The most used reproduction method in beef cattle in Brazil is natural breeding, which corresponds to 84% of calves born. Breeders adopt the bull:cow ratio of 1:25, which results in a sub utilization of bulls, making natural breeding antieconomic and underestimating the reproductive ability of competent bulls. The bull:cow ratio is determined by several factors, such as climate and nutrition, but the most determining factor is the fertility of the bull, estimated with more precision through breeding soundness examination of bulls. The aim of this study was to develop a simulation model as an aid to choose the best bull:cow ratio according to the combination of the many factors that determine this ratio. It is a conceptual, empiric, static, and determinist model which, through the processing of the input data, simulates the best BCR. Developed on the Vensim PLE 6.1 software, the model describes variables related to bulls and cows. Two equations were generated to predict the mating potential of males. In the same way, according to the reproductive status of females, equations were generated to predict the cyclicity rate of the cows. The sum of these equations originated the one that determines BCR according to the reproductive status of females. This model might serve as a tool to support decisions as to the best BCR and could be used with several combinations of models´ characteristics.

Differing conditions in captive breeding and in the wild have impact on the mineral profile of the pheasant carcass and its heavy metal contents. This may be an indicator of environmental contamination. The study evaluated the nutritional composition and selected macro- and trace element contents (heavy metals in particular) in usable sections of pheasant breast and thigh muscles originating from captive breeding and wild birds. The tests were performed on the breast and thigh muscles of 20 wild and 20 farm bred birds from around Lublin, Poland, with equal sex representation. The nutrient and lead, cadmium, chromium, and nickel contents were determined using inductively-coupled plasma atomic emission spectroscopy. The farmed pheasants had a higher proportion of breast muscle. The thigh muscles of all birds had a higher fat content than the breast muscles (5.1 g vs. 3.4 g per kg of natural weight). The macroelement level depended on the muscle type and bird origin. The trace element content also did and gender dependence was also evident. The wild birds contained more cadmium in the breast muscles and lead in both muscles than the farm-raised ones. The high quality and usefulness of wild and farmed pheasant meat is confirmed. It has advantageous macro- and trace element contents and permissible heavy metal contents except for lead in wild birds. The heavy metal level can be a bioindicator of their environmental occurrence. In wild birds, the lead level may also reflect birdshot remnants.