Application of Fermentation Technology in Animal Nutrition: 2nd Edition

Fermentation technology has long been applied in animal nutrition worldwide, with its application primarily focused on animal feed. A core objective of this technology is the long-term preservation of feedstuffs: harvested forages, perishable agro-industrial or food processing by-products, and total mixed rations containing these ingredients are frequently ensiled to ensure year-round palatability, stability, and hygiene. Another key goal of this field is to enhance the nutritional value or safety of underutilized feed resources through fermentation; without such treatment, their use as feed may be restricted due to poor digestibility or potential toxicity. To achieve these aims, a variety of physical, chemical, and microbiological techniques have been developed [1]. This Special Issue, “Application of Fermentation Technology in Animal Nutrition: 2nd Edition”, includes nine original research articles and has received over 13,104 views. Collectively, these contributions demonstrate the promising prospects of applying fermentation technology in animal nutrition research—a field that integrates tradition with innovation, aiming to push the boundaries of fermentation science forward.

With the advancement of animal husbandry, the demand for quality feed has increased significantly, whereas the supply of natural forage resources remains scarce. Corn stover, featuring high yield and abundant nutritional components, has emerged as a crucial roughage source. Applying silage technology to corn stover not only enhances its palatability and nutritional value but also exerts positive impacts on livestock production performance. Liu et al. [2] assessed the effects of different additives and their dosage ratios on the nutrient composition, fermentation quality, and microbial community structure of corn stover silage. Their findings indicated that the synergistic application of cellulase, Lactobacillus plantarum, and xylanase substantially improved the sensory quality of corn stover silage, balanced the microbial community during the maturation period, and optimized the silage’s nutritional profile. This work demonstrated that adding 20 U/g xylanase to corn stover silage significantly enhances silage quality, maturation efficiency, and microbial community stability. Therefore, the incorporation of xylanase is recommended to optimize the quality of corn stover silage.

Fermented feed is widely used in animal production owing to its enhanced palatability and high utilization efficiency. To explore the beneficial effects of feed fermentation on animal health, Qu et al. [3] conducted studies using piglet models and found that supplementation with fermented mixed feed (FMF) activates the Wnt/β—catenin signaling pathway, accelerates the expansion of intestinal stem cells (ISCs), and thereby promotes intestinal development. This finding not only provides valuable insights into the potential applications of FMF but also lays a theoretical foundation for its use as a nutritional supplement to support healthy digestive function in pigs.

To develop cotton straw into a viable feed resource via biological fermentation, Wei et al. [4] conducted a study to valorize this agricultural by-product as a novel feed and assess its feeding efficacy in sheep. The results revealed that diets containing a low proportion of fermented cotton straw (14.50% of the total feed) achieved an optimal short-term fattening effect in sheep over a 50-day trial period. Furthermore, this dietary regimen improved the sheep’s utilization of fat and protein, while enhancing their antioxidant capacity. Fermented cotton straw boosted sheep production performance by increasing the abundance of nutrient-metabolizing bacteria—such as Prevotella, which is involved in the utilization of protein, carbohydrates, and other nutrients. Overall, the biological fermentation of cotton straw enables the efficient conversion of agricultural waste into animal feed, thereby facilitating sustainable agricultural development.

Escherichia coli (E. coli) is a prevalent bacterial pathogen in global poultry production, triggering severe health problems and declining productivity. Additionally, the overuse of antibiotics has fueled the emergence of antimicrobial resistance, which poses a grave threat to both animal and human health. To address this issue, Hai et al. [5] assessed the efficacy of fermented chive (Allium schoenoprasum) with Lactobacillus plantarum 1582 (FC) as an antibiotic alternative for controlling E. coli infections in broiler chickens. Their findings indicate that FC supplementation—especially at a 3% dosage—serves as a promising natural substitute for antibiotics in managing E. coli infections in broiler production.

Feed fermented by different strains of Lactobacillus plantarum (LP) generates unique bioactive substances. Li et al. [6] systematically compared the growth performance, gut microbiota regulation, and immune response indices of Muscovy ducks fed LP81-fermented feed (LP81-FF) against those on conventional diets. Their findings reveal that LP81-FF enhances Muscovy duck production via multiple mechanisms: improving nutrient bioavailability via a feed pretreatment, regulating microbiota-driven metabolic remodeling, and boosting systemic antioxidant capacity and immune function. These results confirm microbial fermentation as a feasible strategy for optimizing sustainable poultry production.

In developing tropical countries, local native grasses and agricultural by-products are the main roughage sources for ruminants. To enhance the efficient utilization of these by-products and mitigate the bottleneck of animal feed shortages during dry seasons, Du et al. [7] used corn stover (CS; Zea mays L.) as a raw material to systematically explore dynamic changes in the silage fermentation quality, bacterial community structure, and pathogenic risks across different fermentation durations. Their results demonstrated that CS contains suitable carbon and nitrogen sources to support natural silage fermentation: Serratia marcescens was the dominant microbial species in fresh CS, which gradually shifted to Lactiplantibacillus plantarum as fermentation progressed. Additionally, the optimal period for coordinating microbial metabolism and nutrient transformation was identified as between days 15 and 30. This study lays a theoretical foundation for optimizing the research framework of agricultural by-product bioconversion.

