Comparison of flock structures using MIDAS.

Abstract

370 Proc. Aust. Soc. Anim. Prod. Vol. 17 COMPARISION OF FLOCK STRUCTURE -USING D.A. FALCONER * MIDAS - MIDAS (Model of an Integrated Dryland Agricultural System)is a whole-farm mathematical programming f o r the crop-livestock farming system of the Western Australian with many regional versions. In its standard form, MIDAS has about 400 activities including 20 different rotations on six different soil types with many different seeding,harvesting,sheep management and crop fertilisation options. About 200 constraints in the model represent the limited farm resources,financial constraints,and biological limits to productian. The major feature distinguishing MIDAS from models isits emphasis on the interdependencies enterprises. These include nitrogen fixation by stubble,grazing bylivestock, pasture suppression grain to sheep and the effect of a pasture phase other mathematical programning of croppingandlivestock leguminous pastures and crqps, followiing cropping, feeding on the costs of weed control. MIDAS has been applied to a wide range of extensionand research issues (see Kingwell and Pannell 1987). The benefits of using a whole far, optimisation model are evident in the results derived by comparing five different self replacing merino flock structures with main selling activity being lambs, hoggets, shippers 18 to 28 months, shippers 30 to 40 months and wethers 48 to 76 monhs of age. Sensitivity of flock structure t o in price also examined. Results for different flockstructuresares~in Tablel. Higher pmportionsofb&hers in the flock are associated with increased profit. With less profitable flockstructures, thereisanincreaseintheareaofthefarmin crop reflecting the reduced profitability of the sheep enterprise. Table1 Sheep numberqnetinwandpercentageof floh structures (-1 price 45Oc/kg). Main selling activity Net incme ($) - &=a Winter DSEs crop% 21268 1568 2745 57 21614 1522 3172 57 farmincropfordifferent wethem 48-76 mth 36527 1329 4324 42 shippers ShippUS 18-28 mth 30-4Omth 30462 1533 3143 57 33499 1662 3939 42 At lcwzr wool prices (3OOc/kg), selling shippers at 30 to 40 ITy)nths of age is the Ilr>stprofitable optionwiththe areaof fannin crop increasingby percent. The importanceofusinga~le-farm~~~fordealingwiththe ccfnplexities of the farmin gsysteminthewheatbelt is evidentfranthis analyses* Partialanalyses mlyallowforchangges inenterprisemixes in respaflse to changing prices or enterprise profitability. MIRAS is a useful tool offeringawfiole-farminsi~ttobothresearchers andextensi~officers. KINGWEZL, R.S. and PANNEIL, D.J. (1987). %IDAS, A Bioeamanic IMel of a DrylanaFarmSystan. (HTDOC: Wageningen). * Department of Agriculture, Sauth Perth, Western Australia 6151