Biofortified feed crops: bridging plant biotechnology and animal-derived functional foods

1 Introduction

The growth in global population has led to increased demand for food production systems capable of sustainably meeting human and animals dietary requirements. Despite substantial gains in crops and animals productivity driven by selective breeding, intensive fertilization, and plant protection practices, current approaches are increasingly insufficient to ensure long-term food and nutrition security (Hasanaliyeva et al., 2023). Projections suggest that by 2050, global food demand will increase significantly, elevating the risk of scarcity and malnutrition unless nutrition-sensitive and sustainable policies are implemented (Verbeecke et al., 2023). Apart from energy and macronutrients, increasing attention is being directed toward micronutrient malnutrition, commonly referred to as “hidden hunger.” This health condition is characterized by insufficient consumption of vital vitamins and minerals (Prom-u-thai et al., 2020). The Global Hunger Index reveals that regions like South Asia and Sub-Saharan Africa suffer from severe forms of hunger caused by both caloric and micronutrient deficiencies. Micronutrient malnutrition is not solely a human dietary issue but is closely related to animals nutrition and feed quality. These deficiencies directly affect animals health, productivity, reproductive performance, and the nutritional quality of animals-derived functional foods. Animals-derived functional foods are products obtained from animals that include bioactive compounds providing health benefits beyond basic nutrition. Therefore, enhancing animals nutrition would directly benefit human health, especially for those relying on dairy products, meat, fish and marine resources (Saint Ville et al., 2019).

Biofortification has become a key strategy for combating micronutrient deficiencies by enhancing the transfer of vital nutrients from soil to plants. It involves not only increasing essential minerals but also enriching crops with vitamins and beneficial fatty acids, especially omega-3 (n-3) polyunsaturated fatty acids (Li et al., 2022a). So far, biofortification has mainly targeted food crops for direct human consumption. However, providing animals with micronutrient-rich feed offers a sustainable way to boost the micronutrient levels in animals-derived foods, establishing a circular system that supports both animals productivity and human health (Tiozon et al., 2021).

This review explores the concept of biofortification, as a long-term strategy to improve the micronutrient content of feed and forage crops. Particular emphasis has been placed on the biofortified feed for animals health, productivity, and on the transfer of essential micronutrients into animals derived functional food. The review also examines biological, environmental, and translational factors that could affect the success of biofortification. These include nutrient interactions, anti-nutritional factors, genotype × environment interactions, animals-specific digestion and absorption and deposition in animals products, feed processing, possible toxicity, environmental risks, regulatory issues, economic feasibility, and consumer acceptance. Studies on food crops are included if they offer mechanistic, technological, or genetic insights pertinent to developing biofortified feed and forage crops in the future. Despite ongoing issues with policy frameworks, consumer acceptance, and technology adoption, biofortification offers a practical and innovative way to combat hidden hunger and enhance sustainable animals production systems.

1.1 Literature search strategies

A comprehensive literature search was conducted using Google Scholar, Scopus, and ScienceDirect to identify peer-reviewed studies published between 2010 and 2026. The search targeted four main concepts: (i) crop biofortification, (ii) feed and forage crops, (iii) nutrient transfer to animals, and (iv) nutritional enrichment of animals-based products. Relevant publications included those that addressed any of these topics: (i) increasing nutrient content, accumulation, or bioavailability in food, feed, or forage crops; (ii) applying agronomic, microbial, nanotech, or genetic techniques for crop nutritional enhancement; (iii) nutrient uptake, transport, or accumulation in plants; (iv) enhancing the nutritional quality, digestibility, or bioavailability of feed; (v) nutrient digestion, absorption, retention, or metabolism in livestock or poultry; or (vi) changes in the nutritional composition of milk, meat, or eggs due to dietary modifications.

Studies were excluded if they did not focus on crop nutritional enhancement or animals nutrition, lacked relevant information for the review’s goals, or concentrated only on traits without meaningful nutritional or feed-related significance. Food-crop research was included if it provided mechanistic, technological, or translational evidence relevant to feed-crop biofortification; however, such studies were considered supportive or translational rather than direct evidence of nutritional improvements in feed and forage systems. Priority was assigned to peer-reviewed original research and pertinent review articles. Publications were initially screened by title and abstract, with full-text review conducted when necessary to verify relevance to the review’s scope.

