simulation model for a nomadic animal production system in southern iran

the first motive for the determination and evaluation of an energy productionsystem is the need to change. such system is dynamic in nature and is influenced bymany factors such as age and physiological status of individual sheep or goat, quantityand quality of available feed and environment including the management systems.traditional pastoral resource assessments do not always account for the complex,interrelated nature of land, forage and livestock. modeling may overcome the limitationsof traditional methods by improving the understanding of complex pastoral systems, andmakes fast repetitive analyses, spanning time, incorporating variability and representingmore realistically complex interactions possible within the system. the estimated valuesof metabolisable energy for maintenance and production in this study are based on theresults of two feeding systems linked together by grazing the energy intake in thenomadic production system (nps) and the dynamic system modeling used to study theassessment of these complex systems. in this study, validation of model relied on theobservations of torki ghashghaii (tg) sheep (like those in bakkan) under pen-fed andintegrated rangeland-cropland feeding systems, and was carried out mainly by studyingthe body weight gain of growing animals and also body weight changes of ewes due topregnancy and lactation. after validation, the study indicated that the mean value ofactual data of male and female lambs (weaners) and ewes were in close agreement withthe simulated data. these results validate the generalized structure of energy utilizationmodels of grazing sheep under production sub- systems of nps. these results will enablethe prediction of carrying capacities in any given situation under conditions similar tothose in bakkan.