Whole-plant corn silage is a pivotal feedstuff in global ruminant production, with its nutrient composition tightly linked to harvest timing. Since starch serves as the main energy source in silage-based diets, exploring variations in starch degradation rates lays a theoretical foundation for optimizing the efficient use of whole-plant corn and its silage in ruminant farming. Accordingly, Zhang et al. [8] employed wet chemistry methods and an in vitro simulated rumen fermentation system to examine the starch content, gliadin content, amylopectin content, disappearance rate, and rumen dynamic degradation parameters of whole-plant corn silage harvested at different times. Their results revealed that silage fermentation enhances the amylopectin content in whole-plant corn starch, elevates the proportion of rapidly degradable starch, reduces gliadin levels, and increases both the rumen disappearance rate and starch disappearance rate of the silage. Additionally, the deposition of starch and gliadin in corn starches of varying structures varied with harvest timing, which in turn induced corresponding changes in the rumen degradation of whole-plant corn silage starch.

Biomass sorghum is distinguished by its high dry matter yield and ratooning capacity, supporting multiple harvests and silage production. Silva et al. [9] assessed the productive potential and fermentation quality of silages derived from ratoon biomass sorghum hybrids. Their findings revealed that these hybrids maintained high dry matter yield potential even under low-rainfall conditions, with all producing silages of satisfactory fermentation quality. The only limitation was a reduced aerobic stability, which can be alleviated via heterofermentative inoculants. Regarding chemical compositions, CMSXS5039 was the most suitable hybrid for high-energy diets, attributed to its superior starch and non-fiber carbohydrate contents. In contrast, BRS 716 and CMSXS5044 were more appropriate for high-protein diets due to their elevated crude protein levels.

Corn silage is a primary forage source for dairy cattle and a key component of intensive beef cattle production systems. Nevertheless, it is susceptible to aerobic deterioration during feedout. Microbial chitinases hold promise for the biological control of phytopathogenic fungi, as they degrade the chitin layer in fungal cell walls, offering a potential eco-friendly approach to curb such spoilage microorganisms. Thus, Niu et al. [10] assessed the impacts of a heterofermentative lactic acid bacterial inoculant—comprising Lentilactobacillus hilgardii and Lentilactobacillus buchneri—either alone or combined with chitinases, on the ensiling process, aerobic stability, and in vitro ruminal fermentation of whole-crop corn silages. Their findings indicated that inoculation with the L. hilgardii and L. buchneri mixture, both alone and in combination with chitinase, improved the aerobic stability and enhanced in vitro neutral detergent fiber digestibility of corn silages. Chitinase alone, however, exerted no such effects.

Collectively, this Special Issue features nine original studies that focus on the application of fermentation technology in animal nutrition, covering research areas such as the silage of agricultural by-products, fermented mixed feed, the isolation and application of lactic acid bacteria strains, the effect of fermented feed on animal performance, and other related topics. These findings are expected to expand feed resources, optimize fermentation quality, and enhance animal performance. While the challenges ahead are substantial, the accompanying opportunities are equally remarkable. By addressing these challenges and pursuing the research directions outlined herein, fermentation technology can be maintained as a critical component in animal nutrition, thereby meeting the evolving demands of the animal husbandry industry.

Future Challenges in the Application of Fermentation Technology in Animal Nutrition

• Difficulties in strain and microecological regulation: Screening high-quality functional strains (e.g., high-efficiency enzyme-producing and stress-tolerant lactic acid bacteria) is time-consuming and costly. Unclear interaction mechanisms of multi-strain synergistic fermentation often cause antagonism or unstable functions, while strain inactivation in complex breeding environments impairs effect consistency.
• Bottlenecks in process standardization and scaling-up: The precise control of solid-state fermentation parameters (temperature, humidity, pH) is challenging, leading to batch-to-batch quality variations. Liquid-state fermentation suffers from high energy consumption, excessive wastewater, and inconvenient transportation. High-temperature pelleting inactivates probiotics and active enzymes, requiring low-temperature processes or post-coating technologies that increase costs.
• Intense safety risk prevention pressure: Fermentation is prone to pathogenic bacteria contamination (e.g., Salmonella) and biogenic amine or mycotoxin production. Raw material batch variations and secondary fermentation may induce nutrient loss (e.g., lysine, methionine) or reduced palatability, necessitating a full-chain detection system.
• Inadequate regulatory and market adaptation: Unified standards for fermented feed strain evaluation, viable bacteria count detection, and safety limits are lacking. Regional regulatory differences (e.g., EU, China) in genetically modified strains and fermentation by-products raise compliance costs, and the low acceptance of fermentation technology among small- and medium-sized farms hinders its promotion.
• Balancing effect stability and cost: Breeding conditions (stress, raw material fluctuations) and animal species/stage differences affect fermented feed efficacy. High costs from high-quality strains, specialized equipment, and long fermentation cycles are unaffordable for small- and medium-sized farms, restricting large-scale applications.