2 Tri-domain nutritional continuum

Crops, humans, and animals share similar dietary needs except for the nutrient sources. Crops cultivated in nutrient deficient soil struggle to grow and offer insufficient nutrition, which can negatively affect human and animals health. To assess nutritional quality effectively, it is essential to understand the nutrient requirements of crops, humans, and animals for optimal results. Crops depend on at least 14 essential nutrients, along with oxygen, carbon dioxide, and water, to maintain proper physiological and metabolic processes (White and Brown, 2010). These minerals play vital roles in key biological processes, such as stomatal regulation, cell elongation–mediated water transport, protein biosynthesis, enzymatic activation, and photosynthesis. Mineral elements contribute to plant health both directly and indirectly. Direct effects include activation of enzymes involved in the synthesis of defense-related metabolites such as lignin, phenolic compounds, glucosinolates, callose, and phytoalexins. Indirectly, mineral availability modulates rhizosphere pH, microbial activity, and root exudate composition, collectively affecting nutrient uptake efficiency and overall crop nutritional quality (Romheld and Kirkby, 2010) (Figure 1).

The nutritional composition of crops significantly affects animals development, reproductive performance, behavior, productivity, and the quality of animals products (Chand et al., 2022). Animals mainly depend on feed and forage crops like maize, sorghum, alfalfa, and napier grass as key dietary sources. The physical development and productive efficiency of animals depend directly on the availability, digestibility, and intestinal absorption of essential nutrients supplied by these feed resources (Dimkpa and Bindraban, 2016). Nutrient imbalances can disrupt metabolic balance, causing growth impairments, lower productivity, and metabolic issues since many macro- and micronutrients serve as cofactors in essential enzymatic processes (Sandhu et al., 2020). In ruminants, insufficient protein intake hampers the growth and activity of rumen microbes crucial for feed fermentation (Lee, 2018). Lipid content in the crop contributes to the production of body fat and milk fat in animals (Figure 2) (Van Dijk et al., 2021). Nutrient deficiencies in feed and forage crops are typically managed with dietary supplements to enhance animals performance. However, relying only on inorganic mineral supplements often falls short of fulfilling daily needs because of poor intestinal absorption and bioavailability, potentially hindering animals growth, health, and productivity (Giri et al., 2021). Therefore, enhancing the natural nutrient density of crops offers a more sustainable and effective way to support rumen health, animals output, and micronutrient enrichment in milk, egg and meat.

In humans, sufficient intake of essential macro- and micronutrients is crucial for maintaining immune function, supporting cognitive development, and ensuring proper metabolic processes. Nutrient deficiencies continue to be common, especially in developing areas (Table 1). These shortages are mainly caused by factors such as poverty, increasing population, and restricted dietary diversity (Dhawi et al., 2015). Global initiatives, especially the CGIAR-led HarvestPlus program, have focused on developing conventionally biofortified crops. These include iron-rich beans, pearl millet, and cowpea; zinc-enriched rice, wheat, and maize; and vitamin A–rich sweet potato, cassava, maize, and banana/plantain (Praharaj et al., 2021).

Table 1. Human nutrient requirements: functions, deficiencies, and dietary references.

3 Factors affecting nutrient availability

A complex network of biological, chemical, and environmental influences controls nutrient availability for crops, animals, and humans. In crops, the interactions between macro- and micronutrients are significantly affected by soil pH, moisture levels, aeration, temperature, root structure, and physiological activities like transpiration and respiration. Together, these factors regulate how nutrients are absorbed, transported, and distributed within cells (Fageria, 2000). The form and mobility of nutrients are both essential. For instance, nitrogen availability relies on microbe-driven transformations (Figure 1), and deficiencies can occur without proper symbiotic relationships (Du et al., 2025).

Additionally, soil pH influences nutrient solubility, as many nutrients are only accessible to plants within specific pH ranges (Etesami and Sina, 2020). Management practices, especially harvest timing, greatly impact nutrient composition and digestibility. Delayed harvests tend to increase fiber and lignin levels, which lower protein content, palatability, and digestible energy, thereby reducing feed quality and animals nutrient intake. As a result, nutrient dynamics at the field level directly influence how efficiently nutrients transfer to animals (Cassida et al., 2000).

In animals, nutrient availability mainly depends on how effectively rumen microflora function, as they ferment plant biomass into energy sources, microbial protein, and vital vitamins (Figure 2). Imbalances in rumen microbes caused by factors like diet, genetics, or age can hinder nutrient digestion and absorption (Cammack et al., 2018). Compounds like tannins, oxalates, and saponins in crops can hinder nutrient absorption (Piluzza et al., 2014). Structural components like lignin, phenolic acids, and phytic acids in plant cell walls hinder enzymatic breakdown in the rumen, which decreases nutrient absorption (Jung and Deetz, 1993). These constraints underscore the importance of improving the intrinsic quality of feed and forage to enhance animals mineral nutrition and productivity.

