Comparative life cycle assessment of a year-round grazing system vs. a hay-feeding system

Grasslands cover around 4.5 million hectares in Florida, primarily consisting of C₄ warm-season forage species, under different managements. In North Florida, beef-cattle operations go through a cool season, a warm season, and a fall gap, which marks the overlap between both seasons. The most widespread practice among producers involves grazing during the warm season and feeding hay during the winter. However, this requires many off-farm inputs and is associated with greater indirect and direct emissions. Thus, a more sustainable alternative is necessary. Year-round grazing has potential, since it takes advantage of different complementary forage species, allowing grazing throughout the year. The goal of this study was to develop and conduct a comparative life cycle assessment evaluating the environmental impact of beef cattle in the backgrounding stage of a year-round grazing system versus hay-feeding systems. Greater environmental impacts were observed for global warming potential, fossil fuel scarcity, and freshwater eutrophication in the hay-feeding system. The global warming potential averaged 2.25 kg CO_2eq kg^-1 liveweight gain for the year-round grazing compared to 4.87 kg CO_2eq kg^-1 liveweight gain for the hay system. Enteric fermentation was the largest contributor to global warming potential. Besides, the hay-feeding system used more inputs, particularly fossil fuels and N-fertilizers, to maintain its high production and profitability. Freshwater eutrophication potential was greater for the hay-feeding system than for the year-round grazing, averaging 0.19 kg P_eq kg^-1 liveweight gain compared to 0.09 kg P_eq kg^-1 liveweight gain, respectively. Similarly, fossil resource scarcity averaged 0.048 and 0.065 kg oil_eq kg^-1 liveweight gain for the year-round grazing and hay-feeding system, respectively. The year-round grazing system is an alternative for reducing the environmental impact of beef cattle operations.