Changes of beef ration composition: an example of utilizing normative and positive mathematical methods | Spremembe sestave krmnih obrokov za goveje pitance: primer uporabe normativnih in pozitivnih matematičnih metod

English. The aim of this paper is to present possibility to combine different mathematical methods for analysis of ration composition changes in actual economic environment. On the basis of mathematical programming models, based on constraint optimization, the influence of price-cost ratios on the trends of efficient beef ration formulation in the period 1998 to 2008 has been analysed. For investigation positive and normative mathematical methods have been utilized. The normative part of methods applies a common linear programming approach supported by penalty function. To find out the “reaction” of rational farmer within given circumstances, simulation was upgraded with positive mathematical programming approach. Obtained results illustrate change in ration composition by increased maize silage quantities and significantly lower amounts of grass silage during last decade. Due to Slovene natural conditions it is obvious that such a dramatic shift is impossible, therefore more attention should be paid to reduction of grass silage production costs.

Slovenian. Namen prispevka je prikazati možnost kombiniranja različnih matematičnih metod za analiziranje sestave krmnih obrokov v danih okoliščinah. Z matematičnimi modeli, ki temeljijo na omejeni optimizaciji, smo proučevali cenovno-stroškovna razmerja v obdobju 1998 do 2008 in iskali morebitne spremembe v sestavi racionalnih krmnih obrokov za goveje pitance. Za analizo smo uporabili normativne in pozitivne matematične metode. S pomočjo klasičnega linearnega programa, nadgrajenega s tehtanim ciljnim programom, smo izvedli normativno analizo. Da bi ugotovili, kako bi se v danih razmerah odločal povprečen rejec, pa smo simulacijo izvedli tudi s pozitivnim matematičnim programiranjem. Dobljeni rezultati kažejo, da se je sestava racionalnega krmnega obroka v zadnjih desetih letih nagnila v prid koruzne silaže, izrazito pa se je zmanjšala količina travne silaže v obroku. Zaradi naravnih danosti v Sloveniji take spremembe niso izvedljive, zato bomo morali več pozornosti posvetiti zniževanju stroškov pridelave travne silaže.