In humans, nutrient absorption and utilization are shaped by dietary traits as well as individual physiological, psychological, and socioeconomic factors. Nutrient bioavailability depends on the food source and its matrix, with animals-derived functional foods typically supplying minerals like iron and zinc in more absorbable forms than plant-based sources, which often contain compounds that inhibit absorption (Nath et al., 2022). Food processing and preparation techniques can increase nutrient release from complex structures, boosting absorption efficiency (Ndidi et al., 2014). Individual factors such as health status, age, sex, gastrointestinal function, medication use, and lifestyle influence nutrient metabolism and needs (Gargano et al., 2021). Socioeconomic factors, cultural norms, and dietary habits influence nutritional outcomes. Restricted access to nutrient-dense foods and low nutrition awareness can elevate the risk of micronutrient deficiencies (Facina et al., 2023). Together, these related factors emphasize the need for integrated approaches that boost nutrient availability, particularly through biofortified feed and animals systems to enhance human micronutrient nutrition.

4 Current Progress, challenges, and opportunities for advancing biofortification of feed and forage crops

Biofortification involves increasing the nutritional value of crops using agronomic methods, traditional breeding, and modern biotechnology. Initially, biofortification mainly targeted food crops for human intake, but there is now a growing focus on boosting the micronutrient content of feed and forage crops to enhance animals nutrition and produce nutrient-rich animals foods (Garg et al., 2018). Incorporating feed and forage-based biofortification into animals systems offers a sustainable way to boost mineral intake, enhance metabolic efficiency, and increase animals productivity, all while decreasing reliance on inorganic dietary supplements.

4.1 Agronomic biofortification of crops

Agronomic biofortification involves adding mineral fertilizers, beneficial microbes, or nanomaterials either to the soil or directly onto plant foliage. This approach enhances the absorption and movement of essential nutrients within crops, making them more accessible for human and animals diets. It is commonly applied to cereals, oilseeds, and fodder crops such as wheat, maize, and rapeseed, using nutrient solutions applied to soil or foliage (de Valença et al., 2017). Key mechanisms include fertilizer-driven nutrient delivery, mineral solubilization in the rhizosphere, and the transport of minerals from source tissues to edible plant parts (Figure 3).

During the Green Revolution, the widespread use of macronutrient fertilizers significantly increased crop yields and helped mitigate shortages, particularly in developing regions. However, modern agricultural challenges extend beyond yield enhancement; they also encompass increasing micronutrient levels in food and feed to support human health and animals well-being (Dobermann et al., 2022). Agronomic biofortification offers a scalable, cost-effective approach to improve feed quality and animals mineral intake, especially when managed carefully through fertilizer formulation, timing, and application techniques (Bhardwaj et al., 2022). Fertilizer enhances soil fertility and boosts the mineral content of feed and forage crops, helping to prevent nutrient deficiencies in animals diets (Table 2). Mineral fertilizers are typically divided into macronutrients (N, P, K, Ca, S) and micronutrients (Fe, Zn, Cu, Cl, B, Mn, Mo). Common inorganic fertilizers like ammonium nitrate, potassium chloride, ammonium sulfate, magnesium sulfate, and triple superphosphate primarily provide macronutrients, though they often lack trace elements (Davydov et al., 2018). Micronutrient deficiencies in feed and forage crops remain prevalent in many developing regions and directly contribute to inadequate mineral intake in animals, negatively affecting growth, productivity, and reproductive performance (Dhaliwal et al., 2022b).

Table 2. Evidences of biofortification of crops through mineral fertilization.

Macronutrients and micronutrients influence plant health in different ways. For instance, Iron (Fe) is vital for nitrogen fixation and assimilation, as it regulates essential enzymes like glutamate synthase and nitrate reductase (Maitra et al., 2022). Applying ferrous sulfate (FeSO₄) both foliarly and to the soil has been proven to increase crop yield, improve photosynthesis, and boost iron levels, in forage crops such as Medicago sativa (Chun-Xia et al., 2017; Zhang et al., 2022). The combined use of Fe and Zn has also demonstrated positive effects on wheat, enhancing grain quality and mineral content (Hafeez et al., 2021).

Zinc (Zn) deficiency in animals often results from inadequate dietary intake, particularly when animals consume forage grown on calcareous soils that are low in Zn (Nielsen, 2012). Zinc sulfate (ZnSO₄), available as monohydrate or heptahydrate, is still the most common Zn fertilizer. Meanwhile, zinc oxide (ZnO) is gaining popularity because it offers a higher Zn concentration and is more affordable. Foliar application of ZnSO₄ enhances forage digestibility and improves associated measures like digestible crude protein, dry matter intake, net lactation energy, feed value, and overall forage quality in maize, resulting in improved animals performance and feed efficiency (Dhaliwal et al., 2022b).

