Livestock Production
3.4 Sustainable Livestock Systems
As already discussed in the previous sections, the consumption of animal products is much more strongly linked to increased resource consumption and environmental degra-dation than the consumption of vegetal products. This connection holds true for the current situation, but is not necessarily true if alternative concepts are taken into ac-count that are based on different concepts than conventional models.
Animal protein can be produced in a way that does not rely on arable land and hence does not compete with crop production. It can even contribute to increased food secu-rity by optimizing the recycling of food waste and fulfil a variety of ecological functions improving the efficiency of cropping systems. The critical aspect is the nutrition of the livestock, which is determining the sustainability of the consumption of animal products.
Judging the sustainability of any livestock system without taking into account the origin and type of feed is fundamentally flawed.
In order to maximize the sustainability of livestock production, it must be integrated into the whole process of food production and waste management as much as possible.
Röös et al. (2016) proposed a concept of sustainable livestock production for Sweden, where only ecological leftovers were fed to livestock, meaning the animals were pasture raised or received by-products from food processing, but no animal feed was grown on arable land. Applying this scenario would result in reduced consumption of animal prod-ucts and substantially reduced environmental impact.
Schader et al. (2015) were modelling a similar approach of sustainable livestock pro-duction as a global scenario for 2050 compared with a reference diet. Animals were only fed from grassland or by-products, as a consequence animal product consumption was reduced, while environmental impacts, such as arable land occupation, nitrogen and phosphorus surplus, pesticide and freshwater use were lessened.
Van Zanten et al. (2015) calculated that if livestock was fed with co-products, food waste and grass-based systems only, without competing with cropland, the amount of animal protein consumed per person would be 21 g per day, which is about two thirds of current global average consumption [van Zanten et al., 2016].
3.4.1 Food Waste and By-Products Recycling
Global food loss is substantial and consists of losses during agricultural production, livestock production, handling, storage and transportation, consumer waste and over-consumption. The proportion of harvested biomass from agriculture that is actually consumed as human food is just 24.8 %, globally.
Food processing comes with a loss rate of 24.2 % of DM (14.7 % for energy and 33.4
% for protein) and consumer waste with a loss rate of 9.0 % of DM (8.6 % for energy and 9.0 % for protein) [Alexander et al., 2017]. It is estimated that about one third of globally produced food is wasted or lost. Most common food waste management strategies include land filling, composting, anaerobic digestion and incineration. For the United States the proportion of food waste that enters landfills lies between 54 and 97
%, while less than 3 % is composted and less than 2.1 % is anaerobically digested for
biogas production [Kibler et al., 2018].
Feeding of food waste to animals is common in a number of states in Asia. For instance in Japan and South Korea, 35.9 % and 42.4 % of food waste is fed to livestock, mostly pigs. The food waste is sterilized through heat treatment to decrease contamination risks and possibly dried prior to feeding. In the European Union, for most types of food waste, feeding to livestock is illegal due to purported contamination risks. If food waste would be used for pig feed at similar rates as in Japan and South Korea, it would support 20 % of EU pork production [Salemdeeb et al., 2017]. In the US, the usage of food waste for growing pigs is permitted in 28 of the 50 states [Mo et al., 2018]. The use of processed animal protein such as meat and bone meal is prohibited in the European Union, due to concerns over the spread of prion disease [Mo et al., 2018].
Hossein and Dahlan (2015) investigated the substitution of free-range village chicken for-mulated feed with dehydrated processed food waste. They found it could be utilized at a substitution rate of 20 % without affecting growth performance [Hossein and Dahlan, 2015]. The utilization of food waste as animal feed is better suited for fish than for pigs or poultry, as the transmission of foot and mouth disease, swine fever, highly pathogenic avian influenza, and transmissible spongiform encephalopathies through intra-species re-cycling (feeding pork to pigs) is recognized as a potential safety concern. However, these four infectious diseases are not related to fish. Feeding fish to fish, even the same species is not perceived as a safety risk.
Food waste can either be heat-treated and dried into a powder or fed to black soldier fly larvae that are harvested, dried and ground. Even though the yield for the first treatment option is substantially higher, the conversion to larvae powder is preferred, as authorization for export and general acceptance are higher with an estimated market value price per ton at least 10 times higher than for food waste powder. The usage of food waste powder as substitution of fishmeal in the diet of several fish should not ex-ceed 20 %, while insect powder would be in the range of 17 - 30 %, according to various feeding trials [Cheng and Lo, 2016].
According to estimations, over 50 % of total fish capture is not used as food. Fish waste that includes bones, intestines, heads and tails can be used to produce fishmeal. This fish waste derived fishmeal would amount to about 50 % of the already used fishmeal in China [Mo et al., 2018].
Fruit and vegetable wastes and by-products from fruit and vegetable processing accumu-late at 55 gt per year for India, the Philippines, China and the USA. For the most part they are being disposed of in landfills or rivers. The livestock sector however, provides an opportunity to recycle these resources by including them into the diet of different species of livestock. Wastes such as apple pomace, banana peels or citrus pulp can be incorporated into the diet of ruminants as well as non-ruminants at levels ranging from 10 up to 30 % without compromising growth performance [Wadhwa and Bakshi, 2013].
