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ABSTRACT
Data obtained from four different capacity housings were evaluated to analyze cultural energy and performance of broilers according to seasons. Capacities of housing were 20,000, 25,000, 30,000 and 60,000 birds per production period, and starting date on feeding was used for assignment to seasons. Accordingly, seasons were classified as winter (December through February), spring (March through May), summer (June through August), and fall (September through November). Production periods included year 2005 in which there were six production periods from each housing. Data collected consisted of starting and finishing dates of production period; number of chicks entered and broilers sold; liveweight at slaughter; carcass weight; feed consumption for starting, growing, and finishing period; labor; medication, vaccination, and disinfectant; electricity consumption; heating and cooling methods, and amount spent; distance for transportation of feed, chicks, broilers, woodshaving, limestone; and other miscellaneous expenditures. During the experimental period of 45 days, chickens received commercial broiler diet and water ad libitum. For cultural energy analysis, feed, transportation, labor, machinery, electricity, brooding, and other inputs were calculated and corresponding values for each input were obtained from literature. For analysis, it was assumed that carcass content would have 18.2% protein and 15.2% fat. Total cultural energy invested in broilers in summer was lower than in other seasons (P < 0.04). Energy input per kg live weight gain and per kg carcass of summer were lower than that of winter (P < 0.02 and P < 0.01, respectively). Summer had lower cultural energy ratio for protein energy output than winter (P < 0.01). Energy output ratio, defined as kcal input/kcal output, was better for summer than winter (P < 0.01). Results of the study show that raising broilers in summer is more sustainable than in winter and higher liveweight gain is not always more sustainable in terms of cultural energy use.