disposal were found to average Dfl. 124,- per culled sow, or Dfl. 9,300,- per year in a 150-sow herd.

Animal Husbandry↗
PubMed1989

Economic aspects of common health and fertility problems for the individual pig producer: an overview.

The income margin in modern pig farming is generally narrow. Controlling the cost of production, therefore, is of great importance. Improving health and fertility can play a major role in this context. In this paper three interrelated issues are discussed from a farm management point of view: (1) the financial losses of common health and fertility problems, (2) the costs and benefits of disease control, and (3) the decision to replace individual sows in case of poor health and/or reduced productive performance. Priorities for further research in the field of animal health economics are also discussed.

Animal Husbandry↗
PubMed1988

Economic and reproductive consequences of retained placenta in dairy cattle.

The financial losses due to retained placenta in Dutch dairy cattle were estimated by using two different methods of calculation. A data-set containing the birth records of 160,188 Meuse-Rhine-Yssel cows provided data on the reproductive performance of cows with and without retained placenta. The fertility of cows after retention of the placenta appeared to be affected. An economic calculation made by adding the losses due to increased calving interval, increased culling rate, loss of milk production and the costs of veterinary treatment and drugs revealed that the total loss due to retained placenta was 471 pounds per year for a 100-cow farm with an average incidence of the condition (6.6 per cent). For a 'problem' farm with a 30 per cent rate, the loss was 2139 pounds per year. A computer farm simulation model, based on a stochastic determination of events, was used to make calculations for circumstances closely resembling those on farms. A 6.6 per cent rate of retained placenta caused a small but significant decrease in net return on labour and management; however, a 30 per cent rate caused highly significant changes. The economic effects of retained placenta were similar in magnitude in herds of high or low productivity and high or low fertility. Sensitivity analysis showed that the greatest financial losses were caused by loss of milk production, followed by the number of animals suffering from complications. The financial losses in herds with an average rate of retained placenta were thus of limited economic importance and therapeutic measures alone should be adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Husbandry↗
PubMed1987

[A stochastic computer simulation model for integrated zootechnical, veterinary and economic instruction regarding managerial decisions on dairy farms].

A teaching version of a (main frame) simulation model is described in the present paper. The primary purpose of this model is to study the background and effects of management decisions with regard to reproductive performance in dairy cattle. The initial information available is derived from a fertility-health chart, commonly used on commercial dairy farms in the Netherlands. The user than goes through the programme in an interactive manner in order to establish the correct diagnosis as well as to give suitable advice. As all the revenues and costs are simulated, it is also possible to consider the effects of advice from the economic point of view. In imitating real farm conditions as closely as possible, various events and effects of decisions are stochastically involved, i.e. as random samples on appropriate probability distributions rather than as fixed values. People involved in herd health programmes, therefore are given the opportunity of exercising in a field in which farmers cannot permit experiments. The experience gained in using the model in teaching veterinary and agricultural students has been positive so far.

Animal Husbandry↗
PubMed1987

Economic losses due to paratuberculosis in dairy cattle.

The results of a study of the economic losses caused by paratuberculosis in dairy cattle are reported. The losses in production and the determination of lost future income due to premature disposal are emphasised. A decrease in milk production of 19.5 per cent compared with the lactation two years before culling was recorded in animals showing clinical signs of paratuberculosis. The decrease in production in the last lactation but one compared with the previous lactation was 5 per cent. In animals with non-clinical forms of paratuberculosis these decreases in production were 16 per cent and 6 per cent, respectively.

Age Factors↗
PubMed1986

[PorkCHOP: an economic microcomputer replacement model for sows].

A computer model called PorkCHOP, was developed in an electronic spreadsheet on the microcomputer to help farmers, veterinarians and other livestock specialists reach economically sound culling decisions in swine breeding herds. It quantifies the benefits of a longer herd life and a shorter farrowing interval, calculates an economic index (Retention Pay-Off) to be used as a culling guide for individual sows within a herd and determines the maximum number of permissible services when sows fail to conceive following the first service. PorkCHOP runs with 'default' settings for the major factors affecting replacement economics, but the user can modify all variables to represent a specific herd more precisely.

Animal Husbandry↗
PubMed1985

[Economic losses to farms due to paratuberculosis in cattle].

The results of a study on economic losses to farms caused by paratuberculosis in dairy cattle are reported. Quantification of the decrease in production and determination of standard losses due to premature disposal using calculations based on a model were stressed. A decrease in production of 19.5 per cent compared with the last lactation but two was recorded in animals showing clinical symptoms of paratuberculosis. The decrease in production was 5 per cent during the last lactation but one compared with the previous lactation. The decrease in production during lactation on disposal was 16 per cent and 6 per cent during the last lactation but one compared with the last lactation but two in animals with non-clinical forms of paratuberculosis. The average cow showing clinical symptoms of paratuberculosis, which was disposed of, caused a total loss of 2,250 guilders, whereas the average cow with a non-clinical form of Johne's disease was estimated to cause a loss of 1,800 guilders.

Animal Husbandry↗
PubMed1984

[The decision to replace dairy cows in case of difficult-to-achieve pregnancy: an economic evaluation].

The question approached is, 'How long will it be profitable to continue breeding dairy cattle in cases of poor reproductive performance, differing in age and milk production potential, until it has to be decided to cull them?' This question was expressed in an economic replacement model for dairy cattle. The essence of the model is a comparison of anticipated incomes from a cow present in the herd an a replacement cow. For herd cows, the critical production level (expressed as a percentage of the herd level, after correction for age and stage of lactation) below which it is no longer profitable to breed empty cows was calculated. This was done at ten stages in each lactation. It was found to be profitable to continue breeding cows with poor reproductive performance for a long period: even up to 8-9 months after calving in young cows showing an average production level or higher. The most important factor affecting the calculated critical production levels was found to be the repeatability of an unduly long calving interval of the cow concerned: if problems regarding reproductive performance are also expected in future lactations, breeding should be stopped earlier in lactation.

Animals↗