Review: Closing nutrient cycles for animal production - Current and future agroecological and socio-economic issues

Nutritive value and condensed tannins of tree legumes in silvopasture systems

Introducing legumes into C4-dominated tropical pastures, may enhance their sustainability but has some pasture management constraints. One potential alternative is using arboreal legumes, but several of these species have relatively high condensed tannin (CT) concentrations, which negatively impact forage quality. There is limited knowledge, however, on how arboreal legume leaf CT content varies over the year and how this might impact forage quality. The objective of this 2 year study was to assess the seasonal variation of CT and nutritive value for ruminants of the tropical tree legumes gliricidia [Gliricidia sepium (Jacq.) Kunth ex. Walp.] and mimosa (Mimosa caesalpiniifolia Benth). The research was carried out in the sub-humid tropical region of Brazil on well-established pastures in which either legume was present with signalgrass (Urochloa decumbens Stapf.). We determined CT and nitrogen concentrations, in vitro digestible organic matter (IVDOM), and leaf δ13C and δ15N from January to October of 2017 and 2018. All parameters were affected (P < 0.05) by the interaction between legume species and sampling time, with generally higher leaf CT content for mimosa than gliricidia, and both were reduced at the start of the dry season, although much more drastically for mimosa. The IVDOM was strongly affected by CT content and increased at the start of the dry season, coincidentally when C4 grass forage quality typically decreased. There is a marked species effect, with CT from gliricidia impacting IVDOM more than the same CT content from mimosa. While N concentration from mimosa also increased at the start of the dry season, that for gliricidia did not vary over the year. We conclude that although these arboreal legumes have relatively high CT contents, these reduce during the dry season when CT concentrations coinciding with a reduced forage quality as the protein content for C4 grasses is usually inadequate in this season.

Feed-food and land use competition of lowland and mountain dairy cow farms

Dairy cows and other ruminants contribute to human nutrition as they are able to convert feed components containing human inedible fibre concentrations (e.g. roughage and by-products from the food processing industry) into valuable animal-sourced food. A number of crops often fed to dairy cows (e.g. soy or cereals) are however potentially edible by humans too. Additionally, land used to grow dairy cattle feed may compete with crop production for human consumption. Two different methods to assess the competition between feed consumption of dairy cows and human food supply were thus refined and tested on 25 Swiss dairy farms. With respect to the potential human edibility of the feeds used in dairy production, the human-edible feed conversion ratio (eFCR) was applied. The land use ratio (LUR) was used to relate the food production potential, per area of land utilised, with the dairy production output. Low to medium eFCR, with values ranging from 0.02 to 0.68 were found, as an average proportion of 0.74 of total DM intake consisted of roughage. In contrast, we found relatively high LUR (0.69-5.93) for most farms. If the land area used to produce feed for cows was used for crop production (applying a crop rotation), 23 of the 25 farms could have produced more edible protein and all farms more human-edible energy. Indicator values strongly depend on the underlying scenarios, such as the human-edible proportion of feeds or the suitability of land and climate for crop production. Reducing the amount of human-edible feeds in dairy farming by feeding by-products from the food processing industry and improving forage quality may be suitable strategies to reduce eFCR, but relying on low-opportunity cost feeds may restrict milk performance level per cow. On farm level, improving overall efficiency and therefore using less land (especially area suitable for crop production) per kg product decreases LUR. However, the most promising strategy to mitigate land use competition may be to localise dairy production to land areas not suitable for crop production. Both methods (eFCR and LUR) should be used in parallel. They offer an opportunity to holistically evaluate the net contribution of dairy production to the human food supply under different environmental conditions and stress the importance of production systems well suited to specific farm site characteristics.

New insights in improving sustainability in meat production: opportunities and challenges

Treating livestock as senseless production machines has led to rampant depletion of natural resources, enhanced greenhouse gas emissions, gross animal welfare violations, and other ethical issues. It has essentially instigated constant scrutiny of conventional meat production by various experts and scientists. Sustainably in the meat sector is a big challenge which requires a multifaced and holistic approach. Novel tools like digitalization of the farming system and livestock market, precision livestock farming, application of remote sensing and artificial intelligence to manage production and environmental impact/GHG emission, can help in attaining sustainability in this sector. Further, improving nutrient use efficiency and recycling in feed and animal production through integration with agroecology and industrial ecology, improving individual animal and herd health by ensuring proper biosecurity measures and selective breeding, and welfare by mitigating animal stress during production are also key elements in achieving sustainability in meat production. In addition, sustainability bears a direct relationship with various social dimensions of meat production efficiency such as non-market attributes, balance between demand and consumption, market and policy failures. The present review critically examines the various aspects that significantly impact the efficiency and sustainability of meat production.