YugoslavAssociation of ResearchInstitutions in the Field of Animal Science COMMISSION ON PIG PRODUCTION. Free Communication Session

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1 YugoslavAssociation of ResearchInstitutions in the Field of Animal Science I Session V COMMISSION ON PIG PRODUCTION Free Communication Session Simulation of different production strategies in sow units Erik J<,1}rgensen& Verner Ruby National Institute of Animal Science, Rolighedsvej 25, 1958 Copenhagen V, Denmark Summary T~o computer simulation models of sow units have been constructed in Denmark, a deterministic and a stochastic model. These models are built with the Danish nationwide monitoring system "Effektivitetskontrol", as a basis. More than 3600 farms are connected to this system. Data from the Danish field-test organisation "Rullende Afpr<,1}vninger",that investigates more than 200 modern, large-scale pig production units, have been used in the model building and -verification steps. The models compute predicted production performances by means of information from the updated registrations in the monitoring system. The deterministic model will be used in budgetting and as a means of testing the farms' actual production performance versus the predicted. The stochastic model will be used as a tool to analyze the "bottle-necks" of the sow production systems, that are currently used in Denmark, and to investigate different management strategies.

2 - 2 - Introduction The use of simulation models to investigate different production strategies in the pig production has increased over the last years (Dent & Blackie, 1979). Research workers have acknowledged the strength of such models in the validation of different strategies (Whittemore, 1979). The on-farm application of the models in the decision-making processes has however been very limited (Blackie & Dent, 1976). Such use of the models calls for a complex registration in each farm and a thorough adaptation of the model to the farm in question in order to secure that erroneous results do not spoil the farmers confidence in the model. This paper describes how we have tried to solve these difficulties in the building of two simulation models for sow units in Denmark. These two models, of which one is a deterministic model for nationwide application and the other a stochastic model for research purposes, are based on the Danish monitoring system, the "Effektivitetskontrol". The purpose of these two models is to advise the farmers on the production strategy, that is economically the most profitable in different housing systems, and to make it possible for the farmers to intervene quickly, if the actual production should differ significantly from the predicted. The models should furthermore help the farmers in budgetting. The basic information system The Danish monitoring system, the "Effektivitetskontrol" (Anonymous, 1980), is used as basis for both simulation models. This system is a unique basis, because currently more than 3600 Danish pig producers use this system as a means of controlling their production. Furthermore, it comprises the basic registration in the Danish Field Test organisation "De rullende Afpr_vninger" (Staun & Ruby, 1980), that investigates more than 200 modern large-scale pig production units. The basic recording in the "Effektivitetskontrol" is the sow and litter record, where information from the litters of each sow is stored, that is for instance, day of mating, litter size at birth and weaning, farrowing-weaning interval. For each litter about 50 informations can be stored.

3 - 3 - The simulation models One of the main reasons why the stochastic model has been built was to investigate the "bottle-necks" of the production systems, that are currently used in Denmark. The model is essentially built as a queue model with the calculations carried out on a daily basis, and the sow as the basic unit, i.e. each sow is represented in the model. Because the scope of the deterministic model is somewhat different, the model uses batches of sows as the units and the calculations are carried out on a weekly basis. The model distinguishes however between sows with 1, 2 and more than 2 litters. The models are built in a way that enables the determinati~n of all inputs to the model from the litter records of the "Effektivitetskontrol". To achieve this, it has been necessary to incorporate certain relations between production traits in the models. In the application of the models to a given production unit, the levels of these relations are adjusted in order to match the production level and efficiency on the farm. These relations have been determined by statistical analysis of data from the field-tests, as these data reflect the existing performance levels in Denmark. The distribution of the different production traits that are used in the stochastic model, are also estimated on the field-test data. Some relations have however been determined from experiments, as the relevant information was missing in the field-test data. In calculating the forecast the model determines the present state of the farm by means of the updated registrations in the "Effektivitetskontrol". This includes the number of sows and litters in each section of the stable, and the age and weight of these pigs. Mean values for the key production traits are also calculated and used in the model. Alternatively these values can be determined by the farmer himself and used as input to the model. It is thus possible to obtain a forecast based on for instance an improvement.

4 - 4 - in the performance level of the herd. After having determined the state of the farm, the model computes the forecast consisting of for instance number of matings, farrowings and weanings per week, number of piglets sold and feed used. All the outputs of the model are presented in a way that allows direct comparison with the output of the monitoring system. This enables the farmer to recognize the different terms that are used in the output, and makes it fairly easy to understand the results of the model. Validation of the models At present the models are being validated. The herds in the field-test and results from some 30 other herds are used as a test of the results of the models. The validation is carried out in close contact with the farmers of the "validation herds" to secure that the results from the models are understood and used by the farmers. Criticism and suggested alterations from the farmers are used for improving the models. We expect that this thorough validation will help to elucidate the strengths and the weaknesses of the models, and thus ensure, that the final simulation model system gives an accurate prediction. In this way the models can serve as a powerful tool in the planning and monitoring of the pig production in Denmark.

5 - 5 - References Anonymous Produktionsstyring pa P-brugene Landsudvalget for Svineavl og -produktion. pp 21. In Danish. Blackie, M.J. & J.B. Dent Analyzing Hog Production Strategies with a Simulation Model. Arner. J. Agric. Econ. vol 58, No. 1, p Dent, J.B. & M.J. Blackie Systems Simulation in Agriculture. Appl. Sci. Publishers Ltd. pp Staun, H. & V. Ruby Neue Formen einer Prufung von Haltungssystemen beim Schwein unter Praxisbedingungen in Danemark. Der Tierzuchter vol. 6. p Whittemore, C.T The Use of Computers. The Pig. Vet. Soc. Proc. vol. 6, p Simulation von verschiedenen Produktionsmodellen in Saubestanden Zusanunenfassung In Danemark sind zwei Computer-Simulationsmodelle fur Saubestande, und zwar ein deterministischer und ein stochastischer, entwickelt worden. Diese Modelle sind auf das danische Uberwachungssystem "Effektivitetskontrollen" aufgebaut. Mehr als 3600 Schweinebestande sind diesem System angeschlossen. Daten von der danischen "fieldtest" Organisation "Rullende Afpr~vninger", die mehr als 200 moderne, grosse Schweineproduktionseinheiten untersucht, sind beim Aufbau des Models und bei den Verifizierungsstufen benutzt worden. Die Modelle berechnen prognosen fur die Produktionsergebnisse basiert auf ajourgefuhrte Registrierungen der produktionskontrolle. Der deterministische Model soli besonders im Haushaltsplan benutzt werden und zur Kontrolle des erwarteten Produktionsumfanges. Der stochastische Model soli dazu benutzt werden die "Flaschenhalse" zu finden und bekommt ausserdem die Aufgabe die Steuerung der danischen Schweineproduktionssysteme zu untersuchen.