Selenium (Se) biofortification in forage crops has gathered significant interest due to enhancement of plant antioxidant defenses and positive effects on animals health. In humans, selenium levels mainly depend on its presence in the soil and the amount of food eaten, since the main source of selenium is a diet high in animals and plant-based products (Estarriaga-Navarro et al., 2026). Selenium-fortified crops tend to have increased levels of beneficial phytochemicals (D’Amato et al., 2020). Se fertilization often uses sodium selenite or barium selenite formulations. Applying sodium selenite as a foliar spray significantly boosts Se levels in Lucerne cultivated on both calcareous and non-calcareous soils (Motesharezadeh et al., 2020).

In alpine meadows of the Qilian Mountains, foliar application of K, N, Zn, B, Cu, P, Mo, and Se enhanced crude protein content by 7.7–23.94% and generally improved dry matter digestibility, while reducing acid detergent fiber. Phosphorus accumulation increased significantly in legumes, whereas nitrogen fertilization enhanced phosphorus content in grasses and legumes. Copper concentrations also increased substantially under Cu, N, Zn, B, and Se treatments. Legumes exhibited comparatively greater Zn uptake, indicating their potential for mineral biofortification of forage systems (Chen et al., 2022).

4.1.1 Microbes-mediated biofortification

Microbial-mediated biofortification is an eco-friendly agricultural strategy that influences beneficial plant–microbe interactions to boost nutrient availability for crops. Regular application of microbial inoculants improves soil fertility, boosts nitrogen cycling, and enhances the nutritional quality of crops, thereby promoting sustainable feed production systems (Table 3) (Verma et al., 2023; Chávez-Díaz et al., 2026).

Table 3. Evidences of biofortification through microorganisms.

Plant growth-promoting rhizobacteria (PGPR) and endophytic microbes are commonly used as biofertilizers to enhance crop growth and mineral absorption. Beneficial microorganisms, including Bacillus, Klebsiella, Acinetobacter, and the Arbuscular mycorrhizal fungus Rhizophagus intraradices, have been demonstrated to boost zinc and selenium uptake in crops like Triticum aestivum, thereby improving the micronutrient content of plant biomass. These microbes promote plant growth and enhance plant health via multiple direct and indirect methods, such as fixing nitrogen biologically, producing hydrolytic enzymes, generating phytohormones, creating siderophores, and solubilizing nutrients like potassium, zinc, and phosphorus that are less accessible (Nosheen et al., 2021).

While plants naturally mobilize nutrients through mechanisms like organic acid secretion, chelation, and phytosiderophore release, these activities alone often cannot transform soil-bound micronutrients into usable forms. Microorganisms produce chelating agents that bind micronutrients, especially zinc, helping to release them at the root–soil boundary. This process boosts root absorption and supports successful biofortification (Kaur et al., 2020). Inoculating with Pseudomonas and Bacillus species has been demonstrated to reduce rhizosphere pH, which speeds up the breakdown of zinc compounds like zinc sulfate, zinc oxide, and zinc carbonate into forms accessible to plants (Muthukumar et al., 2022). Inoculating wheat with Arthrobacter sp. DS-179 and Arthrobacter sulfonivorans notably increased zinc and iron levels, along with related growth parameters (Singh et al., 2017). Applying Bacillus pumilus strain TUAT1 to forage rice significantly enhanced its growth and yield (Agake et al., 2022). Treating berseem and maize seeds with biofertilizers before sowing increased their biomass and green fodder production in both crops (Suryavanshi et al., 2020).

4.1.2 Nanofertilizers for nutrient-dense crop production

Nanofertilizers have become a promising method to improve crop nutrition because nanomaterials possess unique physicochemical properties compared to traditional bulk fertilizers. They offer benefits such as a high surface-to-volume ratio, better sorption capacity, customized nutrient delivery, and controlled-release mechanisms. Consequently, nutrients are used more efficiently, reducing environmental impact. Due to these benefits, nanofertilizers are gaining attention as alternatives to conventional fertilization, especially in sustainable farming. Applications of nanomaterials like nano-selenium, nano-silica, nano-copper, nano-sulphur, nano-zinc, and nano-iron via foliar spray and seed treatments have proven successful across various feed and forage crops (Table 2) (Dhiman et al., 2021, 2022). Numerous studies have emphasized the ability of nanofertilizers to enhance crop biomass and nutrient quality (Qin et al., 2025). Applying selenium nanoparticles (Se NPs) to Festuca arundinacea Schreb notably boosts forage production, crude protein, and ether extract content, which in turn improves feed quality and increases mineral intake for the animals. Likewise, boron nanofertilization in calcareous soils enhanced boron uptake and elevated levels of chlorophyll a, chlorophyll b, and carotenoids in Medicago sativa L., indicating improved photosynthesis and nutritional quality after multiple boron nanoparticle treatments (Taherian et al., 2019). These findings indicate that nanoparticle-based fertilizers can affect both plant development and the nutritional quality of forage crops. Nano-seed priming has been shown to improve seed germination, seedling vigor, early growth, and emergence rates in various medicinal and forage crops, leading to increased biomass yield (Abbasi Khalaki et al., 2021). Additional evidence confirms that nanofertilizers help plants to survive environmental stress. Application of titanium dioxide nanoparticles (TiO₂ NPs) has been shown to increase antioxidant activity and dry matter yield in Medicago scutellata L. (Dolatabadi et al., 2016). Despite these promising outcomes, the effects of nanomaterials are not always consistent and largely depend on the type and concentration of nanoparticles used. However, responses to nanomaterial application are often dose-dependent; zinc oxide, titanium dioxide, copper oxide, and silver nanoparticles have been reported to exert both stimulatory and inhibitory effects on seed germination, plant growth, and yield in oat and berseem crops, depending on concentration (Maity et al., 2018).

