H.H.E. van Zanten

Opinion paper: The role of livestock in a sustainable diet: a land-use perspective

In 2000, the Food and Agricultural Organisation (FAO) projected that global demand for animal source food (ASF) would double by 2050 (Alexandratos and Bruinsma, 2012). Although these projections were revised slightly during recent years, they form the basis of many scientific and policy documents related to livestock production. Those projections, however, are based on global trends for a growing population and increasing incomes and urbanization, but not based on ensuring global nutrition security in a sustainable way. Currently, the world’s livestock sector adds to the total anthropogenic emissions of greenhouse gases and competes for scarce resources, such as land, water and fossil energy. Without changes to reduce the environmental impact, concerns about the environment will only increase further. We asked ourselves, how and why livestock production is essential and what would be the proportion of ASF in human diets to ensure nutrition security in a sustainable way? As land is a strict limitation of nutrition security, we took a landuse perspective, irrespective of socio-economic or technical constraints. In 2012, about 4.92 billion ha was used for agriculture, of which about 70% was used for livestock production, mainly for pasture and production of feed crops (FAO stat). Of the 4.92 billion ha of agricultural land about 1.56 billion ha is used for crop production. Assuming 9.7 billion people in 2050, then about 0.16 ha of cropland is available per person. Production of a vegan diet, for example, requires about 0.14 ha/person. Expanding the area for crop production will lead to loss of grazing areas or deforestation in the tropics, for example, resulting in loss of biodiversity and increased carbon emissions. High productive croplands, therefore, must be used to produce human food instead of livestock feed. No matter how efficiently food is produced, direct consumption of cereals by humans is more efficient ecologically than consumption of livestock fed these cereals. Should we shift, therefore, to vegan diets? Not necessarily! Grass-based ruminant systems on marginal land, that is, land not suitable for crop production, produce human digestible protein more efficiently than food crops (Van Zanten et al., 2015a). Furthermore, compared with a vegan diet, consumption of a small amount of ASF reduced land use per person when livestock were mainly fed with co-products (Van Kernebeek et al., 2015). In addition to biomass from marginal land and co-products, livestock can also upgrade two other biomass streams that humans do not currently consume: crop residues and food waste. Using crop residues as livestock feed, however, can lead to depletion of soil organic carbon, and, therefore, should be left on the field. To be safe, we assumed all crop residues are left on the field. We focus, therefore, on the potential of livestock to convert co-products from human food, food waste and biomass from marginal land, referred to as ‘leftover streams,’ into high-quality ASF. Livestock that eat these leftover streams do not compete with humans for cropland, and, therefore, contribute to sustainable nutrition security. By feeding only leftover streams to livestock, the number of humans fed per hectare is maximized. How much ASF can we consume, however, when we want to avoid feed–food competition by feeding only leftover streams to livestock? To illustrate that we can produce a sufficient amount of ASF, we calculated amount of ASF produced from co-products and food waste, and amount of ASF produced from 100% grass-based systems. Amount of ASF produced from co-products and food waste depends on availability, which depends on consumption patterns of humans. If the 1.56 billion ha of cropland is used for human food production, people consume a vegan diet because no cropland is used for feed production. Consumption of a vegan diet requires annual production of about 129 kg co-products/person (see Supplementary Material S1). We chose those food ingredients in a vegan diet, whose co-products had a high nutritional value for livestock. We assumed, for example, that oil production originates from soy cultivation resulting in soybean meal. Soybean meal compared with other co-products from oil processing, for example, sunflower meal, has a high nutritional value for livestock. This assumption not only has an † E-mail: hannah.vanzanten@wur.nl Animal (2016), 10:4, pp 547–549

Environmental impact of replacing soybean meal with rapeseed meal in diets of finishing pigs.

The major impact of the livestock sector on the environment may be reduced by feeding agricultural co-products to animals. Since the last decade, co-products from biodiesel production, such as rapeseed meal (RSM), became increasingly available in Europe. Consequently, an increase in RSM content in livestock diets was observed at the expense of soybean meal (SBM) content. Cultivation of SBM is associated with high environmental impacts, especially when emissions related to land use change (LUC) are included. This study aims to assess the environmental impact of replacing SBM with RSM in finishing pig diets. As RSM has a lower nutritional value, we assessed the environmental impact of replacing SBM with RSM using scenarios that differed in handling changes in nutritional level. Scenario 1 (S1) was the basic scenario containing SBM. In scenario 2 (S2), RSM replaced SBM based on CP content, resulting in reduced energy and amino acid content, and hence an increased feed intake to realize the same growth rate. The diet of scenario 3 (S3) was identical to S2; however, we assumed that pigs were not able to increase their feed intake, leading to reduced growth performance. In scenario 4 (S4), the energy and amino acid content were increased to the same level of S1. Pig performances were simulated using a growth model. We analyzed the environmental impact of each scenario using life-cycle assessment, including processes of feed production, manure management, piglet production, enteric fermentation and housing. Results show that, expressed as per kg of BW, replacing SBM with RSM in finishing pig diets marginally decreased global warming potential (GWP) and energy use (EU) but decreased land use (LU) up to 12%. Between scenarios, S3 had the maximum potential to reduce the environmental impact, due to a lower impact per kg of feed and an increased body protein-to-lipid ratio of the pigs, resulting in a better feed conversion ratio. Optimization of the body protein-to-lipid ratio, therefore, might result in a reduced environmental impact of pig production. Furthermore, the impact of replacing SBM with RSM changed only marginally when emissions related to direct (up to 2.9%) and indirect LUC (up to 2.5%) were included. When we evaluated environmental impacts of feed production only, which implies excluding other processes along the chain as is generally found in the literature, GWP decreased up to 10%, including LUC, EU up to 5% and LU up to 16%.

Field study on effects of a heat exchanger on broiler performance, energy use, and calculated carbon dioxide emission at commercial broiler farms, and the experiences of farmers using a heat exchanger.

In broiler houses, ventilation removes moisture and maintains ambient temperature and air quality. During cold weather conditions, ventilation can result in undesirable heat loss from the house. Extra input of energy for heating the building is needed then, resulting in extra CO(2) emissions when fossil fuels are used for this purpose. In such a situation, an air-to-air heat exchanger (HE) might be valuable because it recovers heat by prewarming fresh supply air with warm inside air. The aim of this study was to analyze effects of on-farm use of an HE on broiler performance, energy use, and CO(2) emission by comparing production cycles with and without an HE, and to inventory the experiences of farmers using an HE. Data were collected of production cycles finished with (102) or without (149) an HE on 25 farms. Data on mortality, feed intake, water intake, and BW gain were obtained to analyze broiler performance. When available, gas and electricity use were obtained to analyze energy use and to calculate CO(2) emission. Farmers were interviewed about their experiences regarding the HE. The use of an HE tended to increase daily weight gain (56 vs. 55, SEM 0.3 g/d; P = 0.07), but did not affect other performance variables. Based on 13 farms, gas use was reduced by 38% (P < 0.01) after installing an HE. Based on 3 farms only, an HE did not affect electricity use, total energy use, or calculated CO(2) emission. It appeared that farmers were satisfied with the HE because they experienced an increase in job satisfaction, an improvement of climate conditions and litter quality in the broiler house, and a more uniform temperature and broiler distribution in the house. We concluded that the use of an HE reduced gas use and has the ability to improve broiler weight gain but had no effect on other broiler performance variables. Effects on CO(2) emission were unclear. Farmers appeared to be positive about using an HE, because it improved broiler house climate and job satisfaction.