The environmental impact of modern farming and the relentless drive for various extraction and production, often at the expense of replenishment and recycling, demand that we rethink our approach to livestock systems and nutrition. This rethinking must involve using alternative resources responsibly, promoting recycling, and reducing our carbon footprint. Given the growing urgency of this issue and the rapid expansion of research in this field, this editorial aims to highlight and discuss the latest findings, alongside alternative feed resources and additives that can be sustainably used for farm animals (1, 2). Dear readers, tThis Research Topic brings together contributions from around the world that focus on a common goal: adopting eco-friendly feed resources and approaches that improve or maintain animal performance while reducing environmental impacts, particularly greenhouse gas emissions. Collectively, these works reflect a shared vision for a sustainable, circular bio-economy in animal agriculture. The nine articles published (out of eleven submitted) span a broad range of innovative strategies, from valorizing agricultural by-products and developing functional feed additives, to exploring novel proteins derived from algae and insects. Theseis papers came from geographic diverse sources with contributions from Egypt, Italy, South Korea, India, Turkey, China-Italy, Tunisia-Palestine, and two from China alone. The research covered a variety of animals including camels, sheep, cattle, pigs, insects, and even companion animals like dogs. All the papers are original research articles and employ diverse approach, including in vivo trials, in-vitro fermentation studies, and meta-analyses. Valorizing Wastes and Agro-industrial By-products The studies here were evaluated by in-vitro means. For example, Abdelnour et al. investigated the use of biochar derived from date palm (Phoenix dactylifera) seeds as a feed additive for camels. Supplementation significantly enhanced fermentation parameters and reduced methane production in-vitro. This shows biochar's emerging role not only in soil amendment but also in by-product and waste recycling (3), enteric emission mitigation, especially in arid regions where both camels and date palms are abundant. In addition to this, Vastolo et al., evaluated eight polyphenol rich agro-industrial by-products, including grape, tomato, olive pomace, and hazelnut skin using sheep rumen fluid. By products, from with citrus and hazelnut by-products showed the greatest anti-methanogenic potential. Similarly, Ghzayel et al. examined carob leaves collected from Tunisia and Palestine, treated with NaOH, urea, or polyethylene glycol. While treatment effects were highly dependent on the geographical origin of the leaves, the study confirmed the promise of agroforestry residues as viable ruminant feed, particularly in dryland ecosystems. These results promote the integration of regional waste streams into livestock diets as part of circular agriculture systems. Exploring Novel Protein Sources: Insects, Algae, and Fermented Gases The global race to identify viable and scalable alternative feed resources continues, especially in countries where governments sees the importance of livestock farming, whether from a food security, economic, or environmental perspective. A comprehensive meta-analysis by Gao et al. explored the feasibility of using insect-derived meals, such as Tenebrio molitor, Hermetia illucens, and Bombyx mori in ruminant diets. The authors found that moderate inclusion (≤30%) of these high-protein feeds supports digestibility and rumen fermentation, while also boosting growth performance in some trials. Particularly promising was the oriental hornet (Vespa orientalis), which may hold untapped potential among underexplored insect species. Palangi et al., investigated algae-nanoparticles relationship to assess the anti-methanogenic effect of Chlamydomonas reinhardtii combined with magnesium oxide and magnesium sulfide nanoparticles. The in-vitro data showed significant improvements in gas production, digestibility, and volatile fatty acid profiles, pointing to the dual role of algae as a methane inhibitor and nutritional enhancer. While dogs may seem like an unusual inclusion in this special topic, it is important to understand that they are considered part of the broader category of farm animals, not necessarily as food animals (though this occur in some culture), but more commonly as companion animals. In a novel extension of microbial protein sources, Babu et al. conducted a pilot study on dogs using a fermented protein derived from methane gas. The implications of these alternative feed is the the broader viability of insect and single-cell proteins as sustainable feed ingredients across species Additives and Dietary Interventions for Methane Reduction Methane mitigation via dietary supplements was further examined by Zhou et al., who evaluated the combined use of 3-nitrooxypropanol (NOP) and L-malate in dairy cows. The NOP supplementation alone reduced enteric methane by 54%, with no adverse effect on milk yield. When combined with L-malate, methane was reduced by 51%, with added benefits to milk fat and protein composition. This result reinforces the importance of precise feed additives as tools for emission reduction without compromising productivity Replacing Conventional Ingredients Without Sacrificing Performance The feasibility of replacing high-demand ingredients like soybean meal was addressed by Zhao et al., who demonstrated that mixed plant proteins, including rapeseed meal, palm kernel meal, and distillers dried grains with soluble (DDGS), could effectively substitute soybean meal in pig diets without negatively affecting growth or carcass quality. While not directly targeting methane reduction, such substitutions contribute to feed sustainability and reduce deforestation-linked inputs. Meanwhile, Malik et al. conducted a meta-analysis on the effects of DDGS on methane emissions in cattle. Contrary to some expectations, DDGS had no significant effect on methane production or dry matter intake. However, its neutrality indicate it can be used without exacerbating emissions, offering flexibility in diet formulation. Conclusion Collectively, these studies illustrate the need to integrate diverse feed innovations including locally available by-products, novel proteins, targeted additives, and smart replacements that will enable meaningful reductions in the carbon footprint of ruminant system. This Research Topic also emphasizes the need for contextual evaluation as the effectiveness of feed interventions often depends on species, geography, processing methods, and dietary inclusion levels. For example, the performance of carob leaves or polyphenol-rich by-products varied by of origin and treatment method, while the efficacy of insect meals differed by species and inclusion rate. As global demand for animal protein rises, sustainable intensification must become a priority and feed innovation offers one of the most immediate levers for change.
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