4.2 Conventional breeding for nutrient-efficient crops

Traditional breeding remains an essential component for producing crop varieties with higher nutritional and agronomic traits, obtained by hybridizing high-yielding cultivars with donor genotypes that have elevated micronutrient concentrations (Saeid et al., 2019). From a animals production perspective, breeding programs that enhance the micronutrient density and nutritional efficiency of feed and forage crops directly support animals health and productivity. The development of micronutrient-efficient cultivars increases mineral concentration and biomass yield while reducing dependence on fertilizer inputs, particularly in nutrient-poor soils, thereby improving the quality of animals feed resources (Vanisha et al., 2013). Investigations of germplasm variation across crop species have demonstrated that genetic diversity strongly influences nutrient uptake, utilization, and accumulation. These provide opportunities to develop nutrient-rich crop varieties through targeted breeding. Identification of these nutrient-efficient genotypes, mainly in iron and zinc, improved crop performance under nutrient-limited conditions. Genomic resources of major crops, including wheat, rice, beans, and sweet potato, have been systematically explored to identify micronutrient-enriched traits relevant to both human and animals nutrition (Avnee et al., 2023). Backcrossing in Festulolium has generated hybrids with higher, more stable protein content than the parental lines, thereby enhancing forage nutritive value and animals productivity (Humphreys et al., 2014). High-throughput sequencing and transcriptome analysis have paved the way for identifying genetic markers and single-nucleotide polymorphisms associated with nutritional efficiency and biomass attributes in forage genera such as Lolium and Trifolium (Nagy et al., 2013; Blackmore et al., 2016). Quantitative trait locus (QTL) mapping has also pinpointed biochemical markers linked to tolerance against reactive oxygen species and drought resilience, traits that are closely connected to dry matter yield and feed availability during stress conditions (Maghsoodi et al., 2017). Traditional breeding has focused on traits like protein levels, biomass growth, and stress resistance, but paid less attention to improving micronutrient levels. As awareness of nutritional deficiencies increases, breeding initiatives are now increasingly aimed at biofortification. As a result, numerous food crops including wheat, rice, sorghum, maize, barley, soybean, potato, sweet potato, oilseeds, tomato, apple, and banana have been successfully biofortified with iron, zinc, vitamin B, provitamin A, vitamin E, vitamin C, essential amino acids, calcium, and β-carotene (Garg et al., 2018). The knowledge generated by these food-crop breeding programs provides a valuable foundation for extending nutrient-focused breeding strategies to forage crops for animals feed.

A major limitation to conventional breeding for nutrient enrichment in forage crops is the restricted genetic diversity within available gene pools. Despite these challenges, several international initiatives have demonstrated the effectiveness of breeding as a rapid, scalable approach to improving crop nutritional quality. Even with these limitations, breeding has proven to be an effective and scalable strategy for enhancing the nutritional quality of crops. HealthGain Initiative in Europe and the CGIAR-led HarvestPlus program have successfully advanced biofortified staple crops rich in vitamin A, zinc, and iron for deployment in Asia and Africa (Bouis and Welch, 2010). Adopting similar breeding frameworks for feed and forage crops has substantial potential to enhance animals performance and strengthen the nutritional value of animals-derived functional foods.

