Alig M, Wolff V, Nemecek T and Gaillard G.
Agroscope, Institute for Sustainability Sciences ISS, Reckenholzstrasse 191, 8046 Zürich, Switzerland;
martina.alig@agroscope.admin.ch
Abstract
Cattle fattening on pasture is often discussed as a mitigation option to reduce competition between animal and plant production for human nutrition. We performed an life cycle assessment analysis to compare a conventional, concentrate-based beef fattening system with a pasture-based system. Data were obtained from real farms. We calculated 16 environmental impacts, which were analysed related to the animal live weight. Except for deforestation, the pasture-based system exhibited higher impacts for all categories analysed, mainly because of its lower daily weight gain. Targeting the same slaughter weight, the lower daily weight gain of the animals on pasture resulted in a much longer fattening period and a higher need for energy, water and land area as well as higher emissions of methane and nitrogen compounds. In contrast, previous studies on grass based milk production showed that it performed equally well as milk based on feed concentrates. This could be a hint that from an environmental point of view, dairy systems might be preferable over beef fattening systems for drawing value from high-quality grasslands.
Keywords: beef, environmental impact, LCA, roughage, pasture
Introduction
As ruminants are able to convert grass into high value food products, reconnecting cattle to grassland less suitable for crop production might be an option for mitigating the area competition between animal and plant production for human nutrition (de Vries et al., 2015). The majority of the world’s agricultural area is covered by grassland (FAOSTAT, 2015) and therefore, grass is a major agricultural resource. In Switzerland, 70% of the agricultural area consists in grassland (BFS, 2014), and Swiss agricultural policy promotes the use of this important domestic resource. Besides, extensive production systems are often perceived by consumers to have a lower environmental impact than intensive ones (Xue et al., 2010).
However, the sustainability of grassland-based ruminant systems is controversially discussed (Steinfeld et al., 2006; Gerber et al., 2015). In this study, we assessed the environmental impacts of a conventional, concentrate-based beef fattening system and a pasture-based system in Swiss conditions in order to provide a basis for decision-making and facilitate system-optimisation.
Materials and methods
The environmental impacts of the two systems were assessed by life cycle assessment (LCA) according to SALCA (Nemecek et al., 2010), developed by Agroscope for agricultural systems. The following environmental impacts were examined: non-renewable energy demand, global warming potential, ozone formation potential, demand for phosphorous and potassium resources, land competition, deforestation, water use, eutrophication potential, acidification potential, terrestrial and aquatic ecotoxicity as well as human toxicity potential. System boundaries were set at farm gate; all results were expressed per kg live weight.
Data were obtained from 17 and 13 real conventional and pasture-based beef fattening farms, respectively.
Table 1 shows the most important production parameters of the systems analysed.
Results and discussion
Except for deforestation and resource use potassium, the pasture-based system exhibited higher environmental impacts per kg live weight for all impacts analysed (Figure 1). This was due to the lower digestibility of the roughage as main feed ingredient and the resulting longer fattening period and higher total feed intake. Targeting the same slaughter weight, the pasture-based animals lived 1.7 times longer and needed 1.9 times more dry matter intake per kg weight gain than the conventional animals. This led to higher methane and nitrogen emissions as well as a higher need in energy, land, water and infrastructure.
Table 1. Production parameters of the conventional and pasture-based beef fattening systems.1
Conventional beef fattening Pasture-based system
Location of farms Plain region Plain region
Slaughter age (weeks) 53 90
Slaughter weight (g) 568 543
Daily weight gain (g) 1,279 741
Feed intake per kg weight gain (kg DM kg LW-1) 4.8 8.9
Basic ration (kg DM) 1,543 3,326
Pasture grass (%) – 31
Hay (%) 2 25
Grass silage (%) 12 31
Maize silage (%) 73 13
Sugar beet pulp (%) 13 –
Concentrate intake (kg) 763 94
1 DM = dry matter; LW = live weight.
Figure 1. Comparison of the environmental impacts of the conventional and pasture-based beef fattening system. 100% = system with the higher impact.
These results confirm the lower eco-efficiency of grass-based beef fattening systems compared to concentrate-based systems also found in a review study of de Vries et al. (2015), although in this study, the results for acidification and eutrophication differed among the studies analysed. Previous studies comparing grass-based and conventional dairy systems were more ambiguous: There was no clear advantage for the one or other system (Alig et al., 2015). With around 30% lower milk yield, the productivity losses in grass-based dairy farming were less pronounced than in grass-based beef fattening (daily weight gain over 40% lower). Therefore, the productivity losses in milk production could be compensated to a higher degree trough the lower inputs for feed production than the losses in beef production. Although the simplifications inherent to LCA calculations lead to notable uncertainties, this could be a hint that in Swiss or similar conditions, dairy systems could be more suitable for grass-based production than beef fattening systems. This is in line with the fact that beef produced from calves bred by dairy cows exhibits lower environmental impacts than beef from calves bred by suckler cows (Alig et al., 2012; de Vries et al., 2015).
Conclusions
Even in a country with high quality grassland and a good grass growth, the pasture-based beef fattening system could not compete with the concentrate-based system in terms of environmental efficiency.
Previous studies showed more favourable results for grass-based dairy systems. From an environmental point of view, dairy systems might preferable over beef fattening systems for drawing value from high-quality grasslands.
References
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