The aim of this research was to study the energy flow and the modelling of energy use in broiler production in the Guilan Province of Iran. The data were gathered through interview with 25 broiler farm managers out of a total of 146 broiler producers in Rasht, the center of Guilan Province, Iran. The effect of broiler farm size at three levels-small (˂20,000 birds), medium (20,000-30,000 birds), and large (˃30,000 birds)-was evaluated, based on the energy use indices. The Cobb-Douglas model and

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... sensitivity analysis were used to investigate the effects of energy inputs on poultry production. The results showed that the total energy input and energy ratio were 2,605.54 Mcal (1000 birds)-1 and 0.234, respectively. Diesel fuel and feed were ranked the first and second energy inputs for broiler production with the shares of 43.92% and 36.68%, respectively, of the total energy input. The shares of renewable and non-renewable energy forms in broiler production were determined to be 37.33% and 62.67% of the total energy input, respectively. The energy ratios of small, medium, and large farms were computed as 0.232, 0.225, and 0.250, respectively. Consequently, the large-sized farms were more energy efficient than the small and medium-sized ones. Results of the Cobb-Douglas model showed that the impacts of energy inputs of labor, chick, diesel fuel, machinery, disinfectants, and medicines on broiler performance were positive, while the impacts of electricity and feed were negative.