4.3 Transgenic approaches for enhancing forage digestibility and nutrient density

Transgenic approaches involve introducing genes from related or unrelated species into the target crop. Over the past two decades, transgenic technologies have been successfully applied in numerous crop species, establishing their utility as effective single-gene breeding tools for modifying specific agronomic, nutritional, and stress-related traits. Gene delivery in plants mainly occurs via particle bombardment (gene gun) or Agrobacterium tumefaciens–mediated transformation, both allowing precise genome manipulation (Stein and Rodríguez-Cerezo, 2010). In forage crops, transgenic strategies have primarily been employed to enhance biomass production, stress tolerance, and cell wall composition traits directly linked to feed digestibility and animals performance. Several studies have demonstrated that genetic modification designed to improve tolerance to abiotic stresses can simultaneously enhance forage yield and nutritional quality (Cabral et al., 2015; Gondo et al., 2017). For example, Agrobacterium-mediated overexpression of the MsASMT1 (N-acetylserotonin methyltransferase) gene in Medicago sativa L. resulted in pronounced growth enhancement, including increased plant height, larger leaf area, thicker stems, elevated branch number, and augmented vascular development. These anatomical changes were accompanied by increased cellulose content, thereby improving forage biomass and structural integrity (Cen et al., 2020). Additional examples of transgenically modified forage crops exhibiting enhanced digestibility and related quality parameters are summarized in Table 4.

Table 4. Nutritionally enhanced forage crops through a transgenic approach.

Despite these advances, transgenic biofortification of forage crops has largely focused on traits that improve digestibility rather than on directly enhancing micronutrient content. In contrast, substantial progress has been made in food crops, where transgenic strategies have successfully increased concentrations of iron, zinc, and provitamin A by manipulating nutrient transporters, storage proteins, and antinutrient pathways (Table 5) (Malik and Maqbool, 2020). Genetic modification of rice endosperm with soybean ferritin and nicotianamine synthase genes resulted in a six-fold increase in iron concentration without compromising grain yield or quality (Trijatmiko et al., 2016). A major challenge to extending transgenic micronutrient biofortification to forage crops is the incomplete characterization of micronutrient transporter proteins involved in the uptake, translocation, and storage of iron and zinc. While such transporters have been well characterized in cereal crops, their functional counterparts in forage species remain largely unidentified (Dhaliwal et al., 2022c). Advancing this area of research holds significant potential to improve animals mineral nutrition, reduce reliance on dietary supplements, and enhance the nutritional quality of animals-derived foods.

Table 5. Biofortification of crops through a transgenic approach.

4.4 Genome editing and CRISPR Technologies for animals feed improvement

Genome editing technologies enable precise, targeted modification of plant genomes by inserting, deleting, or substituting DNA segments. Compared with earlier genetic manipulation approaches, genome editing offers higher accuracy, efficiency, and reproducibility, significantly accelerating crop improvement programs (Miladinovic et al., 2021). These methods are now widely recognized as transformative technologies in applied plant biology and agricultural innovation, enabling the production of crops with better nutritional quality, stress tolerance, and productivity under adverse environmental conditions (Table 5) (Čermák et al., 2015).

CRISPR/Cas9 and TALEN mutagenesis methods were employed to introduce mutations at loci encoding protein machinery involved in small RNA processing in soybean and Medicago truncatula (Curtin et al., 2018). CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats), a revolutionary genome-editing technique, was developed in 2013. By altering the guide RNA sequence, CRISPR/Cas9 can be readily programmed to target virtually any genomic locus, avoiding the extensive protein engineering required for ZFNs and TALENs. CRISPR-based genome editing in forage and feed crops provides an effective way to improve traits crucial for animals nutrition, such as biomass yield, digestibility, nutrient efficiency, and stress tolerance (Islam et al., 2020).

4.5 CRISPR as a tool for enhancing crop quality and nutrient use efficiency

The CRISPR/Cas platform has transformed functional genomics and crop development by allowing precise genome edits in many plant species. Its versatility and ease of use have quickened efforts to identify and modify genes that significantly impact important agricultural and nutritional traits. In forage legumes and grasses, CRISPR/Cas9 has been successfully used to modify genes that regulate nitrogen fixation, mineral uptake, flowering behavior, biomass accumulation, and stress tolerance, traits that directly influence feed quality and animals performance (Figure 4).

In Medicago truncatula and Medicago sativa (alfalfa), CRISPR/Cas9-mediated gene editing has enabled efficient knockout of target genes, facilitating functional characterization of pathways involved in nodulation, nitrogen fixation, and nutrient assimilation (Table 6) (Trujillo et al., 2019; Bottero et al., 2021). Targeted disruption of regulatory genes such as MsNP1 has been used to generate genic male sterility, shortening breeding cycles and promoting hybrid vigor in alfalfa breeding programs (Ye et al., 2022). Similarly, CRISPR-mediated mutagenesis of genes associated with meiosis and centromere function in Lolium perenne has demonstrated the feasibility of genome editing for improving agronomically important traits in perennial forage grasses (Zhang et al., 2020). Genome editing has also been employed to enhance nutrient acquisition and stress tolerance in forage crops. For example, CRISPR/Cas9-mediated inactivation of the FaSGR gene in Festuca arundinacea delayed leaf senescence and produced greener foliage under heat and salt stress, thereby contributing to sustained forage quality. Disruption of PHO2 in alfalfa produced phosphate-hyper-accumulating varieties, improving phosphorus use efficiency and feed nutrient density (Miller et al., 2022). While CRISPR/Cas technologies have already been successfully applied for nutrient enrichment in food crops such as wheat, rice, tomato, melon, and banana (Kumar et al., 2022), their application for direct micronutrient biofortification of forage species remains limited.