Van Zanten et al. (2013) calculated that just by using co-products and food waste from an average vegan diet, 71 g of pork containg 14 g of protein can be produced per person per day.
3.4.2 Utilization of Non-Arable Land
The current global arable land covers 1.4 billion ha of land. The remaining potential for available arable land is estimated at 1.4 billion ha, without taking into account forests, built-up areas and protected areas [Alexandratos and Bruinsma, 2012]. Perma-nent meadows and pastures are comprising 3.3 billion ha [FAO, 2013], while the majority of this land is not suitable for use as arable land.
Ruminants play an important role in global food security, as they have the ability to turn pastureland into human edible food. As most pastureland is not suitable for crop production, ruminants that are 100 % pasture raised do not present a competition for human food production. Rather do they enable the production of food on land areas that would otherwise hardly produce any food at all [Schader et al., 2015].
According to Poore & Nemecek (2018), global beef production (from beef herds) has a protein productivity of 6.1 kg/ha/y [Poore and Nemecek, 2018]. According to the compiled data of Clark & Tilman (2017), the protein productivity of grass-fed beef according to several different sources averages at 8.32 kg/ha/y, while grain-fed beef av-erages at 11.28 kg/ha/y [Clark and Tilman, 2017].
Through the combination of pasture and trees, called silvopastoral systems, the pro-ductivity of conventional grazing systems can be massively increased. In Australia, the combination of grassland with forage trees, the leucaena-grass-system is very popular.
On 150,000 ha in Queensland, this system achieves a live weight productivity of 250 kg/ha/y (equal to a protein productivity of 25 kg/ha/y, assuming an edible portion of 50 % of the animals’ live weight and a protein content of 20 %). The same system achieves a live weight productivity of 1,000 - 1,500 kg/ha/y (equal to a protein productivity of 100 - 150 kg/ha/y, under the same assumption) when irrigation is provided [Shelton and Dalzell, 2007].
A comparison between conventional grazing systems and intensive silvopastoral systems in Australia, Mexico and Columbio showed an increase in meat productivity of 304 %, 332 - 983 % and 1,353 - 2,257 %, respectively. The leucaena-grass-system is based on the Leucaena tree (Leucaena leucocephala), a nitrogen fixing forage tree that provides many ecological services and boosts beef production capacity tremendously, compared to grassland only. This is mainly due to increased forage production and drought resis-tance. The combination of trees and grazing animals, known as silvopasture systems, has enormous potential to boost global grazing system productivity, while minimizing the need for nitrogen fertilizer due to increased nitrogen fixation capacity and protecting the soil against erosion through more extensive root systems [Cuartas Cardona et al., 2014].
3.4.3 Other Benefits of Integrated Systems
The integration of livestock into crop production can have a multitude of benefits rang-ing from nutrient cyclrang-ing and conservation, utilization of crop residues, vegetation and weed management to economic stability through diversified income. For instance Clark and Stuart (1996) showed that geese would greatly reduce insect damage on apple trees and triple the yield of potatoes by selective weeding when they were integrated into a polyculture system and compared to a control system without geese.
Mixed crop-livestock systems are especially important in developing countries. Livestock is used to plough the fields, the manure is used to fertilize the land and the crop residues are fed to livestock. Additional income from livestock products may attenuate harvest losses in dry years. In India, the employment of improved dual-purpose varieties of sorghum and millet have had substantial improvement in livestock efficiency by increas-ing milk yield from cows and buffaloes by 50 %, while grain yield was unchanged. The dual-purpose varieties are producing more crop residues, directly benefiting integrated livestock production. Globally, 50 % of all produced grain comes from mixed systems already [Tester and Langridge, 2010].
Rice-duck-systems are a traditional practice in China. The ducks are beneficial for the rice cultivation as they serve as a biological pest control by feeding on golden apple snails
that can otherwise be detrimental to the rice crop. On the Philippines, there are rice systems in combination with ducks and fish. The fish also serve as pest control feeding on snails and weeds. In a field trial it was shown that the combination of fish and con-ventional rice cultivation (using pesticides) increased the rice yield by 10 % compared to conventional rice cultivation alone. Without the use of any pesticides, the combination of rice with fish and ducks resulted in a 25 % rice yield increase compared to conventional rice cultivation using pesticides. Additionally it resulted in an income increase of 1,100
% in the third cropping, due to the selling of duck eggs and fish together with more rice and cutting out the pesticides. See section 4.2.4 for further details [Cagauan et al., 2000].
Maughan et al. conducted field trials where they compared corn monoculture systems with crop-livestock integrated systems. In the latter, corn was grown, while the crop residue was left on the field to be grazed by cattle. Additionally winter cover crops were included after the corn harvest that were also grazed by cows. In 4 years of the experiment, the yield of the integrated system was between 5 and 15 % higher than the monoculture system. Soil quality was improved in the integrated system, as total nitrogen content, total carbon content and soil microbial biomass carbon were increased with larger soil aggregates throughout the study period at different soil depths [Maughan et al., 2009].
Silvopasture systems can also be used to combine livestock with timber production.
Clason (1995) showed that a pine timber pasture exceeded the internal rate of return in comparison to an open pasture. Both trees and pasture would benefit from fertilization, while the cattle would keep the grass beneath the trees short, resulting in increased timber production of 5.4 m3/ha more than the untreated pine plantation.