Abstract
Beef production contributes to environmental problems, such as climate change, air pollution, and water
pollution. The present study aimed to compare the environmental impact of the conventional fattening
system for Japanese Brown beef steers (housed and fed large amounts of concentrate) with a year-round
grazing system. We first evaluated the environmental impacts of the two beef fattening systems (year-round
grazing and conventional) through life cycle assessment, then assessed the environmental impacts of the
conventional cow-calf system. The impact of each system was determined regarding its potential contribution
to global warming, acidification, and eutrophication, as well as its energy consumption. From these results
and an evaluation of the carcass characteristics, we estimated and compared the environmental impacts per
unit carcass weight of beef produced by the two fattening systems. The carcass weights were 403 kg (age at
slaughter: 25.3 months) in the year-round grazing system and 465 kg (age at slaughter: 25.0 months) in the
conventional system. The year-round grazing system led to lower environmental impacts per unit body weight
gain of steers during fattening compared with the conventional system with reductions in the global warming,
acidification and eutrophication potentials, and energy consumption of 22, 87, 81, and 57%, respectively.
Unlike the conventional system, imported feed was scarcely used in the year-round grazing system. This led
to a reduction in the environmental impacts associated with feed transportation, the major factor contributing
to the reduction of all the impact categories we assessed. The impacts on global warming, acidification,
and eutrophication potentials, and energy consumption per kg carcass weight of beef in the conventional
system were 30.1 kg CO2eq., 326.7 g SO2eq., 38.0 g PO4eq., and 210.9 MJ, respectively, and in the year-round
grazing system 27.8 kg CO2eq., 153.2 g SO2eq., 20.3 g PO4eq., and 134.2 MJ, respectively. Consequently, the
year-round grazing system led to a reduction in the environmental impacts per unit carcass weight of beef
compared with the conventional system, with reductions in global warming, acidification, and eutrophication
potentials of 8, 53, and 47 %, respectively, and in energy consumption of 36%. We can therefore conclude
that introducing year-round grazing into a conventional beef fattening system can mitigate the environmental
impacts of Japanese beef production.