Table 6. Genome editing tools employed for transforming crops for quality enhancement.

In wheat, manipulation of TaNAS2 and TaVIT2 has been reported to enhance Fe and Zn accumulation and their bioavailability, while targeting LCYE (lycopene ε-cyclase) facilitates the rerouting of carotenoid biosynthesis toward provitamin A (β-carotene) accumulation in the endosperm, thereby enhancing the nutritional value of grain used for both food and feed (Guo et al., 2026; Haider et al., 2026). In maize and soybean, modification of low-phytate pathways involving lpa2, IPK2, and MIPS1 reduces phytate levels and consequently improves mineral bioavailability, an important consideration given their prominent roles as livestock feed ingredients (Kumar et al., 2019; Singh et al., 2020). In sorghum, combined manipulation of CRTI/PSY1/CRTB, HGGT, and PhyA has been investigated to enhance provitamin A and vitamin E while reducing phytate, whereas strategies targeting the NAS pathway and endosperm-specific regulatory elements in rice aim to increase Fe, Zn, and folate accumulation in the grain (Khan et al., 2024; Fan et al., 2025). In forage crops, particularly alfalfa, genetic improvement has predominantly focused on traits affecting forage quality and nutrient utilization. Modification of MsC3H reduces lignin accumulation and improves digestibility, while manipulation of MsFTa1 delays flowering and contributes to improved biomass production and protein retention (Wolabu et al., 2023, 2024). More recently, targeting the NAC transcription factors MsNAP1/MsNAP2 has been associated with delayed senescence, increased biomass and protein accumulation, and reduced fiber content, thereby improving overall forage quality (Wolabu et al., 2026). However, the expanding genomic resources and functional insights generated by CRISPR-based studies provide a strong foundation for future improvements in forage crops with enhanced mineral content, digestibility, and biomass yield. Advancing genome editing in forage systems offers significant potential to improve animals nutrient intake, reduce reliance on mineral supplementation, and strengthen the nutritional quality of animals-derived foods.

5 From biofortified feed to functional animals-derived foods: evidence, transfer efficiency, and biological constraints

Animals-derived functional foods provide an effective way to deliver essential micronutrients, vitamins, and bioactive compounds through diet, with their composition modified by specific feeding methods. Enriching products like milk, eggs, and meat with vitamins A and D, as well as omega-3 fatty acids, has successfully enhanced their nutritional value. This strategy also involves adding minerals such as selenium, zinc, copper, manganese, and iodine, although the level of enrichment varies based on factors like the nutrient’s chemical form, dosage, animals species, physiological condition, and tissue-specific metabolism. For example, selenium supplementation can increase selenium content in eggs and meat, with organic forms like selenomethionine generally offering better retention than inorganic forms (Fisinin et al., 2009; Schrauzer and Surai, 2009). A growing development in this field is dual biofortification, where animals consume plant- or microbe-based biofortified feeds. This approach connects crop biofortification more directly with animals products and may reduce the need for mineral supplements (Ligas et al., 2021). Studies indicate that using enriched biomass, microalgae, sprouts, and other biofortified feeds can increase mineral content in animals-derived foods. For example, enriched feeds have elevated Cu, Mn, and Zn in eggs, while selenium-enriched feeds have resulted in Se-rich eggs and meat (Białowąs et al., 2024a). However, higher mineral intake through feed does not always translate to proportionally higher levels in the final product. Factors like how nutrients are delivered, their interactions with other diet elements, and their absorption and retention by animals play key roles in this process (Brugger et al., 2022a).

This distinction is particularly important in the soil–plant–feed–animals–food–human chain. Nutrient transfer involves complex processes and is not simply direct. While soil nutrient availability influences plant uptake and accumulation, other factors such as plant genotype, soil characteristics, nutrient interactions, and plant physiology also affect the amount and chemical form of nutrients in forage or feed (Dimkpa and Bindraban, 2016). Throughout harvesting, drying, storage, and processing, further losses can alter nutrient availability. When animals consume feed, processes like digestion, transformation in the rumen or intestines, absorption, metabolism, homeostasis, and tissue-specific deposition determine how much nutrient ultimately reaches milk, meat, or eggs. Therefore, measuring only feed nutrient levels does not fully reflect the nutrient content in animals-derived products (Arshad et al., 2021; Brugger et al., 2022).

