IN VITRO AND OMICS METHODOLOGIES APPLIED TO ANIMAL NUTRITION TO ADDRESS FEED-FOOD COMPETITION AND GREENHOUSE GAS EMISSIONS

Global population growth and the growing demand for animal-source food are two challenges for global food security and sustainability of agriculture and livestock production. Meanwhile, the use of food-competing feedstuffs and the greenhouse gas emissions from livestock are two major issues that challenge the global feed and food supply chain. Here, we applied several in vitro and omics methodologies to estimate the potential inclusion of alternative feeding strategies in the frame of the environmental sustainability of livestock production. We focused on two areas: i) the dietary inclusion of food by-products (e.g. former food products) in the diet of piglets and pigs to evaluate their impact on metabolism, and ii) the dietary inclusion of tannins to reduce methane production from enteric fermentation and ammonia in ruminants. The first research project involved the study of the metabolic impact of the dietary inclusion of salty and sugary former food products (FFPs) in pigs from the weaning phase to the finishing phase. To do this, we applied omics technologies to obtain a broad and comprehensive picture of the metabolism of the pigs fed with FFPs. After assessing that both salty and sugary FFPs diets did not alter the growth performance and the feeding behaviour of the pigs, we observed a limited impact of FFPs on the modulation of the metabolome and the proteome-peptidome of piglets and pigs in multiple districts in liver and plasma. Indeed, we observed only a low number of modulated metabolites and proteins and a weak impact on the activation of specific metabolic pathways. We concluded that FFPs can be safely used as alternative and sustainable feed ingredients to reduce the feed-food competition. The second research project involved the study of the effect of two tannin compounds, called gallic acid (GA) and ellagic acid (EA), on the composition of the rumen microbial community and on the end products of enteric fermentation, with methane and ammonia production under the spotlight. To do this, we simulated rumen fermentation using two in vitro approaches, named Hohenheim gas test (short-term batch culture) and Rusitec (long-term continuous culture). The GA and EA molecules, and the combination of both molecules, decreased methane and ammonia production, but they influenced the overall rumen fermentation depending of the dosage used in terms of a reduced production of short-chain fatty acids and degradation of nutrients in rumen. Furthermore, we observed a strong modulation of the rumen bacterial community following tannins’ treatment, with limited impact on rumen archaea. The results of the two projects contributed to increase the validity of in vitro and omics evaluations as preliminary steps in searching innovative feeding strategies to increase the environmental sustainability of livestock production. Further work is needed to increase the robustness of these innovative and sustainable feeding strategies.