A similar challenge exists at the final stage, from animals-derived functional food to human nutrition. Simply increasing the nutrient levels in milk, meat, or eggs does not automatically mean improved human nutritional status. Factors such as the nutrient’s chemical form, food matrix, digestibility, bioaccessibility, intestinal absorption, and interactions with other dietary components all influence its true nutritional value. Additionally, animals-source foods can affect micronutrient absorption; for instance, evidence indicates that muscle tissue may boost iron and zinc absorption from meals, although this effect is less clear for milk and eggs (Consalez et al., 2022). Ultimately, the effectiveness of biofortifying animals products should be judged not just by nutrient concentration but by their bioavailability and the actual health benefits they provide to consumers. Overall, the evidence highlights three key gaps that still need attention: (i) how efficiently animals absorb nutrients from biofortified feed; (ii) the extent to which these nutrients are incorporated into consumable products like milk, meat, and eggs; and (iii) whether this increased nutrient content provides a clear nutritional advantage for humans (Figure 5). To bridge these gaps, research should track nutrients throughout the entire production process instead of focusing on individual stages. This comprehensive approach could elevate biofortification from merely developing nutrient-rich crops to a feed-based strategy that produces functional animals products, thereby connecting crop nutrition, animals health, product quality, and human nutritional security (Białowąs et al., 2024; Santhiravel et al., 2026).

6 Conclusion and future perspectives

Biofortification is a promising approach for enhancing crop nutritional quality, with benefits extending beyond human diets. This review emphasizes that biofortified feed and forage act as vital links connecting crop production, animals nutrition, and the quality of animals-based foods. Increasing the availability of essential micronutrients through forage can impact mineral intake, metabolic and enzymatic activities, antioxidant defenses, immune functions, growth, reproduction, feed efficiency, and milk yield. Therefore, the feed–animals pathway is an underexamined yet potentially significant part of the overall biofortification strategy. Our analysis highlights a significant imbalance in current research. Most biofortification efforts target edible plant parts, especially grains, to boost micronutrient levels for human health. Conversely, studies on forage and feed crops mainly focus on yield, crude protein, digestibility, fiber content, and overall nutritional value, with comparatively less attention to their micronutrient levels, bioavailability, and how these nutrients transfer to animals. The key knowledge gap is not the absence of research on forage minerals but rather the limited integration of forage micronutrient biofortification with animals mineral nutrition and the nutritional quality of animals-derived foods. Several factors currently constrain the translation of this concept into practical use. Micronutrient accumulation and bioavailability are heavily affected by soil properties, crop genotype, fertilizer type, environmental factors, nutrient interactions, and plant physiological processes. Additionally, uncertainties about nutrient transfer efficiency from feed to animals, long-term safety, regulatory hurdles for transgenic and genome-edited crops, and consumer acceptance must be addressed before it can be widely implemented. Notably, there is a lack of comprehensive quantitative evidence linking soil, crop, feed, animalss, and end products like meat, milk, and eggs. Building this understanding is crucial to determine if higher micronutrient levels in forage genuinely improve animals health and the nutritional quality of animals products.

Future research should therefore move toward an integrated crop–animals biofortification framework. Priority areas include: (i) quantifying nutrient transfer and retention at each step from soil to forage, forage to animals, and animals to food product; (ii) determining micronutrient bioavailability, speciation, metabolic utilisation, and tissue deposition rather than relying solely on total mineral concentration; (iii) conducting long-term feeding trials to establish the efficacy, safety, and appropriate application rates of emerging approaches such as nanofertilizers; (iv) identifying the molecular mechanisms and transporters governing micronutrient uptake, translocation, and accumulation in forage crops; and (v) exploiting these mechanisms through precision breeding and genome-editing strategies for targeted nutrient enhancement. Such studies should also consider nutrient interactions, animals species and physiological stage, production systems, and potential environmental consequences. Ultimately, integrating crop biofortification with animals nutrition could shift the conventional focus from improving the nutrient content of crops solely for direct human consumption toward a more holistic soil–plant–animals–human nutrition continuum. This approach has the potential to simultaneously enhance forage quality, animals productivity, and the nutritional value of meat, milk, and eggs while reducing dependence on post-harvest supplementation. However, its success will depend on demonstrating that increased micronutrient accumulation in forage is effectively transferred, bioavailable, and nutritionally beneficial at the animals and food-product levels. Bridging this translational gap could establish animals-mediated biofortification as an important complementary strategy for achieving more sustainable, resilient, and nutritionally secure food systems.

Generative AI statement

The author(s) declared that Generative AI was used in the creation of this manuscript. Generative AI was used to enhance the figures of the manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Footnotes

Edited by: Priya Mishra, Babasaheb Bhimrao Ambedkar University, India

Reviewed by: Mohamed Zarid, Ibn Tofail University, Morocco

Waleed Hassoon, Al-Qasim Green University, Iraq